Superchilling

A FAIRLY new approach in the storage of fish is superchilling, that is, storing fish below 0 deg C, but not to the point that it freezes. Research by Norconserv, the Norwegian Institute of Fish Processing & Preservation Technology, found that salmon stored at -2 deg C had a shelflife of an incredible 31 days compared to 2 days at 20 deg C. More notably, this 31-day shelflife was 21 days longer than that of fish stored at 4 deg C, a not unusual temperature for processors to maintain.The benefits of superchilling are fairly obvious, but maintaining a temperature of -2 deg C throughout the coldchain is difficult - 'It is difficult enough to keep it at 4 deg C!' says Morten Sivertsvik, Norconserv's research manager. So the Norwegian researchers have been looking at superchilling as a pre-treatment to MAP at 4 deg C. This requires flash-freezing the product at -38 deg C, forming a frozen crust. Just one hour after the process, the fish is claimed to have the same appearance as a normal chilled product, and a core temperature of -1.5 deg C (as opposed to 5 or 6 deg C for normal chilled product). In fact, in a recent trial for French supermarket giant Carrefour, the packaged product was found to still have a core temperature of -1.5 deg C after six days.