IMPROVEMENT NUTRITIONAL/ANTIOXIDANT PROPERTIES OF UNDERUTILIZED LEGUME TEPARY BEAN (Phaseolus acutifolius) BY SOLID STATE FERMENTATION

Abstract

The objective of this study was to optimize the solid state fermentation (SSF) process of tepary bean seeds to identify optimal fermentation temperature (FT) and time (Ft) to maximize protein content (PC), antioxidant activity (AoxA), and total phenolic content (TPC) of fermented tepary bean seeds. Response surface methodology was applied to PC, AoxA, and TPC. The experimental design was central composite rotatable with two factors [Fermentation temperature (FT=20-40 °C)/ Fermentation time (Ft=06-108 h)] and five levels (13 treatments). Before fermentation the seeds were soaked (25 °C 8 h-1 ) in acetic acid solution (pH=3), drained, and their seed coats removed manually. Seed coats were dried, milled, packed and stored. The cotyledons were cooked in acetic acid solution (pH=3; 90 °C 30 min-1 ), cooled, and inoculated (Rhizopus oligosporus). The resulting bioprocessed cotyledons were milled and blended with their corresponding milled seed coats to obtain fermented tepary bean flours (FTBF). Regression models for the prediction of PC, AoxA, and TPC in FTBF were also obtained; maximum values for this response variables were attained at FT=37.6 °C and Ft=96.2 h. The SSF bioprocess increased PC (+35%), in vitro protein digestability (+17.54%), calculated-protein efficiency ratio (+32.37%), AoxA (ORAC: +117%, ABTS: +88.7%), and TPC (+196.7%) of tepary bean seeds. The SSF is an effective strategy to increase the TPC of tepary bean seeds for enhancing functionality with improved antioxidant activity