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OVERVIEW 7
INTRODUCTION 8
CONTAMINATED PRODUCTS 11
HACCP 15
REPORT OBJECTIVES 16
PRIMARY OBJECTIVE 16
METHODOLOGY 18
OPTICAL SORTING 33
TERAHERTZ IMAGING 35
MICROWAVE DETECTION 37
1. THE DETECTION OF GLASS FRAGMENTS – IN PARTICULATE FOOD 58
BACKGROUND 58
CURRENT SITUATION 58
MANUFACTURERS PERSPECTIVE 58
CONTAMINANT CHARACTERISTICS 59
– LIQUIDS IN GLASS 60
3. THE DETECTION OF PLASTIC 62
BACKGROUND 62
4. THE DETECTION AND SENSING OF FAT AND GRISTLE 64
BACKGROUND 64
POTENTIAL FOR INNOVATION 65
5. THE DETECTION OF BONE IN MEAT AND POULTRY PRODUCTS
AND IN FISH 67
6. THE DETECTION OF INSECTS IN FRUITS AND VEGETABLES 69
BACKGROUND 69
BACKGROUND 72
8. THE DETECTION OF DAMAGE AND MOULD IN FRUITS AND VEGETABLES 75
BACKGROUND 75
9. THE IDENTIFICATION OF THE WRONG PRODUCT IN A PACKAGE 78
BACKGROUND 78
10. THE DETECTION OF “NATURAL PLANT MATERIALS” 80 BACKGROUND 80
BACKGROUND 82
12. THE DETECTION OF METAL OF ANY SORT OF FOOD PRODUCT 83 BACKGROUND 83
BARRIERS TO INNOVATION 86
GUIDE TO THE RESEARCH COUNCILS 90
TERAHERTZ 91
HYPERSPECTRAL 94
CAPACITANCE 97
BIOSENSORS 100
ULTRASONIC 103
APPENDIX 3: ACRONYMS 114
8/20/2019 Food Report Final Document
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7OVERVIEW
The Food Standards Agency (FSA) publishes data which shows a wor- rying – and increasing - amount of complaints due to contamination in food and drink. Complaints have risen year on year driven by numer- ous factors such as more mechanized process chain, higher consumer awareness, and more readily available and thorough testing equipment.
Physical contamination of food and drink from well-established food industry materials such as metal , plastic and glass still manage to evade the carefully constructed safety mechanisms established to trap them - frustrating manufacturers. Reported Incidents of contamination cause
recalls of a product, costing money and severely harm food companiesreputation - devastating to an industry who rely on consumer con- dence. This problem is complicated given the varied and ever-increasing variety of materials, which are able to nd their way into the food
production chain.
The industry needs to be aware of what innovative sensing technologies are being developed not only in the food sector but in other sectors also.
There are however inhibiting factors to innovation in this sector; food industry representatives are often looking for better versions of what already exists. Engagement events are key to exposing the up and com- ing technologies to food industry representatives to technology areas
outside of their own areas of expertise and sector.
Although a huge industry, the food industry can be very conservative in the adoption of new technologies and it can require much higher rates of return on capital investment than can be delivered, therefore the food industry seeks low- cost solutions that can justify the eort. The idea
that product recalls can be reduced or prevented by better training, procedures etc. is a far more appealing alternative to large R&D invest- ments.
There is however, a plethora of new technologies whose sensitivity, specicity, cost and overall performance are beginning to align with the
needs of the food industry. Optical methods can provide real-time im-
aging across many wavelengths to not only detect, buy characterise food properties as it passes through a factory. Techniques that can penetrate objects and visualise inside packages with abilities beyond what is achievable with X-rays only are being developed for Earth observation and military purposes which could nd an unexpected application.
Valuable insight to this report was provided by interaction with food companies through an online questionnaire, direct discussions and an interactive workshop help on the 25th February 2014 in London which bought together food industry experts, membership organisations and technologists in technologies identied as potentially useful by the
Knowledge Transfer Network prior to the workshop.
OVERVIEW
FOOD AND DRINK CONTAMINATION
Foreign body contamination in food is one of the major sources of complaints against food manufacturers [1]. ‘Incidents’ are hugely damaging for manufacturers as they can lead to injury, loss of brand loyalty and large recall expenses.
Many public incidents such as glass contamination, E-coli , horsemeat in products labelled beef have shaken trust in the industry and made the public aware of how vulnerable parts of the food chain are to both intentional and non-intentional adulteration.
Figure 1 shows the number of ‘incidents’ in food from 2000 in the UK, the increase should cause alarm for all involved (Refs. 2,3,4).
The trend of increase was stalled slightly from 2006 – 2009, the subsequent increase could be due to a few factors;
Since 2009 the number of pesticide residue ingredients has increased
substantially. In 2011 and 2012, this was due partly to increased testing
of okra at border inspection posts

1604
1714
1505
1208
1298
1312
1344
966
789
743
530
476
421
Figure 1. Number of food incidents, 2006 - 2012 adapted from Ref. 3
1. Edwards, M. (2004) Detecting foreign bodies in food, Cambridge: Woodhead Publishing Limited. 2. http://food.gov.uk/multimedia/pdfs/incidentsar.pdf Food Standards Agency (2007) 3. http://food.gov.uk/multimedia/pdfs/incidents-report-2012.pdf Food Standards Agency (2013)
4. It is important to appreciate that these gures are and are expected to be largely underestimated, by as much as afactor of 200 suggested by some at the Workshop. This misrepresentation could be die to a variety of reasons: The severity of some of the incidences will bias gures towards those, for example, people will be more likely to•
report a piece of glass than a sh bone.
Once a problem is identied, mass withdrawals can hide the extent of the actual problem•
Failure to report to the FSA •
Despite these obvious failings of the acquired data, the data is expected to be representative of industries problems.
INTRODUCTION
The Knowledge Transfer Network: Food Sensing Report
Incidents involving strains of salmonella has averaged out at 45 a year
during 2006 – 2009. In 2010 they rose steeply to 118 and fell only to 98
in 2012. Our investigations suggest that this increase was mostly the
result of paan leaves imported from Bangladesh (Ref. 3)
The food and drink incidents are broken down into incident type in Fig- ure 2 for years 2006 and 2012.
Figure 2. Incident by category 2006 and 2012, Ref.3
Physical contamination is one of the key subject areas of this report and in 2012 represented 7 % (the seventh largest category) of the total number of complaints. In Figure 3, specically the incidents relating to
physical contamination incidents
The “number of incidents falling into this category increased from 93 in
2011 to 107 in 2012. In particular, incidents relating to metal contamina-
tion increased from 19 incidents in 2011 to 34 in 2012”, Ref. 3
Water quality
Veterinary medicines
TSE
Radiological
2006
2012
10 UK SENSING TECHNOLOGIES FOR CONTAMINATION IN FOOD
Overall the physical contamination incidents have not been improved by a statistically signicant amount over the past 6 years but for a slight
dip in 2009.
139
123
110
56
116
93
107
Figure 3. Incident of ‘Physical contamination’ 2006 - 2012, adapted from Ref. 3
CONTAMINATED PRODUCTS
In Figure 4, the breakdown of all incidents in 2012 is shown by the food type they occur in. The highest categories of contamination are fruit and vegetables, meat and meat products and nuts and seeds. The range of detection schemes needed by the food industry is compounded by this large number of food mediums available.
