For most people the Ice Age ended thousands of years ago, but for one industry it has continued into the 21st century. Tonnes of ice are used on an annual basis to chill fish and keep it fresh during transport and storage until it reaches the consumer. In 2010 Norway exported 922,000 tonnes of salmon – the vast majority of this packed fresh in polystyrene fish boxes with 5–6 kg of ice per approx. 22 kg of fish. This is equivalent to 7500 articulated lorries full of ice (around 230 million litres of water)!
Should we transport ice cubes?
The ice is there for obvious reasons. It reduces the temperature in the fish to 0 °C and then maintains this temperature. It generally takes 24 hours to chill the fish and around one-third of the ice melts during this process. In an unbroken and good cooling chain, which one should be able to demand of transporters in 2013, there will be minimal melting of the remainder of the ice. In other words, the customer receives 3–4 kg of ice per box of fish, which indicates that the transport and distribution has been in accordance with the regulatory requirements.
Since the 1990s the food research institute Nofima has been working on alternative methods for transportation of fish, in which ice is not used and the chilling and packaging of the fish has been studied. The best method is to store the cold in the fish by reducing the temperature down to the equalisation temperature of the fish, typically -1 to -2 °C. This method is called super chilling or deep chilling. Super chilling is the easiest way of increasing the primary quality period of the fish and may be combined with packaging in a protected environment of carbon dioxide and nitrogen, during both distribution and in consumer packaging. This enables high quality to be maintained for several weeks in a cooling chain that is in accordance with the regulations (0 to +2 °C).
Financial and environmental gains
There are many solutions for super chilling fish, including the use of air or cryogenic mediums, contact and air blast freezers, super-chilled brine and dry ice. The most rapid we have tried is air impingement, in which a processing time of up to a minute provides good results and an equalisation temperature in salmon of around -1 °C after 45–60 minutes. This combined with a simpler distribution packaging, e.g. corrugated fibreboard (which costs half the price of traditional fish boxes and which may be used when melt water is no longer a problem), means that investing in super chilling technology can be worth its while within a short space of time. This solution will result in reduced transport costs, more fish per box when ice is no longer there, more boxes per pallet and better pallet utilization – and, as an added bonus, a more environmentally-friendly solution.