Techno-Functional Properties from Hydrolyzed Wheat Gluten Fractions

Abstract

Many protein sources that are found in the market are obtained as by-products and there is a great interest in using them as protein ingredients with adequate functionality for food formulation. Structure modification permits one to add value and to diversify their uses. The diversification of wheat gluten applications depends on the improvement of its solubility in a wider pH range. One of the alternatives that allow protein modification in these products is the enzymic hydrolysis. The objective of this work was to evaluate foaming properties of protein fractions obtained by extracting, at 3 pH, different hydrolyzed gluten samples. Two commercial enzymes (acid -Ac- and alkaline -Al- proteases) were used to reach 3 different hydrolysis degrees (DH). Extracts pHs (4, 6.5 and 9) were diluted to a protein concentration of 4 g/l. RP-HPLC, free amino groups content, sulphydryl and disulfur content, average peptide chain length were used to characterize each extract. Foam was produced by sparging nitrogen at a known rate through a dilute protein solution. The maximal volume of liquid incorporated into the foam (Vmax) and the rate of liquid incorporation into the foam (Ri) were determined and used as indicators of foaming capacity. The times for half-drainage of the liquid that was incorporated into the foam at the end of the bubbling period (t1/2) and the rate of liquid drainage from the foam were also measured. Regarding Ri, all pH 4 extracts from hydrolyzed samples showed higher Ri than an un-hydrolyzed sample. Extracts from Al hydrolyzed extracts showed higher Ri than those from Ac. In the case of Al extracts, an inverse relation between DH and Ri was observed, but practically no influence of DH on Ri, was observed in the case of Ac extracts. For pH 6.5 extracts, the relation between DH and Ri were in opposite directions, depending on the enzyme, for Ac, Ri decreased with DH, while for Al, Ri increased with DH. At this pH, it was observed that the extracts which foamed more quickly, were those with the highest times for half-drainage of the liquid (t1/2). Some foam parameters correlated between themselves, depending on the extracts. Foaming capacity and stability depend on pH, DH and enzyme and it was possible to correlate parameters with composition evaluated by RP-HPLC.Fil: Drago, Silvina Rosa. Universidad Nacional del Litoral. Facultad de Ingeniería Química; ArgentinaFil: Gonzalez, R. J.. Universidad Nacional del Litoral. Facultad de Ingeniería Química; ArgentinaFil: Añon, Maria Cristina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentin