Thermal Processing of Low Acid Foods and Acidic Foods

I. Objectives :

To study the processing requirements of low acid and acidic

foods

Specific.

To manipulate a manually operated can sealer.

To learn the basic steps and techniques in canning acidic and low

acid foods.

To conduct subjective evaluation on the processed canned

product using the descriptive hedonic sealing method.

II. INTRODUCTION

Canning is the technique of preserving food in a airtight containers

through the use of heat. This process of food preservation is possible

because the heat treatment inactivates and kills microorganisms that

would cause food to spoil during storage.

The canning process is basically the same for home for industrial

canning. High-quality fresh produce is washed, sorted, and prepared

promptly for canning. After it has been peeled and seeds and other

waste have been removed, the product in the canning container (a

glass jar or a metal can) in pieces of the desired size and shaped.

Water or syrup is sometimes added, leaving headspace in the

container. The remaining air is driven out by heating the filled

container for a few minutes. The container is closed in preparation for

the heat processing. (source: Grolier Encyclopedia)

III. REVIEW OF RELATED LITERATURE

Canning is the process in which foods are placed in cans or jars with

lid on or in suitable retortable flexible containers, and heated to a

temperature that destroys microorganisms and inactivates enzymes.

This heating and later cooling forms a vacuum seal. The vacuum seal

prevents other microorganisms from recontaminating the food within

the container. Heat processing kills microorganisms (bacteria, yeast,

and mold) that contaminate food and cause food spoilage and/or

foodborne illness. Processing can be done in a water bath canner,

depending on the food’s acidity.

High acid foods (Ph 4.5 and lower) and acidified foods can be safely

processed in a water bath canner.. microorganisms in or on high-acid

foods are easily killed at boiling temperatures (100°C). Very acidic

products such as pickles and kalamansi juice with much lower pH (pH

2 to 3) may filled hot with no further processing needed.

Low-acid foods (pH above 4.5 such a s vegetables, fish, meat) must

be processed in a pressure canner. Spores of clostridium botulinum

can germinate and produce toxins in low-acid foods but not in acidic

food. Clostridium botulinum, spores which may be present in the foods

being canned can survive for hours in boiling water but are destroyed

within an hour or less at 115.5°C (240°F), the temperature at 10 to 11

pounds pressure, or at 121.1°C (250°F), the temperature at 15 pounds

pressure. The over pressure is usually applied to processing in glass

jars while the higher pressure is used for cams. Please note that

temperature inside the canner is affected by atmospheric pressure, so

that for higher altitudes where the pressure is less corresponding

adjustments are made in the process time. Processing time needed to

destroy botulinum spores consider many other factors: such as the size

of the container, the size and texture of the food being processed. It is

therefore crucial that recommended processes be strictly followed.

If low-acid food is processed in a water bath canner, botulinum

spores on the food will survive. In the absence of air, a condition found

inside a jar after processing, the spores can germinate and revert to its

vegetative state. As the bacteria grow, they form toxins. Eating even a

small amount of food with this toxin can be fatal to humans and

animals. Many cases of botulism have been associated with eating low-

acid foods that were improperly canned at home. Scientists have

determined that 1/1,000,000 g of pure botulinum toxins can kill 1

person or 1 gram can kill 1 million people. One teaspoon can kill 5

million people.

To make sure the canned foods are safe, the canning instructions

should be carefully followed. Process high-acid foods in a water bath

canner and low-acid foods in a pressure canner following

recommended times and temperature established by competent food

authorities. Never process any foods in a conventional oven,

microwave oven or steamer, as these methods may not kill

microorganisms that cause food spoilage and/or foodborne illness

because uniform heating cannot be guaranteed by these methods.

Raw Materials Handling

The quality of raw materials is directly related to the quality of the

finished product. This is true for all kinds of food products and for all

methods of preservation and even just for immediate preparation into

a meal. Other factors important in handling of the raw material include

observation of hygienic practices particularly the implementation of

Good Manufacturing Practices (GMP) and Hazard Analysis and Critical

Control Points (HACCP)

Ideally processors will receive raw materials of uniform and good

quality so that the finished product is of a constant standard, however,

as this is not always possible, it is often necessary to sort or grade the

raw material prior to canning. Grading systems may be for size,

maturity, stage of ripeness and/or other attributes necessary for end-

product quality. It is wise to adopt the GIGO (garbage in-garbage out)

paradigm, which implies that if good quality raw material is processed

a good finished product results but no amount of processing can

convert bad quality raw material into a good finished product.

