In vitro stability of bioactive peptides derived from fermented soy milk against heat treatment, pH and gastrointestinal enzymes

In this study, bioactive peptides (antioxidative and ACE-inhibitory), which had previously been identified in soy milk fermented by a Lactobacillus plantarum strain C2, were examined for stability during processing and after in vitro digestion. Results indicate that, antioxidative and ACE-inhibitory activity of peptides was either retained or enhanced after applying diverse heating conditions (from 25 to 121 °C). Conversely, the peptides retained almost the same ACE-inhibitory activity before and after treatment with pH from 2 to 7, but their ABTS radical scavenging activity was slightly decreased. Moreover, the significant increment (11-35%) in antioxidant activity was documented with different concentrations of trypsin, pepsin and pancretin, whereas ACE-inhibitory peptides showed some resistance to gastrointestinal digestion. This study indicates the high stability of ACE-inhibitory peptides against temperature of processing and gastrointestinal digestion. The ability of soy peptides to resist in various thermal and in vitro gastrointestinal conditions may be useful for their application as an ingredients for the development of functional foods.