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UK P&I CLUB

Reefer mattersA focus on some of the issues surroundingthe carriage of refrigerated cargoes

UK P&I CLUBIS MANAGEDBY THOMASMILLER

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Many shippers and carriers are prepared to accept inadequateinstructions either through ignorance or through unquestioningacceptance of what has been accepted previously

Carriage instructions forrefrigerated cargoes

IntroductionRefrigerated cargoes are invariably perishable to agreater or lesser degree, and their safe carriagedepends on maintaining suitable storage conditionsduring transportation. This is true for all modes oftransport and all cargoes, though conditions are morecritical for longer journey times and for more perishablecommodities.

Refrigerated cargoes include both frozen and chilledgoods, the latter including fresh fruits and vegetables.Generally, frozen goods do not suffer if over-cooled,whereas chilled goods can be damaged by lowtemperatures, either by freezing or by chilling injury tofresh produce. Much tropical and sub-tropical produceis liable to chilling injury if subjected to temperaturesbelow those usually experienced in the growing area.

Successful transportation is dependent on the carriageinstructions, which define the conditions in which thegoods are to be carried. If these instructions areincomplete, inadequate, contradictory, or wrong, thenproblems can be expected. For the shipper, there is therisk of loss of cargo. For the carrier, there is the risk of aclaim even if the goods are undamaged. Many shippersand carriers are prepared to accept inadequateinstructions either through ignorance or throughunquestioning acceptance of what has been acceptedpreviously by themselves or others. Instructions may bebased on goods of different origin, which may havedifferent requirements.

The way in which cargo is stowed into holds or stuffedin containers is important for successful carriage, and isdealt with later.

These recommendations have been drawn up to assistboth shippers and carriers to re-assess their carriageinstructions in order to improve the operation ofrefrigerated transport chains. Any suggestions forimproving these recommendations would be welcome.First, general requirements are considered. Thereafter,

separate sections relate to containerised cargoesand to shipments in reefer vessels. For ease ofreference, points that are the same for both types oftransport are repeated in the appropriate sections.

General requirementsThe responsibility for specifying carriage instructions isthat of the shipper, the owner of the goods. Only theshipper knows the full nature of the goods, their priorhistory and their requirements. Frequently thisresponsibility is passed to the carrier, but in this casethe shipper should agree the acceptability of thespecified conditions prior to shipment. In either case,the exact nature of the cargo needs to be known – in thecase of fruit, for example, carriage requirements mayvary dependent on type, variety, maturity, origin andgrowing season conditions. ● If mixed loads of differing commodities are to be

carried in a single cargo space, it is necessary toconsider compatibility of temperature, atmosphere(especially ethylene levels) and liability to taint. Thiswill usually require specialist cargo care advice.

Generally frozen goods do not suffer if over-cooled

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● It may be necessary to ensure that carriageconditions are specified to all carriers in the transportchain, as on occasions an international journey mayuse different carriers at the start and end of thejourney.

● Items such as relative humidity and maximum timewithout refrigeration should not be over-specified butshould meet the necessary requirements of thegoods.

● Over-specification of requirements is to be avoidedas it tends to lead to more, and sometimes spurious,claims regarding technicalities which have notactually affected cargo quality.

Many of the items listed here may be taken for grantedin the case of regular shipments, but may need to bespecified if a new carrier is used.

Specific requirements for containerised cargoesThe parameters that may be included in carriageinstructions for containerised refrigerated cargo arelisted below:

● Pre-stuffing sanitation.

● Pre-cooling of containers.

● Cooling during part-loaded conditions.

● Prohibition of stuffing cargo at mixed temperatures.

● Stowage requirements.

● Ventilation.

● Carriage temperature.

● Maximum time with refrigeration.

● Air circulation rate.

● Relative humidity.

● Measurement and reporting requirements.

● Special conditions for cold weather.

● Need to pass instructions to subsequent carrier.

● Need to notify if limits exceeded.

For controlled atmosphere shipments,additionally:

● Levels (ranges) for O2, CO

2, humidity, ethylene.

● Permitted time to reach specified levels.

● Procedure in event of CA system failure.

● Safety requirements.

● Discharge atmosphere requirements.

Each of these is considered below:

Pre-stuffing sanitationThe proper cleanliness and lack of odour in containersto be used for refrigerated goods should be a matterof normal good practice, but any special or particularneeds should be identified.

Pre-cooling of containersPre-cooling is only useful when loading fromtemperature-controlled loading bays; in otherconditions, it can result in excessive moisture ingressfrom the atmosphere and is not recommended.

Cooling during part-loaded conditionsPart-loaded containers should be closed andtemperature maintained if there is a delay beforecomplete loading.

Prohibition of stuffing cargo at mixedtemperaturesProperly pre-cooled cargo and substantially warmercargo should not be mixed.

Stowage requirementsAny special stowage requirements, such as a protectedor underdeck stow, should be stated.

VentilationThe rate of fresh air ventilation for fresh produce shouldbe specified. This should be as an absolute figure incubic metres per hour. The specification of apercentage rate of ventilation only has meaning ifrelated to a specific container size and a specific modelof refrigeration unit.

Temperature control panel in ECR

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Carriage temperatureIt is not physically possible to provide refrigeration inthe absence of temperature differences, both betweenair and goods and within the bulk of the goods. Theonly temperature which can be controlled is the setpoint, which corresponds to air delivery temperature forchilled goods and to air return temperature for frozengoods.

The term ‘carriage temperature’ therefore has littlemeaning, and ‘set point temperature’ should bespecified. If appropriate, this may be augmented by amaximum allowable temperature during periods withoutrefrigeration.

Although degrees Celsius (oC) are the internationalstandard, in the USA degrees Fahrenheit (oF) are stillcommonly used. As zero degrees C is a commonchilled goods temperature and zero degrees F is acommon frozen goods temperature, great care isneeded to avoid possible confusion of units.

chilled goods and a lower rate for frozen goods. If aspeed change switch is fitted, low speed operation forchilled goods may be possible, but as this inevitablyresults in a wider range of cargo temperature, it is notrecommended.

Relative humidityWhen equipment with humidity control is used, arange must be specified. It is difficult to measurehumidity regularly to better than the nearest 2 to 3%,so an acceptable range of at least ±5% should bespecified, albeit with a tighter target. Specialequipment is available to maintain either high (e.g.90%) or low (e.g. 50%) humidity. Without suchequipment, relative humidity is not controllable andshould not be specified.

Measurement and reporting requirementsIt is normal to record air temperature in refrigeratedcontainers, and some equipment also records deliveryair temperature. Any specific shipper requirement forreporting temperatures should be stated. When therefrigeration unit is not running, the recordedtemperatures do not reflect cargo temperatures.Shippers may choose to put their own recordingequipment within cargo, in which case they shouldinform both carriers and receivers.

Special conditions for cold weatherSometimes special requirements exist for exceptionallycold conditions. However, it should be noted thatmost transport refrigeration equipment will controltemperature using either cooling or heating asnecessary to maintain specified conditions.

Need to pass instructions to subsequent carrierIf there is uncertainty at the start of a voyage as to whowill be the final carrier, it may be necessary to requestthe initial carrier to pass on carriage instructions.

Need to notify if limits exceededProcedures for notification of out of specificationconditions should be established prior to acceptanceof cargo for shipment. This could apply to warmloading, or to equipment failures, for example. Standardprocedures and safe limits should be available.

Additional requirements for controlledatmosphere shipments

Controlled atmosphere (CA) systems are designed tomaintain an atmosphere different from normal, usuallywith low oxygen and increased carbon dioxide. Theyenhance the storage life of some produce when usedin conjunction with refrigeration. There are additionalrequirements for such shipments, as follows:

For USDA and other cold treatment quarantinerequirements, maximum pulp temperature may have tobe maintained below a specified temperaturethroughout a continuous period of days or weeks, andonly approved equipment may be used.

Maximum time without refrigerationSometimes it may be necessary for statutory or otherreasons to specify a maximum duration of time withoutrefrigeration, either per event or in total for the journey.This should not be necessary if temperature limitsare well defined.

Air circulationSome containers have a high air circulation rate for

Loading a cargo of potatoes

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Levels (ranges) for O2, CO

2, humidity, ethylene

For each of the atmospheric gases to be controlled,upper and lower concentration limits should bespecified.

Permitted time to reach specified levelsThe maximum time allowed to reach the specified levelsmay be laid down.

Procedure in event of CA system failureThe failure of a CA system will not necessarily have adrastic effect on the produce if the refrigerationcontinues to run. In these circumstances it will benecessary to introduce fresh air ventilation to fruit andvegetable cargoes. This should be specified.

Safety requirementsCA produces an atmosphere which is deadly to humans– breathing an oxygen-depleted atmosphere inducesrapid unconsciousness and may result in death.Adequate safety systems must be in place, and thesemay need to allow for the possibility of stowaways in thecargo.

Discharge atmosphere requirementsThe safety requirements extend to those unloadingcargoes. Proper ventilation prior to entering containersand training of workers are both necessary.

Containerised transport ofperishables without refrigerationSome perishable commodities are carried withoutrefrigeration, possibly for very short-duration journeys,or in ventilated equipment. In these cases it is wise toconsider which of the previous requirements may stillapply.

Products with limited temperature sensitivity may becarried under refrigeration for certain journeys only.The following guidelines suggest when this may beappropriate:

● For any goods requiring close temperature control,refrigeration is essential. If temperatures need to bemaintained within a band of 2oC or less, refrigerationshould be virtually continuous.

● At the other extreme, for less sensitive goods with a

maximum temperature tolerance of 30oC or above,refrigeration is only necessary for storage on land athigh ambient temperatures. For containerisedshipments at sea, a protected stow may berequested.

● If the maximum permitted temperature is 25oC or

lower, refrigeration should be used for any journeysthrough the tropics and for any journeys anywhere ina summer season.

● If cargo requirements are marginal, either in terms oftemperature tolerance or in terms of possible delaysat high ambient temperatures, then the only safeoption is to use refrigeration.

● Frozen foods may sometimes be carried withoutrefrigeration for short journeys as long as the cargo isnot subjected to more than the specified maximumtemperature. This should only be done with theconsent of the owner of the goods.

Specific requirements for reefershipsThe parameters that may be included in carriageinstructions for refrigerated cargo are listed below:

● Pre-loading sanitation.

● Pre-cooling of cargo space.

● Cooling during part-loaded conditions.

● Prohibition of loading cargo at mixed temperatures.

● Stowage requirements.

● Ventilation (or lack of) during cooling.

● Ventilation thereafter.

● Carriage temperature.

● Air circulation rate.

● Relative humidity limits or targets.

● Carbon dioxide limits or targets.

● Ethylene limits.

● Measurement and reporting requirements.

● Special conditions for cold weather.

● Need to pass instructions to subsequent carrier.

● Need to notify if limits exceeded.

For controlled atmosphere shipments,additionally:

● Levels (ranges) for O2, and CO

2, humidity,

ethylene.

● Permitted time to reach specified levels.

● Procedure in event of CA system failure.

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● Safety requirements.

● Discharge atmosphere requirements.

Each of these is considered below.

Pre-loading sanitationThe proper cleanliness and lack of odour incompartments to be used for refrigerated goods shouldbe a matter of normal good practice, but any special orparticular needs should be identified.

Pre-cooling of cargo spaceThe pre-cooling of cargo spaces removes heat fromsteelwork and provides a check on the operation of therefrigeration system. However, an excessive pre-coolingtime only wastes energy and time. Duration of 24hoursafter the required temperature has been reached issufficient. The required pre-cooling temperature may bea few degrees lower than required transporttemperature.

Cooling during part-loaded conditionsPart-loaded spaces should be closed andtemperature maintained if there is a delay beforecompleting loading. Care should be taken to ensurethat under these conditions the temperature is not heldat a precooling temperature below the requiredtransport temperature for long enough to damage thecargo.

Prohibition of loading cargo at mixedtemperaturesProperly pre-cooled cargo and substantially warmercargo should not be mixed at loading.

Stowage requirementsAny special stowage requirements should be stated.

Ventilation (or lack of) during coolingFor most refrigerated cargoes, the cargo should beloaded at the required carriage temperature. For somecargoes, notably bananas and the less sensitive citrusvarieties, cooling in transit is normal. In these cases aperiod of 48 hours should be specified, during whichfresh air ventilation is stopped to allow maximumrefrigeration.

Reference is sometimes made to the ‘reduction period’which is the time from hatch closure to the air returntemperature reaching within 18oF of the requested airdelivery temperature. This is a parameter which mayusefully measured and reported but should not bespecified.

