To preserve and extend the shelf-life of seafood such as fish and its products, frozen storage is crucial and quite commonly used. This is because microorganisms do not grow in foods when the temperature is low enough (Bogh-Sorensen, 2000) and the low temperatures also help to reduce enzymatic reactions (Zaritzky, 2000). However, during frozen storage, there will be physicochemical changes that can adversely affect the quality of food products. Ice crystals, which are formed due to freezing, can puncture the cell membrane, causing the release of otherwise intracellular enzymes (Zaritzky, 2000).

 

Besides freezing, thawing also plays a part in membrane disintegration and affecting sensory attributes of the food products. During transportation, storage and consumption, temperature fluctuation will cause the frozen food products to undergo repeated freeze-thaw cycles. Repeated freezing-thawing results in repeated forming and melting of ice crystals which can be detrimental to the texture and physicochemical qualities of products. The presence and activities of intracellular – mitochondrial and lysosomal – enzymes such as α-glucosidase can be used as indicators of membrane disintegration.