| Summary: | 碩士 === 國立臺灣海洋大學 === 食品科學系 === 96 === This study was carried out to investigate the changes of mortality, quality and chemical compositions of hard clam with and without vacuum package during storage at 7℃. The mortality of hard clam (June sample) with vacuum package was 5~23% after 21 days storage, but that without vacuum package was 18~67%. The mortality of November sample was lower than June sample after 28 days storage. The pH value, trimethylamine (TMA), volatile basic nitrogen (VBN) and urea increased, but glycogen decreased gradually during storage of hard clam with and without vacuum package. The change in the latter was higher than that in the former. The predominant organic acid of hard clam was succinic acid. The contents of succinic acid and propionic acid were increased during storage, and the product with vacuum package showed more significant change. The composition and contents of ATP-related compounds showed no marked difference between two packages. AMP was the major compound. ATP, AMP and hypoxanthine increased slightly during storage. However, the adenylate energe charge (AEC) of hard clam without vacuum package was higher than that of vacuum package. The predominant free amino acid (FAA) of hard clam tissue and liquid was taurine, fallowed by glutamic acid, alanine and arginine. The total FAA of hard clam tissue increased gradually during storage. The increase of alanine was more significant in that of vacuum package. Those in liquid remained unchanged. Aerobic plate count (APC) of hard clam tissue and liquid was increased gradually during storage, and that without vacuum was increased more quickly. After 21 days storage, APC was about 2 log CFU/g higher than that without vacuum. Sensory evaluation score decreased slightly during storage, but no significant difference between two packages. The results from this study revealed that mortality, APC, TMA, VBN, urea, glycogen and hypoxanthine could be as quality indicators of hard clam during storage. According to these indicators and sensory evaluation, the shelf-life of June sample without vacuum package was 7 days, and that with vacuum package was 14 days. November sample without vacuum package was 14 days, and that with vacuum package was 21 days.
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