Lactobacillus rhamnosus CRL981 increases antioxidant capacity in fermented soybean enriched with bioactive aglycones.

MARAZZA, J.; NAZARENO, M.A.; GARRO, M.S.; DE GIORI, G.S.

Tucuman

Simposio; III International Symposium on Lactic Acid Bacteria. II Argentinean Lab Net Meeting International; 2009

CERELA

Free radicals and other reactive oxygen species, generated by exogenous chemicals or endogenous metabolic processes in food systems or the human body, may cause oxidative damage playing significant pathological role in aging process and age-related human diseases. The ingestion of antioxidative supplements or antioxidant-containing foods may reduce oxidative damage in the human body. The continuous search for new products from traditional raw material and processes that provide ingredients with new functionalities and cost-effective manufacturing is the main goal of the food industry.Soybeans are known for their potential bioactive antioxidant properties attributed to isoflavones (IS) content. In this substrate, IS are found as glucoside conjugates being less bioactive than their respective aglycones. Some lactic acid bacteria strains with glucosidase activity are able to hydrolyze glucosides. The aim of our study was to examine whether levels of both total antioxidant activity and bioactive IS aglycones increased in fermentedsoymilk with glucosidase-producing L. rhamnosus CRL981. Soymilk was inoculated (4% v/v) with this strain and allowed to ferment at 37°C for 24 h.Samples were aseptically withdrawn at 0, 3, 6, 9, 12 and 24 h to determine IS by HPLC and total soluble phenolic content using Folin–Ciocalteu assay. The antiradical activity, expressed as a percentage of antiradical activity (% ARA), was determinedspectrophotometrically using DPPH radical. At the end of fermentation glucosides IS were hydrolyzed (54.7% of daidzin and 100% of genistin) by glucosidase activity.Total phenolic content did not change (106.2±6.3 ìg of galic acid equivalents/ml) along soymilk fermentation; however free radical scavenging activity of soymilk increased reaching the value of 41.8% ARA at 24 h of fermentation. These results evidence that aglycones IS were responsible for the DPPH scavenging activity detected in this study. L. rhamnosus CRL981 could be used as starter culture for processed soy products enriched in aglycones IS with beneficial effects to consumers.