Water is the main raw material in beer brewing. Brewing water is called "the blood of beer", and generally includes saccharification water and water for washing wheat grains. The characteristics of world-famous beers are all determined by the water quality of their respective brewing water.

​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.

Brewing a high-quality beer is not so easy, because there are always some unavoidable interference factors in the brewing process, which will make the beer have one or another flavor defect. Therefore, understanding the various flavor defects of beer and their causes will help us to effectively control them during brewing, thereby avoiding or reducing their occurrence.

​In the second half of the wort boiling or before the end, take a sample of 250-300ml with a clean triangular flask, put it in the saccharification room at room temperature, cool down to room temperature, observe the wort in the triangular flask, there should be flocs at the bottom of the bottle Or muddy precipitation, the wort in the bottle is evenly distributed with a large number of aggregates, which can be flake, flocculent, etc. The wort is basically clear and transparent, and the smell of the wort has a refreshing hop aroma and malt aroma, and there is no other foreign smell , tasting with obvious sweetness, bitterness and malt smell. Then place the triangular flask in a refrigerator at about 10°C overnight (or for more than 12 hours), and observe the change of the turbidity of the wort.