User:BarryWang3099/draft



= Introduction = Beer is a kind of carbon dioxide-containing and low-alcohol beverages made from the malt as the primary raw material, adding hops and yeast fermentation. The flavor, foam, color, and other indicators of beer are the criteria for testing the quality of beer. The influence of beer flavor is the most important. The higher alcohol aldehydes such as diacetyl organic acids, lipids, and sulfur compounds in beer have an essential impact on the taste of beer. These by-products, together with alcohol and carbon dioxide, constitute the body of the beer and form the unique flavor of the beer. These substances are present at the same time and exert a combined effect on the taste of the beer. When one or more elements are too high, it will change the beer flavor characteristics and form beer flavor defects, especially fermentation by-products, which are very small, but even small fluctuations will bring significant beer flavor impac t.

The flavor defects of beer mainly include sharp taste, bitter taste, long bitter taste, phenol or other chemical taste, aging taste, risotto taste, disgusting grassy taste.

= Different between Beer Faults and Wine Faults = Wine and beer have different flavor defects in the willingness to cause various flavor defects. Wine faults are caused by chemical changes in the components of the wine produced by changes in the external environment, such as poor winery hygiene, dirty, overused wine and rotten oak cork, and temperature fluctuations affecting the wine flavor defects. But the beer faults is caused by brews technology weakness. The lack of chemical elements in the brewing process or malt and hops not fermenting properly during the brewing process will result in the loss of beer flavor.

= Sharp taste = Excessive multi-substance content and multi-substance polymerization degree caused the raw astringency in beer. At the same time, the pH of beer-oxidized beer is too high, the pH of beer-oxidized beer is too high, the hardness of water is too high, the pH value is too high, and the hops are old. Long storage time and high storage temperature will cause beer taste. The corresponding solution is to avoid excessive washing, and the pH of the washing water controlled between 6.0 and 6.5. With fresh hops, hops should store at low temperatures (not higher than 4 ° C) in a dry environment, and oxidized hops cannot use. Improve the degree of malt comminution without affecting the filtration of the wheat meter. Under the premise of ensuring the boiling strength is 10% ~ 14%, the boiling time is controlling at about 80min. The bottom of the sugar and gelatinization pot can use for feeding to avoid the inhalation of oxygen during the saccharification process, the boiling pot is closed and boiled, the number and speed of mashing and stirring are reducing, and CO2 or N2 replace the air in the pot as a protective gas. After removing most of the temporary hardness by adding gypsum to the brewing water, acid is added to reduce the alkalinity in the water and lower the pH.

= Bitter taste =

The cause of bitterness is due to the old hops, severe β-acid oxidation, excessive hops, high polyphenol content, and too high polyphenol content. The pH of the saccharification water is too high, the alkalinity is large, and the wheat is washing. Excessive, the wort boiling strength is not enough to coagulate the nitrogen content. The solution is to adjust the number of hops properly and adjust according to the a-acid content in the sprinkles. Add acid to the brewing water to reduce the alkalinity and lower the pH. Avoid excessive washing; the residual sugar is controlling between 1.0% and 1.5%. Increase the boiling strength between 10% and 14%, and the boiling time is controlling at about 80 minutes. Decreasing the pH of the wort between 5.2 and 5.4 is conducive to the fineness and purity of the sedimentation and separation of the coagulum. At the beginning of the fermentation, open fermentation is carried out to make the fermentation strong. The wort is moderately oxygenated and should not be over-oxygenated.

= Phenol or other chemical taste = The reason is that the paint contains phenol or chlorophenol or the like, or phenolated phenol and free chlorine are washed with high water, saccharified, and washed with a detergent containing free chlorine. Contamination of wild yeast or bacteria can also cause an excessive chemical odor in beer. The solution is to use an odor-free paint on the inner wall of the fermenter and a stainless steel pipe. It is immersed in wheat and saccharified with low phenol, chlorophenol, and free chlorine. Brush the wine pipeline with detergent and bactericide free of free chlorine. Strengthen process hygiene management to prevent harmful bacteria from pollution.

= Aging taste = Oxygen can cause rapid decay of beer to cause some very important aging reactions, and the carbonyl compounds it produces cause aging. The solution measures are: the original auxiliary material is best protected by CO2 or N2 when pulverized, and it is not easy to take too long before smashing. CO2 or N2 protect the equipment during the mashing process, and the bottom feed is using when smashing. The mixing frequency of sputum reduces, and the stirring speed is a reduced pump, seals, valves, etc. can not leak. The maintenance can strengthen; when the wort boils, the pot door should close, and the boiling time should not be too long; after the main leaven finish, the wine should serve as soon as possible. The post-fermenter tank uses cO2 to prepare the pressure, and the speed of the fermentation tank is controlled to be less than 1m/s.

= Risotto taste = The reason for the taste of glutinous rice is that the content of diacetyl in the beer exceeds its taste threshold, and the beer produces a glutinous rice taste. The flavor threshold is also relatively low. For light-colored lagers, the diacetyl content preferably controls below 0.1 mg/L; for high-grade beer, it preferably controls below 0.05 mg/L. The solution is to increase the a-amino nitrogen content of the wort appropriately. Generally, the content of the 12P wort is controlled to be 180 ± 20 mg / L. Too low will lead to the synthesis and accumulation of a-acetic acid, lactic acid; too high will lead to excess nutrients in the yeast and excessive high alcohol content. Reduce the proliferation multiplication of yeast, generally the multiplication factor ≤ 3. Because the precursors of diacetyl and other yeast metabolic by-products are mostly producing during yeast breeding, we can reduce the yeast proliferation rate by adopting a series of measures such as low-temperature inoculation, inoculum, and low-temperature fermentation. Properly increase the fermentation temperature in the late stage of the main fermentation

= Reference list =

=External links=


 * few beer faults and their origin – in a nutshell"