Ventilation thereafterAfter cooling, or throughout in the absence of cooling,the rate of fresh air ventilation for fresh produceshould be specified. This may be as an absolute figurein cubic metres per hour, or as a rate in air changesper hour of the empty volume of cargo space.Alternatively it may be linked to measured values ofhumidity, ethylene or carbon dioxide. Care is necessaryto avoid requirements that conflict.

Carriage temperatureIt is not physically possible to provide refrigeration inthe absence of temperature differences both betweenair and goods and within the bulk of the goods.Carriage temperature for chilled goods must thereforebe specified as the air delivery temperature. Pulptemperatures may usefully be measured and reported.

It may be required to specify a lower temperature for alimited period to ensure rapid cooling of warm cargo,known as ‘shock treatment’. Dual-temperature regimes,in which the delivery air temperature is changed after aspecified period of days, may also be stipulated.

For frozen cargo, it is usually sufficient to specify amaximum temperature that should not be exceeded.This may be subject to qualification for short periods.For example:

Cargo temperature shall not exceed -18oC, except forshort periods during power disconnection or defrosting,when temperatures shall not exceed -15oC. A singlespecified ‘carriage temperature’ is a meaninglessspecification that should never be accepted.

Although degrees Celsius (oC) are the internationalstandard, in the USA degrees Fahrenheit (oF) are still

Kiwi fruit need to be carried using a fresh-air ventilation system,so the possibility of cross contamination of the atmospheres fromdifferent cargoes must be considered carefully at the time of loading- see page 15

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commonly used. As 0oC is a common chilled goodstemperature and 0oF is a common frozen goodstemperature, great care is needed to avoid possibleconfusion of units.

For USDA and other cold treatment quarantinerequirements, maximum pulp temperature may have tobe maintained below a specified temperaturethroughout a continuous period of days or weeks, andonly approved equipment may be used.

Air circulation rateThe rate of circulation of air around and through thecargo controls the range of temperature within thecargo, and also the rate of cargo cooling. Minimumrates may be specified, usually as multiples of theempty volume of the hold per hour. Often thesemultiples are misleadingly referred to as ‘air changesper hour’, or ‘ACH’, a term best used for ventilationrather than circulation rates.

Relative humidity limits or targetRelative humidity may not be specifically controllable inshipments; if there are critical requirements, eitherspecial equipment or special packaging or both will berequired. A sensible specification is as follows:

Relative humidity should be maintained at the maximumpossible, after the delivery air temperature andfresh air ventilation requirements have been met.

Over-specification of humidity requirements is likelyto lead to conflicting instructions. When specialequipment with humidity control is used, a range mustbe specified. It is difficult to measure humidity regularlyto better than the nearest two to three percent, sothat an acceptable range of at least plus or minusfive percent must be specified, albeit with a tightertarget.

Carbon dioxide limits or targetFor many fruits, a maximum level of carbon dioxide maybe specified, this to be the overriding parameter forventilation rate control. Care is necessary to avoidconflicting ventilation requirements.

Ethylene limitsThe measurement or specification of ethylene levels israre, as accurate measurement at very lowconcentrations needs specialised equipment. If limitsare to be specified, the measurement and controlregime must also be specified.

Measuring and reporting requirementsIt is normal for carriers to measure temperatures of theair in ships’ holds. Any specific shipper requirementshould be stated, especially if it involves cargo ratherthan air temperature. Shippers frequently choose toput their own recording equipment within thecontainer/cargo in which case they should inform bothcarriers and receivers.

Special conditions for cold weatherSometimes special requirements exist for exceptionallycold conditions. However, it should be noted thatmost transport refrigeration equipment will controltemperature using either cooling or heating asnecessary to maintain specified conditions.

Need to pass instructions to subsequent carrierIf there is uncertainty at the start of a voyage as to whowill be the final carrier, it may be necessary torequest the initial carrier to pass on carriageinstructions.

Need to notify if limits exceededProcedures for notification of out of specification

Frozen boneless chicken

Plums, being loaded on board this reefer, are climacteric and tendto ripen rapidly during transit and storage

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If the master follows the instructions to the letter, is the shipliable for the damage which arises to what otherwise would havebeen a sound cargo?

Air changes

Ventilation of cargocompartmentsThe term ‘air changes’ can give rise to misleadingcarriage instructions from shippers to ships’ masters, orotherwise correct carriage instructions can bemisinterpreted by ships’ officers. The object of thisarticle is to provide support for those who know whatthey are doing, and to provide non-technical peoplewith sufficient understanding to avoid the usual pitfalls.

Simple air changesA general cargo vessel with a hold ventilation systemwhich is not fan-assisted, can only change the air in thecargo compartments to the extent that the ventilatorcowls, of whatever type, can be trimmed/opened to theexternal atmosphere. This will allow inward passage ofoutside air and outgoing exhaust of stale air. To all

intents and purposes, therefore, this type of vesseltends to fall outside the groups to which this articleapplies and to which the term ‘air changes’ may refer.

Fan-assisted air changesThree modes of air movement in ships’ holds areconsidered:

● Open-circuit systems

● Closed-circuit systems

● Closed-circuit systems with fresh air input.

The term ‘air changes per hour’ refers to how manytimes the fans extract and replace the total volume ofair in the empty cargo compartment in one hour. A fan-rating of ’20 air changes per hour’ for a hold of 1,300cubic metres air capacity, means that, with the fans

conditions should be established prior to acceptance ofcargo for shipment. For example, this could apply towarm loading, or to equipment failures. Standardprocedures and safe limits should be madeavailable.

Additional requirements for controlledatmosphere shipments

Controlled atmosphere (CA) systems are designed tomaintain an atmosphere different from normal, usuallywith low oxygen and increased carbon dioxide. Theyenhance the storage life of some produce when usedin conjunction with refrigeration.

There are additional requirements for such shipmentsas follows:

Levels (ranges) for oxygen, carbon dioxide,humidity and ethyleneFor each of the atmospheric gases to be controlled,upper and lower limits should be specified.

Permitted time to reach specified levelsThe maximum time allowed to reach the specified levelsmay be stipulated.

Procedure in the event of CA system failureThe failure of a CA system will not necessarily have adrastic effect on the produce if the refrigerationcontinues to run. In these circumstances it will benecessary to introduce fresh air ventilation, whichshould be stated.

Safety requirementsCA produces an atmosphere that is fatal to humans –breathing an oxygen-depleted atmosphere induces rapidunconsciousness and may result in death. Adequatesafety systems must be in place, and these shouldalways admit the possibility of stowaways in the cargo.

Discharge atmosphere requirementsThe safety requirements extend to those unloadingcargoes. Proper ventilation prior to opening cargospaces and training of workers are both essential.

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operating at full speed on full power, all the air in thathold could be continuously changed with fresh air 20times in any one hour in an ‘open’ system – or that theoriginal air could be re-circulated within the hold 20times in any one-hour period in a ‘closed’ system. Inother words the fans can generate an air throughput of26,000 cubic metres per hour.

It would seem to follow that, if there is cargo in thathold, the same fans operated in the same mannershould be capable of changing, or recycling, the airsurrounding the cargo at an increased rate becausesome of the hold’s space is occupied by cargo; but it isnot necessarily so. The degree to which that rate maybe increased depends upon the nature of the cargoitself, the manner in which it is stowed, the direction(s)in which dunnage is laid, and the extent to which it isrequired for the moving air to pass through and aroundthe cargo. Those same circumstances may equallydecrease the rate of change due to the ‘blockage’effect of the stowed cargo. And herein lies the first steptowards misunderstanding.

A shipper and/or charterer may specify their need of avessel having a ’15 air change/hour fan capability’ butthe cargo, say, onions in crates and/or slatted bins,blocks most of the hold space to the extent that evenoperating the fans at full speed on full power will notachieve 15 complete air changes per hour. The master,however, may know from experience, that the very thinghe should not do is to run the fans at full speedthroughout the voyage, because to do so would causethe vegetables to dry-out and become unacceptable assound cargo at the port of discharge. So the masterruns the fans at speeds, and at times, in keeping withthe nature of the cargo balanced against the day-to-dayatmospheric conditions encountered during the voyage.But what if the cargo arrives ‘spoiled’ in any event?

When the dust has settled, the three-part question tobe answered will be:

● If a shipper and/or charterer writes that fans must beoperated at a given rate throughout the voyage, mustthe master follow that instruction even though heknows from experience that such continuous forcedventilation will damage the cargo – or lack ofventilation where instructions involve too little?

● If the master follows the instructions to the letter, isthe ship liable for the damage which arises to whatotherwise would have been a sound cargo?

● If he follows his own experience and operates thefans accordingly, is the ship liable for allegeddamage to the cargo even if such damage wasprimarily due to the pre-shipment condition of thecargo itself?

Open-circuit systems

An open-circuit system is one in which external fresh airis drawn into the hold by fan induction and is exhaustedfrom the hold by fan extraction; or, in which onlyinduction or exhaust is created mechanically. Whateverthe exact disposition of the fans, this is totally an‘external for internal air change’ system, because thereis no re-circulation of used air within the system. Therating will be expressed in the ship’s documentation assomewhere within the range 10 air changes to 25 airchanges, per hour, depending upon the type of ship andits individual ventilation arrangements.

Such systems are to be found in many general cargoships, and in purpose-built vessels engaged in thecarriage of perishable commodities which do notrequire artificial cooling, chilling or refrigeration. Suchcargoes are often of the bagged kind, e.g. rice,potatoes, onions, and similar items. Many freshvegetables often require some degree of artificialcooling, depending upon the location of harvest, theport of destination, and the intended length of thevoyage.

Closed-circuit systems

Alternatively, an entirely closed-circuit system isrequired in purpose-built refrigerated vessels carryingdeep-frozen products and in which there is the intentionto retain the foodstuffs biochemically inert so that theyare giving off no odour, gas or moisture. Low-leveltemperatures are the only consideration. Two methodsmay be employed to achieve this end result.

The most modern closed-circuit systems nearly alwaysinvolve fan induction of air through low-level coolingmachinery. In such instances, the fans will be rated as

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so many ‘air changes per hour’. As explained earlier, inthe deep-freeze context this may not refer to outside orfresh air. The phrase, as considered for deep-freezecompartments, relates to the ability of the fans toextract and re-circulate the volumetric air capacity ofthe compartment, when empty, through the coolingmachinery, at so many times per hour. Such a systemhas to be entirely closed, otherwise the vessel’smachinery would continuously be cooling fresh warmair from outside, instead of re-circulating the cold airalready reduced to the required temperature level forthe deep-freeze compartments.

In the alternative closed-circuit system, the deep-freezeatmosphere is attained by, and maintained with, coolingcoils fixed throughout the cargo compartment. In thissystem there is no air change or air movement atall: the atmosphere is entirely static without anycirculation of re-used air, and without any input fromoutside air. In this type of vessel ‘air changes per hour’has no meaning.

Closed-circuit systems with fresh air input

Where closed-circuit systems of the types outlinedabove are involved, there is little doubt in the minds ofthose most closely concerned as to what is requiredand what must be done to achieve it. The difficultiesseem to arise in situations where, while the systemitself is basically ‘closed’, some induction of fresh air isalso required.

In vessels carrying vegetable cargoes which arerequired to be cooled, such as bananas, carrots, oftenpotatoes and tomatoes – depending upon the port ofshipment and the length of sea voyage involved – theremay be a requirement both to reduce the temperature ofthe air within the cargo compartment artificially, andalso to ensure that the natural gases and moisture givenoff from the vegetables/fruit by respiration will not attainlevels likely to cause deterioration of the cargo itself.

For instance, bananas will respire ethylene, which isused in the ripening process. If the ethylene content ina cargo compartment was allowed to accumulate, anexponential ripening process may result independent ofthe exactitude with which the carrying temperature ismaintained.

So the requirement will be for a closed-circuit system,with the means of venting stale air and inputting ameasure of fresh clean cooled air in a mannersufficiently controlled to remove unwanted gases,without giving the cooling machinery an impossible taskand without loss of the required compartment carryingtemperature.

This may be done in one of three ways:

● By fitting trunkways with small slide panels,positioned so that the cooled air circulating fansthemselves can draw fresh air down the ducts at agiven rate, which should be specified as ‘fresh airchanges per hour’. If such rating is given, it willprobably be in the range 6/10 changes per hour andwill relate to the fans’ capacity to change thevolume of air in the compartment that number oftimes through the fresh air system, whether or notthe cooling machinery is in operation. With such a‘fresh air system’ the slide panels can be adjusted toproduce a continuous ‘fresh air trickle’ or,alternatively, opened fully at given times and closedat other times.