Figure 4. Incidents by food type 2012
Incidents not related to a specific food
Other foods
Crustaceans
Non-alcoholic beverages
Animal feeds
Molluscs
Meat and meat products
TYPES OF PHYSICAL CONTAMINATION
The types of physical contamination present in food vary largely depending on the type of food in question, below is a short list of various contaminant types of concern:
Wood•
Plastic•
Metal•
Glass•
Paper and cardboard• and many more•

Figure 5. Breakdown of the complaints made about foreign objects by object type
(2006)

Figure 6. Breakdown of the complaints made about foreign objects by object type
(2012)
The process stages in the production of a complex food are shown in Table 1 - shown also are common points of entry for common food contamination issues. The production stages are taken from Ref. 1
Table 1. Common points of entry for contamination challenges
PRODUCTION STAGE CONTAMINANT
PRIME PRODUCER Insects can enter the chain at any subsequent point in this chain, perhaps
explaining why they are the second biggest complaint for food ‘incidents’,
(Figure 6). Insect and pest contamination at this stage of the supply
chain can occur as producers are under pressure to minimize pesticide
applications. The use of biological pest control may mean that damaging
insects are absent and the crop is in good visual condition, however the
predator insects may be on the produce and brought into the food supply
chain.
Glass as the fourth largest concern can enter at this stage and through out as contaminants in the ground or later contamination by broken lights
etc. although the later contamination risk is mitigated by the prevalence of
factory safe light ttings.
The fat and gristle content of meat varies hugely from animal to animal
and is determined at this stage in the chain.
Incorrect labeling can occur at any point throughout the entire food chain,
making traceability and due diligence a key aspect of food manufacture.
HARVESTING The harvesting process can pick up bad produce as well as physical
contaminants that are present in the environment; screening is usually base heavily on visual inspection at this point.
Whilst plastics can enter throughout the chain, major sources are often at
the industrial processing stages, conveyer parts and tools for example.
Again, for metal, mechanised processes often increase the likelihood of
contamination at the processing stages, nuts, bolts etc.
The fat and gristle content of meat are controlled at this butchery
production stage.
Fruit and vegetables are harvested at their ripest and checked for damage
often by visual inspection after having been harvested indiscriminately.
Depending on their level of ripeness mold contamination can occur at any
stage subsequently.
ABATTOIR)
Bone can remain in meat and poultry products after incomplete lleting
and de-boning.
Extraneous vegetable matter (EVM) can remain during the milling process
due to its similar composition to the parent foodstuff.
COLLATION / TRANSPORTATION
FOOD MANUFACTURER Contamination at this stage can be due to many causes, ve
contamination channels at this stage could be:
Contaminated raw ingredients from the stages above.
Manufacturing machinery- rubber seals, metal swarf, nuts etc.
Packaging that is used for the ingredient or processing steps, for example
blue sacks.
Factory environment – bristles from cleaning brushes
Operators – objects that are introduced by the operators of the machinery, hair, plasters, jewelry etc
FOOD PROCESSING &
STORAGE
RETAIL DISPLAY Contaminants beyond this stage are now out of the manufacturers ability
to monitor.
CONSUMER PURCHASE &
TRANSPORTATION
The consumer assesses ripeness in fresh fruit and vegetables at this
stage.
HACCP
Obviously, for foreign object contamination, prevention is better than cure and systems such as the Hazard Analysis and Critical Control Point (HACCP) exist which set out procedures for maintaining safe to eat food.
Hazard Analysis and Critical Control Point (HACCP) is a system that helps food business operators look at how they handle food and intro- duces procedures to make sure the food produced is safe to eat. Ref. 5. As part of routine inspections, the enforcement ocer will check that
the business has an appropriate HACCP-based food safety manage- ment system in place.
However, when these preventative steps fail, procedures and tests must be in place to detect these objects, ideally identify them and ideally locate the source of the contamination.
Workshop delegates have additionally provided thought on the usefulness of sensors to not only directly detect contamination events, but also in the behavior i.e. the breaches of HACCP which can inevitably lead to incidences.
RECENT HIGH PROFILE INCIDENTS
INCIDENT REF
Metal in Pudding
This document aims to cover current detection systems used for a number of food and drink related complaints with input from food manufacturers current technologies will be assessed for their strengths and weaknesses. Through communication with manufacturers, technologist and consultancies future technologies are also highlighted.
The UKTI have identied key challenge areas to be met in the eld of
contaminant sensing in food production. During the consultation period further challenges (in purple) have been identied and added in addition to the initial 10. This report has been compiled by the Knowledge
Transfer Network through communication with food manufacturers,
sensor technologists and consultants and aims to detail the UK capa-bilities in contaminant sensing in food.
PRIMARY OBJECTIVE
The eventual aim will be to provide to the UKTI a report that can show- case the UK strengths in food sensing in its current state and also the capacity for the UK technology base to innovate the market and respond to the requirements of the food industry.
SECONDARY OBJECTIVE
search groups working in relevant disciplines
REPORT OBJECTIVES
1. The detection of glass fragments in liquid products lled into glass
bottles
The detection of glass fragments in particulate food products such2.
as nuts or breakfast cereals
The detection of plastic in any sort of food product, wet or dry,3.
particulate or homogenous
The detection and sensing of fat, gristle, cartilage etc. in meat,4.
prepared meat and poultry products
The detection of bone in meat and poultry products and bone in sh5.
The detection insects in fruits and vegetables6.
The quantication of ripeness in fruits7.
The detection of damage and of mould in fruits and vegetables8.
The identication of the wrong product in a package (e.g. sh pie in9.
a meat pie packet)
The detection of “natural plant materials which should not be10.
there”, for example stalks in dried fruits, shell fragments in nut
products, dense or wet lumps in breakfast cereals
The detection of hair and bre in any sort of food product11.
The detection of metal in any sort of food product12.
CHALLENGES
Resources for this report have been gathered through a combination of desk research, Internet searching, communication with food industry manufacturers (through the Biosciences community), developers of food sensing technologies and relevant consultants. A full list of organisations assisting in the study are gratefully acknowledged and can be found in Annex 1: Inputs to this study
The rst stage of the project has been to identify the key challenges
in food sensing, 10 were initially suggested by the UKTI - further challenges were identied during the consultation procedure.
The next stage has involved communication with food manufacturers
to see how currently these challenges are being met. Potentially useful technologies were highlighted in these discussions and companies working in these areas were contacted for their input.
The nal stage of consultation was through the running of an interactive
workshop where food industry experts, technologists and membership organisations were invited to attend to discuss a draft report prepared by the Knowledge Transfer Network
This data from the food manufacturers is shown on pages 17 – 46. The methods used are displayed graphically - key comments made were also extracted.
Provide a comprehensive study of the challenges faced by food•
manufacturers
Promote opportunities for sensor companies in the food sector•
Provide a map of UK capability in the contaminant sensing sector•
Provide a networking opportunity for interested parties•
The nal report will be made available on the Knowledge Transfer Net- work website – freely downloadable for all interested parties, who could include:
Sensor companies with an interest in non-destructive evaluation in•
food processing Food processing companies who wish to investigate options for•
detection
People working in linked sectors with an interest in foreign body•
detection
METHODOLOGY
19CURRENT APPROACHES
There are a few important qualiers that a detection scheme should be compared against ultimately determining whether it is appropriate for its purpose. The respondents to the questionnaire were asked to consider the following qualiers.
The cost of a device is always a concern for manufacturers. High instal- lation costs can sometimes be countered by low maintenance costs. However, it should be noted that the price of safety infractions can be very high not only in nes, but in recalls and loss of consumer cred- ibility.
The ease of use covers how complicated the device is to operate and
how easy the results are to interpret. This is linked strongly with cost – if a team of technicians are required to operate, monitor and maintain the device then it may become economically non-viable.
The sensitivity of the device will determine how small a foreign contaminant can be discovered and how accurately a characteristic can be measured. This is clearly an important feature as small shards of glass for example can be just as dangerous and large chunks.
