Preparation And Anti-oxidant Properties Of Peptide Prepared By Alcohol Soluble Protein From BSG

Brewers'spent grain (BSG) is the major by-product of the brewing industry, representing around 85% of the total by-products generated. BSG is the residue left after saccharification, filteration and separation of the wort during the brewing process. BSG is available in large quantities throughout the year, but its main application has been limited to animal feeding. There is a growing interest in increasing and diversifying the exploitation of BSG and related coproducts for economic and environmental reasons. The content of protein in BSG is rich which is nearly 30% in the dry basis. Therefore, brewer's grain protein is a good resource of protein. Preparation of active peptides from protein in BSG has important scientific significance and a good prospect for economic and environmental values. Studies in peptides from proteins in BSG were investigated, the results were as followed:1. Comparison studies on extraction efficiency and amino composition of extracting solution were carried out using two extraction methods of alkali extraction and ethanol extration. The results indicated that these two methods had selectivity in extracting proteins from BSG, glutelin was extracted from BSG by alkali extraction while gliadin was extracted from BSG by ethanol extraction, the gliadin extracted from BSG had a more marked component of amino acid than alkali-soluble protein in BSG. The gliadin contained a marked particular amino acid component of B hordeins: Glu31.18%, Pro18.92% and Lys1.8%.2. Enzymatic hydrolysis of alcohol soluble protein (gliadin) from BSG by Alcalase was optimized by an orthogonal test. Results indicated that the optimum enzymatic hydrolysis conditions were substrate concentration of 2%, temperature of 60°C, pH9.5, enzyme/protein ratio at 40μL/g and hydrolysis for 3 hours. Antioxidant properties of the hydrolysates was evaluated by scavenging capacity of DPPH radical and hydroxy radical, Vc was used as the positive control compound. The results indicated that the optimum scavenging capacity of the hydrolysates toward the two kinds of free radical obtain in different hydrolysis conditions.3. According to the degree of hydrolysis and antioxidant properties of the hydrolysates from BSG's alcohol soluble protein (gliadin) on , three kinds of peptides named PDH, PDPPH and POH which has high degree of hydrolysis and good antioxidant properties respectively were separated by membrane. It indicated that the retentant of PDH, which has a high degree of hydrolysis, after membrane ultrafiltration had no antioxidant ability. In case of PDPPH which had a good scavenging effect on DPPH radical, its components PDPPH2 of membrane separation had a good antioxidant property in high concentrations. The components POH3, which has a good scavenging effect on hydroxy radical, after membrane separation has a steady high antioxidant property in every retention.4. Gel Permeation Chromatograph (GPC) was used to measure the molecular weight of the components of membrane separation according to antioxidant property after membrane separation. Results indicated that the molecular weight of PDH was about 10kDa and the components are homogenous. There was only one component of PDPPH2 and the average molecular weight was about 5470Da. There were five components of POH3 whose average molecular weight was less than 5000Da and one component of average molecular weight of 3889Da was rich.