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What role does refrigeration play in the supply chain?

06 July 2015

Controlling the temperature of food across the whole supply chain is vital to extend shelf life. But how much can be gained by food manufacturers through careful monitoring at all process stages?

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Commercial shelf life of fresh food is mainly controlled by either preventing or limiting microbial growth. While this can be achieved a number of ways – reducing storage temperature, reducing water activity, adding preservatives – there has been an increased consumer demand for food this is considered to be fresh, but has an extended shelf-life. On the other hand, consumers do not always value products that come with a long shelf-life as they associate such products with extensive processing and poor quality. Therefore, foods that use preservatives or thermal treatments are not generally acceptable options for consumers as they affect the food quality and its inherent freshness. 

“Refrigeration is a means to maintain freshness whilst not detrimentally affecting quality through excessive processing and therefore is one of the primary ways to extend shelf life whilst maintaining consumer acceptability,” says Judith Evans, Chairman of the Institute of Refrigeration’s International Refrigeration Committee, which provides a central resource for people across the globe to improve the application of refrigeration. “Refrigeration technologies are vital to enable the consumption of healthy and safe food, particularly in terms of nutritional, organoleptic and microbial quality. For chilled foods, quality and safety are reliant on the food being maintained at a sufficiently low temperature throughout its life to prevent growth of bacterial pathogens and to minimise growth of spoilage microbes. Chilling also has beneficial effects on quality, minimising moisture transport and maintaining flavour, colour and texture.”

Even with increasing demands being placed on the food supply from growing populations and resources growing scarce, most consumers take food for granted, even though it is a vital commodity. The planet is unlikely to be able to support the growing population without better utilisation and improved storage of available food. “Refrigeration has a vital role to play in providing food with extended shelf life,” Evans explains. “Improving the temperature performance of the food cold chain and improving food packaging has already provided consumers with a range of produce and prepared meals that would not have been available 20 years ago. And further improvements are possible at the consumer end of the cold chain, as this is where surveys have repeatedly shown that food temperature is least well controlled.”

There is little chance for bacteria, yeast or moulds to grow at temperatures below -12°C, which means that frozen storage mainly influences food quality, not food safety. Freezing food provides consumers with access to seasonal products that otherwise would not be available year round, unless imported from overseas with the associated cost and environmental impact, and products such as ice cream that could only be created using refrigeration. 

“Freezing food extends shelf life and prevents deterioration of flavour, texture, colour and vitamin content,” explains Evans. “Freezing rapidly after harvest retains vitamin C levels in vegetables and provides consumers with high quality safe products. Refrigeration is key to improvements in the supply chain to meet consumer demand for a wide selection of fresh, nutrient rich produce with a longer life.”

WRAP recently published a report that established that extending product life by even just one day had profound effects on the high level of food that is waste, which is a huge saving when approximately one third of food produced in the world is wasted. WRAP estimated that in the UK alone, shoppers could save around £600 million and businesses could save £100 million by extending food shelf life by just one day – which equates to a five per cent reduction in avoidable waste. 

Studies have shown that if average domestic refrigerator temperatures of 7°C were reduced to 4°C, food storage lives could be significantly extended and the savings in costs and emissions associated with reduced waste were greater than those associated with increased energy consumption at lower temperatures.

Coping with changing habits
Years ago, consumers would go out in the morning and buy all the fresh food they needed for that day from a local greengrocer or market. Today though life is more hectic, and weekly shopping trips are a much more common occurrence these days. This of course means that fresh food with a shelf life of at least a week, particularly fruit and vegetables, is important to the everyday household.

“The shelf life of fruit and vegetables starts from the moment they are cultivated and temperature control is crucial throughout the supply chain from this point,” says Alan Selby, Food and Industry Sales Engineer, GEA Refrigeration UK. “The higher the ambient temperature surrounding the commodity, the higher its rate of respiration; which is a sequence of chemical changes that results in fruit and vegetables consuming oxygen and giving off carbon dioxide, water and heat. Optimum temperatures vary between products and determines low rates of respiration therefore extending storage life, and in addition reduce the rate at which microorganisms such as mould and bacteria can grow.”

It’s not just high temperatures that bring about a decline in the quality of the fruit and vegetables though. “Certain fruits with stalks, for example, will freeze at higher temperatures than the body of the fruit, potentially resulting in loss of market value when restored to ambient conditions,” explains Selby. “Similarly, fruits originating from the tropics are easily affected by low temperatures and they commonly experience damage to tissue at temperatures well above their freezing temperatures if ambient conditions are not strictly maintained throughout the food chain.”

A major cause of produce deterioration can be transit, and depending on where the produce originates and where its destination is, this can be a lengthy period of time for fresh foods. Most fruit and vegetables contain between around 80% and 95% water by weight, some of which can be lost by transpiration – water loss from living tissue. 