● There may be a separate small fan system, to inducefresh air and extract stale air through independentducts – which may or may not be given a ‘rating’.

● Less commonly nowadays, there may be just simpletrunking to allow intake and exhaust served by smallcowls, much on the principle of the old generalcargo ventilators, and opened and closed at certaintimes of the day, only, weather conditionspermitting.

There are many ships whose cooling arrangements arebased on the fixed-coil system, in which the cooledatmosphere is more-or-less static, as indicated earlier.Where fruit and vegetables are being carried in cooledconditions however (as opposed to deep-frozenconditions), there remains the requirement to keep thecompartment air ‘fresh’, which can only be achievedby venting stale air and replacing it with fresh air. Such‘freshening’ may be effected by means of any of thethree options referred to previously. And, of course,nothing excludes the use of refrigerated vessels for thecarriage of some non-cooled cargoes.

ConclusionWhen referring to fan-assisted cargo compartment‘ventilation’, the speaker or writer should make clearthe difference between ‘open-circuit’ and ‘closedcircuit’ systems and the nature of the ‘air changes’.

If it is of the non-cooled general cargo type or of thecirculated cooled type it should be stated as ‘airchanges per hour’.

When it is inducted fresh air/exhaust of stale air in anotherwise closed-circuit system it should be stated as‘fresh air changes per hour’ whenever the rate isknown.

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The shipper should have full knowledge of the history of theproduce and which temperature must be maintained by the carrierthroughout the period under his control

Fresh fruit and vegetables

The transport of fresh fruit and vegetables is acomplicated topic. Differing fruit and vegetables havewidely varying requirements for their safe preservation.The rate at which living fruits and vegetables age andeventually submit to senescence (old age), attack bymicro-organisms and inevitable demise depends uponthe environmental status afforded during storage andtransit. During which periods the quality and conditionof fruits and vegetables are maintained by retention atall times of their optimum temperatures. For safecarriage this will usually require that the commoditiesare pre-cooled and maintained at that temperature priorto being loaded into the transport unit, be it refrigeratedship, container or other mode of transport. Refrigeratedsystems used in transportation of commodities onlyhave the capacity to adjust minor reductions of, and tomaintain, the product temperature.

All fresh fruits and vegetables are living products andtheir life processes continue after harvest; the two mostimportant being respiration and transpiration. Theformer being a complicated sequence of chemicalreactions involving conversion of starches to sugarsand the change of those sugars into energy. The normalrespiration results in the fruit and vegetables consumingoxygen and giving off carbon dioxide; water; andvarying, albeit immense, amounts of heat. The higherthe ambient temperature surrounding the commoditythe greater will be the temperature of the commodityitself and consequently the larger its rate of respiration.The second process, transpiration, is the loss of waterby evaporation which will occur once the fruit orvegetable is removed from its tree or plant which hasbeen the source of water during its formative period.Thus the storage/carriage conditions afforded theproduce should be such that excessive water loss doesnot ensue.

TemperatureMany reference books include tables which providedata, including optimum temperatures, for the safestorage of commodities. Other publications specificallylist the optimum transit (carriage) conditions. Thestorage data may, depending upon the commodity, referto long term refrigerated storage requirements with any

period quoted being that from harvesting to entry intothe marketing chain. Published data applicable to sea-going carriage requirements may indicate slightlyhigher optimum temperatures. However it is essentialto understand that published values of optimumtemperatures for storage or transit are not absolute –the accurate optimal requirements are dependent uponvarietal, climatic and other details of the produce. Theoptimum and required transport temperature of fruitsand vegetables should be provided in writing by theshipper who will, or should, have full knowledge of thehistory of the produce and which temperature must bemaintained by the carrier throughout the period underhis control. Optimum temperatures determine lowrates of respiration extend storage life and in additionreduce the rate of development of micro-organisms.Generally speaking the higher the temperature thefaster will be the growth of moulds and bacterialinfections.

Freezing pointsThe lowest safe limit of temperature for eachcommodity is its highest freezing point. Thistemperature is invariably slightly below 0°C, thefreezing point of pure water, as the natural juicescontain dissolved substances in solution which havethe effect of lowering the freezing point. Thusgenerally speaking the main contents being sugars thesweeter the produce the lower the freezing point.Nonetheless it must also be remembered that stalks offruit contain much less sugar and may freeze at ahigher temperature than the fruit itself, resulting indeath of the stalk tissue with possible consequenceswhen the fruit is restored to ambient temperatures withlikely loss of sound market values.

Chill damageA second factor which establishes the lower safe limitof carriage temperature of some produce is that ofchilling, which is a reduction in temperature that doesnot reach the freezing point of the produce. Numerouscommodities especially those grown in tropicalclimates, or alternatively from plants originating fromthe tropics, are easily affected by low temperatures

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and inclined to injury to their tissues at temperatureswell above their freezing point. Typical symptoms notonly include pitting of surface tissues, discolour of fleshbut also an increased susceptibility to decay.

Relative humidityRelative humidity may be defined as the ratio of thewater vapour pressure present in air at an existingtemperature to the water-vapour pressure which wouldbe present if the vapour were saturated at the sametemperature. Relative humidity is usually expressed as apercentage.

Difference of vapour pressure may cause water vapourto move from or to the produce within the ambient air.The water-retention capacity of air is directlyproportional to the temperature of the air, i.e. an airmass at 90% relative humidity at +10°C contains agreater mass of water than a similar air mass at 90%relative humidity at a temperature of 0°C.

Nonetheless water is lost from produce at about doublethe rate when carried in a compartment whose air is at+10°C and 90% relative humidity when compared withthe same air being at 0°C and 90% relative humidity.

Thus the relative humidity of the air within a cargocompartment of a refrigerated vessel, insulatedrefrigerator container or trailer directly determines theretention of the condition of the products carried.Relative humidity below the optimum range will result inshrivelling or wilting in most produce. The maintenanceof an optimum range of humidity is often one of themore difficult to resolve during the carriage of freshproduce.

Relative humidity of air of 85% to 95% is usuallyrecommended for the carriage of most perishableproduce in order to preclude/impede wilting or shrivelcaused by moisture loss. Exceptions to the aboveinclude the carriage of onions, dates, coconuts, gingerrhizomes, yams, dried fruits and some horticulturalproduce. If the relative humidity increases to 100%condensation may occur which would increase thelikelihood of mould growth within the compartment andon the produce itself.

Air circulationThe circulation of cooling air within cargocompartments must be kept at an even requiredtemperature throughout. Despite variable heat leakageswhich may occur in various parts of the system, and theinevitable increase in the circulating air temperature atreturn compared with delivery, the result of removal ofrespiratory heat from the produce, only a small increase

should be acceptable. The comparison of delivery airtemperatures and return air temperatures being one ofthe critical monitoring requirements of carriage. As themajority of produce carried should be presented to thevessel/container or trailer as precooled, the exceptionswill include cargoes of bananas, the field heat havingalready been removed. The circulating cooling airshould therefore only be required to remove respiratoryheat of the produce and the heat exchanged via exteriorsurfaces. A high velocity of circulating air should beunnecessary and in fact undesirable. Cooling air inmodern refrigerated vessels and containers is usuallycirculated vertically, from the deck/floor, upwards. Thesystem is designed to produce equal air pressures overthe full area of the cargo space. However, anyelaborate arrangement for air distribution can berendered useless if incorrect stowage of the produceeliminates or reduces efficient airflow which tends tofollow the route of least resistance. The difficulties of‘properly and carefully’ stowing packages of freshproduce have become more complex with the use ofpalletised units and pallet boxes/bins.

Air exchangeDuring the carriage of fresh fruits and vegetables underordinary conditions of refrigeration accumulations ofgases such as carbon dioxide (CO

2) and ethylene

(C2H

4) will occur. Undesirable odours or volatiles may

also contribute to off-flavours and hasten deteriorationof the produce. These problems can be prevented byrepeatedly refreshing the circulating air within the holdsby admitting atmospheric air into the system. Theintroduced air entering at a point of lowest pressurewithin the circulation and the polluted air exiting thesystem at a point of highest pressure, or alternatively byuse of an auxiliary air system driven by separate fans.

Rates of respiration and heatgenerationFresh fruits and vegetables and similar produce are liveand as with all living products respire, i.e. the processby which oxygen from the air combines with the organicmaterial of the produce to form, ultimately, water andcarbon dioxide. The by-product of this chemicalreaction being energy released as heat. The rate atwhich fruits and vegetables produce heat varies, somehave high rates of respiration and they require morerefrigeration to maintain an optimum carriagetemperature than those which respire more slowly. Therates of respiration are determined by temperature andas before noted for every 10oC rise in temperature therates may be doubled or in some instances tripled.

The storage life of produce varies inversely with the rateof respiration. Produce with short storage expectancy

14

will usually have higher rates of respiration, e.g. freshbroccoli, lettuce, peas and sweet corn. Converselypotatoes, onions and some cultivars of grapes with lowrespiration rates have longer storage lives. The rate ofrespiration for any given product will depend upon itsvariety (cultivar), area of growth, the seasonal andclimatic conditions experienced during periods ofgrowth.

Climacteric fruit and vegetablesSome varieties of fruit and vegetables have rates ofrespiration which do not decline during their ripeningperiod – that is between maturation and the onset ofsenescence. In fact their respiration rates increase, acritical event or period known as their climacteric.Produce may therefore be categorised as climacteric ornon-climacteric. The former continuing to ripen post-harvest, where as the latter does not. The ripeningprocesses include development of colour, texture (tissuesoftening) and flavour.

Many fruits are climacteric, such as peach, apricot,banana, mango, papaya, avocado, plum, tomato andguava and tend to ripen rapidly during transit andstorage. Examples of non-climacteric fruit andvegetables include cucumber, grape, lemon, lime,orange, temple fruit (satsuma, tangerine, mandarin) andstrawberry.

Weight loss in transitWeight loss from harvested produce can be a majorcause of deterioration during transit and storage. Mostfruit and vegetables contain between 80% and 95% ofwater by weight, some of which may be lost bytranspiration (water loss from living tissue).

To minimise loss of saleable produce weight and topreclude wilting and shrivelling, the produce must bemaintained during transit at the recommended humidityand temperature. Whereas some weight loss willinevitably occur due to the loss of carbon duringrespiration, this will only be of relative minor proportions.

However, the loss of water will not only result in weightreduction but also in produce of poor quality. Loss ofmoisture can often be minimised by the use of protectivepackaging to complement carriage under optimumtemperature and humidity.

Supplements to refrigerationOpportunities have been tried and tested to slow downripening after harvest and thus extend the transit,storage and shelf life of fruit and vegetables – especiallythose in the climacteric category.

This can be achieved with controlled atmosphere(CA) storage and carriage; modified atmospherepackaging (MAP), storage and carriage (MA); oralternatively with edible coatings.

Basically and in all cases the atmosphere created isone of low oxygen (O

2) and high carbon dioxide

(CO2) when compared to atmospheric air. The low

oxygen and high level of CO2 depress the production of

ethylene (C2H

4), a gas emitted in small quantities by

plant tissues, which accelerates during the ripeningprocess and in turn expedites the process itself in theform of a chain reaction, especially true in the case ofbananas.

Caution: Modified and controlled atmospheres are non-life supporting. Proper ventilation instructions ofcompartments/containers under CA/MA must becarefully followed prior to entry.

Edible coatings can create a modified atmosphere,similar to that of modified atmosphere packaging(MAP), which can delay ripening of climacteric fruit,delay colour changes in non-climacteric fruit, reducewater loss, reduce decay and maintain qualityappearance.

It has been stated that edible coatings which should betested and tailored for each product are a simplesafe and relatively inexpensive means of extending theultimate shelf life of fruit and vegetables providedthere are good storage, shipping temperature andhumidity controls.

Carriage of mixed produceAt times carriers are required to load and stow differentproduce in the same vessel, hold, or cargocontainer. Should a mixture be necessary it is essentialthat the produce is compatible in respect of:

● Temperature

● Relative humidity

● Odour production

● Ethylene production.

Generally deciduous fruits, if having the sametemperature requirements, can be stowed together.

Cross tainting should be avoided at all costs wherebystrongly scented fruit and vegetables are stowedtogether. The many products which produceconsiderable ethylene naturally, including apples,avocados, bananas, pears, peaches, plums, melonsand pineapples should not be stowed with or in

15

Prolonged exposure to high levels of carbon dioxide can cause bananas to become ‘green ripe’ with soft ripe pulp and green skin

adjacent compartments to kiwi fruit, water melons,lettuce, carrots etc. which can all be seriously affectedby the ethylene.

