The Research Of Phenolic Compounds And Antioxidant Capacity In Brewing Barley And Malt

Phenolic compounds presented in brewery's barley and malt significantly impacted brewing processes, organoleptic and rheological properties of mash and beer. In the present paper, the difference of extracting solvent of the total free polyphenol yield and free radical DPPH scavenging activity from barley extracts were investigated, the relevance of protein, starch, phenolic content and phenolic enzymes activity of brewing barley were analysed, as well as the relevance of malt and wort total free polyphenol and antioxidative activity. The effects of mashing processes on polyphenol dissolve, phenolic enzymes activity and wort specification were investigated. Research results of this thesis are as follows:1. The extracting solvent significantly influenced the total free polyphenol yield and antioxidant activity from barley extracts. 80% acetone is a selected solvent for extracting phenolic antioxidant from barley. The Folin-Ciocalteu method for total phenolics content and the free radical DPPH scavenging method for antioxidant activity could be used as estimation of barley antioxidant activity.2. The free phenolic compounds and related enzymes activity in different barley had significant difference due to the different variety characteristics and cultivated conditions. The significant positive correlation was found between free phenolic content and antioxidant activity (r=0.794), while there was no significant correlation between free phenolic content and phenylalanine ammonia lyase activity, as well as peroxidase activity and polyphenol oxidase activity, which may due to the fact that there were certain phenolic oxidase and biosynthesizing enzymes in barley. It may be concluded that endogenous antioxidant activity of malting barley can be evaluated by the determination of free phenolic compounds and DPPH radical scavenging capacity.3. Results from the correlation analysis showed that total free phenol content of malt had a significantly positive correlation with its antioxidant activity (P<0.01), also the wort polyphenol content(P<0.05). The antioxidant activity of malt had a significantly positive correlation with the total phenol content and antioxidant activity of wort(P<0.01). The total phenol content of wort had highly positive correlations with antioxidant activity of wort(P<0.01). It can be concluded that the endogenous phenolic compounds contribute to the property of antioxidant capacity for barley malt and wort. The current study provides a reference for the evaluation of barley malt quality in brewing processes.4. The effects of different mashing process on the polyphenol content and antioxidant characteristics of wort significantly. The results indicated that the dissolution, polymerization, precipitation of polyphenol related to the modification of starch and sugar, as well as the complex reactions of protein and polyphenol. The total polyphenol content, antioxidant capacity and other specification of wort(such as color haze and filtration rate) contribute to the fineness, dry and wet grinding method and oxygen limitation.