Improvement of nutritional components and in vitro antioxidative properties of soy-powder yogurts using Lactobacillus plantarum

This research was the first to demonstrate changes in nutritional compositions (isoflavoneand CLA) from the 50% methanol extracts of soy-powder milk (SPM) and soy-powder yogurt(SPY) through fermentation using Lactobacillus plantarum S48 and P1201 strains. The radicalscavenging activities and protective effects against oxidative stress in LLC-PK1 cells werealso investigated. The average physicochemical characteristics including acidity and viablecell number as well as b-glucosidase activity increased with 0.2 / 0.7%, 7.5 / 9.8 log cfu/mL, and 0.0 3 / 1.75 U/g in SPYs. Total average isoflavones were considerably reduced(3180.3 / 2018.3 mg/g) with the increase of aglycone contents (191.8 / 770.2 mg/g), especially,daidzein exhibited the most remarkable increase rate (98.6/460.9 mg/g; > 4.8 times)during fermentation. The CLA and total phenolics also increased with significant differences(ND /1.6 mg/g; 2.4/3.6 mg/GAE/g) between SPM and SPY. Interestingly, the cis-9,trans-11 CLA showed approximately 90% in total content. Moreover, the scavengingcapacities against three radicals markedly increased with about 30% in SPYs, as thefollowing order: ABTS > hydroxyl > DPPH. The protective effects on oxidative stress (pyrogallol:O2 - , SNP: NO, and SIN-1: ONOO_) were also observed high cell viabilities (>10%)under LLC-PK1 cellular system. Our results suggest that SPY may be utilized as a potentsource regarding natural antioxidants and beneficial components for health food andmedical uses.