The speed of a measurement will determine the throughput of food to be checked. Slow time-consuming measurements may end up reveal- ing more accurate results but the time lost may not be worth it, and vice versa a very quick machine that has very high throughput but misses
every other object will not be wanted. Speed also encompasses howquickly results take to be analysed; can they be done on sight? Do they need a lab?
The specicity of the device will determine whether it is capable of identifying specic information about a contaminant. For example, can
it tell the user exactly what type of plastic is in my food? Information such as this is invaluable when locating the source of a contamination – as this can save manufacturers vast amounts of money in lawsuits, shorter shut down periods etc.
What is the size of the detector? The platform for the sensor device can vary from a large factory based scanner, a hand held device, mobile phone integrated sensor, on product sensor (a sticker for example).
There are obviously advantages for more discreet sensors in food production locations where space is at a premium.
Additional extras: are there unique properties to the device that aren’t covered above, can it measure more than one contaminant? Penetra- tion depth? Can it be retrotted to existing lines? – a large barrier to
entry in this market, etc.
The following pages provide some detail on the technologies currently being used, along with their advantages and disadvantages. They are divided into o-line techniques, on-line techniques and potential
techniques for innovation that aren’t yet in wide scale use.
CURRENT DETECTION
The approaches identied are separated into on-line and o-line techniques, they are assessed based on their technological capabilities, their applicability to food contaminant sensing both for liquids in a pipe and particulate food on a conveyor, pros and cons and (if applicable) the UK capabilities
For o-line techniques, comment is not made on their applicability to
pipe and conveyor - they are included for completeness.
As many of the techniques listed below are based on either the absorption of scattering of parts of the electromagnetic spectrum, it is perhaps useful to remind the reader where the dierent regimes lie.
Figure 7. The electromagnetic spectrum, taken from Ref. [15]
15. http://www.physik.uni-kl.de/en/beigang/forschungsprojekte/
CURRENT APPROACHES
ELECTROMAGNETIC SPECTRUM
21ON-LINE TECHNIQUES
X-RAY IMAGING X-ray imaging uses the absorption / transmission of X-rays to produce images. These images relate to the cross-sectional density of the material being probed. Both two and three - dimensional images can be constructed using tomographic imaging. Whilst some manufacturers may express concern over the quality of food after being subjected to X-rays – the World Health Organisation (WHO) have conrmed that food radiation levels up to 10,000 Sv do not aect food
safety or nutritional value - doses used in inspection technologies are signicantly lower than that.
Due to the ability for X-rays to dierentiate materials of diering densities, X-ray imaging can be used to identify contaminants such as metal, stone, glass, dense plastics and calcied bone. These machines are
commonplace in food inspection lines due to their low maintenance needs and the relatively easy interpretation of results. The future for X- ray imaging could include the incorporation of material discrimination and fat analysis into one system.
The sensitivity and range of application of the X-ray inspection meth-
ods could be increased by the addition of energy sensitivity, allowing
unique identication between thickness and material changes, and thus
increasing the contrast of low absorption materials such as plastics and
organics.
The benets of using energy X-ray sensitive detectors to detect impuri -
ties is well understood, but it has probably not been adopted for in-line
food inspection as the existing technology using CdTe or Ge is prohibi-
tively slow and too expensive.
APPLICABILITY TO LIQUID IN PIPES
Due to the low absorption cross-section of materials available for industrial food processing pipework – the application of X-ray imaging systems through pipes is not unusual. There exist on the market pipeline X-ray systems for the continuous inspection of pumped products – suitable for uids, semi-solid products such as sauces and fruit prepa-
rations.
APPLICABILITY TO PARTICULATE FOOD ON A CONVEYOR
X-ray systems are well suited for quickly identifying abnormalities in line product products. The image processing and rejection decisions can be made automatically with pattern recognition software of by human monitoring in a way similar to airport package monitoring.
ON-LINE TECHNIQUES
Table 3. X-ray imaging usefulness in the food sector [16]
PROS AND USES CONS AND LIMITATIONS
Can penetrate deep within the
sample travelling through packag-
non-contact technique
cereals, dairy foods, confectionary,
ing – this causes little to no
damage to the food under in-
spection but can cause health
problems for operators acci-
Limitations:
LINKED SECTORS
Healthcare: Perhaps the most common use of X-ray imaging is in medical healthcare where 2D and 3D images are constructed of patient inte- riors. Hard X-rays are also used in the medical treatment of cancer.
Material Science: Hard X-rays are often used in material science for non-destructive testing of crystallographic information etc.
Astronomy: There are various sources of X-rays in the Universe which are studied by scientists, detectors for hard radiation are used in this sector.
Security: A very common use of X-ray imaging is in security applications to see through packaging and luggage for non-destructive security testing.
16. http://www.loma.com/lo_xray_guide.shtml
X-RAY SPECTROSCOPY
X-ray spectroscopy uses the scattering or absorption of X-rays to provide qualitative information on the electronic structure of the sample. Absorption and scattering of X-rays gives a material dependent spectrum allowing for identication and composition of various materials.
X-ray spectroscopy can be found in o-line and on-line solutions to
food quality testing. Unlike X-ray imaging however the technique often requires more complicated detection systems than X-ray imaging by use of X-ray dispersive optics or solid-state X-ray energy analyzers. Some examples from Ref. 23 of X-ray spectroscopy are EDAX analysis to determine phosphorous content of potato starch and also as trace element detection for specic contaminant detection. A further example
of ham identication is detailed in Ref. [17] – high ux synchrotron radiation identied signatures in cured ham unique to the curing process
helping to establish a test against ham fraud.
For spectroscopy techniques in the photo absorption regime, X-rays are often tuned to core energy levels of electronic structures – this often puts the energy of the X-rays at the low energy end that severely limits the penetration depth. Spectroscopy through pipes and semi solid liq-
uids would be dicult to achieve [18].
An easier application for X-ray spectroscopy measurements would be in particulate solids on a conveyer, X-rays would only penetrate mini- mally into the surface and collection and analytical time may however severely limit throughput.
17. http://www.esrf.eu/Apache_les/Newsletter/ESRFNewsSep2010.pdf
18. There are spectroscopic techniques higher in energy, although the application of these would be fraught with diculty for interpretation.
Table 4. X-ray spectroscopy usefulness in the food sector
Very specic method of
identication
imaging
Capabilities:
Metal•
Glass•
Stones•
Applicable to ready meals,
prepared foods, meat, bakery
products, cereals, dairy foods,
Limitations:
Material Science: soft X-rays are often used in material science for non-destructive testing, electronic structure analysis, magnetic information, compositional analysis etc.
Astronomy: There are various sources of X-rays in the Universe that are studied by scientists, detectors for hard radiation are used in this sector.
Healthcare: In pharmaceuticals X-ray spectroscopy is routinely used for quality control of catalyst concentration and foreign matter.
RAMAN SPECTROSCOPY
Raman Spectroscopy is a method of vibrational spectroscopy long known to the condensed matter physics world and is a technique which provides information on rotational and vibrational modes in materials – as such provides ‘ngerprint’ information of substances that are unique
to that substance.
In Raman spectroscopy, a sample is illuminated by a monochromatic light source, this light is used to promote electrons from vibrational states into higher level virtual states, as the electron falls back into its ground state, light is radiated which is specic to that vibrational state
(Figure 8). The scattered light is then measured on a detector. Summing over all the present vibrational states results in a spectrum that is unique to a substance.