Two commodities that have produced substantialcargo claims, pears and kiwi fruit, are dealt with in thisarticle. There is also a brief comment on research intoprocedures for the ocean carriage of particularlysensitive fruits. Some data in that section also coversthe storage of pears and kiwi fruit.

Pears

Pears are shipped to Europe and North America fromSouth Africa and Chile. They are also shipped inquantity from New Zealand and Australia. Althoughpears are considered to have a relatively long life it isessential that they are picked at the right stage ofmaturity and pre-cooled if optimum life is to beachieved.

There is a scientific procedure for determining thecorrect data for picking which is based on the starchcontent in the fruit. However, once the fruit has beenpicked, the starch is rapidly converted into sugar and itbecomes impossible at a later date to determinewhether the fruit was at a proper stage of maturitywhen picked. Pears are susceptible to variousphysiological disorders caused by chilling, excessatmospheric CO

2, and skin contact (bruising). They are

also subject to microbiological damage resulting frominfection by various organisms prior to harvesting. Thetwo most serious types of disease are mild speciesmonilinia fructigena and botrytis cinerea. The latterspecies can grow at temperatures as low as -4°C andthe growth of this organism can, therefore, only becontrolled by low temperature storage. The rate ofdecay increases rapidly as the temperature rises. Asinvasion usually occurs through damaged tissue theproper selection of fruit at the packing station is ofparamount importance.

The prescribed temperature for the carriage of pears is0°C to -1.1°C. It is therefore recommended the carryingtemperature should be 0°C or marginally lower whereships have equipment which can control the delivery airtemperature to plus or -0.2°C or better. The set pointsfor the carriage of pears in containers should be 0.6° to1.7°C.

Pears may suffer chilling injury at temperatures below -1.5°C. Certain fruit can tolerate lower temperaturesand, even if freezing occurs, very slow thawing at lowtemperatures can result in the fruit remainingundamaged. Thus, claims for damage due to thedelivery air temperature falling marginally below -1.5°Cfor short periods must be viewed with some scepticism.

Because of their comparatively large size and highthermal capacity, cooling of individual fruits throughthe whole tissue is a fairly slow process. Whenchecking a cargo shipped as pre-cooled, the ship’srepresentative should ensure spear temperatures aretaken at the centre of specimens selected for checking.Other points to be checked are the nature of thepackaging and the general appearance of the fruit,particularly skin blemishes. Caution should be observedwhen attempting to assess the maturity of thefruit and a surveyor should be consulted if in doubt.

Pears are susceptible to damage if the CO2

concentration in the atmosphere rises much aboveabout 1% so it is necessary to maintain fresh-airventilation at regular intervals when carrying this cargo.

Where unsatisfactory outturns occur it is essential thatexpert advice is obtained as soon as possible.

Kiwi fruit

These are mainly shipped from New Zealand andCalifornia and increasingly from Chile. They have along storage life if picked at the right stage of maturity

16

and thereafter stored at temperatures in the range -0.5°C to -1.0°C. Storage at temperature only slightlyabove this range (+3°C to +4°C) will substantiallyreduce the storage life.

Kiwi fruit are particularly sensitive to traces of ethylenein the atmosphere. This will prompt rapid ripening.Particular care must therefore be taken when kiwi fruitis loaded, whether in containers, which is usual, or inconventional refrigerated ships to ensure that theatmosphere in contact with the fruit cannot becontaminated with the atmosphere from other sources,e.g. containers stuffed with cargoes such as appleswhich release considerable amounts of ethylene andeven exhaust fumes from certain types of forklift. As itis necessary for the kiwi fruit to be carried using a fresh-air ventilation system, the possibility of crosscontamination of the atmospheres from differentcargoes must be considered carefully at the time ofloading.

Kiwi fruit are also subject to microbiologicaldeterioration, primarily due to invasion by botrytiscinerea.

It is again of paramount importance for expert advice tobe obtained as soon as possible where damage isfeared.

Recent developments in thecarriage of delicate fruits, exoticfruits and similar productsWorld trade in delicate products such as strawberriesand certain tropical fruits has expanded. The productsconcerned frequently have a short shelf-life and aretherefore transported by air when the distance betweenthe growing region and the market methods ofextending the shelf life of delicate products to enablethem.

It has been known for many years that increasing theCO

2 concentration in a cargo space will depress the

metabolic rate of living natural products and this facthas been utilised when carrying apples from Australiato Northern Europe and during storage worldwide.Recent research has developed more sophisticated gasmixtures, for use in containers or similar carrying units,which will not only slow the ripening rate of fruit and theonset of senescence in other living products but alsorender such products less susceptible to decay anddamage caused by micro-organisms, insects andphysiological disorders.

Controlled or modified atmospheric systems involveoriginal dosing to produce an atmosphere of the

composition required and then monitoring theatmosphere with automatic analytical equipmentwhich, coupled to recycling equipment, maintains theoriginal composition of the atmosphere by removing theexcess of some components and dosing to increase theconcentration of others.

Research work carried out has established that:

● Ethylene gas which promotes ripening of fruits is lesseffective in atmospheres containing less than 1%carbon dioxide.

● If the CO2 content of the atmosphere is too high,

serious physiological damage may result.

● As levels of carbon dioxide in the range 10-15%botrytis rot of strawberries and some other fruit issubstantially inhibited.

Storage of certain products in modified atmospherescan cause problems such as irregular ripening inbananas, pears etc. at low oxygen levels (2%).Development of black heart in potatoes and brownheart in pears and apples at lowered oxygen levels areother examples.

Some products which clearly benefit from controlled-atmosphere storage are listed below, showing theoptimum conditions for such storage, as reported byscientists in the USA.

The addition of carbon monoxide at levels of 1-5% inatmospheres containing 2-5% oxygen has been shownto reduce discoloration of damaged or cut lettucetissue. At levels of 5-10% it will inhibit the developmentof certain important plant pathogens. Use of this gashas been the subject of experimentation in the USA.

The following table of temperatures, maximum storage/transit and shelf life etc., is for guidance only. Therequired details of temperature and humidity should beprovided in writing by the shipper who has the fullknowledge of the product history. The shippersinstructions should be maintained at all times.

Commodity Temp. oC % O2

% CO2

Apples 0.5 2 – 3 1-2

Kiwi fruit 0.5 2 5

Pears 0.5 2 – 3 0.1

Strawberries 0.5 10 15 – 20

Nuts/Dried fruits 2.25 0.1 0.1

Bananas 12 – 15 2.5 2.5

17

Fresh fruit and Approx max Optimum transit Container temperature Highest freezing Relativevegetables storage, transit temperature set points points humidity

and shelf life

Days OC OF OC OF OC OF %

Apples – non chilling-sensitive 90-240 -1.1 to +1 30 to 33.8 +1.1 to +2.2 34 to 36 -1.5 29.3 90 – 95

Apples – chilling sensitive 35 – 45 +1.5 to 4.5 34.7 to 40 +4.4 to +5.6 40 to 42 -1.5 29.3 90 – 95

Apricots 7 – 14 -0.5 to +1 31 to 33.8 +1.1 to +2.2 34 to 36 -1.1 30 90 – 95

Asparagus 14 – 21 +2.2 36 +2.2 36 -0.6 30.9 90 – 95

Avocados – Fuerte and Hass 21 – 28 +5 to +8 41 to 46.4 +5 to 12.8 41 to 55 -0.3 31.5 85 – 90

Bananas – green 14 – 21 13 to 14 56 to 58 13 to 14 56 to 58 -0.7 30.6 90 – 95

Blueberries 10 – 18 -0.5 31 1.1 to 2.2 34 to 36 -1.3 29.7 90 – 95

Carrots – topped 30 – 180 0 32 0.6 to 1.7 33 to 35 -1.4 29.5 95

Cherries – sweet 14 – 21 -1.1 30 1.1 to 2.2 34 to 36 -1.8 28.8 90 – 95

Clementines 14 – 28 4.4 40 3.3 to 4.4 38 to 40 -1 30.3 90 – 95

Coconut – flesh 30 – 60 0 32 1.1 to 2.2 34 to 36 -0.9 30.4 80 – 85

Corn – sweet 4 – 6 0 32 0.6 to 1.7 33 to 35 -0.6 30.9 90 – 95

Courgettes 14 – 21 7.2 45 7.2 to 10 45 to 50 -0.5 31.1 90 – 95

Cucumbers 10 – 14 10 50 10 to 11.1 50 to 52 -0.5 31.1 90 – 95

Dasheens 42 – 140 13.3 56 11.1 to 13.3 52 to 56 - - 85 – 90

Garlic 140 – 210 0 32 0.6 to 1.7 33 to 35 -0.8 30.5 65 – 70

Ginger rhizomes 90 – 180 13.3 56 12.8 to 13.3 55 to 56 - - 85 – 90

Grapefruit 28 – 42 13.3 56 14.4 to 15.6 58 to 60 -1.1 30 85 – 90

Grapes 56 – 180 -1.1 30 1.1 to 2.2 34 to 36 -2.2 28.1 90 – 95

Guavas 14 – 21 10 50 9 to 10 48 to 50 - - 85 – 90

Kiwi Fruit 28 – 84 0 32 1.1 to 2.2 34 to 36 -0.9 30.4 90 – 95

Kumquats 14 – 28 4.4 40 4.4 40 - - 90 – 95

Lemons 30 – 180 12.2 54 10 to 12.8 50 to 55 -1.4 29.4 85 – 90

Lettuce – Iceberg 10 – 18 0 32 1.1 to 2.2 34 to 36 - - 90 – 95

Limes 42 – 56 9 to 10 48 to 50 9 to 10 48 to 50 -1.6 29.1 85 – 90

Lychees 21 – 35 1.7 35 1.7 to 2.2 35 to 36 - - 90 – 95

Mandarins 14 – 28 7.2 45 7.2 45 -1.1 30 90 – 95

Mangoes 14 – 25 13.3 56 12.8 55 -0.9 30.4 85 – 90

Melons – Honeydew 21 – 28 10 50 7.8 to 10 46 to 50 -1 30.3 85 – 90

Mineolas 21 – 35 3.3 38 3.9 to 6.7 39 to 44 -1 30.3 90 – 95

Nectarines 14 – 28 -0.5 31 -0.6 to +/-1 31 to 32 -1 30.3 90 – 95

Onions – dry 30 – 180 0 32 0.6 to 1.7 33 to 35 -0.8 30.6 65 – 75

Oranges – Blood 21 – 56 4.4 40 4.4 to 6.7 40 to 44 - - 90 – 95

Oranges – California and Arizona 21 – 56 6.7 44 6.7 to 7.8 44 to 45 -0.8 30.6 85 – 95

Oranges – Florida and Texas 56 – 84 1.7 35 1.1 to 2.2 34 to 36 -0.8 30.6 85 – 95

Oranges – Jaffa 56 – 84 7.8 46 7.8 to 10 46 to 50 -0.7 30.6 85 – 90

Oranges – Seville 90 10 50 11 52 - - 85 – 90

Parsnips 120 – 150 0 32 0.6 to 1.7 33 to 35 -0.9 30.4 95

Peaches 14 – 28 -0.5 31 0.6 to 1.7 33 to 35 -0.9 30.4 90 – 95

Pears – Anjou 120 – 180 -1.1 30 0.6 to 1.7 33 to 35 -1.6 29.2 90 – 94

Pears – Bartlett 70 – 90 -1.1 30 0.6 to 1.7 33 to 35 -1.6 29.2 90 – 94

Peppers – sweet 12 – 18 10 50 10 50 -0.7 30.7 90 – 95

Peppers – hot 14 – 21 10 50 10 50 -0.7 30.7 90 – 95

Pineapples 14 – 36 10 50 10 50 -1.1 30 85 – 90

Plantains 10 – 35 13 57.2 14 57.2 -0.8 30.6 85 – 90

Plums 14 – 28 -0.5 31 1.1 to 2.2 34 to 36 -0.8 30.6 90 – 95

Potatoes – seed 84 – 175 4.4 40 5 41 -0.8 30.5 90 – 95

Potatoes – table 56 – 140 6 42.8 7 44.6 -0.8 30.5 90 – 95

Satsumas 56 - 84 4 39 4 39 - - 85 – 90

Sweet potatoes 90 – 180 14 57 14 57 -1.3 29.7 85 – 90

Tangerines 14 – 28 7 42.5 7 42.5 -1.1 30.1 85 – 90

Tomatoes – green 21 –28 13.3 56 13 to 14 56 to 58 -.5 31.1 90 – 95

Tomatoes – turning 10 – 14 9 48.2 10.6 51 -0.5 31.1 90 – 95

Ugli fruit 14 – 21 4.4 40 5 41 -1.1 30.1 90 – 95

Watermelons 14 – 21 10 50 8 to 10 46 to 50 -0.4 30.9 85 – 90

Yams – cured 49 – 112 16 61 16 61 -1.1 30.1 70 – 80

18

Factors which affect the condition of frozen fish cargoes duringtrans-shipment and transport and advice on how to spot signs thata fish cargo is running into problems.

