This monovalent alcohol (Carbinol, methyl alcohol, wood alcohol, Holzgeist) is a colorless, burning-tasting liquid with a distinctive, sweet smell. Although he is quite different from ethanol (Potable alcohol), it can by overlaying with others flavorings hardly be recognized in alcoholic taste. Already the ancient Egyptians produced methanol by pyrolysis (splitting of organic compounds by high temperatures starting from 200 ° C) of wood and embalmed their dead with a mixture of substances. It was named "methylene" in 1834 by the French chemists Jean-Baptiste Dumas and Eugène-Melchior Péligot. It is composed of "méthy" for wine and "hylé" for wood. Methanol itself is of low toxicity, but its metabolites, especially formaldehyde, are toxic.
Even the smallest amounts of 0.1 g of methanol per kg of body weight are hazardous to health, from 5 times the amount of life-threatening. From there it comes to convulsions, vomiting, difficulty breathing, blindness and in extreme cases to death. Natural levels are included White wine between 17 and 100 mg / l and at red wine about twice as high between 60 and 230 mg / l. These quantities are sanitary harmless. The former of the Austrian specialty Uhudler By the way, the assumed high methanol values have long since proved to be wrong. Within the EU, there are limits defined by wine legislation, which are included spirits 200 g / hl, with ethanol 30 mg / l, with fruit brandy 1,000 g / hl and with brandy 200 g / hl (see also under ADI ).
The chemical difference between the two alcohol types ethanol and methanol is actually very small. Simply put, ethanol has only one carbon chain longer than one atom compared to methanol. Both alcohols are non-toxic (in correspondingly small amounts), but after consumption they have completely different degradation rates. In this process in the human body are ADH (Alcohol dehydrogenases) involved. While ethanol first too acetaldehyde and then very quickly too acetic acid is converted from methanol, the first highly toxic formaldehyde (methanal) and then from this formic acid, The latter is ten times stronger than acetic acid and can only be broken down very slowly, which can lead to a dangerous to life-threatening hyperacidity of the blood.
Methanol is produced in minor amounts as by-product in the alcoholic fermentation by enzymatic degradation of the pectins, which are mainly contained in the cell substances of the berry shells and stems (not from sugars such as ethanol). He is one of the fusel alcohols resulting from the fusel oils form. Through intensive and long mash contact at the maceration or at higher fermentation temperatures arise larger amounts. Therefore, the proportion of red wines (with berry contact) is generally much higher than that of white wines (without). Especially the solid components of the grapevine like leaves and stems (by improper vintage ) and to a lesser extent the pulp lead to increased methanol formation.
Likewise is also in the production of spirits the methanol content higher. This is especially true in the production of vodka the case, because potatoes contain high amounts of pectin. Therefore, at the distillation separated the methanol fraction. This is relatively easy because methanol at 65 ° Celsius an even lower boiling point than ethanol (the drinking alcohol) with 78 ° Celsius possesses. If this separation is not carried out carefully, the distillate would contain dangerous amounts. The separation was earlier in products of questionable producers, such as in times of the American prohibition (1920-1933) because that was much easier and larger quantities of cheap fusel could be produced and sold. But even today, such illegally produced products keep coming into circulation.
An interesting information comes from the website www.chemie-im-alltag.de (Oliver Reiser): Since methanol is oxidized by the alcohol dehydrogenase much slower than ethanol, the best antidote for methanol intoxication, the patient over several days under an alcohol concentration to keep from 1 per thousand. Ethanol acts as a competitive inhibitor of methanol, that is, ethanol binds preferentially to the ADH (about 8,000 times better), so that dangerous for the body oxidation from methanol to formaldehyde and finally to formic acid is prevented. Methanol is then excreted unchanged over several days as a water-soluble substance with the urine. See a list of all wine ingredients below total extract,