In food technologies, Raman spectroscopy may be used as a tool for quality control, for compositional identication (fatty acid composition,
sh and meat muscle quality) or for the detection of adulteration, as well
as for basic research in the elucidation of structural or conformational changes that occur during processing of foods (changes in proteins, water and lipids that occur during deterioration), Refs [19 and 20].
Obtaining Raman spectra from liquids or semi-solid liquids is possible wherever there are molecular bonds – fast moving, inhomogeneous samples however will prove dicult to obtain a good Raman spectrum
for.
The speed of data collection can again cause diculties for on-line detection, but it is classed here as an online technique due to its abilities as a remote detection scheme. Another issue may be the small sample volumes obtainable – as to the best of the authors knowledge, wide- eld Raman imaging is not a well established technique [21].
19. Raman Spectroscopy a promising technique for quality assessment of meat and sh: A review, Food Chemistry,
107, 1642 (2008) 20. The applications of Raman spectroscopy in food science, Trends in Food Science & Technology, 11, 361 (1996) 21. There are methods, however, available for building Raman images, but these often rely on point by po int scanning and can be very time consuming, Raman Imaging: Techniques and Applications. Arnaud Zoubir, Springer Series (2012)
Non-contact
Non-destructive
nanostructures to provide
No commercial solutions for
solutions
LINKED SECTORS
Healthcare: Raman gas analysers are used in medicine for real-time monitoring of anesthetic and respiratory gas mixtures during surgery.
Pharmaceuticals: identication of pharmaceutical constituents can be
made using Raman.
Security : Raman scanners have found a large market in airport security due to their ngerprinting abilities [22].
Figure 8. Example of Raman spectroscopy of native starches from Ref. [23]
22. http://physicsworld.com/cws/article/news/2012/feb/07/raman-technique-peers-into-cabin-baggage 23. Characterization of Irradiated Starches by Using FT-Raman and FTIT Spectroscopy, Journal of Agricultural and Food Chemistry, 50, 3912 (2002)
VISUAL INSPECTION
Visual monitoring of foodstus uses humans as resources to watch the
food move past, any thing that doesn’t conform to the standard is taken from the production line. The denition of non-conformity is vital to be
established from the outset. Many production facilities set out the crite- ria for non-conformity see Refs [24] for examples.
Only very obvious problems can be identied using visual inspection
of food and liquids in pipes, more often that not - visual inspection is
enhanced by providing the use of X-ray technology for the inspector to see through obstructing pipes.
Visual identication is easier for discrete items on a conveyer than in a
pipe, again is assisted by the use of non-standard imaging techniques to assess uniformity. Other sensory inspection could help here, such as smell or touch.
Table 6, Visual inspection usefulness to the food sector
Non-destructive technique
many defects in one
Very resource intensive
Highly variable outputs
24. Guidelines Procedures for the Visual Inspection of Lots of Canned Foods for Unacceptable Defects, CAC/GL 17
INFRARED TECHNIQUES
Near Infrared (NIR) spectroscopy uses the dierent absorption condi- tions of dierent compounds to analyse the constituent elements of a
sample. The NIR region extends – roughly – from 800 nm to 2500 nm and is thus very well suited for the detection of organic compounds. The technique uses transition probabilities of photons to map the states in a material.
In the food industry NIR spectroscopy has been used for many years to determine the food quality in an accurate, non-destructive and rapid way. Due to its sensitivity to organic content (water, sugar, acids etc.) - It can be used to determine moisture, fat and protein content and other components that impact on product quality and safety. some rms are
currently marketing NIR based sorting and grading systems for use with citrus, pome and stone fruits As well as being able to detect the presence of organic content the technique can be used to ngerprint what
the content is (useful for pathogens, allergens etc) and with plastics being composed of organic chains, plastic contaminants can not only be located, but also identied.
MIR is very rich in the information it provides for organic materials in
terms of the ne structure in the spectrum.
APPLICABILITY TO LIQUID IN PIPES There are product solutions of pipe-mounted NIR liquid process cells for monitoring. NIR spectroscopy, however, suers from strong absorption in water, as such applicability to liquids in pipes may be limited and the penetration depth of the NIR beam would severely limit the diameter of the process pipe.
Particulate food on a conveyer is well suited for NIR inspection and there are products that analyse the NIR spectrum of food and beverages. Quicker measurements are available by sing FT-IR spectroscopy
(see one of the following next sub-section).
Table 7. NIR usefulness in the food industry
Easier maintenance than X-ray
Due to its sensitivity to moisture,
proteins, fats and sugars it
is ideally suited for the dairy
industry
sensitive then visible CCDs.
The strong absorption in
water has historically limited
fresh produce
Calibration limitations
LINKED SECTORS
Astronomy: spectral information can tell astronomers about star types and stellar formation and processes.
Healthcare: used to measure oxygen content of blood, and also can be used on the skull to provide information of blood ow related to neural
activity as a partial replacement for fMRI (functional MRI)
Materials: can be used to measure lm thicknesses for optical coat- ings.
The technique is closely linked with hyperspectral imaging (HSI) described in the following section, due to its proximity in the EM spectrum, HSI is where optical measurements are combined with imaging to provide images containing not only spatial information but wavelength information. The dierence in these technologies is often in the detec- tions scheme-in NIR spectroscopic information is often obtained using dispersive elements whereas in HSI, the detector is constructed as to observe many wavelengths simultaneously.
FT – IR SPECTROSCOPY
FT-IR (Fourier transform infrared spectroscopy) is considered a more sensitive and robust technique over dispersive NIR techniques described above by its lack of diraction grating to separate out frequencies – instead interferograms are collected by a interferometer-like setup which represent the Fourier transform of the absorption spectrum.
FT-IR has the following advantages over dispersive and lter methods
of IR or NIR methods:
Table 8. Advantages of FT-IR over dispersive IR, from Ref [25]
PROS AND USES
It is non-destructive
It is possible to easily identify and distinguish between many
organic compounds and inorganic compounds
Precise measurement method that requires no external calibration
FTIR measurements can be made within seconds
Optimal sensitivity – detectors are more sensitive and the optical
throughput is higher. FTIR can identify small concentrations of
contaminants.
Mechanical simplicity – The mirror in the interferometer is the only moving part in the FTIR instrument, therefore making mechanical
breakdown minimal.
25. http://www.aircomp.com/blog/advantages-of-ftir-over-dispersive-methods-of-infrared-spectral-analysis/
HYPERSPECTRAL IMAGING
The hyperspectral imaging (HSI) method combines digital imaging with spectroscopy for give detailed information across multiple ranges of the EM spectrum. Unlike single source detection systems, hyperspectral imagers collect data from across the electromagnetic spectrum. Hy- perspectral imaging can be perceived as an extension of multispectral imaging (MSI); while multispectral imagers look at light from up to 10 wavebands, hyperspectral imagers are capable of obtaining information in a more continuous fashion, over 100 wavebands. Data are therefore not stored as two-dimensional images but instead as cubes, where
the third dimension spans the wavelength range of the detector. These cubes are unique for every produce and serves as a reference for the sorting procedure.
The use in food can be in using the ‘ngerprinting’ ability to determine
what the constituents of the passing food are and whether it should be there. Indeed there exist some commercial solutions already.
Many of the disadvantages of liquid in pipe sensing for NIR are shared with HSI.
HSI lends itself well to conveyor inspection lines - the advantage of simultaneous acquisition across many wavelengths allows quick gath- ering of vast amounts on information, see for example chicken carcass inspection Ref. [26].
Non-contact, non-destructive
Large area detection
Applications in differentiating
LINKED SECTORS
Due to its ngerprinting and identication capabilities hyperspectral imaging can nd uses in various linked industries.
Astronomy: mapping the physical properties of cosmic hot gas.
