Deterioration of Antarctic Krill Muscle during Freeze Storage

The effects of freezing on the heat-induced gelation, Ca²⁺-ATPase activity and myofibril structure of Antarctic krill muscle were investigated. Muscle from freshly caught krill was immediately stored at-20°C in the presence (to prevent freezing) (glycerol krill) and absence (frozen krill) of glycerol. Several protease inhibitors, monosodium glutamate and Ca²⁺ were individually added to glycerol krill to inhibit endogenous proteolysis. The examinations described above were carried out after about 3-month storage at-20°C. In glycerol krill (unfrozen state), viscoelastic parameters of the heat-induced gels and Ca²⁺-ATPase activities of all the krill samples were similar to those of “surimi” (raw fish meat paste) of Alaska pollack which gave gel of good quality, although the micro structure (Z-lines) of myofibrils was different among the glycerol krill samples. In frozen krill, however, the parameters of the gel were different from those of “surimi”, the ATPase activity was completely lost and disruption of the myofibril structure occurred. Refreezing (-20°C) of glycerol krill after removal of glycerol resulted in a marked decrease in the gelation ability. These results suggest that freezing of krill muscle causes deterioration of the gelation ability.