Wine is a mixture of many chemical components, water and alcohol being the main components, in addition to various organic compounds. These organics include: higher alcohols, methanol, polyols, aldehydes, carboxylic acids, esters, acids, etc. These ingredients that determine the quality of liquor are usually very low in content, accounting for about 1% ~ 2%, but there are many kinds, and the proportion of their content is very important, which has a great influence on the quality and flavor of liquor.
The scientific name for alcohol is ethanol. Ethanol is the most abundant ingredient in baijiu after water, and it tastes slightly sweet. The level of ethanol content determines the strength of the wine, the higher the content, the higher the degree of alcohol, the stronger the wine.
Its molecular formula is: CH3─ CH2─ OH; The molecular weight is 46;
The chemical equation of sugar conversion to ethanol is:
C6H12O6 → 2CH3CH2OH + 2CO2
Acids are important flavoring substances in liquor, which together with other flavoring and flavoring substances constitute the unique aroma of liquor. Less acid containing wine, wine taste is light, after the short taste; If the acidity is strong, the wine tastes rough. Appropriate amount of acid in the wine can play a buffer role, can eliminate after drinking on the head, taste disharmony and other phenomena. Acid can also enhance the sweetness of the wine, but too acidic wine reduces the sweetness, and also affects the taste. The content of acid in high quality liquors is generally higher, about twice as high as that in ordinary liquors and twice as high as that in ordinary liquors. If the amount of acid is insufficient, the wine will lack the inherent flavor of liquor, but if the amount of acid is too high, the wine will have evil and miscellany taste and reduce the quality of wine. Therefore, the maximum acid content of liquor should not exceed 0.1%.
Acids in liquor can be divided into volatile acids and non-volatile acids. Volatile acids are formic acid, acetic acid, propionic acid, butyric acid, caproic acid, caprylic acid. Formic acid is the strongest irritant, but the content is very small. Acetic acid has strong stimulation and high content. Wine with too much acetic acid is acid. Butyric acid, pentyl acid and hexanoic acid are sweat odor. Some unsuccessful lulu wine contains more butyric acid and has a prominent odor. However, when the content is thin, it may also become aroma and fragrance ingredients when mixed with other aroma substances. There must be a certain amount of acetic acid in lu type wine. Octanic acid and more fatty acids of carbon chain are oily, but the content is not high. Non-volatile acids include lactic acid, malic acid, gluconic acid, tartaric acid, succinic acid and so on. Lactic acid is milder and gives baijiu a good flavor, but in excess it produces astringency.
Acetic acid and lactic acid are the two most abundant acids in liquor. They are not only the important flavor substances of liquor, but also the precursors of many flavor substances. General liquor, acetic acid close to lactic acid, long-term fermentation of high quality wine, lactic acid amount increased greatly.
The amount of flavor substances in liquor is the largest, and the ester is the most influential. In general, the ester content of high quality baijiu is relatively high, averaging 0.2% ~ 0.6%, while that of ordinary baijiu is less than 0.1%, so the flavor of high quality baijiu is stronger than that of ordinary baijiu.
Esters in liquor are the products formed by alcoholysis of acyl coenzyme A generated by yeast in the process of energy consumption. Esters in liquor mainly include ethyl butyrate, ethyl acetate, amyl acetate, amyl butyrate, ethyl lactate and so on.
Liquor has different main flavor types because of its different flavor types. Flavored liquors, such as Fenjiu and Xifeng, are mainly ethyl acetate and ethyl lactate. Luzhou-flavor liquors, such as Luzhou Tequ and Wuliangye, use ethyl acetate and ethyl butyrate as the main aroma. Thin ethyl butyrate is fruity, only after hydrolysis of butyrate decomposition of acid to have a “sweaty smell” smell. In good Luzhou-flavor liquor esters, ethyl acetate should account for 30% ~ 40%, ethyl butyrate about 4%. The main aroma of Maotai-flavor liquor has not been confirmed yet. The ester components of Maotai-flavor liquor are the most complex. The total ester content of Maotai-flavor liquor is lower than Luzhou-flavor liquor, and the ethyl acetate content is medium, which is less prominent than Luzhou-flavor liquor. But from the low boiling point of ethyl formate, to the medium boiling point of ethyl octanoate and other various esters, is an important feature of it. Therefore, Maotai-flavor liquor has the style characteristics of “low but not light, fragrant but not brilliant”.
The generation of various esters in liquor is inseparable from the open production mode. Acetic acid bacteria and lactic acid bacteria inhabiting various parts of the workshop invade the fermentation pond and generate a variety of organic acids, which are esterified with ethanol through the action of yeast. Ethyl acetate and ethyl butyrate, derived primarily from fudulent bacteria, which are co-leavened with yeast and esterified. However, the esterification process is relatively slow, so the content of ester in high quality liquor with long fermentation period is generally higher.
