Freezing Technology

1.3.2 Changes in eating quality

Changes in the eating quality of chilled fish during storage can be assessed by daily organoleptic examination of the cooked flesh.

Phase 1: The fish is very fresh and has a sweet, sea weedy and delicate taste. The taste can be   very slightly metallic. In cod, haddock, whiting and flounder, the sweet taste is maximized 2-3 days after catching.

Phase 2:  There is a loss of the characteristic odour and taste. The flesh becomes neutral but has no off-flavours. The texture is still pleasant.

Phase 3:  There is sign of spoilage and a range of volatile, unpleasant-smelling substances are produced depending on the fish species and type of spoilage (aerobic, anaerobic). One of the volatile compounds may be trimethylamine (TMA) derived from the bacterial reduction of trimethylaminoxide (TMAO). TMA has a very characteristic “fishy” smell. At the beginning of the phase the off-flavour may be slightly sour, fruity and slightly bitter, especially in fatty fish. During the latter stages sickly sweet, cabbage-like, ammoniacal, sulphurous and rancid smells develop. The texture becomes either soft or watery of tough and dry.

Phase 4: The fish can be characterized as spoiled and putrid.