A beer fault or defect is caused by the chemical change of organic matter in beer due to the wrong production process and storage mode and leads to beer deterioration. The chemicals that cause flavour defects in beer have been produced in beer. For example, the aldehydes such as dactyl organic acids, lipids and sulfur compounds in beer influence the taste of beer. When the concentration of one or more elements exceeds the standard threshold, the flavour characteristics of beer will change and form the flavour defect of beer. In particular, fermentation byproducts, even small fluctuations of just over 1% above the threshold can have an impact on the flavor of the beer.