The alcoholic fermentation of mash produces fermentation by-products, in addition to ethanol and carbon dioxide. These accompanying substances infiltrate the distillate during the distillation process. Typical fermentation by-products are methanol, ethyl acetate (typical “glue smell”), butanol, isoamylalcohol and hexanol.
The thorough separation of head and tail during distillation ensures that most of the fermentation by-products are eliminated. Incorrectly distilled or diluted spirits may contain fermentation by-products, such as methanol, and may cause very serious or even life threatening health problems when consumed excessively.
AGES examines hundreds of spirit samples – gin, fruit brandy, rum, tequila, vodka – for methanol from food and beverage retailers, as well as from smaller distilleries.
Regulation (EC) No. 110/2008 specifies the maximum levels of methanol in distilled alcoholic beverages. The regulation prescribes a maximum level of 1,000 g methanol/hl for brandies made from apricots, cherries and pomaces, 1,200 g for brandies made from pears, apples, plums and raspberries and a maximum level of 1,350 g for brandies made from elderberries, currants and rowanberries, calculated based on pure alcohol.
Methanol is released from pectin during the fermentation of plant-based raw materials. The varying pectin levels in the raw ingredients are the reason why different maximum levels for methanol have been defined for fruit brandies. Methanol itself is only toxic to a slight degree, opposed to its degradation products: the enzyme alcohol dehydronenase (ADH) transforms methanol into formaldehyde and formic acid in the liver. Ingesting 0.1 g methanol per kg body weight is believed to have an adverse effect on human health.
Typical symptoms of methanol poisoning are nausea, vomiting, dizziness, abdominal cramps, headaches and disorientation. Later symptoms include damaged nerves and macular oedema that cause visual impairment (up to blindness in extreme cases), heavy breathing, loss of consciousness and, finally, respiratory paralysis.
Important: Should any of the symptoms mentioned above occur following the consumption of high-proof spirits, visit a doctor or a hospital immediately! The Ministry of Health recommends generally abstaining from the consumption of high-proof alcohol from unknown sources to avoid health-related problems.
Methanol poisoning is primarily treated by giving an ADH inhibitor and ethanol, in the form of 40 % abv schnapps, for example. Ethanol has a higher affinity to alcohol dehydrogenase than methanol, thus, slowing down the transformation process of methanol into formaldehyde and formic acid.