Purine Content In The Process Of Beer Brewing

Beer is one of the most important low alcohol beverages in the world. Because of the relationship with gout, purines in the beer were concerned by the consumers. In this paper, 14 kinds of beer were chosen randomly from the market and the contents of Adenine (A), Guanine (G), Hypoxanthine (H), and Xanthine (X) in them were detected by reversed phase high performance liquid chromatography. Correlativity between purines and indexes of beer was analyzed by SPSS10.0. As indicated by literatures, the content of purine in wheat malt was lower than that in barely malt. Also as the raw material of beer brewing, wheat malt has lots merits, such as high saccharification power, highβ-glucanase activity, and high leaching rate, etc and it is preferred by the brewing companies and consumers because of the unique beer flavor. In this paper, five worts were prepared by using different dosage of wheat malt (20%, 25%, 30%, 35%, 40%) in saccharification and contents of A, G, H, and X in the worts were investigated. Correlativity between purines and indexes of worts was analyzed by SPSS10.0. The contents of A, G, H, and X were determined in the brewing and correlativity between purines and indexes of fermentation broth was analyzed by SPSS10.0. Effects of beer fermentation process on the contents of purines were studied. The main results were as follows:1 The contents of A, G, H, and X in 14 different kinds of beer (one black, one dry, and two foreign beer were included) were studied. The conclusions were that the content of Total Free Purine (TFR) was 7.11mg/L~24.93mg/L and Total Purine (TP) was 28.65mg/L~79.35mg/L in these beers. Free Adenine (FA) and TFP had extremely significant correlation with the original gravity (P<0.01), respectively; and Free Hypoxanthine (FH) and Free Xanthine (FX) had significant correlation with original gravity(P<0.05), respectively. The results indicated that free purine in the beer mainly come from brewing materials. The contents of FA and FH had extremely significant correlation with alcohol content and chroma in the beer (P<0.01), and the content of Free Guanine (FG) had significant correlation with pH value of beer (P<0.05). Beer with high purine content, its purine content in one unit of the original gravity may not be high, and vice versa.2 The contents of purine in the raw materials of beer brewing were studied. The results showed that there was no H and X in the long rice and total content of A and G was 0.48mg/L. There was no A, H, X in the hop, and the content of G was 0.28mg/L. The content of FA was the highest one of the free purine in the wheat malt and barley malt. G was in the form of bound primarily. The contents of A, G, and X in the wheat malt were lower than that in the barely malt. But the content of H in the wheat malt was higher than that in the barley malt. The contents of total purine in the wheat malt and the barley malt were 47.30 mg/L, 73.32 mg/L, respectively.3 The 9oP wort was prepared by using 20%, 25%, 30%, 35%, and 40% wheat malt dosage. The normal indexes and A, G, H, X were determined. Compared with the wort with 20% wheat malt, in the wort with 40% wheat malt, the A content reduced by 30-40%, the H content increased about 10%, the X content increased about 30%, and the TP content decreased from 63.70mg/L to 57.37mg/L. The contents of FG, TFP, Total Guanine (TG), and TP in wort had extremely significant correlation with wheat malt dosage (P<0.01). The contents of them decreased as the wheat malt dosage increased. The FX and Total Xanthine (TX) contents showed significant correlation with wheat malt dosage (P<0.05). The content of them increased as the wheat malt dosage increased. The contents of FG and TG had significant correlation with the most of wort indexes (P<0.05). The contents of all kinds of purine had no correlation with original gravity, reducing sugar, pH value,α-AN, andβ-glucan.4 The purine content was monitored during the brewing process of twelve batches of 9oP beer. The results showed that the content of FX was the highest in free purine (up to 11.29mg/L), followed by FG, FA, FH. The content of TG was the highest in total purine (up to 20.20mg/L), followed by TX, Total Adenine (TA), Total Hypoxanthine (TH). During the fermentation, the content of TFP decreased from 20.02mg/L to 11.28mg/L; and the content of TP reduced from 44.03mg/L to 34.85mg/L. The results of the analysis of variance showed that there was significant difference between the first day and the following nine days for the contents of FA, FG, FH, and TH (P<0.05), while there was no significant difference from the second day to the end of fermentation (P>0.05). Both FX and TX contents had no significant difference during the fermentation. There was no significant difference between the first day and the tenth day for the contents of TA, TFP, and TP. But there was significant difference between the first day and the following eight days. There were no significant differences between the first day and the second day, the ninth day and the tenth day for the content of TG. Also the content of TG had no significant difference among the middle six days.The contents of FA, FG, FH and TA, TG, TH showed extremely significant positive correlation with the pH value, reducing sugar,α-AN, and real extract content (P<0.01); and extremely significant negative correlation with the total acid, alcohol content, and real attenuation in the fermentation broth (P<0.01). The content of TFP decreased as alcohol content and real attenuation increased. The FX and TX had significant (P<0.05) or extremely significant (P<0.01) positive correlation with the total acid,α-AN, original gravity, and yeast generation; had extremely significant negative correlation with the number of yeast cell (P<0.01), and showed no correlation with pH value, reducing sugar, alcohol content, real extract content, and real attenuation. The TFP and TP had extremely significant positive correlation with pH value, reducing sugar,α-AN, and real extract content (P<0.01), and had extremely significant negative correlation with alcohol content and real attenuation (P<0.01). Furthermore, the TFP had great significant positive correlation with original gravity, yeast generation (P<0.01), and had extremely significant negative correlation with the number of yeast cell (P<0.01).