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Although we are still donning our jackets and looking forward to hot soup and cosy evenings in front of the heater, we know that our winters are short and our summers much longer. With summer a few short months ahead, we need to plan for this period which presents a major challenge for cold displays and cold trucks transporting our favourite foods.
The cold chain is one aspect of the farm to fork experience that can be managed to perfection, provided that the regulations and rules
that apply to cold chain management, are followed meticulously.
The integrity of the cold chain is critical to perishablef ood distribution. The term “cold chain” refers to the unbroken, constant, temperature-controlled supply chain by which temperature sensitive perishable products are transported from producers, distributors, processors and manufacturers to wholesaler and retail store fridges, and ultimately to the consumer’s fridge.
The chain includes actions ranging from the handling and packing to the distribution of fresh and frozen food products and keeping them at a constant temperature to ensure safety and quality from the farm to the plate. Cold chains are evaluated and controlled by the use of thermometers and data loggers, recording temperatures in cold rooms and refrigerated trucks. When the temperature barrier is broken and products are exposed to ambient temperatures, the freshness, quality and shelf life of the products are compromised.
Perishable products
A perishable product is one that is liable to perish or decay. Perishable foods include foodstuffs such as butter, fruit and meat. Seafood and meat make up the biggest portion of perishable foods produced and distributed by air across the world. This is followed by fruits and vegetables, flowers and plants, pharmaceuticals and other foodstuffs such as dairy (ice cream, milk, butter, yoghurt, etc).
The cold chain is not only important for local transport and storage of perishable products, but also for import and export opportunities. International companies will not consider exporting to a country where the infrastructure does not support a solid cold chain. A few years ago the US food company, General Mills Inc, was literally stopped in its tracks in India, where the retail supply chain simply could not support the import of Haagen-Dazs ice-cream.
Agro-processing of subtropical fruit
China, although it is the largest consumer and producer of food in the world, also lacks sufficient capacity for cold chain transportation, with less than 1% of its trucks being refrigerated.
The chill factor
Chilling food (not freezing) involves reducing temperatures to below ambient temperatures, but keeping it above -1⁰C. This effectively preserves food in the short term, but it does not mean that food is completely non-perishable – microbial and biochemical reactions are merely retarded. Quality will be preserved for extended periods, but will deteriorate progressively throughout the process.
An unbroken cold chain, which will retard the spoilage process substantially, is therefore of critical importance. Thus begins a process of manufacture, rapid chilling and low temperatures throughout storage, handling, distribution, display and storage by the consumer.
Temperature monitoring is the most powerful tool throughout the cold chain. Core temperature is the temperature that has to be maintained here, and not surface temperature. Core temperature refers to the internal temperature of the chilled food item.
When checking for temperatures, excessive temperatures displayed by the thermometer should always be cause for concern. A good rule of thumb is that temperatures for chilled foods should never be warmer than +4⁰C. Table 1 represents the maximum temperatures at which different foodstuffs should be kept chilled (R918 of the Regulations Governing General Hygiene Requirements for Food Premises and the Transport of Food, 1999).
Chilled food cabinets are intended for holding food and not for chilling it. Introducing warm products into cabinets can cause increases in
temperature, rendering the cooling function ineffective. Poor stocking and stacking can also cause significant problems for temperature maintenance.
Visual checks can go a long way in maintaining the cold chain – if you notice icing up of chill cabinets, this is a good indication of incorrect thermostat settings and defrosting regimes. Regularly inspect air temperature recorders and thermometers.
One important thing to remember [refer to article 8(5) of R918 of the Regulations Governing General Hygiene Requirements for Food Premises and the Transport of Food, 1999] is that any food which is marketed as a frozen product and has thawed, but the surface temperature of which has not exceeded 7⁰C, may be refrozen. However, this is subject to the refrozen product being handled in accordance with good manufacturing practices.
But how is various food products requiring different chilling temperatures transported in the same vehicle? Transporting different foodstuffs requiring different temperatures in the same vehicle, is referred to as multi-temperature loads or deliveries. Using one vehicle to carry one load at one temperature has become very expensive, not only in fuel, but in time too.
There are a number of considerations to be taken into account when transporting multi-temp loads – not only the different temperature of the products, but also the mixing of different foodstuffs, says Mike Westcott, marketing director at Bamic Enterprises in Cape Town.
“Take for example ice cream, other dairy products and meat,” Mike explains. “These products tend to readily absorb odours and therefore should not be placed in the proximity of seafood or other strongly scented products. Some products can be safely mixed, but ethylene sensitive vegetables should not be mixed with ethylene-producing fruits. Dry vegetables should not be mixed with other fruits and vegetables and so on.”