The aldehydes in liquor include formaldehyde, acetaldehyde, furfural, butyraldehyde and valeraldehyde.
A small amount of acetaldehyde is a beneficial aroma component in liquor. Generally high quality liquor contains more than 20 milligrams of acetaldehyde per 100 milliliters. Acetaldehyde and ethanol and further condensation into acetal, its amount is larger, some high quality liquor can reach more than 100 mg, become one of the main components in liquor. The content of these two ingredients in fine wine is 2-3 times higher than that of ordinary white wine. It has a clear aroma and is good for enhancing the taste sense.
However, high levels of aldehydes make liquor have a strong stimulating taste and spicy taste, drinking can cause dizziness. Aldehydes are the main source of spicy taste in wine. As long as there is a trace amount of acetaldehyde, it combines with ethanol to form spicy taste. Wine as a stimulant taste, appropriate spicy, of course, is necessary, but not too spicy, too much will hurt the flavor. When furfural is produced in excess by five-carbon sugars, it has a very strong scorched taste, which is also harmful to the human body. The acrolein produced by the action of yeast and lactic acid bacteria on glycerol is not only spicy but also has a persistent bitter taste. Acrolein and acrylol are the main components of tear-inducing gas bombs, which are extremely toxic to human beings and must be eliminated.
The fusel oil in liquor is a mixture of macromolecular alcohols, including iso-amyl alcohol, butanol, iso-butanol, propanol, isopropanol and a small amount of ring alcohols. Among them, iso-amyl alcohol and iso-butanol are more. Because it appears in the liquid in the form of oil, so called fusel oil. The amount of fusel oil content and the composition ratio of various alcohols give an important influence to the flavor of liquor.
Higher alcohols don’t taste very good by themselves. Except for isoamyl alcohol, which is slightly sweet, isobutanol, n-propanol, and n-butanol are all bitter, while the keratol from tyrosine has a mild aroma but a long, bitter taste. Therefore, the content of fusel oil in liquor should not be too high, otherwise it will bring unbearable bitter taste (the so-called “fusel oil taste”), the taste of liquid wine is largely caused by excessive fusel oil.
But fusel oil in liquor is not simply a harmful component, it only in excess is harmful flavor, appropriate fusel oil is an indispensable aroma component and flavor component in liquor. If there is no fusel oil at all or very lack of fusel oil, liquor taste will be very weak; If 0.0390 higher alcohol is added into the diluted alcohol, the liquor will produce a certain fragrance. Therefore, it is also a substance that plays an important role in the composition and style of liquor aroma. The key is that the fusel oil content must be appropriate, not too much. At the same time, the ratio of fusel oil to acid and ester, as well as the ratio of different kinds of fusel oil also have an important effect on liquor flavor. If the ratio of alcohol to ester is high, the fusel oil smell is unpleasant, and if the ratio is moderate, even if the fusel oil content is slightly higher, it is still not unpleasant. Liquor alcohol ester ratio should be less than 1, acid: cheese: high alcohol; 1:2:1.5 is more suitable. If the higher alcohol is higher than the ester, the taste of liquid wine will appear.
In addition, if the ratio of isobutanol to isobamyl alcohol in the wine is appropriate (1:2-2.5), the odor caused by fusel oil is also significantly reduced.
Wine contains a number of polyols, such as glycerol (glycerol), 2, 3 – butanediol, cyclohexanol, mannitol and so on. Sugar can’t get into wine, so most of its sweetness comes from polyols. Glycerin is sweet, butanetetol (tetrineol) sweet than sucrose two times, pentpentanol (arabinol) is also sweet, hexhexanol (mannitol) has a strong sweet taste, in the sweet fruit plays an important role. These substances are viscous and can give liquor a rich mellow feeling.
Polyol is produced when yeast in fermented grains produces alcohol and ferments sugar. The amount of polyol production was related to bacteria species, number of bacteria and raw materials, as well as fermentation speed and composition of fermented grains. Some wild yeast, under suitable conditions, can produce more glycerol and a small amount of arabinol, tinea alcohol, these substances are also an important source of alcohol sweet ingredients in wine. Slow fermentation at low temperature is beneficial to the formation of polyols and other alcohols.
The methanol in liquor is a kind of anesthetic strong colorless liquid, its specific gravity is 0.791, boiling point is about 64℃, can be infinitely soluble in water or alcohol. Methanol looks and smells like alcohol, and is indistinguishable when mixed with alcohol.
Methanol does not give wine any special flavor or odor, but it is highly toxic, so its content should be strictly limited.
To sum up, the strength of liquor depends on the content of ethanol. The main aroma components of liquor are low fatty acid ester and low carbon carbonyl compounds. The main flavoring substances of liquor are acids, higher fatty acid esters and polyols. In addition, phenolic compounds, aromatic compounds are also important aroma components in some wines.