1. Produce beer "yeast flavor". After the yeast autolys […]
1. Produce beer "yeast flavor". After the yeast autolysis, a large amount of intracellular substances enter the beer, which makes the beer produce "yeast flavor". Its representative level is ethyl decanoate, and when the content exceeds 1.5×10-6 (1.5ppm), it can make people feel very uncomfortable.
2. Beer is bitter and astringent is aggravated. The amino acids released by yeast autolysis have many taste substances, which will increase the bitterness of beer when entering the beer. Commonly known as "bitter yeast", the astringency will also increase and reduce the refreshing taste of beer.
3. Produce diacetyl odor. After yeast autolysis, diacetyl and its precursor ɑ-acetolactate will enter the beer, and acetyl decarboxylase will generate diacetyl, which will inevitably cause the diacetyl content in beer to increase or even exceed the standard, resulting in unqualified products. , Loss of re-drinking.
4. Affect the stability of beer
After yeast autolysis, autolysase decomposes its own protein to produce a series of large, medium, and small molecular nitrogen-containing substances, which are difficult to be removed during filtration, which affects the blending of beer and causes beer to lose gloss and precipitate. The change of the ph value will also cause the beer colloid to lose its balance and decrease its stability.
5. Foam that affects beer
The nucleic acid substances in the yeast solution increase the total acid content in the beer. On the other hand, after the proteolytic enzyme is released into the beer, it hydrolyzes the foaming protein in the beer, thereby destroying the foaming and persistence of the beer foam.
6. Affect the acidity of beer
Yeast increases the total acid content in beer from nucleic acid substances in the solution. On the other hand, protein substances reacted with naoh during the acid-base titration and denatured, resulting in increased consumption of naoh titration, and the calculation results increased the total acid content. The release of amino acids and proteins after yeast autolysis will change the pH value of beer. Although the high isoelectric point of amino acids and proteins increases the ph value of beer, the beer itself has a buffering capacity, so the ph value of beer does not change much and is not linear.
7. Impact on beer filtration performance
The macromolecules formed by the autolysis of beer will block the pore size of the media in beer filtration. Autolyzed yeast will increase the viscosity of beer, causing filtration difficulties and increased soil consumption, thereby increasing filtration costs. Yeast autolysis is one of the important reasons that affect the filtration rate of beer.