Temperature settings in vehicles are determined by the products being transported. “We know that temperature-sensitive products such as ice cream need to be stored and transported at -25⁰C, while fruit products listed at 1⁰C to 5⁰C, are sensitive to freezing at lower temperatures. Some fruits are stored at lower temperatures to temporarily ‘halt’ the ripening process for a longer shelf life, but all fruit and vegetables are sensitive to freezing during storage and transportation.”
Temperature settings in vehicles are determined by the products being transported. “We know that temperature sensitive products such as ice cream need to be stored and transported at -25⁰C, while fruit products listed at 1⁰C to 5⁰C, are sensitive to freezing at lower temperatures. Some fruits are stored at lower temperatures to temporarily ‘halt’ the ripening process for a longer shelf life, but all fruit and vegetables are sensitive to freezing during storage and transportation.”
When transporting foodstuffs requiring different temperatures in the same vehicle, it is recommended that a “thermal partition” of some sort be utilised to divide the truck into compartments of varying temperature zones. Transporters have tried various methods of compartmentalising their vehicles – some have been successful, others not.
Invest in technology
Another cost-effective way of protecting products in a multitemp load vehicle, would be to use thermally insulated covers or mats.
“When a vehicle’s temperature has been set at minus degrees to protect and transport frozen products together with chilled products,” Mike explains, “the thermally insulated covers can be used to cover and protect the chilled products from the freezing truck temperature or it can be used to cover frozen products in a vehicle set at a minimum temperature of 1⁰C to 5⁰C to halt the defrosting process. However, a good thick insulation material is needed for this.”
Usually long distance deliveries of food products are packed onto pallets to accommodate space-saving in vehicles. Shorter town deliveries normally use security rolltainers (cages on wheels) to deliver dry goods, but the practice of using rolltainers with thermally insulated covers to deliver perishable products is becoming more the norm as this is a far more efficient way to deliver perishable products to stores and effectively not break the cold chain.
Bamic’s range of thermal covers and blankets for products ranging from fruit and veg, to meat and flowers, represent a choice of solutions for cold chain transport on land and in the air. Visit their website at www.bamicenterprises.com to find out more about their range of products.
Sensing freshness
The Perishables Products Export Control Board (PPECB) is South Africa’s official certification agency for the export of perishable products and applies global standards. A number of years ago, the PPECB gave its seal of approval to the so-called Xsense System for use in perishable cargoes. The Xsense Cold Chain Monitoring System allows the user to monitor the temperature and relative humidity of perishable products as they travel through all links in the cold supply chain. It allows for real time alerts so that corrective action can be taken before it’s too late. Xsensers are but one form of technology supported by the PPECB in its bid to ensure that perishable products are handled, stored and transported and specified/ optimum temperatures. The body delivers cold chain certification services that entail equipment checks, load monitoring, temperature instruction, handling protocols, standard procedures and work instructions.
An unbroken chain
In order to avoid breaking the cold chain, additional protection should be used for products, particularly during transportation which is where the cold chain is often broken. In summer months heat flow must be reduced and the thermal radiation reflected rather than absorbed, for products to maintain their given temperature. This can only be achieved by using thermally insulated products such as covers, mats, et
cetera. Depending on the temperature sensitivity of the product, the thermal cover could be used in combination with ice packs or eutectic plates.
Insulating materials will control the three functions of conduction, convection and radiation, known as its Lambda value. Thermal insulation creates a barrier against conduction; suppresses air movement, thus restricting convection and limits the effects of radiation. Insulating materials such as thermal covers will protect products and assist in maintaining temperatures at critical times when the cold chain is broken or compromised.
More dos and don’ts
- Never overload chilled cabinets, cold trucks or display fridges.
- Maintain chill (+4⁰C) temperatures during storage, transport and display.
- In the case of frozen food, maintain temperatures of between -12⁰C and -18⁰C during storage, transport and display.
- Strictly maintain hygiene at all stages of the cold chain and train staff in the correct and hygienic handling of frozen and chilled foods. At chilled temperatures of between 0⁰C and +4⁰C, growth of micro-organisms are slowed substantially and food spoilage is inhibited significantly.
- The cold chain should entail a continuous, unbroken operation with zero delay between temperature-controlled areas.
- Perform regular temperature checks using calibrated instrumentation.
- Ensure that thermometers are placed in such a way, that it is easy to read, but cannot easily be tampered with. – Lynette Louw, AgriOrbit
