低场核磁结合理化指标分析对虾冻藏期间的表观品质变化

The effect of physical and chemical parameters at low field NMR of white shrimps Litopenaeus vannamei on frozen shrimp during its storage

研究了预煮(沸水中煮制5 min)处理后的南美白对虾在冻藏期间的表观品质(色差和质构)、水分含量及LF-NMR弛豫时间T_2的变化,并对各指标间的相关性进行了分析。结果表明,随着冻藏时间的增加,熟制南美白对虾水分含量和持水力持续降低,亮度(L~*)和红黄值(a~*、b~*)逐渐降低,硬度增加,而弹性降低;自由水的比例(P22)逐渐增高,而含量最高的中间水比例(P21)有降低的趋势,说明冻藏对虾肌肉水分发生了部分迁移。对各指标之间的相关性分析结果说明,对虾硬度指标与游离水相对比例(P22)呈正比,弹性指标与中间水比例(P21)呈正比,水分含量与硬度指标和色差值(L~*、a~*、b~*)呈反比。实验结果说明,在冻藏期间,熟制南美白对虾水分含量和分布的改变导致了其表观品质(色差和质构)的降低。

Apparent quality （texture and color） , moisture content, LF-NMR T2 relaxation time after cooked in boiling water for 5 rain, and the correlation coefficients among measured variables were investigated. The results showed that moisture content and water holding capacity increased with the increasing of storage time, accompanied L , a , and b decreased, hardness increased, and elasticity decreased; P22 increased gradually, while the highest percentage of water P21 somehow reduced which indicating that water in shrimp was migrated during frozen storage. The correlation coefficients result showed that hardness was directly positively correlated with P22, texture of elasicity was positively correlated with intermediate water P21, moisture content was negatively correlated with hardness and L , a, and b value. The result revealed that water content and distribution change caused the decrease of the quality （texture and color） of pre-cooked white shrimps Litopenaeus vannamei during frozen storage.