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Beer faults

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Beer faults
Beer Mythos Chania.jpg
Beer
Main ingredientscereal grains, Alcohol, water

Beer faults or defects are caused by the chemical changes 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 compound 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....[1]

Brewers need to be familiar with the taste of every beer that has gone bad to judge the quality of their brew. The precision of controlling materials and processes is reflected in whether the taste of beer is defective. Brewers also need to find a solution to the flavour defect by tasting different types of beer.[1]

Beer faults and wine faults[edit]

The change of the external environment and the wrong production process are also the reasons of wine flavour defects. The lack of wine is due to the turn of the external environment caused by the chemical changes in the composition of the wine, such as the poor sanitary conditions of the winery, dirty wine, excessive use and oak cork rot, and the influence of temperature fluctuations of the wine flavour defects. Different from the flavour defect of wine, in the brewing process of beer, the concentration of inorganic chemical elements is too high due to improper production, or the malting of malt and hops in the brewing process causes microbial deterioration, which leads to the loss of beer flavour.

Diacetyl[edit]

Diacetyl

Diacetyl is produced in yeast during fermentation and is reabsorbed in the process. Since the external ambient temperature during fermentation is lower than 26°, diacetyl is absorbed insufficiently, resulting in a threshold of less than 0.04 mg/litre in beer, which gives the beer a mouthfeel like cream cheese[2]. This odour will persist over time. Since the decomposition of α-acetolactate produces a large amount of diacetyl, the method can avoid the beer flavour defects caused by diacetyl as follows: boil the container and clean it before the yeast fermentation. The wort should avoid contact with oxygen when the fermentation begins[3]. The temperature is raised by 2°-3° within 2 minutes of the end of the fermentation process, which allows the yeast to reabsorb faster so that the diacetyl content reaches 0.04 mg/L in the beer and does not cross the threshold.

Risotto taste[edit]

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[4]. 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.

Acid[edit]

Octanoic[edit]

Octanoic Acid

Octanoic is a fatty acid produced by the metabolism of yeast during fermentation. When the content of caprylic acid in the beer exceeds 4-6 mg/l, the beer will have a high concentration of spicy taste. Storage of beer in an environment below 26° will reduce this spicy taste. The use of fresh yeast and removal of the beer from the yeast cake immediately after the fermentation is completed will also keep the octanoic acid content within the threshold[5].

Butyric Acid

Butyric[edit]

Butyric is an acid produced by bacteria that produce syrup for a beer or that are mixed with oxygen during the production of wort to cause a decrease in Ph value. When the content of butyric acid in beer exceeds 2-3 mg/litre, the taste of beer tastes like metamorphic milk or rotten butter. Acidic sputum should be kept above 90°F and avoid contact with oxygen. This method can avoid excessive butyric acid content. Beer production environment must be clean. External factors such as pollution can not monitor the syrup can also control the content of butyric acid[6].

Isovaleric acid

Isovaleric[edit]

Isovaleric is an acid produced by mixing with octanoic acid in the oxidation of alpha acids in beer, which causes the beer to smell the odour. The acid is present in the beer at a level of from 0.7 to 1 mg per litre. A clean and hygienic production environment avoids the mixing of caprylic acid with isovaleric acid. Hops should be stored in an oxygen-free vacuum tight container to prevent bacterial infection[7]

Sour[edit]

The acid produced during the fermentation of the raw materials of beer or the yeast produces natural acid when fermented, and is present in a large amount in beer. When it exceeds 170 mg/litre, it will create a strong sour taste of yoghurt or pepper. Acids above the threshold are significant flavour defects in beer. The method of avoiding the presence of acid above the threshold in beer is, first of all, a hygienic production environment, followed by mashing the yeast strain for less than two hours and the fermentation temperature not higher than 50 °C. Brewing supplies and equipment should use non-marking equipment, because of the scratched fermentation device, tiny bacteria will remain inside the scratches. These bacteria can cause yeast to be contaminated during fermentation[8]

Alcohol[edit]

Thiol[edit]

Beers with thiols can produce rotten vegetables or smelly gullies. The threshold for mercaptans in beer is 1 microgram per liter. Mercaptan is caused by autolysis in the fermentation process of yeast strains, and may also be caused by anaerobic bacterial infection[1]. The solution to the thiol is to suck the beer from the yeast four weeks after the start of the fermentation, thus avoiding the beer absorbing the mercaptan present from the dead yeast.

lightstruck[edit]

Lightstruck tastes like a sulphur in beer. The desire to cause this taste is produced by the chemical reaction between riboflavin and hop alpha acid in beer by natural light or artificial light. This is also the reason why most beer bottles use green packaging. If the beer bottles are not green or not placed in the dark, the rate of aging will increase. In addition to being packaged in green bottles, storing beer in the dark is also a way to avoid lightstruck[9]

Aldehyde[edit]

Acetaldehyde[edit]

Acetaldehyde causes the beer to taste like a green apple when the presence of acetaldehyde exceeds the threshold (5-15 mg/l). During the fermentation of beer, the ethanol present in the yeast is contacted with air due to improper storage, which produces a large amount of oxidation reaction to turn ethanol into acetaldehyde. Therefore, in the production process, fresh yeast should be fermented at a suitable ambient temperature, and the production environment should be hygienic. After the start of the fermentation, the fermentation is sealed with a material having a high sealing property. Prior to bottling, highly airtight materials transport beer to reduce oxygen entering the bottle.[10]

Phenolic[edit]

The presence threshold of phenolic in beer is 0.05-0.55 mg/L, and the beer with phenolic content exceeding the threshold has bitterness and smoky flavor. The washing water of the yeast is derived from tap water, and the chlorophenol in the tap water and the disinfectant containing the chlorine water are brewed to make the beer contain phenolic. Therefore, an effective way to reduce phenolic is that tap water can be filtered prior to use. Non-chlorine disinfectants can also be selected for the type of disinfectant. The extraction of wort is at least 1.008 SG.

