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Grain alcohol is the name by which ethyl alcohol produced from the fermentation of sugars and carbohydrates present in different grains such as barley, rye or corn is known . It is a commercial form of alcohol that has different applications, which can be both recreational and industrial and of other types. Grain alcohol can be obtained with various alcoholic contents that can range from as little as 5 or 6%, to values as high as 90% or more; however, it is common for the alcohol content to be low.
Characteristics and properties of grain alcohol
- It is composed of ethyl alcohol or ethanol, whose molecular formula is C 2 H 5 OH. It can also contain variable amounts of water.
- It is a colorless liquid with a penetrating alcoholic odor.
- It is a flammable liquid. When it has a high degree of purity it can be used as a clean fuel.
- It is used for the preparation of many strong alcoholic beverages including vodka, whiskey and sake, as well as milder ones such as beer.
How is grain alcohol obtained?
The industrial process to obtain grain alcohol consists of several stages, the main ones being fermentation and distillation of the ferment. The following describes each of the steps required to transform most grains into grain alcohol.
Stage #1: Initial grinding
The first step is to take the clean and dry grains and grind them into a fine flour. This step ensures that as much of the starch in the grains as possible is available for the series of biochemical reactions that will later convert it to alcohol.
Stage #2: Liquefaction
In this stage the flour is mixed with water and with an enzyme called amylase, which degrades starch by breaking the 1-4 glycosidic bonds of its structure. In this way a mash or wort is produced that is rich in simpler sugars, including maltodextrin, as well as some free monosaccharides such as glucose.
Stage #3: Saccharification
In this stage, a second enzyme is added that degrades the maltodextrin until it is converted into a fermentable monosaccharide. Together, stages 2 and 3 seek to transform all the carbohydrates present in the grains into different forms of sugars digestible by yeast.
Stage #4: Fermentation
Ethyl alcohol is obtained through the ethyl fermentation process. This is an anaerobic process carried out by different species of yeast to obtain energy in the form of ATP.
The fermentation process of the monosaccharides obtained after saccharification (mainly glucose, C 6 H 12 O 6 ) involves a set of enzyme-catalyzed biochemical reactions, the net effect of which is to break each sugar into two molecules of ethanol (CH 3 CH 2 OH) and carbon dioxide. The overall reaction is:
Stage #5: Distillation
The fermentation process cannot produce high purity ethyl alcohol since, after a certain concentration, the alcohol inhibits the fermentation itself and becomes toxic to yeasts. Therefore, the ferment must be distilled by means of different techniques to separate the ethanol produced from both the reaction residues and the yeasts that were used for fermentation.
It is common that, after the first distillation, successive distillations are carried out to obtain grain alcohol of a higher degree of purity, as necessary.
Optional additional steps depending on the application
- Dehydration: Grain alcohol has different applications, some of which do not tolerate the presence of water in the mix. In these cases, after distilling the alcohol, a dehydration process must be carried out, which is achieved in different ways. In some cases it is done through the use of molecular sieves that allow water to be removed while preventing ethanol molecules from passing through. Another common technique is azeotropic distillation.
- Denaturation: In those cases in which grain alcohol is not intended for human consumption, its denaturation must be carried out by adding different additives that alter its properties. In some cases denatonium benzoate is added, which is one of the most bitter substances known to man. In other cases, such as when alcohol is intended to be used as fuel, other fuels unfit for human consumption are often added.
Grain Alcohol Purity Grade
After fermentation and the first distillation of the ethyl alcohol, a highly concentrated solution of ethyl alcohol in water is obtained, typically containing 95 – 96% alcohol. Neither simple nor fractional distillation (which is used in industries that produce grain alcohol) is capable of purifying ethanol above 96%, since said mixture corresponds to an azeotrope at normal atmospheric pressure. However, various dehydration techniques such as those mentioned above can be used to further purify the alcohol to bring it to greater than 99% purity.
Grain alcohol in alcoholic beverages
In most grain alcohol applications, which mainly involve the production of alcoholic beverages, they are prepared with a much lower concentration of alcohol, so there is no need to purify it beyond 96%. In fact, when preparing beer, whiskey or vodka, the opposite is actually done, mixing the alcoholic distillate with pure water to thus obtain the desired alcoholic strength.
In the case of beer, a final alcohol concentration of between 4% and 10% by volume is targeted. In the case of spirits or strong alcoholic beverages, the final concentration is usually between 37.5% and 60%. However, there are a small number of alcoholic beverages that use virtually undiluted grain alcohol. The king of all is Vodka Spirytus, the strongest alcoholic beverage in the world with an alcoholic content of 96% by volume; closely followed by Everclear 190 and Corocoro, two liqueurs that have 95 degrees of alcohol.
Grain alcohol in rubbing alcohol
In the health field, different alcohols are often used as antiseptics to clean and disinfect wounds or to clean surfaces and thus combat the spread of infections. Alcohols are also used in the preparation of antibacterial gels, which have become particularly popular with the explosion of the COVID-19 pandemic. Isopropyl alcohol is used in many of these applications, but grain alcohol is also being used with increasing frequency.
Both in antibacterial gels and in the case of antiseptic alcohol that we can buy at any pharmacy, grain alcohol must have a minimum concentration of 70% by volume. However, you can also find some presentations in which it has a degree very close to 100%, which has been prepared through the resolution of the azeotrope by different means. We can easily recognize these because they are generally identified as absolute alcohol .
Grain alcohol for use as fuel
Grain alcohol can be considered a sustainable biofuel and there are many vehicles powered by internal combustion engines that use it as a source of energy. The grain most commonly used for this purpose is corn and in all cases the azeotrope obtained after distillation must be separated by means of molecular sieves or azeotropic distillation, since water interferes with combustion.
Examples of grain alcohol
- Vodka is an alcoholic beverage prepared with wheat, barley , or corn alcohol; in some cases it can even be prepared with potatoes.
- Absolute ethanol for antiseptic use in many cases is prepared by distillation of grain alcohol. There is no specific grain that is used for this purpose.
- Beer is usually brewed with alcohol from wheat or barley.
- Grain Scotch whiskey is prepared from malted and unmalted barley. There are also some that are made from corn or wheat, and there is even a whole range of blended whiskeys that contain grain alcohol from different sources.
- Sake is an alcoholic beverage of Japanese origin that is prepared with rice alcohol.
References
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Cereals and alcohol . (2015, November 12). The Connoisseur Magazine. https://revistaelconocedor.com/cereales-y-alcohol/
alcoholic fermentation . (nd). Chemistry.is. https://www.quimica.es/enciclopedia/Fermentaci%C3%B3n_alcoh%C3%B3lica.html
maize. (2007, January 17). Production systems used to obtain ethanol . http://www.maizar.org.ar/vertext.php?id=246
Méndex, C., Briones, AI, Sandoval, F., & Pérez, A. (2018). Optimization of the saccharification of starchy products for the production of bioethanol. Journal of Technologies in Industrial Processes , 2 (3), 27–32. https://www.ecorfan.org/taiwan/research_journals/Tecnologias_en_Procesos_Industriales/vol2num3/Revista_de_Tecnolog%c3%adas_en_Procesos_Industriales_V2_N3_4.pdf
Wines and Spirits in bulk. (2018, December 5). grain alcohol . https://www.vinosyalcoholes.com/producto/alcohol-de-grano/
