LF-NMR动态分析4种干燥方式下鱿鱼干的复水特性

LF-NMR Dynamic Analysis of Rehydration Characteristics on Dried Squid by Four Drying Methods

以鱿鱼为研究对象,采用自然晒干、热风干燥、热泵干燥、真空冷冻干燥4种干燥技术干制鱿鱼,结合鱿鱼干的肌纤维微观结构和复水率,通过低场核磁共振(LF-NMR)动态分析鱿鱼干复水过程的水分迁移和分布,探讨干燥方式对鱿鱼干复水的影响。结果表明,4种干燥方式中,真空冷冻干燥的鱿鱼干水分含量最低,氧化程度也最低(比其它3种处理的低1.5~6.7倍)。电镜扫描图显示鱿鱼干肌纤维内部有大量疏松多孔的蜂窝状结构,且真空冷冻干燥复水最快。复水过程,部分结合水向不易流动水迁移,不易流动水含量明显增加,且占比90%以上,自由水含量也有所提升。LF-NMR分析也表明真空冷冻干燥的鱿鱼干复水效果最好,复水后可截留更多的自由水。热泵干燥的鱿鱼干复水效果与自然干燥接近,热风干燥的复水率最差。干燥方式对干制品复水效果影响明显,真空冷冻干燥和热泵干燥技术有利于水产品干制。

Squid was dried by sunshine drying,heat air drying,heat pump drying and vacuum freeze drying,respectively.Combined with the microstructure and the rehydration rate,the moisture migration and distribution of the dried squid were analyzed by low field nuclear magnetic resonance(LF-NMR)during dry rehydration,and the effects of drying methods on rehydration of dried squid were discussed.The results showed that,among the dried squid treated with four drying methods,the dried squid by vacuum freeze drying had the lowest moisture content and the lowest oxidation degree(1.5~6.7 times lower than those other three treatments).Its scanning electron micrograph showed lots of porous honeycomb structure.Moreover,it owned the fastest rehydration rate.In the process of rehydration,part of the bound water migrated to the immobilized water.The immobilized water increased significantly,accounting for more than 90%,and the content of free water also increased.LF-NMR analysis also showed that dried squid treated with vacuum freeze drying had the best rehydration effect,as well as more free water intercepted.The rehydration effect of the dried squid treated by heat pump drying was close to that of sunshine drying,while that of heat air drying was the worst.There was significant effect on the rehydration of dried products with different drying methods.Vacuum freeze drying technology and heat pump drying technology were conducive to the drying of aquatic products.