Protein digestibility, protein patterns, and antioxidant activities of quinoa natto supplemented with Thai traditional herbs

A quinoa natto protein herb product was developed as an alternative to traditional protein foods. The current study aimed to introduce a new approach for producing quinoa natto from quinoa seeds to enhance their bioactive properties and increase antioxidant activity. <i>Bacillus subtilis</i> subsp. natto was chosen as the fermentation strain due to its widespread use in fermented foods. Both quinoa natto proteins (QNPs) and quinoa natto proteins with herbs (QNPHs) were evaluated for total soluble proteins and trichloroacetic acid-soluble peptide content. Gel electrophoresis and antioxidant assays were conducted to evaluate protein alterations and bioactive properties of QNPs during fermentation, as well as for each QNPH formula. The QNPH formulation with curry powder (F3) showed the highest antioxidant activity in terms of DPPH scavenging inhibition, 72.0%. F3 had the highest total flavonoid content, 8.2 (mg QUE/g), compared with unfermented QNPs, 4.7 (mg QUE/g). Additionally, the amino acid profile of F3 contained L-lysine, L-valine, L-leucine, and L-threonine. The results showed that the highest level of L-leucine was up to 356.4 μg/spot and 594.0 mg/g dry extract. Moreover, L-leucine as a ligand molecule was predicted and confirmed based on antioxidant and antimicrobial properties using molecular docking with various protein active sites (type-1 angiotensin II receptor, parathyroid hormone-related protein (Caco-2 cell protein receptor), 3-oxoacyl-[acyl-carrier-protein] synthase 1 of <i>E. coli</i>, and nucleoside diphosphate kinase of <i>S. aureus</i>).