The quality of craft beer is related to the metabolism of brewer's yeast

To ensure the quality of craft beer, experienced brewers will pay great attention to fermentation. Because they know that if they want to control the quality of craft beer, they must understand the metabolic process of beer yeast, so as to master the quality of craft beer.

Several metabolic processes of brewer's yeast are concerned:

(1) Glycolysis and carbohydrate metabolism

(2) Protein metabolism

(3) Fat metabolism

(4) Mineral metabolism

• Glycolysis

Saccharomyces cerevisiae is the only living organism that can use fermentation metabolism to obtain energy under anaerobic conditions.

(1) Alcoholic fermentation process as anaerobic glycolytic metabolism;

(2) Energy acquisition during fermentation.

• Protein metabolism

The protein content in the dry matter of brewer's yeast cells is about 35%-60%. When generating new cells, brewer's yeast needs a large amount of nitrogen source in the form of amino acids in the wort.

Beer yeast cells only absorb low-molecular amino acids, but on this basis, beer yeast can synthesize the proteins they need, and when they are synthesized, they will be converted into higher alcohols and secreted into the wine.

Many metabolic products are secreted into the wine liquid, which have an impact on the taste, taste stability, and foam stability of craft beer, so the protein metabolism process also determines the quality of craft beer.

• Fat metabolism

Fats, proteins, and phosphorus, in the form of phospholipids, make up the cell membranes around brewer's yeast cells and organelles inside the cells. Because brewer's yeast consumes lipids during fermentation.

Brewer's yeast absorbs the fatty acids in the wort, but brewer's yeast can also synthesize fatty acids themselves. In protein and fat metabolism, Saccharomyces cerevisiae will give priority to protein metabolism, and fat metabolism will start only after protein metabolism consumes most of the nitrogen source.

Fat metabolism requires aerobic participation, so there should be enough oxygen in the wort at the beginning of fermentation.

• Mineral metabolism

Beer yeast cells are very much in need of phosphorus and sulfur in minerals, and of course some trace metal ions. Phosphorus is mainly derived from phosphate in malt; sulfur is absorbed by yeast cells mainly as inorganic sulfate, but also in the form of sulfur-containing amino acids. Other minerals also play a big role:

Potassium: The process of carbohydrate metabolism requires the participation of potassium.

Sodium: Sodium ions activate enzymes and have a major impact on the transport of substances across cell membranes.

Magnesium: During the fermentation process, the reaction between magnesium and phosphorus has a greater impact and cannot be replaced.

Calcium: Calcium ions delay the recession of brewer's yeast and promote coagulation.

Iron and manganese: Iron and manganese ions are important trace elements necessary for respiratory metabolism and cell budding.

Zinc: Zinc ions affect protein synthesis and are also an important trace element in the fermentation process. If the content is insufficient, it will cause serious fermentation problems.

The above are some changes that occur during the metabolism of brewer's yeast.