Fu brick tea extract supplementation enhanced probiotic viability and antioxidant activity of tofu under simulated gastrointestinal digestion condition

Abstract

In this study, a novel tofu (named as bio-tofu) was developed by adding Fu brick tea extract (FBTE) into soymilk and using the probiotic Lactobacillus plantarum B1-6 as a bio-coagulant. The influence of FBTE supplementation at a level of 0.25% on the antioxidant activity of tofu and the survival of L. plantarum during fermentation and simulated in vitro gastrointestinal digestion was investigated. The results showed that FBTE supplementation significantly promoted the growth of L. plantarum whereas it decreased the pH during bio-tofu manufacture, as well as improved the survival of L. plantarum resistance to cold storage and simulated gastrointestinal conditions. The phenolic compounds in FBTE were well maintained by the acidic environment which is generated by the L. plantarum fermentation. Furthermore, the antioxidant activity of tofu was significantly enhanced for the supplementation of FBTE. Throughout the gastrointestinal digestion process, the phenolic compounds and antioxidant activities of bio-tofu were kept at a relatively stable and high level. Meanwhile, this study also found that using L. plantarum as a bio-coagulant could remarkably enhance the total phenolic and isoflavone aglycones contents, and antioxidant activity of tofu. Total phenolic, catechin and isoflavone aglycones contents were highly correlated with antioxidant activity. Thus, this study demonstrated that FBTE supplementation improved L. plantarum viability and the antioxidant activity of tofu, and the product could be considered as a novel functional food with high populations of probiotic viability and strong antioxidant activity. The combination of FBTE and probiotics for the manufacture of bio-tofu may open a new field of functional food development.