γ-聚谷氨酸对面筋蛋白冻藏稳定性的影响

Effect of Poly-γ-glutamicacid on Freezing Stability of Gluten Protein

为提高面筋蛋白的冻藏稳定性,采用核磁共振仪、傅里叶红外光谱仪、差示扫描量热仪、热重分析仪、动态流变仪和扫描电子显微镜测定冻藏条件下添加γ-聚谷氨酸的面筋蛋白体系中水分分布、二级结构、热力学特性、流变学特性及微观结构。结果表明,添加1%γ-PGA使冻藏期间面筋蛋白中弱结合水向自由水的转化量显著减少,抑制了面筋蛋白二级结构中α-螺旋下降和无规则卷曲增大,提升了面筋蛋白的热力学稳定性,冻藏49 d时相比对照组面筋蛋白变性温度提高4℃,失重率提升较小;随冻藏时间延长,添加1%γ-PGA的面筋蛋白储能模量及损耗模量的下降不明显,且面筋蛋白三维网络结构较均匀,孔径较小,连续性较好。γ-PGA能有效减弱冻藏对面筋网络的破坏,提升面筋蛋白的冻藏稳定性。

Nuclear magnetic resonance instruments （NMR）, Fourier transform infrared spectrometer （FITR）, differential scanning calorimetry （DSC）, dynamic rheometers （DHR） and scanning electron microscopy （SEM） were used to study the effect of poly γ-glutamicacid （γ-PGA） addition on the stability of gluten protein during frozen storage. Gluten protein was measured on days 0, 7, 21, 35 and 49, respectively. The thermal hysteresis activity of γ-PGA was measured by DSC. The results showed that γ-PGA had good antifreeze activity. The obtained results showed that supplementation with 1% γ-PGA lowered the conversion of immobilized water to free water in gluten during frozen storage. γ-PGA inhibited the decrease of α helix and the increase of random coil during frozen storage, and the addition of γ-PGA significantly increased the α-helix content. The results of DSC and TGA showed that the addition of γ-PGA improved the thermodynamic stability of gluten protein. The denaturation temperature of gluten protein increased by 4℃, and the increase in weight loss caused by frozen storage was also smller than that of the control group. With the extension of frozen storage time, the decrease of G′ and G″ of gluten protein added with γ-PGA was lower than that of control group. The electron microscope results showed that the gluten network structure with γ-PGA added was more uniform, smaller in pore size and better in continuity after 49d of frozen storage. The above results indicate that γ-PGA can effectively inhibit the growth and recrystallization of ice crystals, weaken the destruction of gluten network by frozen storage, and improve the frozen storage stability of gluten.