Changes in taste characteristics of shellfish by cooking and during storage - Why raw cockle is not eaten ? -

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Physicochemical changes of Japanese cockle foot parts occurring by cooking and during cold storage at 4℃ for 10 days were examined. Raw samples lost their weight by 27 % during cooking process at 85℃ for 15 s. Both raw and cooked samples lost their weight at the same extent of 22-23 % during the cold storage for 10 days. The levels of ATP and related compounds as well as those of free amino acids were higher in raw than cooked samples, although the former sample were found by the sensory evaluation to have stronger fishy odor. Raw samples started decreasing ATP content after 5 days of the cold storage, showing the K' values of 18 and 42 % after 5 and 7 days, respectively. The L value in Hunter scale color evaluation increased during the cold storage of raw samples, revealing the gradual disappearance of its original purple grey color. Meanwhile, the L value of cooked samples remained constant during the cold storage. The tensile strength of cooked samples was significantly higher than those of both raw samples before and after the cold storage, indicating increased toughness by cooking.The effects of humidity stabilizing sheet containing glycerol, pulp, and an absorbing polymer on raw cockle foot during cold storage were also examined. The raw samples wrapped in the humidity stabilizing sheet lost their weight by 32% during storage at 4℃ for 10 days because of dehydration. However the L value of wrapped samples remained constant during storage. Changes in the levels of ATP and related compounds and in the freshness indices indicate that samples wrapped in the sheet were superior to those without wrapping. Samples wrapped in the sheet remained their fresh appearance for a longer time than those without wrapping by the sensory evaluation.