The usaul contaminate in beer are bacterium,fungus and wild yeast, most of them are anaerobion causing the muddy, flavor chaging and turning sour, Beer anaerobic culture medium should be found out.

啤酒的常见菌有细菌、霉菌、野生酵母菌,但要存在危害性较的菌是细菌的厌氧菌,会使啤酒产生浑浊、变味、变酸等。