Beer should have no obvious turbidity and precipitation during the shelf life, otherwise it will be unqualified. According to the standard, the shelf life of 12 degree high-quality beer is 120 days, 60 days for first-class beer, 40 days for second-class cooked beer, 7 days for bottled draft beer and 3 days for canned draft beer. Consumers can calculate according to the production date marked on the beer trademark, and don't drink expired beer.

We can identify the quality of beer from four aspects.

1, slowly pour the beer into a clean glass, and the foam will rise immediately, showing a white, thin and uniform color, which can last for 4 to 5 seconds. If the foam is thick, yellow in color and dissipates quickly, it is inferior if the foam does not hang on the cup.

2. At present, most of the beer on the market is light beer, which requires the glass to be clear and transparent, and the whole glass is golden yellow and pleasing to the eye, such as turbid wine color. Poor transparency, high viscosity and even suspended solids are inferior products.

3. With your nose close to the beer, you can smell the rich aroma of hops and malt. Inferior beer is high-quality beer, but it has no aroma of hops, and some have strange smells such as raw wine, fishy smell or aged smell. 4. At the entrance, you feel that the taste of the wine is pure and refreshing, the bitterness is soft, the aftertaste is mellow, and the aroma is pleasant. It is a high-quality beer with "killing taste".

4. "Killing the mouth" means that the carbonic acid gas in wine has a strong and pleasant stimulating effect on the mouth. In addition, beer should also have a refreshing bitterness from carbon dioxide and hops. If the beer has obvious sour taste, it means that the acidity is too large and unqualified. If the beer has obvious bad taste, it means that the diacetyl content is too high and it is also unqualified.