“When you consider that some fruits and vegetables have a maximum storage, transit and shelf life of anything from 7 to 10 days, any artificial degrading of the quality of the fruit by poor temperature control could stop the product from even getting onto the shelves for the consumer to buy,” Selby points out. “It’s only diligent temperature and humidity control that will stop the premature wilting and shrivelling effect of water loss.”

Extending the shelf life
With today’s food and drink manufacturers and retailers becoming increasingly reliant on ‘just in time’ deliveries, companies are now concerned with finding ways to guarantee product quality and minimise environmental impacts.

“The freezing and up-tempering processes have the ability to extend shelf life and offer speed of response to be able to call stock off quickly when needed,” explains Kevin Hancock, Managing Director at Rick Bestwick, a coldstore and distribution operations specialist. “This helps them to meet commercial requirements, keep food in optimum condition from farm-to-fork, and substantially reduce food waste.”

All food deteriorates in quality over a period of time, and refrigeration or freezing can reduce the speed at which this occurs to preserve food and store it for longer periods, but just how much time can be added to shelf life using these processes?

“Chilling food at 0°C to 4°C can yield a shelf life of two to seven days, while deep chilling chilled food at -2°C to -4°C can extend it’s shelf life by up to four weeks,” says Hancock. “Lower temperatures will generally achieve longer storage and blast freezing products at -32°C to -40°C is particularly effective. This is a fast process which is flexible enough to freeze a range of products for extended periods of time and preserves the quality, safety and nutritional content of food at a level close to its initial values. It also ensures items retain their structure when thawed, even fruit and vegetables which can be more delicate, and helps to cut food waste.”

The second stage in the process is microwave up-tempering, which brings products in a frozen state up to a chilled temperature rapidly as required while maintaining the integrity of the food. This results in extended shelf life for raw materials and finished retail packs.

“Although the general public believes that once a product has been frozen and defrosted, it cannot be refrozen, this safely occurs in the cold chain,” Hancock points out. “It can also in fact enhance the taste and quality of items like chocolate, cheese, confectionery and bakery products, amongst others. The blast freezing / up-tempering process provides a flexible and efficient way to extend shelf life and fulfil just-in-time requirements. This enables manufacturers to feed production lines, as well as supply finished goods to retailers as required, while also cutting spoilage.”

Continuous refrigeration
As the importance of cooling and / or chilling products begins from the point of origin – regardless of whether the product is produced, picked or killed – and continues throughout, energy efficiency is a vital concern for companies. 

“Continual growth in the refrigerated food market and ongoing food safety challenges, paired with heavy consumer demands for higher quality, longer lasting and more environmentally friendly food products, means energy efficient refrigeration processes are a critical element of the supply chain process,” says David Allen, Managing Director at food processing specialist ACE Refrigeration. “Different products can be cooled, chilled and frozen at the processing stage but all refrigeration applications are geared to maintain the integrity of the products and prolong shelf life.”

Some applications are better suited to a particular food product, such as for those working with fish, seafood or in the meat industry who may find ice generators to be an effective application. Ice is made by the tonne in thin shards, which are then used to pack product, which preserves their quality straight away. These differ in size and specification, depending on the manufacturer, with capacity varying from one tonne of ice to more than 20 tonnes of ice every 24 hours.

On the other hand, there are technologies that can work for any sector of the food and drink industry. “Chilled production facilities, cold rooms and freezer rooms, frozen food rooms as well as blast chillers and blast freezers all play their part in locking in the freshness regardless of whether you are working with fish or seafood, meat or poultry or fruit and vegetables and dairy,” says Allen. “Production areas which are designed to complement your flow processes and temperature controlled holding and loading bays are also essential if you want to maintain quality and integrity at all times.”

Time and temperature are both vital for controlling and monitoring food to ensure that there is no spoilage or deterioration. One way to ensure temperature control is to use monitoring and management systems, such as remote data logging or installing control probes into the refrigeration design of any food production plant, which gives the processor the confidence they need to ensure the total and complete integrity of their products at all times.

“Temperature monitoring systems should offer full traceability, as with most systems the data manager continually monitors and logs the temperature, and all data recorded is stored historically within the data manager for full verification,” adds Allen. “Temperature recordings are logged at set intervals and can be viewed as a graph or in a table. Usually, the data can also be retrieved on a PC via a browser-based system or through a USB stick.”

Allen also points out that temperature monitoring systems can help with HACCP (Hazard Analysis and Critical Control Point) accreditation, BRC (British Retail Consortium) compliance and contributes to conforming to USDA FSIS (Food Safety and Inspection Service) standards. 

“As well as refrigerated transport, most logistics companies have also expanded on their cold storage warehousing in recent years from cold rooms to freezer rooms, frozen food rooms and many now also include blast freezers on site too,” Allen explains. “So continuous refrigeration is no longer simply optional, and throughout the entire supply chain it has become an essential factor. The focus moving forward has to now be on how the supply chain improves the energy efficiency of its refrigeration in line with retailers and consumers own environmental standards. Pushing for more energy efficient refrigeration which reduces energy use and wastage can not only help save the planet, but it can reduce operating costs too.”

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