CONICET | Buscador de Institutos y Recursos Humanos

Phaseolus vulgaris is a valuable source of phenolic compounds and precursor proteins of bioactive peptides exhibiting several bioactivities. Fermentation has been used as a cost-effective process for biopeptides release, ã-aminobutyric acid (GABA) production and bioconversion of phenolic compounds which ultimately lead to enhancements of their bioactivity. Therefore, there is an increased interest in the application of fermentation for production of bioactive compounds. The objective was to produce bioactive compounds with antioxidant and potential antihypertensive activities by liquid (LSF) and solid state fermentation (SSF) of kidney beans (P. vulgaris var. pinto). LSF of bean flour was performed either naturally (NF) or induced by Lactobacillus plantarum (LP). SSF of cracked seeds was carried out by Bacillus subtilis (BS). Soluble fractions were used to analyse free-amino groups (by TNBS method), GABA (by HPLC), antioxidant activity (by ORAC-FL), total phenolic compounds (TPC, by the Folin Ciocalteu method) and angiotensin I-converting enzyme inhibition (by fluorescence). In addition, selective and differential agarized media were used for specific microbiological counts (Log CFU/ml). LSF of kidney bean for 48 h (both NF and LP) led to an extended protein hydrolysis and higher (P<0.05) GABA content, antioxidant and ACE inhibitory activity (>93% inhibition). In contrast, no significant differences for TPC were found. SSF for 48h and 96h gave rise to water-soluble fractions with higher TPC that was accompanied with a noticeable increase in antioxidant activity. Unlike LSF, protein hydrolysis was observed after 48 h of SSF. In addition, kidney bean fermented by B. subtilis for 48 and 96 h brought about lower (P<0.05) GABA content and ACE inhibitory activity (33% inhibition). Indigenous lactic acid flora in NF adapted well to fermentative conditions since viability increased 8.8 log units up to 48 h and remained unchanged thereafter. In LP, L. plantarum grew 2 log units from the beginning, reached the maximum after 48 h to 9.15 log CFU/ml, and a viability of 5.85 log CFU/ml after 96 h was found. It is worth to notice that contaminant flora (enterobacteria, moulds and yeast) was detected at low but detectable levels along all NF process, while it disappeared after 48h in LP. Differences could be due to the different acidifying activity of L. plantarum against the natural microbiota, as it was observed in the found pH after 48 and 96h. In SSF, B. subtilis counts increases 3 log units from an inoculum of 5.5 log CFU/g, and the bacterial growth was linked to the alkalinization of medium throughout the solid state fermentation. No contaminant flora was identified under the experimental conditions. In conclusion, LSF of kidney bean could be used as a cost-effective process in the production of bioactive compounds exhibiting antioxidant and potential antihypertensive activities for the formulation of functional foods for cardiovascular health