The role of acid protease in alcoholic fermentation

Acid protease is refined and refined from fine strains of Aspergillus niger. It can effectively hydrolyze protein under low pH conditions, and is widely used in alcohol, liquor, beer, brewing, food processing, feed addition, leather processing and other industries.

The acid protease action product is an amino acid, which is the best nutrient for yeast growth and a promoter of fermentation. In addition to a large amount of starch, the corn raw material also contains a certain amount of crude protein that is closely combined with the starch, which affects the hydrolysis rate of the starch. In the fermentation process, acid protease is added to release some difficult-to-hydrolyze starch by hydrolyzing protein, creating conditions for the saccharification of amylase and providing more abundant nutrition for fermenting yeast.

Specifically, acid protease has the following enzymatic functions in the process of alcohol fermentation:

1. Promote the dissolution of raw material particles

Acid protease is highly soluble to the granular material of brewing raw materials, which creates favorable conditions for saccharification and fermentation. In addition to its own dissolving effect on granular substances, acid protease can also release the adsorbed α-amylase, so that the saccharification and fermentation can be carried out smoothly.

2. Conducive to the proliferation of microorganisms

The acid protease of mold plays an important role in the proliferation of microorganisms. Because it decomposes and produces L-amino acids, it can be directly extracted and utilized by microorganisms. In alcohol fermentation, acid protease is added to better decompose the protein in the raw material, provide more free amino acids for yeast, and shorten the fermentation time.

3. Promote alcoholic fermentation

The reason why acid protease promotes alcohol fermentation is to increase the level of FAN in the mash, promote the growth and reproduction of yeast, and reduce the loss of substrates and energy consumption caused by the bacteria used for synthesizing amino acids.

4. Influence on the viscosity of fermentation mash

Acid protease has a certain influence on the viscosity of fermented mash. The research shows that the increase of acid protease increases the viscosity of fermented mash obviously. Since the viscosity of the fermented mash is reduced, the pump efficiency and the effect of plate heat exchange and cooling can be improved, and the separation effect of hydraulic filtration of distiller's grains after distillation can be improved.

5. Provide aroma precursor substances and flavor substances

In the acidic environment of winemaking, acid protease hydrolyzes raw protein into amino acids, which are the preconditions for the production of aroma components in liquor.

6. Degrading yeast protein bacteria

Acid protease can effectively decompose yeast cell proteins, and has the ability to decompose dead yeast cells, but does not work on live yeast. After a large number of dead yeasts are decomposed by acidic protease, they are not only good nutrients for microorganisms, but also effectively provide precursor substances for the aroma components of liquor.