pH修饰豌豆蛋白调控肉蛋白/PUFA/多酚复合物中蛋白氧化稳定性和凝胶强化的机理研究

Comminuted meats are emulsion-gel type products widely consumed in the modern society. However, this type of products often suffers from loss of water and oil-binding capacity as well as decreases in springiness due to protein oxidation. Pea protein isolate (PPI) is a common functional ingredient used in processed muscle foods. Previous studies have shown that pH-shifting treatments (exposures to extreme pH followed by neutralization) could induce unfolding, namely, exposures of protein internal hydrophobic residues and sulfhydryl group, thereby markedly enhancing the emulsifying properties, gelling capacity, and antioxidant activity. The objective of this proposed research is to explore the efficacy of pH-shifting processed PPI(dephenolic/nondephenolic compound) itself, or PPI-coated high PUFA emulsions, in the inhibition of protein and lipid oxidation in radical-stressed muscle protein (MP) gelling systems, and investigate the microstructure and structure-reinforcement in the MP composite gels containing pH-shifting treated PPI and its emulsions. The mechanism of gel formation and the regulation of protein oxidation by pH-treated PPI will be elucidated through the analysis of interactive chemical forces and rhelology of the complex gelling systems. The outcome of the research will likely demonstrate that extreme pH-shifting treatments of PPI are effective means to promote the gelation of MP-PPI composites under the meat processing condition where oxidation is normally inevitable. It is hoped that the original findings will be valuable for new processing technology developments aimed at both broadening the commercial application of pea protein and assuring high-quality of comminuted meat products.

作为一类乳化凝胶体系，肉糜制品往往会由于蛋白氧化或乳化体系失稳而引发析水、析油、弹性变差等品质劣变。豌豆分离蛋白经极端pH 偏移处理后内部疏水基团、巯基等暴露，其乳化性、胶凝性及抗氧化性均得到显著改善。因此，本研究将pH 改性豌豆蛋白-多酚-油形成的微粒填充到肉蛋白交联形成的网络结构中，通过界面蛋白和乳化颗粒间非共价键相互作用的增强及乳化颗粒间二硫键的增加来改善复合凝胶的性质，通过pH改性后蛋白疏水氨基酸的暴露和多酚的释放来调控肉蛋白的氧化。项目拟以未氧化的肉蛋白体系、脱多酚豌豆蛋白/氧化肉蛋白混合体系、豌豆蛋白/高亚油酸甘三酯乳化液/氧化肉蛋白复合体系为对象，研究三类体系的氧化稳定性、乳化稳定性和凝胶稳定性，分析三种体系中豌豆蛋白与肉蛋白之间的物化相互作用及微观结构，阐明pH 偏移处理蛋白对复合乳化凝胶体系中蛋白氧化和胶凝乳化的影响机理，为豌豆蛋白在低温肉制品中应用提供理论基础。

豌豆蛋白经过极端pH处理后，PPI三级结构变化，原本处于球蛋白内部的疏水侧链部分、巯基等暴露出来，使得蛋白质达到疏水-亲水平衡，明显改善其乳化性、凝胶性和抗氧化性等功能性质。被包裹油脂的PUFAs种类和含量差异对O/W乳化液的稳定性具有很大影响，山茶油（含81%油酸）乳化液表现出较好的氧化稳定性，但乳化稳定性最差，即使是被改性后的PPI包裹，也易絮凝分层；而亚麻籽油（含56.2%亚麻酸）乳化液则恰好相反。随着均质压力的增加，乳化液乳化稳定性增加，而氧化稳定性降低；蛋白经过pH12偏移处理后，均质压力对乳化液乳化稳定性和氧化稳定性的影响减小。稳定的乳化体系（pH 改性豌豆蛋白-多酚（有/无）-油）填充到肉蛋白交联形成的网络结构中，脱酚后豌豆蛋白乳化特性大大提高，抗氧化能力增强；脱酚后的豌豆蛋白制备的凝胶透明有光泽，凝胶强度是脱酚处理前的两倍多，可以与极端pH12处理的改善效果相媲美。且脱酚处理后的PPI更容易和肉蛋白结合并形成强的凝胶，在储藏过程中，能较好地维持香肠质构、延缓香肠氧化。凝胶性的增强主要是通过界面蛋白和乳化颗粒间非共价键相互作用的增强及乳化颗粒间二硫键的增加达到的。添加外源酚类物质-没食子酸对脂肪氧化和蛋白羰基的形成有一定的抑制作用，主要表现在巯基和安吉的减少，同时诱导蛋白发生聚集和交联，蛋白结构的展开和二硫键的形成促使凝胶强度增加近50%。本研究结果阐明了 pH 偏移处理蛋白对复合乳化凝胶体系中蛋白氧化和胶凝乳化的影响机理,为豌豆蛋白在低温肉制品中应用提供理论基础。