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Keeping Fish Fresh

In the fall of 1991 a swordfish boat called the Andrea Gail set sail from Gloucester, Massachusetts, on the US east coast. Ignoring warnings of a massive storm, the crew headed out into the North Atlantic for one last catch before the season ended.

And, sadly, it really was their last catch. When the storm hit, the Andrea Gail was more than 900 kilometers out to sea and, potentially, away from danger – the boat just needed to stay put until the storm abated. But then the ice machine broke. In a desperate bid to save the catch on which their livelihood depended the crew decided to risk heading home into the storm and paid the ultimate price.

The story, immortalized in the film The Perfect Storm, is a powerful example of the dangers that fishermen face. It also shows how much the modern fishing industry relies on refrigeration.

Professional chefs will argue that fish should, ideally, be served within three days of being caught. To qualify for Japanese sashimi quality – fit to eat raw – it has to be on the plate within 24 hours. Experts believe that after a fish is caught, it loses a day of its shelf life for every hour it is not stored on ice.

Refrigeration is paramount

Given the distances of the sea voyages undertaken by large fishing vessels and then the sheer logistics involved in transporting their huge catches from the port for distribution to shops around the world, the need for refrigeration is paramount.

Consumer demand for fish is growing worldwide. Without the ability to chill or freeze fish it would be impossible to meet this demand, particularly for more exotic deep sea species such as swordfish, and maintain freshness from ship to shop.

Commercial fishing fleets require powerful, flexible and reliable refrigeration systems. Many vessels are like floating factories where fish are gutted, filleted, processed and frozen almost as soon as they are caught. Such ships can be at sea for several weeks at a time.

Nowadays refrigeration must comply with strict regulations aimed at countering the effects of global warming. Many countries have banned ozone-depleting manmade refrigerants in new installations in favor of natural refrigerants like ammonia and carbon dioxide.

GEA Refrigeration Technologies, a market leader in refrigeration for the shipping industry, is currently installing state-of-the-art, environmentally-friendly cooling and freezing installations on board the trawler Willem van der Zwan. The flagship of Dutch ship owner W. van der Zwan & Zonen, the trawler was almost destroyed by fire in January 2007 while undergoing a major refit. Now it is being rebuilt and is expected to be seaworthy in early 2009.

“This is a huge vessel and the on-board refrigeration system we are building will be the largest in the world,” says Simon Kortleven, Sales Engineer for GEA Grenco Marine Refrigeration. “It will have the capacity to freeze up to 500 tons of fish a day.”

Refrigeration pioneers

He adds that the order, the largest in GEA Grenco Marine’s history, will provide a system that is 30 per cent more energy efficient than traditional systems, saving on power.

The company has boosted its green credentials further by being the first to develop an absorption refrigeration system suitable for use on board ships. This success is the culmination of ten years’ work by a team of GEA engineers.

Unlike traditional refrigeration units, which are powered by electricity, absorption refrigeration works on surplus heat from a diesel engine. But, until now, the technique has been confined to land-based installations.

Øyvind Gausvik, Sales Manager Marine at GEA Grenco, explains: “The situation is very different on board a ship, particularly because of the movement and vibration. Also there are corrosion issues caused by the sea air.”

The GEA team has spent ten years finding the best ways to overcome the problems. Stig Remøy, owner of the Norwegian shipping company Olympic Prawn and a well-known innovator in the industry, will be the first to use the absorption refrigeration principle for his new ship which is being built at Havyard Solstrand in Norway.

“The ship will be sailing in the far north and will have to comply with the Norwegian government’s strict regulations,” says Gausvik. “Using absorption refrigeration will improve the ship’s green profile because, as well as saving energy, it will reduce annual carbon dioxide emissions by more than 500 tons.”

By running on surplus heat the absorption system will use 80 per cent less electricity, saving more than 200,000 liters of fuel a year. The system is easy to operate, with few moving parts. This is particularly beneficial as the industry is finding it increasingly difficult to find qualified engineers for on-board operations.

 

Scale of fishing

According to the Food and Agriculture Organization commercial fishing vessels caught 93.2 million tons in 2005, while fish farms accounted for a further 48 million tons. Unfortunately, large-scale commercial fishing is taking its toll.

A major international study, published in Science magazine in 2006, showed that a third of global fish populations had reduced dramatically and, if this trend continues, fish stocks could collapse within 50 years. Some fishing methods can also harm whales, dolphins, turtles and birds.

Fish farming, which involves raising fish in controlled conditions, is increasingly being seen as an alternative solution to feeding the demand for fish.