Security: in forensics hyperspectral imaging can be used for detection of forged documents and ngerprints at crime scenes.
Environmental monitoring: Hyperspectral imaging can be used to monitor vegetation and has been equipped to UAVs to detect large images.
Medicine: extent of burns and bruises below the skin of the human body, skin imaging for the diagnosis of skin cancers. In pharmacology it can be used discern the makeup of drugs that look identical to the naked eye and conventional imagers.
Figure 10. The image on the left shows raisins with impurities in between (paper,
plastic). The blue and green arrows point two spectral positions of raisins. In the
graph on the right it can be seen that points with similar color also have similar
spectra behind. The red arrow points a dierent color. Taken from Ref. [27].
27. http://www.perception-park.com/what-is-chemical-color-imaging.html
OPTICAL SORTING
Optical sorting methods use advanced image recognition equipment to automatically identify shapes, size, color and patterns of items that do not t set parameters, current systems. The spectral information /
images could be from any other optical sensor techniques shown above – more often than not however, they are based on monochromatic or tri-chromatic cameras.
Optical sorters are widespread in the food industry due to its in-line, non-destructive and low human resource use. Compared to manual sorting, which can be is subjective and inconsistent, the non-reliance on human resources helps improve quality of products, maximize throughput, increase yields and reduces labour costs. From Ref 28, in meat, it has been used to characterize muscle colour, marbling, maturity and muscle texture. In other applications sorting technologies have been used in agricultural products such as fruits, vegetables or grain.
In general, and optical sorting system is composed of four major components; the feed system, the optical system, image-processing system and the separation system. The optical system can be integrated with advanced technologies such as hyperspectral sources which as a great deal of functionality to the system.
The applicability and usefulness in pipes is essentially the same as that for inspection by humans, except it takes out the uncertainty and random errors associated with human monitoring.
See above
28. Irudayaraj, J and Reh, C. (2008) Nondestructive testing of food quality, Blackwell Publishing Ltd.
Table 9. Optical sorting usefulness in the food industry [29]
These systems can be very
specic
robotics, can be reasonably
not applicable to all types of defects
Limited to transparent /
surface incidents
LINKED SECTORS Pharmaceutical: in this sector optical sorting is used for optimizing the end products of pharmaceutical products ensuring quality, ecient and
reliability.
Industrial: can be used for automated machine building tasks, waste recycling, tobacco processing.
A comparison of RGB imaging, NIR spectroscopy, multispectral imaging and HSI are shown below for a comparison (adapted from Ref. [30]).
Table 10. Comparison of RGB, NIR, MSI and HSI techniques
29. http://www.buhlergroup.com/global/en/process-technologies/optical-sorting.htm#.Uut1lHm4ml 30. Potential application of hyperspectral imaging for quality control in dairy foods, Gowen et al, Image Analysis for
ATTRIBUTE RGB NIR MSI HSI
Spatial information P P P
Spectral information P Limited P
Multi-constituent information Limited P Limited P
Sensitivity to minor components P
TERAHERTZ IMAGING
Terahertz (THz) radiation lies in-between microwave and the far infrared on the EM spectrum generally with a wavelength range of between 100 µm and 1 mm corresponding to frequencies of 0.3 to 3 THz. Unlike microwave radiation it can penetrate a wide variety of non-conducting materials. Non-destructive evaluation, the energy of the THz band is 1 – 10 meV. T-rays are inherently sensitive to water; they are very suitable for moisture detection. Transparent to opaque materials such as plastic, fabric, ceramic and paper so the technology has the ability to see through some packaging materials.
THz has applications in food technology due to its strong interaction with water. Moisture content can be used to infer dierent properties of
a foodstu – fat content, ripeness etc. Its ability to see through plastics
and card also make it perfect for NDE of packaged food
High water content materials are almost completely opaque to THz radiation, this in conjunction with possible metal piping means that THz imaging and spectroscopy has very limited uses to liquid phase food.
For less water intense materials, the opaqueness of water to THz can provide a wealth on information for moisture detection. Its ability to see through paper, plastic can check for missing items on a conveyor.
Table 11. THz usefulness in the food industry
On-line, non-destructive
compared with IR)
as water) completely opaque
LINKED SECTORS
Due to the ability of THz radiation to penetrate common packaging and clothing materials there is interest from sectors such as:
Healthcare: unlike X-rays THz radiation is non-ionising and therefore a safer alternative for medical applications. It also has the ability to distinguish areas of dierent density and water content.
Security : the non-ionising properties of THz radiation also makes it an attractive method for concealed weapon detection through clothing, the additional method of THz spectroscopy allow the unique ngerprints of
substances to be exploited and identify concealed substances. Manufacturing: uses in manufacturing, quality control and process monitoring due to the transparent properties of cardboard and plastic, the inspection inside packaged goods can take place.
MICROWAVE DETECTION
Microwaves are no stranger to the food industry – the ease at which microwaves are generated coupled with the strong absorption by water make them ideal for microwave heating devices. Detection systems that operate in the microwave part of the spectrum are far lower power - Ref. [1].
Microwave imaging is uncommon as the large wavelength for small objects result in diraction eects and a severely limited image when
compared with X-ray imaging for example. Microwave detection systems instead rely on measuring the transmitted microwave eld passing
through a product and the local variation in dielectric properties between foreign objects and the product. Dielectric discontinuities are seen as absorption change of phase. Similar to THz radiation, though possess- ing higher penetration depths microwave radiation has a wavelength range of between around 1 cm and 30 cm corresponding to a frequency range of 200 MHz to 300 GHz.
Active microwave technology for this area is much closer to commer- cialization than THz equipment, with sources and detection methods well established from areas such as telecommunication. Unlike microwave ovens, the radiation used in low power and more similar to an X- ray imaging set-up. Additionally due to its response to water, microwave
wavelengths have been proposed for use in measuring water contentfor ripeness determination, see Ref. [62].
A Swedish company – Food Radar – has commercialized a product using microwave radiation; the transmission of the microwave radiation is dependent on the permittivity of the transmission medium. Foreign objects change a materials permittivity and the detected radiation can thus be monitored for contamination – applicable to liquids and emul- sions. It is claimed that glass (10 mg pieces), metal lings (5 mg), plastics, stones, wood and other organic materials can be detected with microwave techniques,
Microwave sensing can still be applied to food on a conveyor provided they are not in metal packaging – unpackaged, wood, plastic etc. But the technique is best suited for homogenous, piped foods if possible.
Table 12. Microwave radiation usefulness in the food industry
Non-contact, non-destructive
materials detectable by their
the food-processing system.
measure wood, stones, plastics,
shells, rubber, seeds, paper
No UK commercial solutions
Not ideal for imaging
LINKED SECTORS
Astronomy: the microwave background in the Universe provides evi- dence of the forming of the universe and various other extra-terrestrial microwave sources.
Communication: Many communication protocols operate in the microwave range. An advantage of microwaves over radio waves is that the microwaves have a higher frequency and therefore can encode more information.
Healthcare: There are examples of microwave imaging being used for the detection of breast cancer
ULTRASOUND
Ultrasound uses the transmission and reception of high frequency, low power ultrasound (pressure waves) to locate foreign bodies by being able to dierentiate discontinuities in acoustic impedance by analysis of
original and reected waves. In doing so, can determine composition,
structure and physical state.