PRE-TREATMENTS

Pre-treatment covers the range of operation involving preparation

before filling into cans or other containers . example of pre-treatment

is for fishery products include, washing gutting, washing, nobbing,

filleting, shucking, shelling (peeling), cutting, brining, and dipping.

Each of these steps has the common objective of bringing the raw

material closer to the size, form or composition required for retorting.

For fruits and vegetables, the pre-treatments are: washing, trimming,

cutting, blanching, and sometimes pulping.

PRE-COOKING

For some products, pre-cooking is needed. This is usually carried

out in various ways, using steam, water oil, hot air or smoke, or a

combination of these.

Canned specific dishes such as lechon paksiw, pork dinuguan, laing,

embutido are precooked according to the recipe for such products, but

the cooking process may differ from the procedure used for immediate

serving. Adjustments have to consider that the product will undergo

retorting after filling. Pre-cooking conditions significantly affect yield

and sensory quality. An excessinve treatment tends to reduce yields,

wheras inadequate pre-cooking means that the purpose of the

treatment is not achieved.

A time-temperature plot for the product as it moves down the

processing line is used to identify potential danger areas, where delays

in production can adversely affect the safety and quality of the

product. Some points in production before sterilization can be effected,

may favour rapid, microbial growth. These are points: immediately

after pre-cooking before filling or between sealing the containers and 1

retorting/pressure cooking and the time between sterilization and

cooling. Process controls should be established and monitoring

systems set up, so that corrective action can be done to maintain the

safety of the product.

FILLING

Fill weights, and fill temperatures are monitored because both affect

the heating at the slowest heating point in the container durimg

retorting. Variations in fill weight and/or fill temperature may affect the

safety of the product.

For consumer point of view, it is important that the container

appears full, but adequate headspace must be provided to allow for

the expansion caused by heating the product from filling temperature.

If no space is allowed for expansion, the pressure build up can damage

the hermetic seal or in the case of bottles will cause the lids to flip

during processing.

Under normal circumstances can seams withstand the strains

generated by internal pressure, however, in extreme cases this causes

permanent deformation called peaking or buckling of the can end.

Such deformation damage the seams which will lead to the entry of

contaminants particularly during cooling when the cans draw a

vacuum. Excessive pressure build up in glass containers during

retorting will dislodge the cap and cause spillage of the contents.

Excessive internal pressure in the container can, can prevented by

controlling filling at the proper temperature. The higher the filling

temperature, the less the pressure generated by heating the contents

to processing temperature. As a result of hot filling a vacuum forms in

the container after thermal processing and cooling; A temperature of

85°C is the standard fill temperature.

Vacuum closing of cans and glass jars may also be done, which

has the effect of counteracting the increase in pressure caused by

heating the product in a sealed container. Vacuum closing is achieved

by mechanical evacuation of the headspace gases just prior to sealing,

or by steam-flow closing. In this method, super-heated steam is flushed

accros the top of the container immediately before the can end or jar

closure is sealed in place. A special vacuum closing equipment is

needed for this purpose

EXHAUSTING

Exhausting is the removal of air from the food in the container. The

removal of air will insure a vacuum in the canned food. Vacuum in

canned foods is obtained by heating the food before or after filling into

containers. Hot filling described above is one such method. Heat is

employed to expand the product and drive out occluded and dissolved

gases and to rarify the air in the head space prior to sealing/capping.

Heating can be accomplished by passing the open containers in a

steam or hot water exhaust box. An internal temperature, measured at

the slowest heating point of the container 85°C is commonly used in

the industry.

Vacuum is necessary for the preservation of canned/bottled foods for

the following reasons:

1. Prevention of distortion of container during thermal processing.

2. Maintenance of can ends or bottle caps in concave position

during normal storage.

3. Reduction of oxygen which can react or discolor the product.

(source: Sonido, D.G., et. Al., (2010). Practical Food

Preservation and Processing. National Book store:

Mandaluyong City, Philippines)

Canning is the technique of preserving food in a airtight containers

through the use of heat. This process of food preservation is possible

because the heat treatment inactivates and kills microorganisms that

would cause food to spoil during storage. The airtight packaging

protects the food from recontamination following sterilization, thus

permitting storage at room temperature for many months without

spoilage.

HISTORY

In 1795 a prize was offered by the French for the invention of a method

of keeping food safe for military troops. Nicolas Appert, a chef in Paris,

won the prize when he developed the canning process. At about the

same time, the tin-coated metal can was patented in England.

