| Summary: | 碩士 === 國立臺灣海洋大學 === 食品科學系 === 105 === Glazing, as a quality protecting tool, has a long history and a common practice in frozen seafood processing. The aim of this study is to investigate “can this procedure re-define and extend shelf-life for seafood food which has limited shelf-life, e.g. within 3 months?” Criteria for glazing practice include surface/weight ratio, dipping time, and dipping cycle. Three species and processing types, salmon fillet, halibut fillet, and capelin whole fish, varied mainly by their lipid contents, were selected and quality index, TRARS, TVB-N, and drip-loss were used to evaluate their quality changes during normal, -25℃, and accelerated storage test, at -15℃ and -5℃ up to 12 weeks.
Results indicated, the highest glazing pick-up rate can be achieved at smaller surface area, thinner, and longer dipping time. However, there are no significant difference in pick-up rate between second and third glazing cycles. Hence, a reference glazing table was developed indicating the suitable practice to achieve the target glazing pick-up ratio. Glazing pick-up ratio were set at 0% (control),15% and 30% for fish samples. During 12 weeks’ storage period, gradually but significantly increased TBARS and TVB-N were observed for all treatments, while there was no significant difference among drip-loss changes. Arrhenius equation was used to calculate the activation energy (Ea) for TBARS and TVB-N of the tested samples which were then used to predict the expected shelf-life of these short shelf-life products. Results suggested that TBARS is a better quality index for high-fat fish, such as salmon in this study, while TVB-N is a more suitable index for low-fat or smaller whole fish.
Results showed that smaller area-weight ratio, the more glaze uptake. 15% glazed is adequate and effective to guarantee the final quality of higher fat fish samples (>20%) during frozen storage. Excessive glazing (>15%) will have the adverse effect on the quality changes due to longer time exposure to higher environmental temperature.
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