Regarding the quality of frozen spotted mackerel
Scomber australasius, it was examined how the freshness of the fish before freezing temperature i.e. the freezing speed influenced on the state of ice crystals formed in the muscle tissue of fish when frozen. And the amount of the drip oozes out when the frozen-stored fish was thawed. First of all, in order to prepare the fish samples differing in freshness, the fish just caught were kept at a temperature of 4
℃ for different lengths of time: 3, 27, 51 and 123 hours. The freshness of the fish was assessed by the K value. These fish samples (fillets) with different freshness were frozen at three different temperatures: -20
℃ -30
℃ and -60
℃, and frozen-stored at the respective temperature for one month. As to the size of ice crystals formed in the muscle tissue, the lower the freshness, larger crystals were observed, and the lower the freezing temperature, the smaller crystals. Between the size of ice crystal and the production of the drip, a positive correlation was seen. In case of fish with low freshness, relatively large sized ice crystals were observed and a relatively large amount of drip was measured, although the fish were frozen at lower temperature such as -60
℃, namely, these factors indicate that the quality of the fish was less desirable.
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