TECHNIQUES

The canning process is basically the same for home for industrial

canning. High-quality fresh produce is washed, sorted, and prepared

promptly for canning. After it has been peeled and seeds and other

waste have been removed, the product in the canning container (a

glass jar or a metal can) in pieces of the desired size and shaped.

Water or syrup is sometimes added, leaving headspace in the

container. The remaining air is driven out by heating the filled

container for a few minutes. The container is closed in preparation

for the heat processing.

The food must be heated to a high enough temperature and for a

long enough time to ensure that microorganisms that are present

have been killed. Many fruits are high in acid, and the

microorganisms present in them will be killed if the jars or cans are

processed in boiling water for periods of slightly less than half an

hour, depending on the foods. Meats, fish, poultry, and vegetables,

however, are low in acid and must be heated at least 115.5°C for

periods of half an hour or longer, again depending on the food. This

temperature can be reached only by processing under pressure;

commercially, a retort (a large, steam-pressured vessel) is used,

and in the home a pressure canner must be used. Water bath

canning, processing for appropriate periods of time in closed jars

covered with boiling water although adequate for processing some

fruits, is dangerous because spore of the organism Clostridium

botulinum are not killed in vegetables, meat products, and certain

fruits. Even when canned under pressure, home-canned meats and

vegetables should be boiled actively for 20 minutes before they are

even tasted, to prevent the possibility of botulism, an often fatal

type of food poisoning.

(source: Grolier’s Encyclopedia of Knowledge)

IV. Experimental Procedures

A. Materials and Equipments

ITEMS QUANTITY SPECIFICATIONS

knife 1 pc.

aluminum bowl or

basin

1 pc.

Colander 1 pc.

Salinometer 1 pc.

Refractometer 1 pc.

Graduated cylinder 1 pc. 250 ml capacity

Chopping board 1 pc.

Casserole 1 pc.

Glass jars 2-3 pcs. With hermetic seal tin

cans or jitney

Weighing scale 1 pc.

Pressure cooker 1 pc.

Water bath cooker 1 pc.

Pen 1 pc.

Manual can sealer 1 pc. With accessories

Spoon or ladle 1 pc.

B.Procedures

1. For Fruits (acidic)

Fruit cocktail (Pineapple, papaya, melon, mango, cherry

and pears)

a. Select firm ripe fruits and wash. Peel and cut into

uniform sizes. Weigh.

b. Prepare medium syrup (1:2), preferably 50B. bring

to a boil. Remove scum formation on the surface of

the boiling syrup.

c. Add the sliced fruits gradually to the syrup, harder

fruit first and soft fruit last. Boil for 10 minute to

plump the fruits. Remove from flame and allow

syrup to cool down to room temperature

d. Drain fruits, boil syrup and adjust sweetness and

acidity of syrup. Pack in sterile jars or cans and

cover with hot syrup. Exhaust for 15 minutes at

82.2 C (180 F). Seal can completely and process in

water bath for 30 minutes at 100 C. Sudden cool

can in running water while jars must be air cooled

only in an inverted position.

e. Drain and dry the jars. Label and store in a cool

dry place. Observe products for one week and

evaluate using the hedonic scaling methods.

2. For Meat, Fish, Poultry and Vegetables (Low Acid)

Canned Fish (Bangus, Tamban, Galunggong and Tunsoy) per kilo

A. Ingredients

Sardines Style

ITEMS QUANTITY SPECIFICATION

Tomato sauce 100 g

Tomato paste 47.5 g

Oil 26g Corn

Hot pepper 7.2 g Extract

Salt 5.75 g

Portuguese Style

Black pepper 6 pcs. Whole

Bay leaf 2 pcs.

MSG 0.2 g

Pepper 4 pcs. Labuyo

Carrots 5 pcs Traversely cut

Pickes

Oil vegetable

Salmon Style

ITEMS QUANTITY SPECIFICATION

Brine solution 2 %

Oil vegetable

B. Procedure

a. Scale fish and remove the head fins, tail and belly flaps and

internal organs. Wash thoroughly to remove blood and other

foreign matters.

b. Cut the fish transversely to fit the size of the containers. Soak

in 10 % brine for 20 minutes. Drain.

c. Fill the containers with the heated sauce mixture

approximately ¼ inch headspace.

d. Exhaust filled container to 180F (82 C) for 15 minutes. Seal or

close containers. Process for 80 minutes at 250F (15 psi).

Rapid cool in running water. Drain and dry. Store in a cool and

dry place. Observe for a week.