Ultrasound has been used in food technology for many years [31]. It can be divided into two areas; high frequency, low power and low frequency, high power, the low energy is used for quality assurance and process control and high power ultrasound is an emerging technology area for modication of food (not the focus of this report). For process monitoring, recent publications detail the use of ultrasound on canned foods, Refs [32,33]
Impedance matching is far easier for liquids in pipes than discrete objects as better contact can be made between transducer and the object of interest. The transducer can assume various geometries and the pipe itself can act as the transducer as it will always be in contact with the food material - Ref. [34]
Dicult to achieve in practice due to the requirement of contact, al - though there have been proof of principle demonstrations of ultrasound applied to canned foods and cheese, Refs [35-36]. Detection is more dicult in inhomogeneous samples.
LINKED SECTORS
Whilst high-power ultrasound has many applications in industrial processing, low power ultrasound is generally used for non-destructive evaluation (NDE) an has many applications:
Healthcare: 2D and 3D imaging are possible in human and animals using ultrasound and is an attractive technique due to its lack of ionizing
radiation and relatively inexpensive and portable equipment.
Industrial processes: used extensively in the aerospace industry for evaluating cracks and detects in composites and metals. Can also be used for materials such as wood, concrete and cement.
Security : Commonly used in underwater applications as SONAR for range nding and object location
31. Applications of Ultrasound in Food Technology, Acta Sci. Pol., Technol. Aliment. 6(3), 89 (2007) 32. Detection of foreign bodies in canned foods using ultrasonic testing, International Food Research Journal 19(2),
453 (2012)33. Online Detection of Contaminants in Packaged Foods with Ultrasound using Signal and Image Processing and Soft Computing, Mittal and Basir, IEEE (2009) 34. Ultrasound in Food Processing, M. J. W. Povey, Springer Books () 35. Detection of foreign bodies in canned foods using ultrasonic testing, International Food Research Journal, 19, 543 (2012) 36. Ultrasound detection and identication of foreign bodies in food products, Food Control, 12, 37 (2001)
Rapid
liquids in pipes very well. Well suited for, large acoustic
impedance contrasts, missing
bottles
systems.
MAGNETIC SEPARATION
Magnetic separation can be used to lter out the “tramp” iron that can
nd its way into a production from elds or processes. Low intensity
magnetic elds are applied to the moving sample of solid or liquid food.
The eld may be applied from a permanent magnet (high eld rare-earth
magnets such as SmCo 5 or Nd
2 Fe
The eectiveness of magnetic separators is reduced in damp food; the
technique however is eective in free owing liquids
Embedded metal contaminants will remain embedded in large, dense food objects. Instead the ideal situation for magnetic separators are small, discrete foodstus like nuts, our etc.
Table 14. Magnetic separation usefulness in the food industry
Non power consuming, passivedetection
can remove objects as small as a
few microns.
our
hazardous to health
owing or damp mediums
LINKED SECTORS Industrial processes: such as mining iron, removing useful magnetic components from scrap etc.
METAL DETECTION
In standard metal detection techniques, an RF signal transmitted by the detector is compared with the one received. Non-metallic material passing through the RF eld does not distort the RF eld. Metal passing
through the signal elds however will distort the normal pattern of the
electrical elds. Distortion limits can be set to detect very small metal
inclusions.
Solutions exist for pipeline metal detectors as RF signals can be used through pipes and metal work. The contamination being present in a liquid phase does not complicate the detection signicantly.
As RF signals can penetrate deeply through a medium – large, dense objects can be screened by metal detection techniques.
Table 15. Metal detection usefulness in the food sector
High level of sensitivity
Only detects conductive
LINKED SECTORS
Archeology: both as a hobby and industrially metal detectors are used to locate metal objects of interest underground.
Military: a very common use of industrial metal detection is in the security sector capable of measuring very small metal objects.
SAMPLING
Sampling techniques involve sampling parts of the production line as to get a statistical idea of the quality of the entire production line. The sampled section of the line can then be subjected to further o-line
tests to check for conformity.
Sampling can be performed for both liquids and particulate objects. Careful consideration must be given to the sampling frequency as under sampling can result in poor coverage and oversampling can be time
inecient and expensive.
See above
Table 16. Sieving and sampling usefulness to the food sector
Can perform any measurement on
the sample once the foodstuff has
been samplede
LINKED SECTORS
Visual inspection, sieving and sampling are used for all industries as at very least a check that automated processes are performing correctly.
ELECTRICAL IMPEDANCE
Perhaps one the most simple measurements one can perform to locate foreign objects is to utilize the change in impedance inherent with a foreign object contamination event.
For an AC signal, the change in resistance, capacitance and inductance are related to the complex impedance of the sample, which aects the
signals magnitude and phase. Changes in a materials complex impedance will result in measurable signal changes which can be used as an indicator of contamination.
Certain physical changes in food structure and state can have an eect on the electrical properties. As a couple of examples electrical transport anisotropy of meat was able to determine the ageing of meat, Ref. 37.
In Ref. [1] is shown an example of how an electric system tuned close to resonance can act as an eective foreign body locator in piped foods. in
a steady ow the resistance should be xed – foreign objects would af- fect the resistance of this ow. The sensitivity of this device comes from
its proximity to resonance – and thus its susceptibility to any change in the resistance. Shown in Figure 11 is an example of the detection of small non-metallic impurities by phase measurements. Foreign objects
alter the output electrode signal close to the resonant frequency of the system resulting in a large output change (again from Ref. 1).
One current application of impedance-based system is designed to detect damage in bottles (a key cause of glass contamination) – the system applies a high voltage electric eld to four points around the
circumference of the bottle, any damage shows itself as a change in the impedance when compared to a reference sample and is capable of detecting hairline cracks, Ref. [1].
Table 17. Electrical usefulness in the food industry
Non-destructive
different impedance properties to
No UK commercial use
37. Electrical impedance probing of the muscle food anisotropy for meat aging control, Food Control, 10, 931 (2008)
LINKED SECTORS
The electrical properties of materials are used across many industries as it can give detailed information on the microscopic behavior of the charge carriers.
Figure 11. Response of the impedance sensor to non-metallic foreign bodies taken
from Ref [1]
BIOSENSORS
Biosensors are devices that detect an analyte that combines a biological component with a physiochemical detector component. In the food industry these sensors are often associated with the detection of pathogens and food toxins. Although may have applications where the analyte is not a pathogen but another indicator of interest, ripeness for example. The potential uses for these are very broad. Advances in sensor production mean that these can be made very cheaply.
Table 18. Biosciences usefulness in the food industry 38
Wide range of detectable
[38]
contamination testing
Contact method
LINKED SECTORS
Taken from Ref [39]
Healthcare: increasing lifetimes with increasing ailments, increasing auence and expectation of well-being are expected over all times- cales and with the large functionality of biosensors this is an important driver.
Industrial processes: Energy costs and resource eciency are issues
that will extend to the long-term
Environmental: Legislation and public opinion, global climate are medium and long-term drivers. Much work is being done in this area to develop generic biosensors that can detect a range of contaminants in water / air necessitated by EU legislation.
Security: one-o events and global conict can initiate both short-
term needs for example (for anthrax detectors) and longer-term policy changes.
38. http://www.ripesense.com 39. UK Sensor Company Capability and Opportunities Study, To be published 2014, ESP KTN
OFF-LINE / LAB-BASED
NUCLEAR MAGNETIC RESONANCE
Nuclear magnetic resonance (NMR) uses RF excitations to cause nuclei to precess in the presence of a magnetic eld, the relaxation of the nuclei give great detail on the content of the sample and its environment. Due to the historic use in the medical industry this technique is very well suited for meat analysis. Ref [40] gives a detailed overview of where the technique is currently being employed by the food industry – although still limited to the academic world due to high equipment costs and resource ineciency.
Whilst there exist many commercial solutions, these remain expensive and bulky due to the requirement of high elds. Earth eld NMR ma - chines do exist but fail to deliver resolutions that are required for industrial practices.
