In this study, soy-powder yogurt (SPY) with enhanced levels of γ-aminobutyric acid (GABA) and isoflavone aglycone was produced from sprouting high-protein soybeans (HPSs). The fermented steam-HPS sprouts (0 to 4 cm) were fermented (72 h) with Lactobacillus brevis, and the total free amino acids (FAAs) of the formed mixtures were determined to be 79.53, 489.93, 877.55, 780.53, and 979.97 mg/100 mL in the fermented HPS (FHPS), and the fermented steam-HPS with 0 cm (FSHPS-0), 1 cm (FSHPS-1), 2 cm (FSHPS-2), and 4 cm sprouting lengths (FSHPS-4), respectively. The levels of glutamic acid (GA) and GABA were observed to be the highest, 100.31 and 101.60 mg/100 mL, respectively, in the unfermented HPS (UFSHPS-1, 1 cm) and FSHPS-1 sprouts, respectively. Moreover, the total contents of the isoflavone glycoside form decreased proportionally to the increasing total levels of isoflavone aglycones after fermentation in FSHPS-0, FSHPS-1, FSHPS-2, and FSHPS-4. The levels of isoflavone aglycones were detected as 350.34, 289.15, 361.61, 445.05, and 491.25 μg/g in FHPS, FSHPS-0, FSHPS-1, FSHPS-2, and FSHPS-4, respectively. While FSHPS-1 exhibited the highest DPPH (63.28%) and ABTS (73.28%) radical scavenging activities, FSHPS-4 contained the highest isoflavone aglycone ratio (81.63%). All in all, the FSHPS-1 mixture prepared in this study exhibited high GABA content and functional prosperity, thereby making it suitable for potential applications in the soy-dairy industry.

In this study, contetnts of phenolic acid and isoflavone, and biological activities of soy sauce were compared the soy sauce added bitter melon powder (BMPs). After the fermentation, pHs were decreased from 5.83 (0% BMP), 5.47 (5% BMP), and 5.32 (10% BMP) to 5.28, 5.36, and 5.16 at 90 days, whereas the acidities of soy sauce were increased from 0.06%, 0.07%, and 0.09% to 0.30%, 0.28%, and 0.36% at 90 days, respectively. In addition, the salinities of soy sauce were decreased, while viable cell numbers including Bacillus and yeast were increased. The contents of total phenolic, isoflavone-aglycone, and phenolic acid and antioxidant and α-glucosidase inhibition activities were significantly increased for 90 days, while the isoflavone-glycoside contents were decreased. In Particular, soy sauce with 10% BMP at 90 days showed the highest contents of glutamic acid (GA, 9,876.09 mg/100 mL) and γ-aminobutyric acid (GABA, 325.02 mg/100 mL) contents than among other samples. Additionally, the radical scavenging activities (DPPH, ABTS, ⦁OH, and FRAP) and α-glucosidase inhibition activities of soy sauce with 10% BMP at 90 days were shown to be high 96.07%, 97.27%, 59.47%, 1.98%, and 79.96%, respectively.