Preparation of potential antioxidant ingredients by fermentation of pea flour by the autochthonous microbiota

Abstract

Fermentation is an economic method to produce and preserve food. Sourdough is a flour and water mixture that is spontaneously fermented by the indigenous microbiota of seeds composed by stable associations of acid lactic bacteria (LAB) and yeasts. LAB can present specific protease activities able to release bioactive peptides. Legumes ?peas among them- are widely consumed and present interesting nutritional and functional properties. The aim of the present work was to evaluate the fermentation of pea flour by autochthonous microbiota in the preparation of a functional ingredient containing potentially antioxidant peptides. Yellow peas (Pisum sativum var Yams, culture 2016) were used. Dispersion of flour in distilled water (6 g flour + 10.5 ml water) were prepared and incubated at 30 and 37 °C with agitation. pH evaluation was registered obtaining values of 6,24 ± 0,03 at t = 0 and 3,92 ± 0,09 after 48 h for both incubation temperatures. Protein hydrolysis degree was evaluated by reaction of free amine groups with trinitrobenzenesulphonic acid (TNBS); results were 13 ± 2 and 17 ± 2 % after 24 h at 37 °C y 30 °C respectively, without differences after 48 h. Protein solubility (soluble protein in PBS buffer (Lowry method)/100 g total protein (microKjeldahl method)) was similar for all ferments (54 ± 2 %), while at t = 0 solubility was 68 ± 4 %. Electroforesis SDS-PAGE and tricine-SDS-PAGE as well as gel filtration FPLC chromatograpy (Superdex 75 and Superdex 30 columns) suggested the formation of aggregates and also the appearance of low molecular mass molecules (< 6.5 kDa) after fermentation. Antioxidant activity was studied by the ORAC (Oxygen Radical Absorbance Capacity) assay, dose-response curves were obtained and IC50 values calculated. All ferments registered an increment in the antioxidant activity respect to the starting dispersion, decreasing IC50 values between 1.3 and 2 times, fermented flour after 48 h at a 37 ºC showed the greater ORAC capacity (IC50 = 0.065 mg protein/ml). These results point to the fermented pea flour as a potential functional antioxidant ingredient.