Frozen fish on reefer vesselsand in containers

IntroductionAccording to the UN’s Food and AgriculturalOrganisation, there are more than 28 million peopleengaged infishing operations worldwide. The annualworld catch of fish exceeds 100 million tonnes, ofwhich around 25 per cent is processed into frozenfishery products. Each year, a high proportion of thesefrozen products enters international trade and is carriedby sea.

Sometimes cargoes of frozen products are found to bedamaged when they are unloaded from ships andrejected, leading to claims against shipowners andagents alleging that the damage is due to negligenceon the part of the masters and crews of the carryingvessels.

Clearly a vessel is not liable for damage that wassustained before loading, or during handling if due tothe actions of third parties. Frequently it is difficult toestablish the precise cause and chain of events leadingup to the damage. Specialised knowledge is required tosample and inspect fishery products, and relate theircondition to the events of the voyage. However, vesseloperators also need adequate technical knowledge tominimise the risk of problems occurring, and to act inthe event of a claim.

These guidelines are intended to advise ships’ masters,officers and crew on good practices to be observedduring the loading, storage, carriage and discharge offrozen fishery products carries as bulk cargoes. Theyalso provide detailed guidance on how vessel operatorscan limit their liability for damage, by ensuring adequatepre-shipment inspection and by acting promptly topreserve evidence when a problem occurs. Othersections also provide background information onfactors which affect the condition of frozen fishcargoes during trans-shipment and transport and advice

on how to spot signs that a fish cargo is running intoproblems.

Frozen fishery productsTypes of frozen fishery products

A variety of frozen fishery products are carried by sea inreefer vessels and reefer containers. The main types, inapproximately descending order of frequency are asfollows:

Whole, gutted1, or dressed2 fish individuallyfrozen1. Gutted fish are whole apart from removal of the viscera.

2. Dressed fish have heads and guts, and perhaps tails and fins removed

Tuna intended for canning is a typical example.

Whole, gutted, or dressed fish in blocksThis is a common form of presentation for small andmedium-sized fish intended for further processing.Blocks are rarely more than 10cm thick or more than50kg in weight. Common sizes are 25 and 50kg. Blocksare either unwrapped or wrapped in plastic film and aresometimes packed in strapped cartons.

Fillets of fish frozen in blocksFillets of fish are often frozen into geometrically shaped

Whole fish individually frozen

19

blocks. Blocks are usually wrapped in plastic film andpacked into inner display packs. The display packs arethen commonly packed in outer cartons.

Fillets of fish, individually frozenThese are fillets frozen as separate pieces, and perhapsthen coated with batter, or batter and breadcrumbs.

Fillets are either placed in packages for retail sale orloosely packed in plastic bags. Small display packs arepacked in outer cartons while loosely packed fillets maybe packed in bags within outer cartons.

Cephalopods, frozen in blocks or as packagedproductsThese include squid, cuttlefish and octopus. Bothprocessed and unprocessed products are typicallyfrozen in blocks weighing 10 or 25kg. Blocks areoccasionally individually packaged, but more usuallyare overwrapped in plastic with several blocks beingpacked together in a single outer carton.

Crustacean shellfish, frozen in blocks or aspackaged productsThese include lobster, crayfish, shrimp and crab.Smaller crustaceans and crustacean meats are oftenfrozen in blocks weighing up to 1kg. Blocks are packedindividually in cartons or over-wrapped in plastic filmand then packed into outer cartons.

Crustacean shellfish, individually frozenLarge crustacea, for example lobsters and crayfish areindividually frozen, whole or as tails, wrapped andpacked in cartons.

Freezing and storage of fisheryproducts

Introduction

The master of a vessel carrying frozen fishery productsdoes not generally need to be concerned with howthe products have been frozen and stored beforedelivery to the vessel. Indeed, he has no means ofknowing or verifying these conditions, except perhapswhen fishery products have been prepared and frozenat sea and transhipped directly to the carrier vessel.However, the quality of the cargo discharged from thevessel is affected by freezing, storage and distributionpractices before transfer to the vessel, as well as bythe manner of loading, stowage and carriage on thevessel.

The following is intended to inform masters and crewabout the technologies involved in freezing andstorage of frozen fishery products, and the effects offreezing and storage on product quality.

The freezing process

When a fish product is cooled in a freezer itstemperature drops rapidly to about -1oC, when icebegins to form. However, not all the water in the fishturns to ice at this point. As more heat is extracted,more ice forms, but the temperature of the productdrops only slowly until about -3oC. This period, whenthe product temperature changes very gradually, isknown as the ‘thermal arrest period’.

The product’s temperature then begins to drop rapidlytowards the operating temperature of the freezer.(Fig A)

When the product is allowed to thaw, the temperaturewill follow a curve similar to Figure A, but in thereverse direction. oC, then slowly to about -1oC as itpasses through thermal arrest, then rapidly again untilthe product reaches the ambient temperature.

Fillets of fish, frozen in a block, wrapped and packed in a carton

Cephalopods(squid) frozen in blocks

20

It is important for the quality of the frozen product thatthe thermal arrest period is as short as possible,preferably less than two hours. This rate of cooling canonly be achieved in equipment designed for thepurpose – merely placing fish in a cold store will notachieve a sufficiently high freezing rate. The

The frozen block is knocked out of the tray, protectedby some form of over-wrapping and perhaps packedinto cartons.

The quality of frozen fishery products

Quality of productsComplaints about defects in the quality of frozenfishery cargoes usually fall into one or both of twocategories:

● Abnormal and offensive odours, flavours or texture,or any other defects that will influence theconsumers’ perception of quality.

● Physical damage affecting the processability ormerchantability of the product (can occur during thefreezing process, though more usually happensduring handling of the frozen product).

Quality defects in both categories can arise duringhandling, processing and storage of the product beforedelivery to the vessel, during loading into the ship’sholds, and while the product is stored on the reefervessel.

Loss of quality can occur both before and afterfreezing. However, the nature of the defects differs inthe two circumstances and an experienced assessorshould be able to distinguish between them.

Loss of quality before freezingFish of all kinds are notorious for the speed at whichthey spoil (even when chilled) and for the unpleasantnature of the spoiled product. Spoilage affects theappearance, odour and flavour of the product.Freezing halts the spoilage process and fixes thequality as it was at the time of freezing. When frozenproducts are thawed out, the quality can be no betterthan it was at the time of freezing. If defects in thequality of frozen fishery products at time of delivery areshown to be a consequence of spoilage, then no blamecan be attached to the carrier of the frozen goodsunless the product had thawed out during the voyage.

Loss of quality during frozen storageFrozen fishery products are not completely stable inthe frozen state and will deteriorate over time, resultingin changes in texture, odour and flavour of the product.Changes in texture are similar in character across mostfishery products – the product becomes dry, stringy andtough. But changes in odour and flavour depend on thetype of fishery product. Lean fish with low oil content(such as cod) develop the characteristic odours andflavours described as ‘musty’, ‘cardboard’, and ‘wetdog’, while fish with high oil content (like tuna, herringand mackerel) develop rancid odours and flavours

refrigerated holds of reefer ships are designed as coldstores to maintain the temperature of already frozenproducts; they do not have the refrigeration capacity tofreeze products at the required rate.

Examples of freezing methods

Brine freezing of individual fishBrine freezing is used for larger, whole fish like salmonand tuna. The technique is used almost exclusivelyonboard fishing vessels, particularly tuna-catchers. Thefishing vessel is fitted with one or more insulated tankscontaining refrigeration coils. Before fishing starts,these tanks are filled with sea water, which is thencooled to around 0oC. As fish are caught, they aredropped into the tanks. When a tank is full, salt isadded to lower the freezing point of the brine and thetemperature is lowered so that the fish freeze. Thetemperature that can be achieved depends on theconcentration of the brine – the minimum, when thebrine is saturated, is about -21oC. In practice, fishingvessels aim for a solution giving a temperature ofaround -12oC. Once the fish are frozen, the brine isdrained from the tank and the fish are held in drycondition with the refrigeration system on.

Freezing of blocksSmall products, including small fish, fish fillets, squid,octopus and shrimps, are often frozen in blocks. Theproduct is laid in trays and frozen, either in a tunnelthrough which cold air is passed or between pairs ofhollow plates through which refrigerant is circulated.

Fig A. Freezing curve of fish initially at 5oC

5

0

-5

-10

-15

-20

-250 1 2 3Hours in freezer

4

Pro

duct

tem

pera

ture

(Cel

sius

)

THERMAL ARREST PERIOD

21

reminiscent of new leather, linseed oil or old-fashionedoil paints. Odour and flavour changes in frozencrustacean shellfish and cephalopods are similar tothose in lean fish. Oily fish deteriorate faster, andproduce off-odours more quickly than lean fish duringfrozen storage.

The main factors influencing the rate at which fisheryproducts deteriorate during frozen storage aretemperature of storage and exposure to air. The lowerthe storage temperature the slower the productdeteriorates. The storage life of fishery products carriedat -18oC ranges from 3 to 12 months. In general,storage life is halved for each 5oC rise in storagetemperature. For example, a product with a storage life8 months at -18oC will have a storage life of 4 months at-13oC. Since ship’ refrigeration systems can maintainproducts at temperatures below -18oC, and sincevoyages are generally less than a month long, thereshould be no significant loss of quality due to frozenstorage-related defects during a voyage.

Rate of deterioration is also affected by exposure to air.Block-frozen products are usually protected by closewrapping with plastic film or by coating with a waterglaze. To maintain quality, it is important that this cover,film or glaze is not damaged or lost.

Another defect arising during frozen storage isexcessive loss of moisture from the product, whichleads to general or localised dehydration known as a‘freezer burn’. The dehydration is signified by whitepatches which appear where glaze is lost or wherethere are tears or breaks in the protective wrapping. Inunprotected material, dehydration occurs first in thinparts of the product such as the fins of the whole fishand the tail-ends of fillets, or at the corners of blocks.These dried areas do not re-hydrate when the productis thawed and are indicated by blemishes in the thawedproduct.

Physical damage to frozen productsPhysical damage takes a number of forms, butcomplaints about the quality of reefer cargoes areusually concerned with distortion or compression of theproduct. This kind of damage, which affects individuallyfrozen fish or blocks of products, occurs when warmfishery products (i.e. warm relative to the recommendedstorage temperature) are subjected to pressure, forexample in a stack of fish stored in the ship’s hold.

When water is frozen, it changes from a liquid to a hardsolid, ice, at 0oC. Although fish typically contain70-80% of water – the exact percentage depends onthe species – the situation is more complicated thanfreezing water alone. Water in the fish tissues starts to

freeze at about -1oC but at this point only a proportionof the water is converted to ice. Progressively, morewater freezes as the temperature falls. At -18oC, themaximum temperature usually specified for carriage offrozen fish in reefers, around 90% of the water hasturned to ice. It is very hard to deform frozen fish at thistemperature and below, except under extremely highpressure.

If the product warms at all, some of the ice melts. Thefish tissue holds an increasing proportion of liquid waterand a decreasing proportion of ice as its temperaturerises.

As the proportion of ice decreases, the fish tissue,though still partly frozen, becomes softer and can bedeformed by moderate pressure. For example, it ispossible to deform the surface of a product at -7oC bypressing hard with the point of a pen, a temperatureprobe, or even a thumbnail. At -3oC, ‘frozen’ fisheryproducts are soft enough to deform and to sag undertheir own weight. If the cargo in the hold of a reefer isstacked to a height of 4 or 5 metres, as is often thecase, there is sufficient pressure to distort fish to someextent at -7oC, and to distort and compress fishconsiderably at -5oC or higher.

Individually frozen fish can be severely indented wherethey lie across each other, and tend to take up theshapes of the surfaces they are pressed against –ridged floor plates or edges of structures in the hold. Inan extreme case, a stack of fish can be compressedtogether into a solid mass, with almost no spacesbetween the fish. Blocks of products are squeezed,flattened and distorted and will extrude into gapsbetween cartons, they can also be indented by floorplates or pallet boards.