V. Discussion of Results

A. Evaluation of Results

TABLE 1.Parameters of Evaluation

Parameters of

Evaluation

Fruit Cocktail Portugese style Tunsoy

Color 5 5

Texture 4 2

Taste 5 3

Odor 4 4

Hedonic Scale 8 7

Parameters of evaluation

COLOR TEXTURE TASTE ODOR

5 Bright Firm and crisp Very desirable Very

acceptable

4 Moderate Firm Desirable Acceptable

3 Slightly

moderate

Slightly firm Moderate Moderate

2 Neither pale

nor slight

Soft Slight Slight

1 Pale Mashy undesirable Not

acceptable

ACCEPTABILITY HEDONIC SCALE

9- extremely like

8- very much like

7- moderately like

6- slightly like

5- neither like desirable

4- dislike slight

3- dislike moderately

2- dislike very moderately

1-Extremely dislike

Analysis and Explanation.

The color of fruit cocktail and portugese style tunsoy are both

bright. For the texture, fruit cocktail is firm while portugese style tunsoy is

soft. For the taste, fruit cocktail is very desirable while portugese style

tunsoy is moderately desirable. For the odor, fruit cocktail and portugese

style tunsoy are both acceptable. Lastly, for hedonic scale fruit cocktail is

very much like and nearly to be extremely like, while for portugese style

tunsoy taste good but not as good as the fruit cocktail. It is moderately like.

B. Summary

The processed canned products almost maintain their color, texture,

taste and odor for how many days after the method had done. Even in

hedonic scale which measures the palatability of the product they are mostly

like. Compare to other types of preserving foods particularly pasteurizing,

canning is more effective method for it last longer.

C. Conclusion

The manually operated can sealer had been manipulated. The method

used gave the group to control or manipulate the can sealer.

The basic steps and techniques in canning acidic and low acid foods

had been familiarize, discovered and learned by the group. The basic

steps and techniques for canning had been taught.

The subjective evaluation had conducted on the processed canned

products by the use of hedonic scale. Grading the processed canned

products with descriptive hedonic scale summarizes the measures of

palatability of the processed food.

D. Recommendation

Further research and learning for canning methods must be

obtained individually. The basics in canning method had taught and it is our

responsibility to enhance our knowledge about the topic.

E. Learning Experience

I have learned the basic steps and techniques in canning acidic and

low acid foods. I also learned the general information and basic knowledge

that may be used in my day to day activities. The cause and effect that

might cause illness because of improper preparation or even handling of

canned products has also discovered.

VI. BIBLIOGRAPHY

Sonido, D.G., et. Al., (2010). Practical Food Preservation and

Processing. National Book store: Mandaluyong City, Philippines

Grolier Encyclopedia of Knowledge (1999)

http://en.wikipedia.org/wiki/Canning

http://www.parade.com/food/knowledgebase/knowledge/kitchen-advice/

kitchen-techniques/canning-vegetables-and-fruit/Canning-Preparation-for-

Vegetables-and-Fruits.html

http://www.westernmontanafair.com/files/2010PremiumBook/

HOMECANNINGMEATPOULTRYANDFISH.PDF

VII. Appendices

Guide Questions

1. Why do you rapidly cool thermally processed canned foods?

> Cans should be rapidly cooled to 40°C. If allowed to remain warm,

surviving thermophilic spores can germinate and multiply during labeling,

packaging into cartons, palletizing and storage. Cooling immediately will

prevent the germination of these thermophiles which causes spoilage.

Thermophilic spores germinates at 55°C or a bit higher.

2. What is exhausting? Can you omit or delete this process in canning of

foods? Why?

> Exhausting is the removal of air from the food in the container.

3. Differentiate processing requirements for low acid and acidic foods with

regards to

a. processing time and temperature

microorganism in or on high-acid foods are easily killed at boiling

temperature while low-acid foods at 115.5°C for an hour or less

(Practical Food Preservation and Processing)

b. processing equipment used

acidic foods uses water bath canner while low acid foods use pressure

cooker.

c. pre-processing operations conducted

pre-processing operations of low acid and acidic food may differ by

what kind of food to be processed. High acid foods are fruits which

don’t need to be cooked while low acid foods are meats and

vegetables which need to be cooked first before canning.

4. What other packaging materials can be used for canned foods?

Enumerate.

> Glass jars

> Metal can/tin cans

5. Cite factors that may influence processing time to be employed in

canned foods.

> Type of canner or cooker to be used.

> Type of packaging materials

> The level of acidity of the food.

VIII. Terminologies

a. low acid – pH above 4.5, ex. Meats and vegetables.

b. High acid or acidic – pH lower than 4.5, ex. Fruits.

c. Hedonic scale - is the testing differences in average acceptability using

parametric statistics.