Caracterización de proteínas obtenidas a partir de harina de Firiguero (Vigna unguiculata L.) y de sus hidrolizados mediante electroforesis SDS - PAGE y RP-UHPLC

Abstract

This research was aimed to characterize Firiguero protein concentrates from Vigna unguiculata L. variety, obtained by solubilization at pH 8,0 followed by isoelectric precipitation at five pH values 2,0 - 6,0 by SDS-PAGE electrophoretic- and RP-UHPLC chromatographic technics. Extraction yields at the assayed pH values ranged between 12 and 17 percent for products extracted using flour provided by two suppliers from Loja, being the highest yield 17,45 percent at pH 4,0. Quantification of protein content of concentrates was conducted by Dumas automated method. It showed that all the obtained products have protein contents higher than 60 percent as compared to 21,14 perecent - 21,59 percent found in the flour. Therefore, alkaline solubilization and isoelectric precipitation are effective methods to isolate proteins. Firiguero protein concentrates were subjected to an in vitro gastric and duodenal hydrolysis, simulating human physiological conditions. In the gastric phase, partial hydrolysis was obtained, while in the duodenal phase, higher proteins breakdown was attained. Additionally, it was determined that addition of 2 mg of protein concentrate per mL of olive oil exerts a protective effect against lipid oxidation as determined by incubating the protein-oil mixture at 100 Celsius degree for 48 h. Protein concentrates prevents the formation of secondary products inherent to oxidation, evaluated by the thiobarbituric acid method. The percentage of TBARS thus formed ranged between 43,63 percent and 72,86 percent as compared to 32,86 percent when the antioxidant ascorbic acid is added. The polyphenol content evaluated by the Folin method in the supernatants of the protein concentrates varied between 180,4 to 358,8 mg GAE per 100 g flour.