Causes and measures of beer turbidity and precipitation

1. Biological turbidity:

In short, bio-turbidity of beer occurs for two reasons:

First, the fermentation process contaminates other microorganisms, causing the death temperature of beer to rise. If wild yeast or Lactobacillus is contaminated, or even yeast spores are produced, the sterilized PU value must be above 40 to kill, and the PU value of brewery generally sterilized finished beer is controlled at 10-20, so it is difficult to kill the contaminated microorganisms. .

The second is that when the finished beer is sterilized, the water temperature of the sterilizer is low, or there is a dead corner of the spray, and the yeast and polluting bacteria are not killed.

For a specific bottle of beer, whether biological turbidity occurs is generally related to the following eight factors:

① The types of microorganisms present in the beer, the growth rate, and whether they damage the beer.

②The state of microorganisms, whether they are damaged by heat or in a state of starvation.

③ the number of microorganisms.

④ oxygen content in beer.

⑤ The residual fermentable sugar content in beer.

⑥ Alcohol content in beer.

⑦ Temperature and time during beer sterilization.

③ Keep the ambient temperature of the beer.

2. Abiotic turbidity:

Generally, the causes of non-biological turbidity are: unstable macromolecular proteins, polyphenols and oxygen.

The unstable macromolecular protein comes from: the malt is not dissolved well; the wort boiling strength is low, the protein coagulation is not good; the yeast is autolyzed, and the basic protein is precipitated.

Polyphenols come from: malt and hops, mainly malt polyphenols. Well-dissolved malt has a low polymerization index; poorly dissolved malt has a high polymerization index; after the malt and beer are oxidized, the polymerization index increases.

Oxygen comes from: oxygen inhalation in the process of fermentation broth transportation, filtration and sake storage; oxygen inhalation in the bottle neck air during filling.

3. Frozen turbid:

When beer is frozen at low temperature, that is, after the beer is deeply frozen below freezing point, irreversible turbidity is formed. If dyeing inspection is carried out, the main turbidity in frozen beer is β-glucanodextrin and calcium oxalate.

4. Other turbidity:

Mostly due to special external reasons, too many metal ions, or mixed with other abnormal substances, will also cause the beer to be cloudy.

Measures to prevent turbidity of finished beer

Appropriate measures can be taken when the cause of the cloudy precipitation is discussed. like:

1. Strengthen the process control of malt quality and saccharification process. Select the dissolved malt, adjust the pH of the mash (protein decomposition stage) to 5.2 to 5.5, boil the wort to pH 5.1 to 5.4, and the wort thermal coagulation nitrogen <2.0mg/l.

2. Shorten the cooling time of wort to reduce the oxidation of wort at 90-95℃.

3. Fully remove the cold coagulation of wort.

4. Do a good job of fermentation hygiene, so as not to contaminate the harmful bacteria of beer.

5. When fermentation and diacetyl reduction are over, yeast should be eliminated in time to reduce yeast autolysis.

6. Appropriate wine age. Before filtration, the temperature of the wine is lowered, and the mature fermentation broth is cold-treated to precipitate cold coagulated proteins.

7. Reduce the bottle neck air of filling, vacuum and fill carbon dioxide filling; high-pressure water or carbon dioxide stimulates foam, and discharges the top air.

8. Master a certain PU value for pasteurization of finished beer, sterilization and watering are uniform, and there should be no dead ends.

9. Beer is stored at low temperature to reduce shock.

10. Reduce dissolved oxygen in beer.

11. Other suitable methods.