Studies On The Techniques Of Producing Low-purine Beer

Beer is a kind of low alcohol drink, which is brewed from the main raw material of malt. It is famous of its attractive color, cool and refreshed taste, and pleasant aroma, which is loved by most people. With the increasing of beer consumption, there are some problems caused by beer drinking. One of the problems that the beer lover has to face is the gout.The beer contains a lot of purine which may lead to gout. In this paper,28kinds of beer were chosen, which is popular in the market. And the contents of Total Purine, Adenine (A), Guanine (G), Hypoxanthine (H), and Xanthine (X) in them were detected by reversed phase high performance liquid chromatography. The control of beer purine needs to control the raw material and adjunct. To find proper raw material and adjunct, large numbers of material’s purine was detected. Besides, the treatment of samples was studied. To solve the problem of beer purine, it took the enzymatic method and acid boiling to improve the content of free purine in the wort. And then the free purine could be absorbed by yeast. In the processing of research, the method for evaluating of guanosine enzyme activity was established. And the hydrolysis rule of adenosine and guanosine was studied. Besides, the impact of the acid boiling on the wort and fermentation was detected. The brewing condition was also studied. The main results were as follows:1. The content of purine in28different kinds of beer were studied.The conclusions were that the content of Total Purine was39mg/L～126mg/L in these beer, which most of them was70mg/L～80mg/L. The study found that the content of Guanine was the highest of the four kinds of purine followed by Adenine. The Guanine’s content was more than50%of the content of Total Purine. The data analysis showed that the content of beer purine has significant correlations with original wort concentration.2. There are three sample treatment method, mashing method, water extraction and direct method. The appropriate method is mashing method whose detected result was the most reasonable of the three. The contents of purine in many raw material and adjunct were studied. The result showed that the highest content of Total Purine was a kind of malt with1505.2mg/L. The lowest one was corn syrup with28.9mg/L. The content of Total Purine in malt was1100mg/L～1500mg/L, the average was1300mg/L. There was obviously different between malt from different producing areas and strains. The content of Total Purine in rice, corn starch and corn syrup was20mg/L～100mg/L. The purine content of hops commonly used was500mg/kg～800mg/kg, which could only offer a little purine for beer considering the addition quantity in beer. In the end of brewing, the yeast should be removed immediately to prevent the autolysis of it, which could bring purine for beer.3. One method to detect the enzyme activity of guanosine nucleosidase was established, through the study on the nature of guanosine nucleosidase in barley malt. The barley malt powder was homogenized with4part (w/v) cold buffer. The supernatant was filtered to obtain a crude enzyme solution. Enzyme activity was assayed using guanosine (0.8mmol/L in9mmol/L potassium dihydrogen phosphate-dipotassium hydrogen phosphate buffer (pH6.8) at40℃for30min. The enzyme catalytic reaction was stopped by boiling in hot water.) The product guanine was assayed using the HPLC. After detecting the enzyme activity of some kinds of barley malt, it’s confirmed that it was difficult to improve the content of the free purine in wort using the guanosine enzyme which had low enzyme activity.4. The hydrolysis rule of adenosine and guanosine was studied in this paper. The conclusions were that guanosine and adenosine could hydrolyze in both acidic condition and alkaline condition. But it was better for them to release purine in acid condition. Based on the rule, the way to increase free purine in wort was studied by boiling in acidic condition. The content of wort purine could be significantly increased through releasing it from non-free purine in this way. The key point of this technology was pH and time when boiling. Under the condition of pH1.5,2h boiling, the purine in wort could be released absolutely. Because the increasing of the free purine, the yeast could breed better, which acid boiling technology wouldn’t have negative influence on the ability of yeast absorbing purine.5. The influence of yeast condition on beer purine was studied. The study found that different yeast had obvious difference in the ability absorbing purine. The inoculation rate could affect the content of purine, which went against decreasing beer purine with high inoculation amount. It was also found that yeast assimilation rate could increase as temperature when the brewing temperature ranged from10℃to22℃. At the same time, it benefits improving the yeast assimilation rate when lowering the brewing pH.