Effects of Starter Candidates and NaCl on the Production of Volatile Compounds during Soybean Fermentation.

We inoculated different combinations of three starter candidates of Bacillus licheniformis, Staphylococcus succinus, and Tetragenococcus halophilus, into sterilized soybeans to predict their contributions to volatile compounds production through soybean fermentation. Simultaneously, we added NaCl to soybean cultures to evaluate its effect on the volatile compounds profile. Cells in soybean cultures (1.5% NaCl) reached almost their maximum growth in a day of incubation, while cell growth was delayed by increasing NaCl concentration in soybean cultures. The dominance of B. licheniformis and S. succinus in the mixed culture of three starter candidates switched to T. halophilus as the NaCl concentration increased from 1.5% to 14% (w/w). Seventeen volatile compounds were detected from the control and starter candidate-inoculated soybean cultures with and without the addition of NaCl. Principal component analysis of these volatile compounds concluded that B. licheniformis and S. succinus made major contributions to producing a specific volatile compound profile from soybean cultures where both species exhibited good growth. 3-Hydroxybutan-2-one, butane-2,3-diol, and 2,3,5,6-tetramethylpyrazine are specific odor notes for B. licheniformis, and 3-methylbutyl acetate and 2-phenylethanol are specific for S. succinus. Octan-3-one and 3-methylbutan-1-ol were shown to be decisive volatile compounds for determining the involvement of S. succinus in the soybean culture containing 7% NaCl. 3-Methylbutyl acetate and 3-methylbutan-1-ol were also produced by T. halophilus during soybean fermentation at an appropriate level of NaCl. Although S. succinus and T. halophilus exhibited growth on the soybean cultures containing 14% NaCl, species-specific volatile compounds determining the directionality of the volatile compounds profile were not produced.

Black soy peptide supplementation improves glucose control in subjects with prediabetes and newly diagnosed type 2 diabetes mellitus.

The present study aimed to determine the effect of black soy peptide supplementation on glucose control in subjects with prediabetes (impaired fasting glucose or impaired glucose tolerance) and newly diagnosed type 2 diabetes mellitus (DM). In this double-blind, placebo-controlled study, subjects with prediabetes and type 2 DM were randomly assigned to the placebo control group or the black soy peptide intervention group. We determined fasting serum concentrations of glucose, hemoglobin A1c, insulin, and free fatty acids, performed a 2-hour postload glucose (2-hour PG) test, and compared serum lipid profiles before and after the 12-week supplementation. In particular, subjects with fasting glucose ≥ 110 mg/dL who consumed black soy peptides tended to have lower fasting glucose levels (two-tailed test, P = .098; one-tailed test, P = .049) and had a significant reduction in 2-hour PG level (two-tailed P = .012, one-tailed P = .006), compared with baseline levels. The changes in 2-hour PG levels were also statistically significant in the intervention group (-41.25 ± 13.67 mg/dL) compared with the placebo group (12.42 ± 9.80 mg/dL; two-tailed P = .015, one-tailed P = .008). In contrast, hemoglobin A1c levels were not significantly improved by the dietary intervention. In conclusion, black soy peptide supplementation may be beneficial for controlling fasting blood glucose levels and 2-hour PG levels.