Breeding Of Low Purine Beer Production Strains And Fermentation Process Optimization

Purine content of the beer in the market is about40-100mg/L. The human purine metabolism generates uric acid and the uric acid metabolism disorders can cause disease-gout. At present, there are about75million gout patients in China, therefore developing low purine beer that gout patients can enjoy has a undoubtedly far-reaching significance, which will help to expand the beer consumption market. In this dissertation, ARTP method and ultraviolet mutagenesis for Saccharomyces cerevisiae, combined with the high auxiliary material proportion and the high concentration fermentation technology in the brewing process was examined, the purine content in fermentation beer finally decreases by45.61%, compared with the conventional methods.First of all, the dissertation established HPLC method to detect purine content in the beer. Detect conditions were as follows:column, Agilent TC-C18(250mm×4.6mm,5μm); mobile phase,0.02mol/L potassium dihydrogen phosphate buffer solution(pH4.0) mixed with methanol into the column with a ratio of95:5; detection wavelength254nm; flow velocity,1.0mL/min; column temperature30℃; the injection volume10μL. Precision of the method was1.14-1.48%, four kinds purine adding standard recovery was between94.4%and105.3%. The experimental results showed that this method was simple, rapid and precise for the determination of purine content in beer.In the second place, the dissertation identified ARTP mutagenesis and UV mutagenesis conditions. ARTP mutagenesis conditions was treatment distance,2.5mm; working gas, helium; gas flow rate,10.0SL; mutagenesis time,60s. UV mutagenesis conditions:treatment distance,25cm; UV lamp power,30W; mutagenesis time,15min. In order for mutation breeding of low purine Saccharomyces cerevisiae, the dissertation inspected four kinds purines in beer by HPLC under the circumstance of maintaining the fermentation performance of yeast and the quality of fermentation beer. The purine content in beer fermented by using the mutant strain was23.6%lower than that of the initial strain, and after several generations, the inherited performance remained stable, indicating that mutation breeding process of lowering purine in the yeast species was feasible and effective.Orthogonal experiment was designed to optimize malt saccharification conditions, the malt root was added in the experiments and the results showed below:the optimal conditions in combination was55℃of protein repose temperature,30minutes of protein rest time,60℃of saccharification temperature,40minutes of saccharification time,1:4of the ratio between raw materials and water, malt root adding amount1.5%of the weight of malt, all of these played significant roles on reducing the non-ionizing purine content in wort. The effects of excipients proportion, wort concentration, inoculum concentration on fermenting low purine beer by high concentration and high excipients were investigated to make sure that high excipients and high concentrations in producing low purine beer was feasible with the fermentation conditions following up:40%of auxiliary material proportion, the wort concentration15°P, inoculum15-20million/mL.Using the strain and optimization conditions in the above, total purine content of beer was58.94mg/L, reduced by45.61%(the original concentration of10°P total) in comparison with the beer before optimization, whilst the flavor in the beer tasted normal, which realized the intended purpose.