Oat-Based Vegan Yogurt Alternatives Enriched with Mung Bean and Black Bean Protein Isolates: Nutritional and In Silico Potential Bioactive Peptide Estimation

Although the development of fermented plant-based milk alternatives has become quite popular, the relatively low nutritional value and functional properties of these products present significant challenges. This situation is driving the search for alternative protein sources to improve the quality of plant-based products, and legume proteins are attracting attention as promising components. Accordingly, this study aimed to enrich oat-based vegan yogurt alternatives with different legume protein isolates and evaluate their effects on product quality. In the present study, physicochemical, microbiological, antioxidant capacity, FAA profile, peptide profile, and FTIR analyses were performed on vegan yogurts produced using oat milk as well as mung bean and black bean protein isolates. It was determined that different plant protein isolates used in vegan yogurt production had a statistically very significant (n = 2, p < 0.01) effect on dry matter, protein, pH, L. acidophilus, antioxidant capacity, and all FAA profiles except asparagine and aspartic acid. The addition of legume protein isolates to vegan yogurts contributed to an increase in dry matter content (11.57–14.14%), protein content (2.92–5.20%), ash content (0.22–0.32%), and pH value (4.49–4.59) compared to the control group. Similar effects were also observed in S. thermophilus count (5.79–6.38 log cfu/g), L. delbrueckii subsp. bulgaricus count (5.72–6.43 log cfu/g), DPPH inhibition (10.29–19.93%), and ABTS inhibition (14.66–28.48%). It was determined that the addition of mung bean protein isolate (MBPI-2 and MBPI-4), compared to black bean protein isolate, contributed more to nutritional properties in vegan oat yogurt samples. Vegan yogurts were found to match more frequently with antioxidant, ACE inhibitor, DPP III, and DPP IV inhibitor activity in potential bioactivity predictions. FTIR analysis revealed that using different legume protein isolates in vegan yogurt production did not result in the formation of new absorption bands, but it did affect the intensity of existing regional bands. In conclusion, the addition of different legume protein isolates to oat yogurt was found to generally contribute positively to the parameters examined and represents a promising approach for individuals who cannot consume cow milk due to health problems, as well as for vegans.