The UK academic community has ample access to NMR machines often based in material science department at Universities such as Warwick, St Andrews, Cambridge, Sheeld, Durham, Nottingham, Glasgow, Ox- ford, Birmingham, Queen Mary University of London, Imperial College London, York, Bristol, Southampton, Liverpool, Newcastle, Sussex
Table 19. NMR usefulness in the food industry
Very sensitive
Non-contatc, non-destructive
LINKED SECTORS
The technique of NMR has applications in many other sectors such as: Material science: NMR spectroscopy can be used to study the chemical structure of a material, time domain NMR spectroscopy is used to molecular dynamics of systems by matching the RF frequency to element of interest.
Healthcare: a very important application for NMR is that of magnetic resonance imaging (MRI) - the 3D imaging and analysis of human and animal tissue has revolutionized medical diagnosis and is perhaps the best known use of the technique.
40. Davenal et al, Advances in Magnetic Resonance in Foods (1999) p. 272
Figure 12. NMR spectra from beef and horse meat samples, taken from Ref. [41]
Figure 13. Slices of decomposing worm-eaten apple, from Ref. [42]
41. http://www.oxford-instruments.com/ 42. http://alisi.isibrno.cz/en/nuclear-magnetic-resonance
MICROSCOPY
Microscopy uses focused light / electrons to probe very small sample volumes, scanning electron microscopy for example, boasts a resolu- tion of around 1 nm, as such it is not often used as a alert indicator for foreign contaminants in food. Its used in food is instead because it can be used to identify the origin of a contaminant. The origin can be identied through a range of microanalyses; topological microscopy (by
identifying very small surface marks), and compositional microscopy (EDAX microanalysis) to identify what the contaminant has been in contact with and through this information, identify where the contamination
has come from.
As an example of the techniques usefulness Figure 14 from Ref. 43 shows a failed weld repair on a tubeplate from a piece of food processing equipment, demonstrating a dierent metal composition in the
welded area. EDAX microanalysis showed the presence of titanium in the welded area, absent in the rest of the sample, and indicating that the wrong welding rod had been used for the repair.
Table 20. Microscopy usefulness in the food sector
Can be highly specic in terms of
origin of contamination
used once contamination is
LINKED SECTORS
The highly specic nature of microscopy means that it has many cross-
sector applications, such as pathology, fundamental science, archeology, forensics etc.
43. Microscopy for the Food Industry, Royal Microscopy Society, Issue 6, 47 (2007)
Figure 14. A backscattered SEM image of a failed weld repair described in the text.
MASS SPECTROMETRY
In mass spectrometry samples are ionised by high-energy electrons, the fragments are then separated using a magnetic eld to analyse the
spectrum of the weight (m/Z) of the sample. This spectrum is unique to the sample and can give highly accurate, quantitative information of contaminant levels in a sample.
An example of where the high sensitivity and high accuracy characteristics of the technique are useful is in allergen testing for allergens such as egg and milk allergens in baked goods. Traditionally allergen testing would be done using PCR or ELISA assays, which can suer from false
negatives and lack a truly quantitative output.
Table 21. Mass spectrometry usefulness in the food sector
Very specic Destructive, off-line testing
Resource intensive
Healthcare: Drug analysis and clinical diagnosis use mass spectrometry techniques to ngerprint the constituent atoms.
Forensics: The unique ngerprinting ability of mass spectroscopy allows accurate identication of substances to be made.
Figure 15. Example of trace analysis of fruit (taken from Ref 44)
44. Screening of agrochemicals in foodstus using low-temperature plasma (LTP) ambient ionization mass spectroscopy, Wiley et al, Analyst, 135, 971 (2010)
CHROMATOGRAPHY
Chromatography uses the dierent speeds in which dierent substances move through a mobile phase and uses that to separate out the continuants chemicals. Through this separation the method can provide quantitative determination of carbohydrates, lipids, proteins, peptides, amino acids, vitamins, aroma and avor compounds in a wide variety of
foods and food products (from Ref. 45).
Table 22. Chromatography usefulness in the food industry
Can be specic in its identication
of contaminant
Quick measurements
Environmental: Thin-layer and liquid chromatography can detect pollu- tion compounds and pesticides or insecticide residues.
Security: gas chromatography can be used to detect bomb substances, drugs and alcohol
Forensics: can be used to compare bers found on a victim and analyse the dye composition of bres, RNA ngerprinting, separating and
testing histamines and antibodies.
45. Cserhati, T. and Forgacs, E. (1999) Chromatography in Food Science and Technology, CRC Press
POLYMERASE CHAIN REACTION
Polymerase chain reaction is a versatile, sensitive and reproducible process that exponentially amplies a DNA fragments over several or- ders of magnitude to test organic material for its make-up. The develop- ment of real-time PCR using uorescence means that information can
be gathered during the amplication process - not only at the end.
Aspects of food quality such as genetically modied organisms (GMOs),
allergens and food authentication are of huge current interest to manufacturers as such real-time PCR is a promising technique for addressing these. Speed, excellent detection limit, selectivity, specicity, sensitivity
and potential for automation are among the most important advantages of real-time PCR, Ref. 46.
Table 23. PCR usefulness in the food industry
PCR test results report very
close to 100 % specicity and
sensitivity.
receive results.
LINKED SECTORS
Healthcare: PCR is regularly used in medicine for genetic testing, for screening, tissue typing, mutation monitoring etc.
Forensic pathology: DNA fragments found at crime scenes can be used to ngerprint uniquely suspects.
46. Rodrîguez-Låzaro, D. (2013) Real-time PCR in Food Science, Norfolk, Caister Academic Press
ENZYME-LINKED IMMUNISORBENT ASSAY
The enzyme-linked immunisorbent assay (ELISA) is a technique that uses antibodies and colour change to identify a substance, usually an antigen but could be an antibody. Common uses of the technique are in home pregnancy test kits
In the food industry primarily for use in identifying food allergens such as milk, peanuts, walnuts, eggs etc. In the industry the most common and preferred methods for detection are ELISA and PCR. The ELISA method detects the actual allergen protein molecule by binding antibodies to the allergen and ten use enzyme-linked conjugate to create a colorimetric change, from Ref. 47
Table 24. ELISA usefulness in the food industry
Non-hazardous equipment
techniques
Expensive
LINKED SECTORS
Healthcare: diagnostic tool for pathogens in medicine, such as the HIV virus.
47. http://www.elisa-antibody.com/index.php?page=food-industry
ATP BIOLUMINESCENCE
Adenosine triphosphate (ATP) Bioluminescence is a biological reaction between ATP and the enzyme luciferase that produces light that is detectable – the intensity of the light is a measure of concentration. ATP is an indication of life. A pen-like device containing reagents is swabbed in an area and then inserted into a light monitor. The reading in RLU (rel- ative light unit) is an indication of the presence of organic substances. ATP bioluminescence is used in the food industry as an indicator of life and therefore biological contamination.
Table 25. ATP usefulness in the food sector
Reading within seconds
microorganism
LINKED SECTORS
The linked sectors are in any industry where live cell cultures need to be quantied as perhaps a hygiene concern.
TECHNOLOGY SUMMARY TABLE
Table 26. Technology versus sensing challenges and their abilities to meet them
CURRENTLY USED
G L A S S ( L I Q U I D )
G L A S S ( P A R T I C U L A T E )
P L A S T I C S
F A T , G R I S T L E E T C
B O N E
R I P E N E S S
D A M A G E T O F R U I T S E T C .
