Study On Phenolic Acids- The Inner Antioxidant In Beer

The content of 10 kinds of phenolic acids in Tsingtao beer was researched , and the content scope of phenolic acids was preliminary conformed. The anti-oxidant ability of phenolic acids could be presented by the sum of DPPH free radical-scavenging activity of gallic acid and ferulic acid, which was called the anti-oxidant ability of phenolic acids. There was a good relationship between the anti-oxidant ability of phenolic acids and DPPH scavenging ratio ,TRAP value, TBA value during the aging process when it was related to one kind of beer. The changes of the anti-oxidant ability of high, middle, low beer were investigated, and it was found that the anti-oxidant ability of phenolic acids was higher than DPPH scavenging ratio at the initial aging stage and declined faster than it at the late aging stage. It was showed that the phenolic acids provide more anti-oxidant activity, and other reducing substances also make a contribution in anti-aging process.A smaller anti-oxidant ability and the lowest content of aging materal were provided by Australia malt, which was one of the stuff of the fixed beer, and it was proved to be more conductive to beer flavor stability. The anti-oxidant ability of unitα-acid by aroma hop was stronger than bitter hop. Phenolic acids declined fast during the aging process of hop. During the saccharification process, the phenolic acid content was decreased with the increase of protein rest temperature, and there was not significant change with the change of protein rest time and saccharification time. There was no significant change of phenolic acid anti-oxidant ability and DPPH scavenging ratio in the fermentation process. +(-)catechins had an increasing trend in the entire fermentation process. Phenolic acids increased and aging materials decreased with addition of tannin.An analytical method of xanthohumol in hop and beer using high performance liquid chromatography(HPLC) has been developed. The separation was achieved on a reversed-phase Agilent Zorbax Eclipse XDB-C18(250mm×4.6mm, 5μm) in a linear gradient, and the mobile phases were consisted of water with formic acid(0.1%, v/v)(A) and methanol(B) with a flow rate of 0.4 mL/min. In addition, the column temperature was maintained at 25℃. The detection wave length was set at 370nm. There was a good linear relationship. The average recoveries of hop and beer were between 95.05%-104.30% and 91.21%-95.58%, and RSD﹤2%. It was proved to be a convenient and accurate method for analyzing xanthohumol content in hop and beer.