Abstract Protein digestibility of soybean obtained from the main manufacturing steps for natto, such as soaking (soaked soybeans ‘S’), boiling (boiled ‘B’), and fermentation (fermented ‘F’), was examined in this study. Biochemical indices processed each step those digested fractions by simulated vitro gastrointestinal digestion were also evaluated. The result showed a significant ( P < 0.05)...