The importance of polyphenols in beer

Polyphenols in beer mainly come from barley and hops. About 80% of them come from barley and 20% from hops. The phenols in barley are about 0.1% ～ 0.3% of its dry weight, mainly distributed in wheat husk, aleurone layer and endosperm. With the dissolution of malt in the process of malting, it is free and brought into wort and beer through the saccharification process. Phenolic substances in hops account for 4%~10% of the dry matter, mainly distributed in the bracts and rachis of hops.

The role of polyphenols in beer:

1. Effect on abiotic stability

The non biological stability of beer refers to the quality problems such as light loss, turbidity and sedimentation that are not caused by microbial pollution. This quality problem caused by non biological factors is mainly due to the complexation of polyphenols and proteins in beer. Polyphenols with low degree of polymerization in beer are very easy to combine with protein to form precipitation. However, the activity of high molecular polyphenols is poor, which often affects the color and taste of beer.

2. Effect on flavor stability

Polyphenols are both reducing and oxidizing. On the one hand, it can catalyze the oxidation of fatty acids and higher alcohols to form aldehydes (such as trans-2-nonenal) in the oxidation state, directly or indirectly promoting the aging of beer taste. On the other hand, it can avoid oxidation of some substances in beer, such as low molecular weight polyphenols, which can give beer strong reducing power, thus prolonging the fresh-keeping period of beer.

3. Influence on chromaticity

In the wort boiling process or in the presence of oxygen, the color of polyphenols will deepen after oxidation and polymerization, thus affecting the beer color. The color of beer will deepen with the oxidation of polyphenols in the saccharification stage; In the fermentation stage, with the decrease of pH value, a part of polyphenol protein complex is gradually separated, and the chromaticity will decrease.

4. Impact on foam

Polyphenols in beer have the function of coagulating high molecular proteins, which will lead to the reduction of proteins that make up beer foam. Excessive coagulation of proteins will affect the stability of beer foam.

5. Impact on taste

Polyphenol is the assistant of beer taste. Low molecular weight polyphenols have reducibility, which can not only improve the mellow taste of beer, but also increase the bitter taste of beer. Oxidized macromolecular polyphenols will cause bitter, bitter and hard beer taste. When beer contains a large amount of polyphenols, it will give the beer a plump feeling. However, if these polyphenols undergo dimerization, trimerization and other reactions to form polyphenols, the taste will become bitter and rough and will form larger particles and precipitate in the future, thus affecting the taste and quality stability of beer. However, excessive elimination of polyphenols will make beer taste insipid.

Therefore, the existence of appropriate polyphenols in beer is beneficial to the taste and quality stability of beer. On the contrary, too much polyphenols will also have a lot of effects on beer quality.