Addition of xylanase and glucose oxidase to gluten-soy protein mixture. Effect on the chemical interaction and creep properties

ROCCIA P; RIBOTTA PD; PEREZ GT; LEON AE

Congreso; 2nd International ISEKI_Food Conference “Bridging Training and Research for Industry and the Wider Community”; 2011

The aim of this work was to study the influence of xylanase (Xyl) and glucose oxidase (Gox) on the chemical interactions and creep properties on gluten-soy proteins after mixing. For this, commercial vital gluten (VG, 24 g), isolated soy protein (ISP, 6 g) a water (1:1.8; solids:water) were kneaded. Enzymes were added to solids at two levels: 0.006-0.012 and 0.005-0.01% w/w for Xyl and Gox, respectively. Images from mixtures were taken with a scanning electron microscope. Creep properties of samples were determined using a texturometer. Chemical properties (protein-protein interaction, sulfhydryl groups and soluble-insoluble pentosans content) were determined from freeze-dried mixtures. For the study of protein-protein interactions, two protein-sequential extractions were made. Procedure 1: extracted with a) 150 mM phosphate buffer pH 7.6 (PB), b) PB containing 1.5% SDS (PB+SDS), and c) 0.063 M Tris-HCl pH 6.8, 1.5% SDS, 3% mercaptoethanol (SDS+BME). Procedure 2: extracted with a) PB, b) PB containing 1.0% DTT (PB+DTT), and c) 0.063 M Tris-HCl pH 6.8, 1.5% SDS, 3% mercaptoethanol (SDS+BME). Protein content and SDS-PAGE pattern of supernatants were determined. Insoluble pentosans of VG-ISP mixture were hydrolyzed by Xyl action and a consequent increment of soluble pentosans was observed. The removal of the physical barrier created by insoluble pentosans on VG-ISP matrix formation, favours the increment of non covalent and covalent interactions between GV and ISP. These changes were expressed as an increment of rigidity and elastic capacity of VG-ISP mixture. Also, microphotographs showed a more continuous matrix when Xyl was added to the system. On the other hand, Gox incorporation to GV-ISP mixture decreased the free sulfhydryl group content with the consequent increment of disulfide bonds. Sequential extractions of proteins confirmed that Gox did promote the formation of disulfide linkages; besides, it showed an increment of non covalent and tyrosine-tyrosine interactions between proteins. Consequently, Gox addition to VG-ISP mixture led to the formation of a stronger matrix, with higher elastic capacity and viscosity.