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The wheels of chain

Prakash Krishnamoorthy, Sales Manager (Middle East Area) at Carrier Transicold Europe – Gulf Office, was a presenter on Day 2 of Food Chain UAE. Here, in Part 3 of our continuing coverage of the seminar, we bring to you excerpts from his presentation from a transport refrigeration perspective on cold chain management, in which he addressed critical issues of concern …

| | Jul 30, 2011 | 10:55 am
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Prakash Krishnamoorthy, Sales Manager (Middle East Area) at Carrier Transicold Europe – Gulf Office, was a presenter on Day 2 of Food Chain UAE. Here, in Part 3 of our continuing coverage of the seminar, we bring to you excerpts from his presentation from a transport refrigeration perspective on cold chain management, in which he addressed critical issues of concern …

A chain is only as strong as its weakest link. Any interruption to the cold chain constitutes a hazard to the health of the consumer, because it ought to be remembered that cold does not kill microbes, it just slows their development. Hence, a robust cold chain is not just essential but critical.

Prakash Krishnamoorthy

Prakash Krishnamoorthy

So what are the general risks associated with refrigerated transportation in the event of an interruption to the cold chain? There are three types – microbial, chemical and physical.

In the case of microbial risk, a cursory glance at the temperatures of the principal pathogens where multiplications stops, does tell quite a story. For the toxicogenesis of staphylococci and Clostridium botulinum A and B, the temperature is +10°C. It is -12°C for all bacterial multiplication and -18°C for microbial multiplication. In short, owing to the clear danger from microbes, any interruptions in the cold chain, even for a short period of time, are hazards for consumer health.

Chemical risks are owing to accidental contact with a non-food substance, such as lubricating oil spilt on the floor or on cooling units. Also, presence of residues from cleaning products or disinfectants can lead to chemical risks.

Physical risks are caused by solid particles of various types and sizes. Air-borne dust circulated by a unit’s fans, or introduced via the air vent or when the vehicle doors are opened, is one such situation. Also, dirt from vehicle floors, refrigerating chambers and handling areas can lead to contamination. As far as physical risks are concerned, the moral of the story is: the vehicles must be clean and the packaging adequate.

At this juncture, it is worth looking at ATP (Agreement on International Transport of Perishables Foodstuff), which is regarded as a key regulating body of the transport refrigeration industry. ATP is basically the agreement on the international carriage of perishable foodstuffs and on the special equipment to be used. The first ATP regulation was defined as far back as 1971. Seven countries signed the regulation. From 1975 onwards, there have been progressive agreements among 35 additional countries, including the United States, and belonging to the European Union, Eastern Europe and Northern Africa.

ATP’s mission is simple: Ensure the minimum equipment specifications for international transport and ensure the quality of perishable foodstuffs during their transportation.

ATP’s regulations, revised each year by a UN working group, are applicable to all national and international transport activities.

ATP stakeholders include box manufacturers, unit manufacturers, installers and transporters.

In the case of box manufacturers, ATP stipulates that in the case of isothermic devices, the coefficient of heat transfer (k) must be certified by a test in a tunnel by a certified laboratory. And in the case of carriers, the refrigeration capacities must be certified for each model by an authorised laboratory; the test results are valid for six years.

In the case of an assembler of a refrigerated vehicle, which basically constitutes the box and the refrigerated unit, the refrigeration unit should have a safety coefficient > 1.75, which corresponds to a pull down time of six hours to reach -20°C with a 30°C ambient. A higher safety coefficient is considered when chilled produce are involved, as many are extremely temperature sensitive.

And in the case of a transporter, the refrigerated vehicle must have an ATP certificate delivered by an institution with a governmental agreement (TUV in Germany, Cemafroid in France and CRT in the United Kingdom).

The transportation temperature of the products, according to their nature, must be specified.

  • Class A: set point from 12°C to 0°C
  • Class B: set point from 12°C to -10°C
  • Class C: set point from 12°C to -20°C

A key element in transport refrigeration is a set of loading practices for goods. We need to keep in mind that transport refrigeration is designed to only maintain temperatures and not to cool the product. Poor air distribution is one of the primary causes of product deterioration.

Typically, the sources of heat ingress are conduction (from the product), convection (through open doors) and radiation (through the trailer floor, sides and roof). Hence, a simple action like trying to park the vehicle in the shade, when not in use, helps remove the heat that has entered the body from the sun.

The loading should be done after pre-cooling the box to the desired temperature. Care should be taken to ensure that products are always loaded at the correct temperature and that they are loaded from a refrigerated bay. This is extremely critical to maintain the cold chain.

The benefit is as much in the details. For instance, care should be taken to ensure that fresh produce are not wrapped in plastic, as doing so prevents air circulation from reaching the load.

It must be ensured that the evaporator is not obstructed with the loaded goods and that air circulation is not impeded at all times. Equally important, it is essential to defrost 30 minutes after loading for fresh products and to stop the unit at the time of opening the doors.

Correct pallet use is also part of transport refrigeration best practices, wherever used. For instance, orientation should allow airflow to the head of the body. Pallets should allow airflow through and under the load. Airflow down the side of the load (minimum 25mm airflow around the sides of load, and preferably 50) is important. Airflow from the rear door (minimum 100mm from the rear door) is equally important. A word of caution: loading to the ceiling will cause short cycling.

Correct loading

Generally speaking, correct loading means not mixing refrigerated and dry goods in the same compartment. Speaking of which, in the event of a second compartment, it should not be cooled by a fan from the first compartment for good hygiene and to maintain better temperature control.

Speaking of hygiene, transport refrigeration is as much about the personnel involved. They should be trained to uphold hygiene rules, cleanliness, cold chain and products temperature. Personnel health should be controlled regularly, and this includes the wearing of clean clothes.

The loading personnel must control:

  • The cleanliness of the inner sides (walls, roof and floor)
  • Product temperature before loading
  • Proper product packaging
  • Separation between non-packaged food and packaged food
  • Separation of incompatible products

Refrigerated transport is a very important link in the cold chain. Higher risks of cold chain failures occur during transportation, as the environment – in the forms of speed and external temperature, to name two – changes continuously.

Risks of cold chains failures can be minimised by following ATP standards and by respecting good loading and hygiene practices. Doing so will lead to improved quality of transported products and consumer health protection.

Did you know?

What is multi-temperature concept?

The same truck can carry different products

  • At different temperatures
  • Products that are not compatible
  • Maintaining precise temperature regulation with sufficient air flow ensuring product safety
  • Maintaining various compartment configurations to suit the customer’s requirement

The advantages of multi-temperature units include negating the need to send two (say) trucks to carry things at different temperatures, flexibility (different compartments can carry loads at different temperatures), better fleet utilisation, fuel savings and reduction in carbon emissions and noise pollution.


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