The Study Of Antioxidant Activity And Flavor Stability Of Beer

Flavor stability is one of the most important quality attributes of beer. How to delay the staling and improve flavor stability of beer is the urgent problem to resolve and the main challenge for beer industry. The flavor stability of beer is affected by many factors, but there are many reports in recent years to show that beer flavor stability is determined by the endogenous antioxidant activity of beer itself and antioxidant activity is mainly influenced by antioxidants in beer. The contribution that antioxidants make to the antioxidant activity of beer and the effect of antioxidants and antioxidant activity on the flavor stability during staling was studied in this paper. The antioxidant activity during brewing and the effect of different conditions of fermentation on antioxidant activity of beer were researched in this study, which was used to confirm key factors of influence on antioxidant activity of beer and provide theoretical guidance for improving flavor stability of beer.The contributions of total phenolic content, melanoidins and total content of SO2 to antioxidant activities, including DPPH radical scavenging activity, ABTS radical cation scavenging activity, oxygen radical absorption capacity(ORAC), reducing power, metal chelating activity and the antioxidant activity composite index built by principal component analysis, were analysed in 42 commercial beers. The result found remarkable positive correlations in total phenolic content, melanoidins and antioxidant activity. However, no relationship was found between the total content of SO2 and antioxidant activity. Results from multilinear stepwise regression showed that total phenolic compounds in beer mostly contributed up to DPPH radical scavenging activity, ABTS radical cation scavenging activity and metal chelating activity, and melanoidins was mostly contributed up to oxygen radical absorption capacity(ORAC) and reducing power. The total phenolic content and melanoidins explained 56.5% and 16.7% of total variation of antioxidant activity composite index respectively.The total phenolic content, total content of SO2 and antioxidant activity had significant inhibition effect on the levels of staling substances in beer during forced aging. Significant negative correlations were found between total phenolic content, total content of SO2 or antioxidant activity and staling substances in beer with different degree of aging. Stepwise linear regression further demonstrated that DPPH radical scavenging activity made main responsible for inhibiting the formation of 3-methyl butyl aldehyde, trans-2-nonenal and increasing of TBA value, and the formation of 2--methyl butyl aldehyde, 2-acetyl furan,benzaldehyde and 2-phenylacetaldehyde can be inhibited by increasing ABTS radical cation scavenging activity, and reducing power was observed to make significant contributions to inhibit the formation of 2-furfural and nicotinic acid ethylester, as well as increasing the content of SO2 could decrease the content ofγ-nonalacton.The antioxidant activity during brewing process and the effect of different conditions of fermentation on antioxidant activity of beer were studied in this paper. The result showed that antioxidant activity was improved during malting, mashing, boiling and fermentation in brewing process, and improving antioxidant activity can be realized by using high content of wort and low generation of yeast, increasing the number of yeast and reducing the temperature of fermentation.