基于MP-KG凝胶体系研究微观结构影响质构特性的调控机制

Insight into the Regulatory Mechanism of the Microstructure of Myofibrillar Protein-Konjac Glucomannan Gel Systems on Their Textural Properties

以肌原纤维蛋白-魔芋胶(myofibrillar protein-konjac glucomannan,MP-KG)为模拟体系,利用质构仪、石蜡切片和扫描电镜分别测定复合凝胶质构特性、空间分布和蛋白三维凝胶网络结构,进而阐释复合凝胶微观结构对质构特性的调控机制,为KG在低脂肉制品中的应用提供一定的理论基础。质构特性结果显示:随着KG添加量增高,复合凝胶断裂形变时应力变化呈现抛物线形,说明KG对复合凝胶应力的改善具有添加量极限。复合凝胶断裂形变时应变的变化趋势和应力相似,但是两者的添加量极限不同。低场核磁结果显示:在添加1%KG时不易流动水的弛豫时间最低且其相对百分比最高,分别为274 ms和92.79%,说明KG能够促进蛋白之间的交联,进而提高蛋白基质对水分子的束缚。石蜡切片显示随着KG添加量的提高,MP-KG凝胶体系的空间分布从填充结构转变成互穿结构。扫描电镜显示:对照组的MP凝胶网络结构中布满了相互交错的水沟壑,这些沟壑的存在导致MP凝胶网络结构比较疏松。添加少量KG能够减少蛋白三维网络结构中相互交错的水沟壑,MP凝胶网络结构更加致密均一。添加过量的KG会形成KG连续相,反而破坏蛋白网络结构的整体性。因此,KG以水相稳定为主要作用时,其能够改善复合凝胶的质构;当KG以互穿结构形式存在时,其反而会劣化复合凝胶的质构。

In the present study,model gel systems of myofibrillar protein(MP)and various concentrations of konjac glucomannan(KG)were evaluated for textural properties,spatial distribution and MP gel networks using a texture analyzer,the paraffin section method and scanning electronic microscopy(SEM),respectively.The regulatory mechanism of the microstructure of MP-KG gel systems on their textural properties was elucidated in order to provide a theoretical basis for the application of KG as a fat replacer in low-fat sausages.The textural analysis results showed that the fracture stress and fracture strain exhibited a parabolic trend with KG concentration,but they reached their maximum at different KG concentrations.The results of low-field nuclear magnetic resonance(NMR)showed that the shortest relaxation time(274 ms)and highest percentage(92.79%)were observed for immobile water in composite gels with 1%KG,suggesting that KG could promote cross-linking of MP and consequently enhance MP binding to water molecules.Paraffin section showed that the spatial distribution of MP-KG gels was transformed from the“trapped structure”to the“penetrated structure”with increasing KG concentration.The SEM micrographs showed that the MP gel networks in the control group were filled with crisscrossed moisture channels and consequently were loose.Addition of a small amount of KG reduced the crosslinked moisture channels,and promoted the formation of compact and well-aggregated MP gel networks.On the other hand,excess addition of KG resulted in the formation of a continuous phase,damaging the MP gel networks.In conclusion,KG could improve the gel strength through stabilizing the water phase and deteriorate the texture of composite gels through the penetrated structure.