冻融循环过程中冷冻罗非鱼片呈味物质的变化

为探究冷冻水产品冷链流通过程中的品质变化，以罗非鱼为研究对象进行7 次冻融循环。分析8 组样品基本营养成分差异，通过电子舌确定其整体滋味轮廓差异，并分析游离氨基酸、呈味核苷酸、呈味无机离子的含量，并结合人工感官评分分析呈味物质的变化。结果显示，罗非鱼片冻融循环过程中整体滋味轮廓可有效区分，随着冻融次数的增加，鲜甜味氨基酸和核苷酸含量下降，苦味氨基酸和核苷酸含量上升，与感官评分的趋势一致，游离氨基酸总量呈下降趋势，在4 次冻融后下降显著（P＜0.05），对鲜味有辅助作用的Na＋含量显著降低。综上，随冻融次数的增加，罗非鱼片整体滋味逐渐变差，该结论可为冷链流通过程中呈味物质变化提供参考并为后续品质调控提供理论依据。

Changes of Taste Substances in Frozen Tilapia(Oreochromis niloticus) Fillets during Freeze-thaw Cycles

In order to explore the quality changes of frozen aquatic products during distribution in the cold chain, tilapia (Oreochromis niloticus) fillets were repeatedly frozen and thawed for up to seven cycles. The differences in the basic nutrients in eight samples (i.e., one frozen-thaw sample and seven repeatedly frozen-thawed samples) were evaluated. Then, the differences in overall taste profile were determined by electronic tongue, and the contents of free amino acids, flavor nucleotides and taste inorganic ions were also measured. In addition, the changes of flavor substances were analyzed by sensory evaluation. The results showed that the overall flavor profile of tilapia fillets could be effectively distinguished during freeze-thaw cycles. With the increase in the number of freeze-thaw cycles, the contents of umami and sweet amino acids and nucleotides decreased, while the contents of bitter amino acids and nucleotides increased, which was consistent with the trend of sensory scores. The total content of free amino acids showed a decreasing trend, and decreased significantly after the fourth freeze-thaw cycle (P < 0.05). The content of Na+, which had an adjunctive effect on umami taste, was also significantly decreased. The above results showed that the overall taste profile was gradually deteriorated as the number of freeze-thaw cycles increased. The results of this study may provide a theoretical basis for further research on quality control of frozen aquatic products.