大豆酸奶发酵过程中不同蛋白组分理化性质与风味变化研究

Study on physicochemical properties and flavor changes of different protein components during fermentation of soybean yogurt

大豆酸奶是一种营养健康的新兴植物基酸奶。该研究通过盐析等电点沉淀法从大豆中分离纯化出大豆乳清、7S和11S蛋白组分,探究不同组分在乳酸菌发酵过程中pH值、酸度、乳酸菌增殖、蛋白水解度、粒径的动态变化,以及发酵产物流变特性、微观结构、挥发性化合物以及感官特性的差异,以期阐明不同蛋白组分对于大豆酸奶质地与风味形成的贡献。结果发现,随着发酵时间的延长,大豆11S蛋白发酵物的pH值显著(P<0.05)下降,酸度、乳酸菌增殖数量、水解度和平均粒径显著(P<0.05)增加。同时,流变结果表明11S蛋白发酵物的黏稠程度最高,微观结构表现出粗糙的颗粒状以及更紧密均匀的蛋白聚集状态。此外,GC-MS和电子鼻结果证实7S蛋白经发酵后能产生大量2-己酮、2-辛酮、2-壬酮、2,3-丁二酮、2,3-戊二酮和乙偶姻等酸奶香气化合物,而11S蛋白则产生较多己醛、戊醛、(E)-2-庚烯醛、(E)-2-己烯醛、1-己醇、1-戊醇、1-辛烯-3-醇、苯甲醛、乙酸和2-戊基呋喃等豆腥味化合物,感官接受度较低。结果表明,11S蛋白是酸奶质地形成的关键组分,同时也是与豆腥味化合物相互结合与作用的主要组分。该研究将为大豆酸奶制品的品质优化和风味改善提供理论参考。

Soybean yogurt is a new plant-based yogurt with healthy nutrition.In this study,soybean whey,7S and 11S protein components were isolated and purified from soybean by salting-out isoelectric point precipitation method.The dynamic changes of pH value,acidity,lactic acid bacteria proliferation,protein hydrolysis degree,and particle size of different components during fermentation were investigated,as well as the differences in rheological properties,microstructure,volatile compounds,and sensory characteristics of fermentation products,to clarify the contribution of different protein components to the texture and flavor formation of soybean yogurt.Results showed that with the increase of fermentation time,the pH value of 11S protein fermentation products decreased significantly(P<0.05),and the acidity,the lactic acid bacteria number,the protein hydrolysis degree,and the average particle size increased significantly(P<0.05).At the same time,the rheological results showed that the 11S protein fermentation products had the highest viscosity,and the microstructure showed rough granular and more compact and uniform protein aggregation.In addition,GC-MS and electronic nose results confirmed that 7S protein could produce a large number of yogurt aroma compounds such as 2-hexanone,2-octanone,2-nonanone,2,3-butanedione,2,3-pentanedione,and acetoin after fermentation,while 11S protein produced more beany flavor compounds such as hexanal,pentanal,(E)-2-heptenal,(E)-2-hexenal,1-hexanol,1-pentanol,1-octen-3-ol,benzaldehyde,acetic acid,and 2-pentylfuran,with low sensory acceptance.Results showed that 11S protein was the key component of the yogurt texture formation,and it was also the main component of the interaction with beany flavor compounds.This study would provide a theoretical reference for the quality optimization and flavor improvement of soybean yogurt products.