Indentations caused when warmed, soft tuna were pressed on toridged floor plates by the weight of the stack of fish above them

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Frozen products at low temperatures are often brittleand prone to damage by rough handling. For example,tails are easily broken off whole fish and blocks can beshattered or chipped.

Products can also be damaged by contamination. If oilor chemicals are spilled, they may penetrate thewrappings and affect the contents. When cartons andwrappings are torn, the contents are more vulnerable toboth contamination and dehydration.

Pre-shipment inspection

The need for inspection

Loss of quality in fishery products can be caused bydamage both before and after freezing. Carriage offrozen fish by sea is just one stage in a long sequenceof processing, handling, distribution and storageoperations – products can be damaged or decline inquality at any stage. Receivers of damaged cargoes offrozen fishery products might allege that loss of qualityoccurred solely while the material was in the chargeof the shipowner.

Pre-shipment inspection is therefore essential, todetermine as far as possible the condition and qualityof the product at the time of loading, and to note anycircumstances that could lead to an exaggerated lossof quality during carriage in the vessel. Suchinformation has an important bearing on any claim thatloss of quality or damage occurred during carriage inthe reefer. The inspection should take into account thenature of the material, its packaging and itspresentation.

Pre-shipment inspection by the ship’s officers isgenerally confined to visual inspection of the cargo andto measurement of physical properties such astemperature. Officers are not expected to carry outdetailed evaluations of the quality of the material,which would require examination of material afterthawing and perhaps also after cooking.

Nature of the consignment

The deck officer should check that the materials to beloaded are consistent with the bill of lading. However,information provided on a bill of lading is usually verybrief – a cargo may be described as ‘fishery products’,which encompasses many different product types.Wherever possible, deck officers should record anyadditional information, for example, in the case ofindividually frozen fish, the species or variety, thepresentation (whole or dressed) and the name of thefishing vessel.

It is also important to record the details of any labellingon wrapped or cartoned material, particularlyproduction dates or batch codes. The absence of anylabelling, particularly of batch or production codes,should also be noted.

Information on the nature of the consignment and alldetails of labelling should be recorded on the mate’sreceipt. If labels are detachable, one can be removedand attached to the receipt.

Temperature of the consignment

It is essential to measure the temperature of frozen fishpresented for loading. Since fishery products sufferdamage if they are stowed at a high temperature,temperature records provide important evidence of thestate of the product at the time of loading.

The terms of carriage normally stipulate thetemperature, or at least the maximum temperature, atwhich the cargo should be carried. Holds of reefervessels are intended for storage of frozen materialloaded at the required temperature of carriage.

Refrigeration systems have little spare capacity tolower the temperature of products which are put intothe hold at above its operating temperature. Materialthat is above the operating temperature of the hold willtake a long time to cool down and will lose quality as aresult.

The terms of contract between the provider of thefrozen products and the recipient sometimes specifythe maximum temperature at which the productsshould be stored and delivered to the vessel – amaximum temperature of -10oC would be typical forfrozen tuna delivered from a tuna fishing vessel. Even ifthere is no specific requirement for the cargo’stemperature on delivery to the vessel, the master mayrefuse to accept a product if he considers thetemperature too high and the product at risk of damageduring stowage and carriage.

The deck officer should ensure that sufficientmeasurements are taken to provide an adequatesummary of the temperature cargo, and that themeasurements are accurately recorded. Guidelines fortemperature measurement are given in the Appendix atthe end of this article.

During loading, supervising officers should note anysoftening of the flesh of fish during transfer to thevessel – this can be gauged by pressing the surface ofthe fish with a thumb nail or the point of a temperatureprobe. Even when the temperature measured at the

23

core of a fish is low, the flesh on the outside can be softenough to be damaged by the pressure of a stack withinthe hold.

Condition of the material

It is not easy to assess the intrinsic quality of frozenproducts by visual examination, but, with experience,one can get some indication of pre-freezing quality fromthe appearance of the eyes and skin in the case ofwhole fish, from the colour of the shell in the case ofshell-on crustacean shellfish, and from the colour of theskin in the case of cephalopods. Of course, theseindications of quality will not be visible in packagedproducts unless some of the cartons are opened.Whenever possible, photographs should be taken ofany defects.

Visual indication of spoilage in individuallyfrozen fish

The inspecting officer should examine frozen fishindividually for signs of spoilage before freezing. Thetable below summarises the difference in appearancebetween good quality and stale fish.

Wrapping, which may or may not be supplemented byfurther packaging in a carton, is intended to preventcontamination and dehydration. Wrapping is onlyeffective in protecting against dehydration if it is sealedor is closely applied to the product. The record shouldinclude details of the type and condition of anywrapping.

Nature and integrity of packaging andwrapping

Packaging is intended to protect the product fromphysical damage. The inspecting officer should recordany damage to outer wrappings, particularly if thedamage has caused exposure of the contents.Sometimes the packaging includes strapping,particularly where a carton contains individuallywrapped, heavy products like blocks of fillets. Thenature and integrity of any strapping should be noted.

The officer should note any staining of cartons andouter wrappings, including the character and nature ofthe stain – lubricating oil, fuel oil, water, fish juices, forexample. Oils tend to be dark in colour and leave thewrappings soft, even when frozen; fish-juice stains areyellowish or reddish. The officer should note if thestaining is extensive, covering all or most of thecontainer or wrappings, or localised. When stains arelocalised, note whether they are predominantly oncorners or edges of packages or on the sides.

Blemishes, stains and contamination of theproduct

When the surface of the product is visible, it should beinspected for blemishes and contamination. Blemishesinclude surface damage to whole fish like abrasionsand tears to the skin or splits in the flesh, and surfacedamage to blocks such as patches of freezer burn. Anattempt should be made to assess the proportion of theconsignment affected.

It is important to record an unusual discolouration orstaining, and if possible the nature of the defect, forexample, blood or bloody brine (particularly on brine-frozen tuna), oil, and chemicals. The product shouldalso be examined for contamination by dust, organicmatter such as fish offal or vegetable debris, and anyother foreign matter.

Damage to outer carton, though wrapping and contents lookunharmed

Good quality fish Stale fish

Colours bright, demarcated degraded and dull

Eyes clear or slightly cloudy; yellowish or reddish;flat to the head or even sunken or missingprojecting slightly

Skin clean – no discoloured abraded and covered withslime or coating with yellowish slime

or blood-stained brine;head region of tuna takeson a diffuse pinkish hue

Tuna spoiled prior tofreezing – note sunken,discoloured eyes, dullcolours, pinkishdiscolouration of head,loss of skin and dirty,bloodstained slime

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In all cases of blemishes or contamination, theinspecting officer should note the extent of the damageand estimate the proportion of the consignmentaffected.

Individually frozen whole fish often have slight pressuremarks formed during the freezing process. These minordistortions must be allowed for during examination offrozen products. The nature of the marks depends onthe freezing process. For example, fish frozen in traysare slightly flattened or have indentations on one sidewhere they have lain on the trays during freezing. Brinefrozen fish tend to float in the brine tanks and arerestrained below the level of the brine by a grating. As aresult, the fish may have slightly flattened sides wherethey have been compressed, or shallow cylindrical-shaped depressions where fish lay across each other asthey froze. Sometimes the pressure on tuna duringbrine freezing results in splitting of the skin and flesh,usually on the dorsal surface at the base of the dorsalfin. Any other splitting should be noted by the officer.

Any distortions other than slight flattening or thepresence of minor depressions suggest that the producthas warmed up, softened, and refrozen in the distortedshape. The officer should note the nature and extent ofany distortions.

Blocks of fish should reflect the sharp angles andregular, geometrical shape of the tray or former in whichthey were frozen. Blocks of fish which have thawedwhile stored on pallets or in stacks show signs ofslumping, bending, or compression and material is oftensqueezed into spaces between blocks. Restraints suchas strappings and the framing of pallets and shelf-supports cause indentations in the blocks of fish. Again,the inspecting officer should note the nature and extentof distortions.

Release of liquid

Fish release liquid as they thaw. The cargo officersshould check for pools of liquid collecting withinwrappings, and for signs that liquid has been squeezedfrom the blocks and has refrozen on the sides of the

Signs of thawing or partial thawing

Sometimes claims are made against shipowners on thebasis that a cargo had thawed or partially thawedduring the voyage, and had then frozen again to thestipulated carriage temperature. It is thereforeimportant to check that a potential cargo does not showsigns that it had thawed and refrozen before it had beenpresented for shipment. Such thawing or near thawingis often indicated by distortion of product shape andrelease of liquids from the product.

Distortion

Distortion of whole or blocks of fish indicates that thematerial has thawed or partially thawed since freezing,or was distorted during the freezing process.

Oil-stained cartons

Carton has been stained by fish juices when the block partiallythawed

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stack or on shelves and pallets. Staining of cartons issometimes an indication that the contents havethawed and released liquid.

Transfer, stowage and carriage

Temperature control during loading

It is very important for maintaining quality that frozenfishery products be held at low temperatures at alltimes. Although it is inevitable that the product’stemperature will rise during loading into the hold, theloading operations must be conducted so as to keepthis rise to a minimum. The product’s quality suffers notonly due to the immediate rise in temperature asmaterial is stowed in the hold, but also because of thetime taken to bring the product back down to therequired temperature after stowage.

As far as possible, the cargo should be loaded at, orbelow, the required temperature of carriage – typicallyaround -18oC. Officers and crew should attempt tominimise warming of the cargo while it is being loadedand stowed in the holds, preferably so that thetemperature of the cargo is not above -10oC by thetime it is stowed. Although the ship’s crew may havelittle control over loading operations, the master shouldco-operate with the ship’s agent, and particularly withthe stevedoring company, to ensure that good practicesare adopted during loading and stowing.

Good practices during loading

● Ensure that delivery to the ship’s side is matched toloading onto the vessel to reduce the time thatproducts are waiting on the quay.

● Products should be delivered in insulated containersor lorries, or at least in covered vehicles.

● If the material must be unloaded onto the quay orheld on the deck of the reefer, it should be placed onpallets or on an insulating base, packed as tightly aspossible and covered with a tarpaulin or similarprotection against sun and wind.

● The cargo should be protected from exposure towind, rain and sun until it is about to be transferred tothe vessel.

● In tropical climates, avoid loading for two or threehours either side of noon and consider loading thevessel at night.

Good practices during stowage

● Ensure that the hold is cooled to below the carriagetemperature before loading begins.

● During breaks in loading, cover holds or decks with atleast the hatchcovers, even if the thermal covers arenot put in place.

● Refrigeration to the holds should be turned on duringlong breaks.

● Transfer cargo as rapidly as possible from the quay ordischarging vessel to the hold.

● Once loaded, the cargo should be covered withtarpaulins.

● Where consistent with efficient loading, use only onehatch at a time to avoid through currents of air in thehold.

Maintaining low temperatures duringcarriage

There is usually an explicit or implicit requirement to holdthe cargo below -18oC during carriage. The ship’srefrigeration system must be capable of delivering air tothe holds at a temperature a few degrees below thetarget temperature to allow for heat leaks though theship’s structures. Cargo spaces in reefers are usuallycooled by re-circulating air systems, which are onlyeffective if the air can circulate freely through andaround the stow.

Most heat leaks into the cargo hold occur through thesides and bulkheads, and it is important to ensure thatthere is free circulation between the cargo and thestructures to the hold. Sides and bulkheads should befitted with vertical dunnage (without horizontal battenswhich could obstruct air flow) to keep the cargo awayfrom the structures. There should be an even gap of atleast 20cm between the top of the stowed cargo and thelowest part of the deckhead.

Cartons should be stacked with gaps between themwhile stows of individually frozen fish will inevitably havespaces between the fish unless the fish are deformableand have been compressed.

The ship’s engineer should ensure that refrigerationequipment is well maintained and can achieve thedesign temperatures. Evaporator coils must be defrostedas required to maintain the cooling capacity. Frequentneed for defrosting is a sign of high temperatures in thecargo and should be noted in the engine room log. Inaddition, the engine room log should recordtemperatures at critical and meaningful positions in therefrigeration system – for example, the outlet and returnair streams in air cooling systems, and the outlet andreturn fluid temperatures in pipe-cooled systems.

It is vital to take and record temperature measurements

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in the hold. How meaningful these measurements aredepends on the location of the temperature sensors.Material in the centre of the stow is the slowest to coolbecause the source of refrigeration is mainly around thesides of the stow. Refrigerated air percolates gapsbetween fish or between cartons and the cooling effectdepends very much on the existence of uninterruptedspaces. Sensors attached to the sides or bulkheads ofthe hold are exposed to cold air circulating through thedunnage against the sides or bulkheads and thereforetend to indicate temperatures lower than the bulk of thecargo. Sensors should be attached to posts or otherstructural members running through the hold, wherethey are more likely to reflect the temperature of thebulk of the cargo accurately.

