In the daily production of beer, when fermenting, be produced from time to tome by miscellaneous bacterium pollution, these are harmful microbial have very big effect to the character of beer. According to the demand to oxygen, common miscellaneous bacterium cent is: Good oxygen is microbial, small good oxygen it is microbial, good to hold a gender concurrently oxygen is microbial, absolutely good oxygen is microbial 4 kinds big group. Specific and main sort has:

One, alvine path bacterium: Ferment the workshop often can detect, the bacili that capture mood is belonged to, changeful bacili is belonged to etc, in plant of their consist in, soil and water. Alvine path bacterium is progenitive in barley rapid, can produce the odour of sodden Chinese cabbage, have the taste of H2S even. Ferment in Mai Zhihe earlier, breed quickly extremely easily also, endanger the gust of beer. But it is under PH4.0, cannot breed in 2.0% alcohol beer.

2, be out of shape corpulent bacili: The meeting after pollution makes beer produces ingredient of 2 armour sulfur. It is in PH under 3.9 when cannot grow, but be able to bear or endure 6.0% alcohol.

3, lactobacillus: It is the main bacterium that beer works pollutes, include lactobacillus and sufficient coccus among them two are belonged to. They are extensive consist in ferments in fluid of incomplete of coal tub, conduit, valve, beer. Former do not be able to bear or endure hops and grow below microtherm slow, do not pollute beer to ferment so process; Latter meeting brings about beer acidification, produce double acetyl ingredient, can secrete pod film polysaccharide at the same time, make beer ropy, cloudy.

4, acetic acid bacterium: Can pollute beer through air. The meeting after pollution makes beer has apparent tart flavor and cloudy. Not sensitive to hops, acid-proof be able to bear or endure alcohol is strong.

5, ferment bacterium of single born of the same parents: Grow inside wider PH range. The meeting after pollution makes beer changes flavour. Not sensitive to hops, acid-proof be able to bear or endure alcohol is strong.

6, other miscellaneous bacterium: If beer is gigantic,the metropolis such as form coccus brings bad taste to beer.

Accordingly, in beer brew process, ? Make sure beer is planted yeasty absolutely dominant position, and increase as far as possible right other microbial control, it is the key that assures beer character.