加水量对面筋蛋白水分分布及结构的影响

Effect of Water Addition on Hydration and Structure of Gluten Protein

利用核磁共振仪(NMR)、扫描电子显微镜(SEM)、傅里叶变换红外(FITR)、差示扫描量热仪(DSC)和旋转流变仪(DHR)测定不同加水量下面筋蛋白的水分分布、微观结构、蛋白二级结构、热力学特性和流变学特性。结果表明,随加水量增大,面筋蛋白中结合水相对含量显著下降5.15个百分点,自由水相对含量显著升高8.21个百分点,弱结合水相对含量先增大后降低;面筋蛋白网络孔洞更加密集,孔径更加细小,但当加水量大于160%后,网络强度减弱;面筋蛋白二级结构表明,当加水量小于等于130%,随加水量增大,二级结构中β-转角及无规则卷曲相对含量显著下降,α-螺旋、β-折叠相对含量显著增大,当加水量大于130%,面筋蛋白二级结构变化趋势减缓,且无明显变化规律;面筋蛋白热变性峰值温度呈现先升高后降低的趋势,当加水量为150%时,取得最大值82.4℃,表明其热力学稳定性随水分增加而得到提升;面筋蛋白储能模量 G ′及损耗模量 G ″均呈下降趋势,加水量大于130%时下降趋势减缓,且加水量150%时其弹性高于140%加水量。由此表明,150%是面筋蛋白的较优加水量。

Effect of water addition ongluten protein was investigated by using nuclear magnetic resonance( NMR),scanning electron microscopy( SEM),Fourier transform infrared spectroscopy( FITR),differential scanning calorimeter( DSC) and rotational rheometer( DHR). The results showed that the amount of water had a significant effect on the hydration,structure and functional properties of gluten protein. With the increase of water addition,the bound water content of gluten protein was decreased significantly from 22. 42% to 17. 27%,the free water content was increased significantly from 0. 04% to8. 25%,and the weakly bound water content was increased first and then decreased,and the water was preferentially converted into bound water and weakly bound water. The gluten protein network had more dense pores and smaller pore size,but when the water was added more than 160%,the strength of the network was weakened. The secondary structure of gluten protein showed that when the water addition amount was not more than 130%,the β-turn angle and the random curl was decreased significantly with the increase of water addition,and the α-helix and β-folding were increased remarkably. When the water addition amount was more than 130%,the secondary structure change of gluten protein was slowed down,and there was no obvious changing rule. The heat denaturation temperature of the protein was firstly increased and then decreased. When the water addition amount reached 150%,the maximum value was 82. 4℃,indicating that the thermodynamic stability was increased with the increase of water.The storage modulus G’ and the loss modulus G″ of gluten protein all showed a downward trend. After the water addition was more than 130%,the downward trend was slowed down. When the water content was150%,the elasticity was higher than 140%. The above results indicated that 150% may be the better water content of gluten protein,which also laid a foundation for further revealing the mechanism of water addition to wheat dough.