Hydrogen sulfide[edit]

Hydrogen sulfide produces a rotten egg flavor in beer. All yeast strains produce a certain amount of hydrogen sulfide during the fermentation process. The threshold of hydrogen sulfide in beer is 4 μg/L, and most of the hydrogen sulfide is doped in the released nitrogen dioxide, so when carrying out a large amount of fermentation, it takes a lot of time before bottling. Fermentation. Healthy yeast is used and fully oxidized wort, which increases the zinc content of the wort and reduces the hydrogen sulfide content.

Ferrous sulfate[edit]

Ferrous sulfate is caused by the contact of beer with metal materials during the brewing process, resulting in metal ion leaching. Excessive levels of ferrous sulfate can make beer taste like rusty iron and copper. If the content of ferrous sulfate in beer exceeds 1-1.5 mg/litre, drinkers will develop symptoms of dizziness. Drinkers can improve symptoms of poisoning if the beer contains a lot of ferrous sulfates. Therefore, in the process of producing beer, the water used for brewing is subjected to a metal ion reaction. Containers for fermented and finished beer should also be used in food grade plastics. Beer should be avoided in contact with any corrodible container to reduce the number of metal ions in the beer[1].

Oxygen[edit]

Oxygen can cause rapid decay of beer to cause some aging reactions, and the carbonyl compounds it produces cause aging. The original auxiliary material is 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.[11]. The maintenance can strengthen; when the wort boils, the pot door should close, and the boiling time should 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[1]

Dimethyl[edit]

Dimethyl sulfide exhibits a sour-sweet cream flavour when it exceeds 0.025 mg/l in beer. Dimethyl sulfide is derived from sulfur-based organic compounds produced during malt development[12]. Bacterial contamination occurs during the fermentation of yeast, and bacterial contamination can also cause sulphur to produce dimethyl sulfide. If the beer uses a particular variety of malts, such as pulses malt, barley malt and other sulfur-based organic compounds, the content of dimethyl sulfide is higher than ordinary ale, so the beer in the production process should reduce the use of such products. Too much water in the wort can also produce large amounts of sulfur-based organic compounds, so the malt should be stored in a dry place. Based on the volatility of dimethyl sulfide, the wort can be volatilized by boiling at a high temperature for 60 minutes to 90 minutes to liberate 90% of dimethyl sulfide.

Oxidation[edit]

The oxidised beer presents the mouldy taste of old newspapers. Beer with 100% oxygen exposure has the fastest oxidation rate. Temperature is another cause of oxidation, which produces a lot of oxygen in a high-temperature environment[13]. This oxygen also accelerates the price of beer oxidation. To avoid excessive beer exposure to oxygen, the headspace reserved for the beer to be placed in the bottle is less than one inch. If the beer is to be stored, the temperature inside the bowl should be below 50 degrees Fahrenheit[14].

References[edit]

  1. 1.0 1.1 1.2 1.3 1.4 "18 Common Off Flavors In Beer (And How They're Caused)". Kegerator.com. 2016-07-01. Retrieved 2019-05-31.
  2. White, Christopher. "Diacetyl Time Line" (PDF).
  3. "The role of diacetyl in beer". Drayman's. 2016-06-12. Retrieved 2019-05-31.
  4. "Controlling Diacetyl". Brew Your Own. Retrieved 2019-05-17.
  5. Kabay, Nalan (2015), "Boron Removal From Geothermal Water Using Membrane Processes", Boron Separation Processes, Elsevier, pp. 267–283, ISBN 9780444634542, retrieved 2019-05-31
  6. "Common Off-Flavors - How to Brew". howtobrew.com. Retrieved 2019-05-31.
  7. "The Oxford Companion to Beer Definition of isovaleric acid,". Craft Beer & Brewing. Retrieved 2019-05-31.
  8. "Temperature Factors - How to Brew". howtobrew.com. Retrieved 2019-05-31.
  9. "Beer bottles: The answer is not clear". Brews News. 2010-08-07. Retrieved 2019-05-31.
  10. "Oxygen's Role in the Fermentation of Beer | MoreBeer". www.morebeer.com. Retrieved 2019-05-31.
  11. "ORAL PENICILLINS CAN CAUSE RAPID SEVERE ANAPHYLAXIS TOO". InPharma. 164 (1): 4–4. November 1978. doi:10.1007/bf03310487. ISSN 0156-2703.
  12. "Dimethyl Sulfides (DMS) in Home Brewed Beer | Home Brewing Beer Blog by BeerSmith™". beersmith.com. Retrieved 2019-05-31.
  13. "Continuous ethanol fermentation by beer yeast". Journal of Fermentation Technology. 65 (1): 116. January 1987. doi:10.1016/0385-6380(87)90078-1. ISSN 0385-6380.
  14. "Beer bottles: The answer is not clear". Brews News. 2010-08-07. Retrieved 2019-05-31.

External links[edit]


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