Studies On The Oxido-reductases Of Domestic Brewing Barleys

The oxido-reductases which are peroxidase (Abbr. POD ), superoxide dismutase (Abbr. SOD ) and polyphenol oxidase (Abbr. PPO ) of different domestic barleys were studied in this paper. The alternation of these enzymes during malting and mashing were studied, also the primary study of the their effects on the wort and beer quality was done in this paper. The results can be concluded as following:The POD, SOD and PPO were affected significantly by the barley varieties but had little relationship with the barley protein content, which could be tested by the results of R~2 values and P values (R~2=0.1849, 0.2096, 0.07673;P=0.4524, 0.3766,0.8382).The study on these enzymes during malting and storage showed that: the POD activity increased 4-5 times by the end of germination, for the SOD was 4-7 times and for PPO was 2-7 times. The enzymes' activity decreased during the phase of kilning, and the POD activity increased by 24.4% in the end of kilning, however, the SOD and PPO lost their activities. The POD activity decreased by 36.4% and 59.1% according to prolonging the kilning time and elevating the kilning temperature. The enzymes' activity recovered by different percentage according to the time, water and temperature during storage. The results showed that the higher the storage temperature, the bigger recovery percentage reached.The primary study on the wort and beer showed that the POD decreased the wort quality by increasing the haze, colour and TBA value. By controlling the POD activity through malting which could significantly decrease the TBA value by 19.1% and increase the antioxidant potential by 42.8%. It was benefit to improve the domestic barleys' brewing characteristics.