冻融循环对南极磷虾虾肉糜滋味成分的影响

以南极磷虾虾(Euphausia superba)肉糜为原料，通过测定南极磷虾虾肉糜在反复冷冻和解冻过程中ATP及其关联产物、游离氨基酸等的变化，分析冻融循环对虾肉糜滋味成分的影响。结果显示，随着冻融循环次数的增加，南极磷虾虾肉糜的ATP及其关联产物降解加剧，呈鲜味的核苷酸含量逐渐减少，呈苦味的核苷酸含量逐渐增加。1次冻融对应的鲜味苦味比为3.32；2次及以上的冻融循环会造成鲜苦比的显著降低(P<0.05)，同时K值迅速增大，表明鲜度发生大幅下降；3次冻融循环后，K值显著增大(P<0.05)；4次冻融对应的K值为(86.88±3.58)%，南极磷虾虾肉糜已不新鲜。冻融循环次数的增加导致游离氨基酸总含量增加，鲜味氨基酸和甜味氨基酸比例逐渐减小，苦味氨基酸的比例逐渐增大，导致虾肉糜的滋味进一步劣化。研究表明，冻融循环次数控制在2次以内，可较好地保持南极磷虾虾肉糜的滋味。

Effects of Freezing and Thawing Cycles on Taste Components of Minced Antarctic Krill

Antarctic krill (Euphausia superba) stocks produce large biomasses and contain useful, high-quality proteins. Krill protein has been suggested to be a good source of protein for humans, due to its well-balanced amino acid composition and high biological value. In this study, minced Antarctic krill was studied. The effects of freezing and thawing cycles on changes in the content of adenosine triphosphate (ATP) and related compounds and free amino acids in minced Antarctic krill were investigated. Changes in taste components during freezing and thawing cycles were also analyzed. Results showed that with increasing freezing and thawing cycle times, the degradation of ATP and related compounds increased rapidly, the content of umami nucleotides gradually decreased, and the content of bitter nucleotides gradually increased. The flavor/bitter ratio was 3.32 at the first freeze-thaw cycle, and then after two freeze-thaw cycles the flavor/bitter ratio decreased significantly (P < 0.05). At the same time, the K value increased rapidly, which indicated that the freshness had dropped sharply. After a third freeze-thaw cycle, the K value increased significantly (P < 0.05). The K value was (86.88±3.58)% at the fourth freeze-thaw cycle, meaning that the minced Antarctic krill was no longer fresh. After the fourth freeze-thaw cycle, the K value did not significantly change. The total content of free amino acids increased as the number of freeze-thaw cycles increased. However, the proportional content of umami amino acids and sweet amino acids decreased, while that of bitter amino acids gradually increased. The total taste activity value of bitter amino acids was the highest during the freeze-thaw cycles, which indicated that bitter amino acids made the greatest contribution to the resultant taste. This led to the further deterioration of the taste components of minced Antarctic krill. Therefore, it was concluded that the number of freeze-thaw cycles should be controlled to be within two to better preserve the flavor of minced Antarctic krill.