Protecting the cargo from contamination

Every effort must be made to protect the cargo fromcontamination. Good shipboard practices will preventdirect contamination by sea water, bilge water, fuel oiland the like, but it is important to be aware that fisheryproducts are rapidly tainted by odours picked up fromthe ambient air. This is a vital consideration when usingair-cooled refrigeration systems – the air must notbecome polluted by odiferous materials such as fuel oil,paints or chemicals used on the ship. A simple guidelineis that if the air circulating through the hold has anodour, then that odour will be picked up by the fishproducts.

Unloading

When a cargo is unloaded from the ship, similarprecautions should be taken to those recommendedduring loading to minimise warming. Unloading shouldbe completed as quickly as possible and the cargoshould be protected from wind, rain and hightemperatures.

DocumentationThe importance of documents

Documents are fundamentally important in theinvestigation of any claim involving damage to cargo.They will be examined by the technical surveyors, andmay be used as evidence in any subsequent legalproceedings. The following documents are likely to beimportant in the event of a claim.

● Ship’s log.

● Bill of lading.

● Mate’s receipts and attached record of theinspection of the cargo prior to and during loading.

● Deck log of loading and unloading.

● Stowage plan.

● Engine room log.

● Any documentation arising from disputes duringunloading and/or receipt of cargo.

In addition, photographs and video recordings canprovide important evidence in support of statements inthe logs and inspection reports.

Mate’s receipts

The mate’s receipts should include the record of thepre-shipment inspection (see previous section). Thisrecord should detail all observations on the cargo’scondition at time of receipt, including results of at leasta visual inspection of each part of the consignment.

Records should also include temperaturemeasurements, taken at sufficiently frequent intervalsto provide a fair indication of the average temperatureof the cargo.

Any observations which indicate that cargotemperature is high, or that cargo was delivered in adamaged or deteriorated condition, should besupported as far as possible by further evidence. Thisevidence might include photographs taken during pre-shipment inspection or results of reports by cargosurveyors.

The mate’s receipt should include any information onthe nature of the consignment supplementary to the billof lading, as well as details of any labels.

Deck log for loading

LoadingMany charterparty agreements specify a minimum rateof transhipment or loading. To demonstrate compliancewith this, and to provide evidence in case of claimsconcerning damage to the cargo during loading, thetiming and sequence of events during loading should benoted in the deck log. At minimum, the log recordshould include the following:

● Time alongside.

● Where cargo was loaded from – quay, lighter, fishingvessel.

● Times of opening and closing of hatches.

● Arrival and departure of stevedores onboard.

● Times when the refrigeration system was turned onand off.

● Start and finish of cargo stowage.

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● Any breaks in loading.

● Weather conditions (sun, wind, rain, ambienttemperature).

● Any unusual or irregular events which might affectthe condition of the cargo during stowage orsubsequent carriage.

Deck log for unloading

UnloadingNormally, unloading may be the responsibility of thereceiver, and the master of the vessel could considerthat his responsibility for the cargo is over. However, thedeck log should continue to record conditionsduring discharge, logging similar information as listedabove for loading.

Stowage plan

A stowage plan should be drawn up for all cargoes –an accurate plan is a central piece of evidence in anydamage claims arising against the vessel.

The stowage plan should indicate the location of eachconsignment and part of consignment and shouldinclude the following information:

● Number of units (pallets, cartons or blocks) in eachlocation.

● Gross and net weight.

● Origin of each part.

● The corresponding bill of lading.

Engine room log

The engine room log is one of the most importantdocuments, since it contributes evidence about thetemperature of the ship’s cargo during stowage andcarriage.

The log should document at least thefollowing:

● The locations of temperature sensors in theholds.

● Temperatures at the sensors in the holds.

● Times when compressors were turned on and off.

● In air-cooled systems, the temperatures in the airstreams entering and leaving the holds andcompartments.

● In pipe cooled systems, the temperatures ofrefrigerant to and from the cooling pipes.

Actions in case of disputeAction by the master of the vessel

The master must load the cargo in apparent good orderand condition and act to maintain it in this state. Thissection describes actions to be taken when a potentialproblem is identified.

In the event of any concern or dispute over thecondition of the cargo while loading or unloading, themaster of the vessel should contact his owners orcharterers or his P&I correspondent. Best practicewould indicate that loading or unloading should ceaseuntil instructions have been received, although this maynot always be possible.

As soon as any question is raised over the condition ofthe cargo, the ship’s master should begin to documentthe events surrounding the discovery of defectivematerial, and the nature and possible extent of thealleged defects.

If possible, loading or unloading of the vessel should behalted and the hatches closed until a cargo surveyor ispresent. Ideally, cargo should be inspected andsampled while still in the hold, or even during discharge,allowing the surveyor to determine if the nature andextent of the damage is in any way related tothe position in the hold.

Once the cargo has been discharged into store, relatingdamage to location in the hold is obviously moredifficult, or impossible, unless the cargo is adequatelylabelled. Therefore, if loading or unloading mustcontinue, the master should ensure that each cargo unitis labelled with the hatch number and deck as well aslocation within the hatch and deck, as it leaves thehold. The deck log should also record the destination ofthe material and the agent responsible for handling it.

Records

The master should ensure that all records anddocuments relevant to the dispute are secure, and thatthey are only made available to parties representing theship’s interests.

Services of surveyors

When a problem is identified during loading orunloading – for example, if the temperature of thematerial is too high – loading or unloading should ceaseuntil the cargo has been inspected by a specialistsurveyor.

If the dispute concerns the quality of the product, it willprobably be necessary to call in at least one

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specialist surveyor to examine the cargo, establish itscurrent quality and determine the nature and cause ofany defects.

If it is suspected that defects result from maritimecauses – for example, physical damage frommovement of cargo, or from contamination with seawater, fuel oil or bilge water – an expert in shipoperations should be called in. However, if the defectscould be attributed to the initial quality of the materialwhen loaded, or to the way the product was stowedand carried on the vessel, a specialist surveyor wouldbe appropriate.

Many of the surveyors appointed by local shippingagents are general marine surveyors, often with aseagoing background; they are not necessarily skilled inthe evaluation of the quality of fish cargoes. Mastersand agents are therefore advised to check the expertiseand qualifications of surveyors carefully to ensure thattheir technical background and experience areappropriate for the particular job.

As a general rule, a single surveyor should not becommissioned for both a cargo survey and a survey ofvessel condition. Since the skills required for each typeof assessment are very different, it is unlikely that oneperson would have experience in both areas at thelevels of expertise required. A fish cargo surveyorshould have a background in food science and theinspection of food products, and, ideally, someexperience in assessing the quality of frozen fisheryproducts.

Official inspectors and samplingprocedures

Where official inspectors – for example, port healthofficers or veterinarians – are involved, the mastershould document the authority under which the officersvisited the vessel and the name and status of eachofficer.

The master is also advised to record the nature andamounts of any samples taken by representatives of theowners or by officials. Such records should include thelocation of the samples within the hatch or deck, theauthority under which the samples were taken and thedestination of the samples.

If part of the sample is given to the master, he shouldensure that it is fully labelled, and, if possible, that it issealed in a container under the impress of the persontaking the sample. The master should store the samplein a secure place, under conditions such that thequality of the sample will not change.

If the cargo is in store, the surveyor should take intoaccount the manner of discharge and delivery to thestore, in case these operations could have affected thequality of the product or could in themselves beresponsible for any damage.

AppendixMeasuring the temperature of frozenfishery products

EquipmentThe most convenient thermometer for measuring thetemperature of frozen food products is a water resistantK-type thermometer with a digital display reading to0.1oC. Typically, these thermometers have a measuringrange down to minus 50oC and an accuracy of ±0.5oCin the range required when measuring temperature ofchilled or frozen foods. This accuracy is adequate forthe purposes described in these guidelines.

Thermometer and probe

There are several types of probe available for plugginginto the instrument. The best all-round probe formeasuring temperatures of fishery products is a 100mmlong, 3-4mm diameter, stainless steel penetration probeon a 1m lead. There are also stouter, hammer-in probeson the market for forcing into frozen fish (provided thetemperature is not too low), but these have longresponse times. It is usually preferable to drillholes and use a thinner probe.

Measuring the temperature of frozen fishIt is not usually possible to push a probe into frozenproducts. Normal practice is to drill a hole, with an

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ordinary engineer’s hand or power drill, of such adiameter that the probe fits tightly. The bottom of thehole should be at the thermal centre of the object that isat the position that will cool down or warm up mostslowly. The thermal centre is usually at the backbone inthe thickest part of a fish, or at the centre line of a blockof fillets. The hole should be around 100mm deep – thatis, sufficiently long to take the whole length of theprobe. This may mean that the hole must be drilled at anangle to the surface of a fish, or along the centre line ofa block from one of the smaller side faces.

good thermal contact with the probe. Record theminimum reading. Pushing the probe between cartonswill result in some frictional heating, so five to tenminutes may be required to reach equilibrium. Whenmeasuring temperatures of cartons, it is useful to haveseveral probes, cover the stack to avoid heat loss, andallow 5 to 10 minutes before connecting the probes inturn to the thermometer.

When cartons are loosely stowed, it is necessary tomeasure the temperature within cartons. If thecontents are loose – IQF fillets, for example – theprobe can be forced through the side of the carton intothe product.

Thermal contact is poor in such cases – it may take 10minutes, or more, to reach thermal equilibrium. If thecartons contain blocks, it should be possible to insertthe probe between blocks to drill a hole in a blockthrough the side of the carton. The carton usually hasto be split to locate gaps between blocks and thecentres of faces of blocks.

Calibration of the thermometer and probesInstruments are calibrated by their manufacturers, butit is possible to check thermometer/probecombinations at 0oC on the vessel.

Finely crush some ice made from fresh or distilledwater, and pack it tightly in a vacuum flask or jar. Addcold water to fill the flask and insert the probe to its fulllength in the ice/water mixture in the centre of the flaskand leave the flask and probe for a while in a coolplace – perhaps a refrigerator or chill room – beforetaking a temperature reading. Since a mixture of iceand fresh water at thermal equilibrium has atemperature of 0oC, any deviation of the probe/thermometer combination from 0oC is the correctionfor that system.

Measuring temperature within a carton

Once the probe has been inserted, note the lowesttemperature reading given in the next 2-4 minutes.While the hole is drilled and the temperaturemeasurement taken, the product warms up, someasurements should be taken as quickly as possible,and preferably while the product is still in the hold.

Measuring the temperature of products incartonsProducts in cartons may be delivered in regular stacksor in random loads. In a regular stack of cartons – forexample cartons on pallets – temperatures can bemeasured by inserting the probe between cartons. Thewarmest areas are the corner of the stack.

