Department of Food and Drug, University of Parma, 43124 Parma, Italy.
Food Funct. 2021 Apr 7;12(7):3033-3043. doi: 10.1039/d0fo02916e. Epub 2021 Mar 12.
Okara is the main soybean by-product resulting from the processing of soy milk and tofu. Despite being a product with a lot of potential and rich in many bioactive compounds such as polyphenols, it presents an unpleasant, rancid aroma. For this reason its use in the food industry is limited. In this study, we have reported the integral use of okara in a solid state fermentation process, conducted with wild strains of lactic acid bacteria, to evaluate the effect of bacterial metabolism on the volatile and polyphenolic profiles. Strains belonging to Lactobacillus acidophilus, Lacticaseibacillus rhamnosus and Pediococcus acidilactici species were used in monoculture and, for the first time, in co-culture. The results showed an improvement in the aromatic fraction showing a decrease in hexanal, responsible for off-flavour, and an increase in ketones with fruity and buttery notes in fermented okara. Polyphenols were also affected, and, in particular, a bioconversion of glucoside isoflavones to the aglycone forms was highlighted in all fermented substrates. In addition, the appearance of both phenyllactic and p-hydroxyphenyllactic acids as well as the increase in indole-3-lactic acid was observed for the first time upon okara fermentation. Overall, the co-culture appears to be the most promising for biovalorization of okara, thereby opening the possibility of its use in the development of functional ingredients.
豆渣是豆浆和豆腐加工过程中的主要大豆副产物。尽管豆渣是一种具有很大潜力的产品，富含多酚等多种生物活性化合物，但它具有令人不快的腐臭气味。因此，其在食品工业中的应用受到限制。在这项研究中，我们报告了豆渣在固态发酵过程中的综合利用，该过程使用了野生乳酸菌菌株，以评估细菌代谢对挥发性和多酚谱的影响。使用属于嗜酸乳杆菌、鼠李糖乳杆菌和乳酸片球菌的菌株进行了单培养，并首次进行了共培养。结果表明，芳香族物质得到了改善，具有异味的己醛减少，具有水果和奶油味的酮类增加。多酚也受到了影响，特别是在所有发酵的基质中，发现了糖苷型异黄酮向苷元形式的生物转化。此外，在豆渣发酵过程中，首次观察到苯乳酸和对羟基苯乳酸的出现以及吲哚-3-乳酸的增加。总的来说，共培养似乎是豆渣生物增值最有前途的方法，从而为其在功能性成分开发中的应用开辟了可能性。