W R O N G P R O D U C T S
N A T U R A L P L A N T M A T E
R I A L
H A I R
POTENTIAL TO BE USED
PCR
ELISA
MICROSCOPY
S P E
C T R O S C O P Y X-RAY SPECTROSCOPY
X-RAY IMAGING
NEAR IR
OPTICAL SORTING
O T H E R O N - L I N E MAGNETIC SEPARATION
SAMPLING
METAL DETECTION
VISUAL MONITORING
T E C H N O L O G I E S O F P O T E N T I A L
FT-IR
ULTRASOUND
NMR
Each challenge - either suggested by the UKTI or identied subsequently - is analysed in the following way. Firstly, the challenge is put in context given its impact on UK recalls, and its potential health and safety implications. Secondly, the contaminant is analyzed for its physical, chemical and biological properties – this could aid in identifying pre- viously unconsidered techniques for detection schemes. Thirdly, data from UK manufacturers is used to obtain a general image of how the challenges is currently being met and nally potential technologies are
listed which may in the future result in new detection systems that can be employed.
Comments and feedback from either manufacturer questionaires or cap-tured from the workshop in London are incuded in quotation marks.
CHALLENGES
1. THE DETECTION OF GLASS FRAGMENTS – IN PARTICULATE FOOD
BACKGROUND
One of the most dangerous contaminations to nd in food or drink is
glass; it can cause internal bleeding and even be fatal. Glass fragments from food factories are occasionally found, for instance from such items as broken bottles from lling lines, broken uorescent light tubes and
broken glass viewing panels. Glass was the fourth most complained about foreign object in food in 2012.
CURRENT SITUATION
The current main methods for detecting glass in particulate food and liquids with X-rays is that the density of these materials are often very similar, and as X-ray imaging operates on a density dierentiation principle, will fail. Other methods used include visual inspection and sampling, however, the identication of small clear shards that can cause
serious damage, is often non-trivial.
Once contamination is conrmed, then microscopy examinations often
take place. These examinations quantify features such as size, colour, curvature, surface scratches and deposits. This can be further followed
up by X-ray microanalysis in the SEM. This non-destructive test gives a spectrum of the elements found in the sample to allow identication of
the likely source of the contamination.
MANUFACTURERS PERSPECTIVE
X-ray imaging
Lab Analytical
CONTAMINANT CHARACTERISTICS
CHEMICAL Composed of SiO 2
BIOLOGICAL N/A
POTENTIAL FOR INNOVATION
Proof of principle experiments exist which show how THz imaging can highlight buried glass in chocolate and meat, Ref [48,49]. With increasing levels of pattern recognition – this could be extended to particulate food.
Figure 17. (left) THz image of glass in chocolate from Ref. 45 and (right) glass in
meat from Ref. [46]
THz
2. THE DETECTION OF GLASS FRAGMENTS – LIQUIDS IN GLASS
BACKGROUND
In glass bottled liquids fragments can arise from not only the source mentioned on the previous page, but also from the bottles themselves. Monitoring must therefore be performed over the entire production as glass contamination could occur at any point. Glass was the fourth most complained about foreign object in food in 2012.
CURRENT SITUATION The current main methods for detecting glass in particulate food and liquids with X-rays is that the density of these materials are often very similar, and as X-ray imaging operates on a density dierentiation principle, will fail.
Other methods used include visual inspection and sampling, however, the identication of small clear shards that can cause serious damage,
is often non-trivial. Once contamination is conrmed, then microscopy
examinations often take place. These examination quantify features such as size, colour, curvature, surface scratches and deposits. This can be further followed up by X-ray microanalysis in the SEM. This non destructive test gives a spectrum of the elements found in the sample to
allow identication of the likely source of the contamination.
Existing technologies for checking glass bottle integrity, such as ‘bottle-
vision’ are expensive
The detection of small glass fragments within bottled uids is dicult
Used extensively for soluble coee granules in Glass Jars. Glass is seri -
ous customer complaint. There are still some ‘blind spots’ with X-Ray at
certain points in the glass - would like to eliminate.
Proof of principle experiments exist which show ultrasonic measurements on canned and bottled goods. Restrictions exist in the geometry of the set-up and impedance matching requirements. But in principle extra reections due to foreign bodies are measurable.
Methods for mechanical sepration by spinning the liquid and bringing the contaminant to the surface
The sound of glass being chipped could serve as a detectable signal
PHYSICAL Sharp; hard; reect, refract and transmit light
CHEMICAL Composed of SiO2
3. THE DETECTION OF PLASTIC
BACKGROUND
Plastics are an increasingly prevalent material of use in the food industry, both in manufacture and in packaging. Plastics were the second most complained about foreign object in food in 2012. The threats they pose however are not simply in choking and cutting but also in intro- ducing a chemical and biological hazard to the consumer – depending on the source. Ultra-high molecular-weight polyethylene (UHMW PE) is probably the most widely used plastic in food processing facilities and
also is used in conveyor guide rails. The detection of plastic is a big potential market for detection compa-
nies with many seeing it as one of their biggest challenges
CURRENT SITUATION
Currently used methods for plastic detection are visual inspection, optical sorting and X-ray imaging. Identied problems with these techniques are that:
Plastics do not possess the density contrast that metals do, thus making the detection of them with X-rays problematic
Plastics are composed of carbon and oxygen, making the elemental
makeup of the plastic very similar to organic food tissues
The optically transparent nature of many plastics used in the food industry mean that visual inspection can often miss the presence of plastic.
Solutions such as altering the properties of the plastic so that they may
be detected by metal detection / X-ray sources have been trialed. Whilst
seemingly advantageous in terms of ability to retrot, they are unpopular
for cost reasons, and for the diculty of getting ‘new’ plastics into the
industry. Additionally, altering process plastics would fail to detect con-
tamination from random events.
Filter medium + sieves are used to remove any particulates.
Polycarbonate plastic pieces in moulded chocolate bars. Serious H&S
issues. Huge expense. Detection generally involves retrospective inves-
tigation, embargoes etc.
rounded, small to large, varying densities
CHEMICAL mostly composed of complex hydrocarbon
chains, but have a large range of chemical
properties
Ordinary plastics cannot be detected by metal detectors however, it has
been suggested that magnetic additives to the plastics used in manu-facture could assist in detection – thus utilising one piece of equipment.
Similarly for X-ray detection, inclusion of a heavy element (such as bar- ium) will cause the plastic to uoresce under X-ray examination.
… clearly however, this relies on the plastic contaminant being identied
and replaced.
Highlighted due to its innate suitability to organic materials and its sub- tle ability to dierentiate foodstus from plastics due to the structure of
the sample.
4. THE DETECTION AND SENSING OF FAT AND GRISTLE
BACKGROUND
Fat and gristle are very important to the meat industry as they determine yield. Nobody wants to buy a steak that is mostly inedible. Luckily, fat and meat tissue have dierent properties; moisture content, density,
colour etc. and thus can be dierentiated.
CURRENT SITUATION
On farms, ultrasound measurements can give important information on
fat and muscle depths, Ref. 50. In processing fat, gristle and meat content in food industries are currently determined by using the dierence
in absorption of fat and meat in NIR spectroscopy, NIR relies on the dierence in absorption of dierent organic compounds and can give
information on key qualities such as texture, juiciness and avour.
ELISA is used for quantitative analysis of fat content but is an o-line
destructive method. For often, simple visual inspections of the meat are used to determine fat and muscle content.
There appears to be a large number of approaches to sensing fat, gristle
and cartilage. Most of these techniques are involve moisture detection
– IR, microwave etc.
A comprehensive list of physical, chemical and biological characteristics of muscle, fat and gristle etc are presented in Ref. [51]
50. Improving sheep carcass quality using CT scanning 51. Handbook of

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