Temperature should be measured at diagonally opposedtop and bottom corners and in the centre of aface. Insert the whole length of the probe betweencartons, or between the flap and body of a carton, onthe mid-line. Insert the probe between verticallystacked cartons rather than horizontally adjacentcartons as the weight of the cartons above ensures a

most of probewithin product

probe fits snuglyin hole

point of probe atthermal centre

Fig B. Inserting temperature probe into frozen fish or block of fish

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Instructing party Date and time of

-instruction

-survey

Origin and nature of cargo Place of survey Reason for survey (alleged damage/condition Name of ship Voyage number Name of

-Master

-Chief officer

-Chief engineer

-Reefer engineer

-persons from whom information was

obtained

General particulars of ship -former names of ship -flag -port of registry -year of build -official number -IMO number -class -gross tonnage -net tonnage -summer deadweight -length -beam -max summer draught -service speed -main engine type -generators type and capacity -number of generators -max capacity hfo/ifo -max capacity mdo/go -daily consumption of fuel oil (type) -daily consumption mdo/go -Owners -Operators -Managers -Voyage charterers -Time charterers

Certificates -Certificate of registry -Class certificate -Class RMC -International tonnage certificate -Safety construction certificate -Safety equipment certificate -Cargo gear General arrangement of ship (see Appendix no.1) -number of holds -type of hatch covers -hatch square minimum opening sizes -number of decks -capacity of each deck -deck area of each cargo compartment -deck heights -type of gratings -type of cargo gear -location of superstructure compared to hatchways

Refrigeration arrangement -type of refrigeration machinery -type of air circulation in the compartments, and whether decks are paired or independent

-capacity of air circulation -type of refrigerant, and whether direct or indirect system

-location of air coolers and fans in the compartments (see Appendix no.2)

-type of fresh air system -capacity of fresh air system -location of fresh air inlets -location of fresh air outlets -records about calibration of temperature-, humidity-, etc., sensors

Controlled atmosphere arrangement

-type of equipment (fixed or portable) -classification society (if portable) -type of machinery -type of control equipment -condition of equipment for injection -condition of equipment for monitoring of atmospheres

-arrangement of injection and control to decks -separation zones -arrangement of electrical supply

The following lists show the type of information that is needed tohelp the Club deal with a refrigerated cargo claim

Dealing with claims

History -previous loading/discharge port -previous cargo carried -hold cleaning method after discharge of previous cargo

Cargo particulars -b/l number -b/l place and date of issue -type of b/l -description of commodity -marks and numbers -shippers -consignee -notify address Loading particulars -name of load port -date and time of arrival at load port -cargo hold inspection before loading -where was the cargo stored before loading -how was the cargo brought alongside -how was the cargo loaded on board -type of forklift trucks used in the cargo holds (electric/combustion)

-delay, during removal of the cargo from cold store, truck, etc. and loading on board

-weather conditions during loading -stoppages during loading -times of loading of each individual deck -did cargo cover entire deck area -way of securing of cargo in the decks -who secured the cargo in the decks -was cargo properly stowed/secured -extent of free area for circulating air above the cargo

-particular occurrences during the loading -remarks on the cargo documents Stowage plan (see Appendix no.1) -number of packages and weight in each deck -volume of cargo in each deck -extent of un-covered deck area -actual stowage factor of the cargo in each deck Voyage particulars -date and time of departure from load port -weather during the voyage to discharge port (wind force/direction and course of the ship)

-particular occurrences during the voyage -inspection of cargo in compartments during the voyage

Discharge particulars -name of discharge port -date and time of arrival at discharge port -inspection of cargo in compartments before the discharge

-how was cargo discharged (lifting, rolling, etc.) -cargo was discharged into (shed, truck, etc) -type of forklift trucks used in the cargo holds (electric/combustion)

-weather conditions during discharge -stoppages during discharge -times of discharge of each individual compartment

Temperatures -carriage instructions -pre-cooling of cargo compartments before loading

-spike/pulp temperatures of the cargo during loading (individual readings; no averages)

-outside air temperature during the loading -temperatures in compartments on commencement of the loading

-temperatures and other parameters (delivery air, return air, space, RH, CO2, O2) in compartments after final closing (see Appendix no.3)

-temperature and other parameters (delivery air, return air, space, RH, CO2, O2) during voyage

-reduction period (see Appendix no. 4) -fresh air inlet regime during voyage -temperatures and other parameters (delivery air, return air, space, RH, CO2, O2) in compartments on opening for discharge of cargo (see Appendix no.5)

-spike/pulp temperatures of the cargo before the discharge (individual readings; no averages)

-spike/pulp temperatures of the cargo during discharge(individual readings; no averages)

-spike/pulp temperatures of the cargo during the survey (individual readings; no averages)

-USDA sensors

Condition of cargo -details of the commodity involved (variety, count, number per package)

-description of package -marks and numbers of packages -picking and packing dates -name of grower/packing station -other codes on packaging -description of condition of the cargo -number of cartons on the pallet -construction of pallet load -difference in condition when considering grower, picking date, packing date, variety, count, location on pallet, location in cargo compartment or other compartment

-location in cargo compartment of cargo claimed upon

-history of commodity before loading -estimated sound market value of the cargo (c.i.f./ f.o.b.)

-estimated depreciated value of the cargo -estimated total extent of the claim Further particulars -condition and cleanliness of cargo holds and air ventilation/circulating ducts

-presence and condition of gratings -presence and condition of side shoring -presence and condition of blocking of air gaps in the stow and behind side shoring

-cleanliness of discharge premises Further points of interest

Documents to be attached -copy of B/L (both sides) -copy of cargo manifest - -copy of certificate of origin -copy of phytosanitary certificate -copy of letters of protest -copy of sea protest -copy of commercial invoice -copy of document validating the sound market value of the goods

-copy of packing list -copy of carriage instructions -copy of temperature records, recording discs (partlow), other temperature records

-copy of comparative seal discrepancy -copy of charter party -copy of statement of facts -copy of notice of readiness - - oom log book -copy of relevant scrap notes -copy of statements - -photographs taken by other parties -set of photographs

Appendix no. 1 General arrangement and stowage 4 3 2 1 Appendix no.2 Refrigeration arrangement and airflow 4 3 2 1

A

B

C

D

E

A

B

C

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Reporting format guidelines to surveyors - refrigerated cargo ships by courtesy of International Cold Chain Technology/Van Ameyde Marine

Appendix no.5 Date, time and parameters in each individual compartment before opening in discharge por Compart- ment

Date / time Delivery air temp

Return air temp

Space temp

CO2 % O2 %

Appendix no.3 Date, time and parameters in each individual compartment after final closing in loading por Compart- ment

Date / time Delivery air temp

Return air temp

Space temp

CO2 % O2 %

Appendix no.4 Reduction period Compart ment

First recorded temperature after final closing

End of reduction period Duration of reduction period(hours)

Date Time Delivery air

Return air

Date Time Delivery air

Return air

Normally the plant will produce 90 air circulations per hour at full speed (by volume of empty hold space). Usually the cooler rooms will be inspected once or twice daily for the purpose of taking manual temperatures of the cargo in the hold through the cooler room access doors. Also CO2 and humidity can be examined at the same time if required.

Investigate if fixed equipment (hot gas for example) has been used for defrosting. If manual defrosting has been carried out find out why. Check the dimensions / construction of the drain pan under the evaporators and was crew in attendance in cooler rooms to observe the defrost operation and to see to it that the drain pan did not overflow into cargo compartment.

Fresh air ventilation Where applicable control of the fresh air ventilation is equally important as the air circulation and requires proper attention. Fresh air may be bled into the air circulation as required. For frozen cargoes and some groundnuts fresh air is not required and the circulation fans and fresh air ventilation should both be shut off as stated in the carriage instructions.

Fruit and vegetable cargoes are nearly always ventilated (as well as being cooled) to reduce the ethylene gas produced, (as reflected by the CO2 content), which is detrimental to the condition of the produce and in the case of fruit may lead to early ripening. Fresh air ventilation can be controlled generally between the 2 6 changes per hour (by volume of empty hold space) utilising the fan speed and adjustment of fresh air ventilation flaps which can be opened and closed according requirements. In colder weather there may be a conflict between the need to maintain circulated air delivery temperatures and the need to ventilate and to introduce cold fresh air. Air circulation fans are normally run on the specified speed. It is a good idea to check the remote fan switches in the deckhouses personally when possible. Any difficulties with the operation of the air circulation of the fresh air ventilation systems or with the maintenance of temperatures should be reported to all parties.

Arrival discharge port

For vessels discharging under survey it is customary for the surveyor to visit all the cooler rooms in turn to take temperatures and other prior to discharge commencing In addition the surveyor may wish to see the data logger before all the circulation fans are switched off.

Discharging Care of the cargo and cargo records should be carried out as if the vessel were at sea. Tight stowage

purpose of maintaining a tight seaworthy stow and to prevent or minimise any shifting damage, tight stowage also being necessary to maintain proper air circulation. For these purposes it is necessary to visit working compartments at frequent intervals and to point out any problems to the stevedore foreman. When necessary protests should be made instructions to the agent to forward the stevedores copy to the stevedore on board and to their management on shore as soon as possible.

Narrative The aim of this form is to obtain an uniform and comprehensive reporting format and at the same time it is a aide memoir for the surveyor. The questions should be answered as much as possible but at the same time it is to be considered that the questions to be answered should be in relation with the claim

remarks. General arrangement

Appendix no.1 can be used for indicating the number of holds and the number of decks as well as for the capacities and dimensions of the compartments. Most of the reefer ships have hydraulic operated folding hatch covers, however, other ships have single wire pull hatch covers and older ships may have insulated pontoons. Nowadays most of the ships have so-multiplex of approx. 1X1 meter. Another type of grating uses perforated sheets of moulded aluminium. The cargo gear is cranes or derricks. Some ships have additional pallet cranes. These cranes are restricted in load but have a higher working speed.

Refrigeration arrangement

The most common refrigeration machineries work on refrigerants like freon. These machineries are of the direct expansion type; the evaporators are present in the cargo compartments. Other ships have machineries with brine as cooling intermediate. The evaporators, with which the brine is cooled, are outside the cargo compartments. The brine is circulated through pipes inside the cargo compartment in the circulating airflow. The most common type of air circulation is that the cooled air (after having passed the evaporator) is introduced into the cargo compartment in the forward or aft end (at some ships in the forward end as well as in the aft end) under the gratings from side to side. The cooled air is forced through the cargo and removed from the compartment via gratings along the ceiling at the same end of the compartment where the cooled air was introduced. Some ships have a Robson type of air circulation. With this type the air is introduced into the compartment over its full length at port and starboard side under the gratings. After having been forced through the cargo the air is removed via gratings along the ceiling of the compartment. Appendix no. 2 can be used to indicate the location of the machinery of refrigeration machinery and the direction of the circulation airflow as well as to show the location of the insulated decks.

Loading particulars This block is to indicate the Port arrival and berthing times as well as the times of each loading (discharging) period for each compartment. Further more all relevant details about the loading can be recorded.

Condition of cargo This block is for the description of the particulars of the cargo and in particular about the condition of it. The most common type of packaging is open folded cartons made of cardboard, but also telescopic cartons are used, in particular for bananas.

There is also room to indicate whether the condition of cargo of a specific grower, packing date, etc. differs from the cargo of other growers, packing dates, etc. Also the position in the compartment of the cargo concerned is of importance as well as whether the condition of the cargo on the individual pallet is uniform.

It should be considered that most of the shore-based cargo pre-cooling units are on horizontal airflow. Also the packaging (position and number of air slots) is mostly on the basis of horizontal airflow.

In this block there is also room to describe the pallet load, i.e. the number of packages per layer and also the number of layers of packages. Also the construction of the pallet load is to be mentioned, such as (but not restricted to) whether sheets of cardboard or other material are present between the layers or on the top of the pallet load and whether the layers of packages are full, i.e. no chimneys present in the centre of the pallet load.

Further points of interest

This block can be used for all particulars which are considered to be of importance or of interest in connection with the subject matter. Some further points of interest are;

Load readiness

Investigate all fittings in good condition gratings, side shoring, lighting, ladders, access openings, cooler room doors, hatches operable and water tight with no hydraulic leaks, plugs fitted as necessary at access hatches, or as required by the ventilation arrangements, drains, scuppers and bilge wells, compartments be odour free (low temperatures mask odours), no remnants of previous carried cargoes.

Instrumentation Investigate last calibration in ice (each voyage) and last electronic calibration (each docking or as required). Inspect data loggers and printouts working properly. Coloured trace recorders to be properly supplied with ink. Also check for slackness in the pen drive wire which should be tight.

USDA equipment Not recommended for use if USDA not fully certificated as for a USDA voyage. Note that these fittings are at the ships side or on the deck head where there is a strong airflow,

sometimes without a box cover. Due to the strong airflow, the temperatures are likely to be significantly higher in the cargo than recorded by the nearby USDA sensor not placed within the cargo itself.

Pre-cooling Investigate details of pre-cooling and compliance with instructions.

In the event that pre-cooling is not completed in time for loading bananas or exotic fruits as required by the carriage instructions, and providing the plant is fully operable and the shippers issue full indemnities in agreement with owners / operators, it will sometimes be preferable to load the cargo as soon as possible, rather than to leave it in open shed s or transport with no cooling.

Special attention is to be paid to the time of loading of (for example) bananas an thus the time that the fruit is exposed to the cooling down temperature being lower than the carriage temperature.

Carriage instructions Investigate crew understanding the carriage instructions and any ambiguities or errors. Were the carriage instructions available for all relevant officers / engineers? ICCT guidelines on carriage instructions are available at www.crtech.co.uk/ICCT

Pulp temperatures

No average temperatures to be reported, unless the maximum and minimum temperatures are mentioned as well as the tenor of the differences.

The voyage

The voyage begins for each compartment on final closing at the load port where after the data logger will record the compartment air circulation delivery and return temperatures, CO2 content and humidity (also CA parameters) every four hours.

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UK P&I CLUBIS MANAGEDBY THOMASMILLER

For further information please contact:Loss Prevention Department, Thomas Miller P&I LtdTel: +44 20 7204 2307. Fax +44 20 7283 6517Email: karl.lumbers@thomasmiller.com