Of fusel oil

Isovaleric acid, Me2CHCH2COOH, is a colourless liquid with the unpleasant odour of valerian, b.p. 177 "C. Occurs in the roots of valerian and angelica together with an optically active form of methylethylethanoic acid. Prepared by oxidation of isoamyl alcohol. A mixture of acids similar to that obtained from valerian roots is prepared by oxidation of fusel oil. 

A mixture of 10 cc. of alcohol and 0.20 cc. of 15 per cent sodium hydroxide solution, when evaporated down to 1 cc. and supersaturated with dilute sulphuric acid, should not have the odor of fusel oil. 

Guymon (21) reported the composition of tray liquids for brandy distilled in continuous column, respectively, at 130°, 170°, and 181° proof. The maximum level of fusel oil occurred on the tray nearest in proof to about 130°. This is the second tray below the product tray for the customary 170° proof of distillation of the product. 

Guymon, J. F., Principles of Fusel Oil Separation and Decantation, Amer. 

EXAMPLE The aqueous liquid from 50 grams of fusel oil weighed 2x0 grams and contained x-6% by weight of alcohol, so that the 210 grams of aqueous... 

Alcohol is distilled up to a content of 96% in one or more stages. About 1 % of ethanol consists of fusel oils (degradation products of amino acids) which can be used as solvents for lacquers and resins. Solids from the processed liquor containing proteins, carbohydrates, mineral salts, riboflavin and other vitamins are used in poultry, swine and cattle feeds. C02 and H2 produced in butanol-acetone-butyric acid production can be used for the chemical synthesis of methanol and ammonia, or are burned. 

Aldehydes, especially the longer chain saturated and branched chain aldehydes (i.e., propanal, butanal, 2-methyl-1-propanal, 2-methyl-1-butanal, and 3-methyl-1-butanal) are also intermediates in the formation of fusel oils. These pathways involve anabolic metabolism of sugars or transamination of amino acids. During ethanol fermentation, the aldehydes may be reduced to the corresponding alcohols by ADH enzymes and excreted into the media. Herraiz et al. (19) found that longer chain aldehydes were not as readily reduced and excreted by the yeast, e.g., 35% reduction was observed for pentanal compared to 3% reduction for decanal. 

When starch is the starting material, there is obtained, in addition to ethyl alcohol, a smaller amount of fusel oil (German Fusel, inferior liquor), a mixture of primary alcohols mostly isopentyl alcohol with smaller amounts of /2-propyl alcohol, isobutyl alcohol, and 2-methyl-1-butanol, known as active amyl alcohol amyl pentyl). 

The liquid should be dear and should give no turbidity with water. It should give no smell of fusel oil, and practically no residue on evaporation (o oi per cent.). It should be as free as possible fron acidity. 

Fusel oil may be detected by adding water, shaking out with chloroform, separating, and allowing the chloroform to evaporate. The residue wifh addition of dilute sulphuric acid should give no smelt of fusel oil. Fusel oil may he estimated quantitativdy by oxidation to valeric arid. 

Derivation Distillation of fusel oil or the mixed alcohols resulting from the chlorination and hydrolysis of pentane. 

Fusel Oil and Succinic Acid, etc.—It has been shown that this group of by-products derives not from the sugar but from other materials present in the fermenting liquor. F. Ehrlich in many researches (1904-1910) has shown that the higher alcohols and aldehydes, which when mixed we call fusel oil, are formed by the deammination of amino acids resulting from the hydrolysis of proteins. Thus isoamyl alcohol, which is the chief constituent of fusel oil, is closely related to leucine, amino-isohexoic acid, and active amyl alcohol is similarly related to isoleucine, a-amino-/ -... 

British brandy and whiskey prepared in a similar way from potato starch need to be freed from a rather larger percentage of fusel oil than does barley spirit. 

Somewhat harsh, chemical odor, reminiscent of fusel oil, but not as heavy, however, more penetrating, nauseating, cough-provoking (Arctander, 1967). An odor threshold of 0.5 ppm is given by Flath et al. (1967). 

For detecting fusel oil in alcohol, Mr. E. X. Kent finds pure r.ulphuric acid tho best test. Half fill ft tost tube with tho spirit to be tested, then fill up slowly witli puro concentrated milpburic acid. Pure spirit remains colorless iinpuro spirit becomes colored in proportion to tho amount of fusel oil present. 

Azeotropic and extractive distillation are old processes which have become widely used since about 1930. In 1908 Emile Guillaume patented an extractive distillation process for the removal of fusel oil from fermentation alcohol.10 The name extractive distillation is said to have been introduced by Dunn et al.6... 

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