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Although rare, there have been a few reported deaths due to cyanide poisoning from foods containing cyanogenic glycosides. These reports include deaths from elderberry juice that was thought to contain stems and/or leaves (the stems and leaves contain much higher cyanogenic glycosides than the berries, and ripe berries by themselves are considered safe) <ref>[http://www.cdc.gov/mmwr/preview/mmwrhtml/00000311.htm Poisoning from Elderberry Juice -- California. CDC website. 1998. Retrieved 08/30/2016.]</ref>, apricot kernels (pits), choke cherry pits, and improperly processed cassava (a staple food in parts of North Africa) <ref name="who"></ref>. A lethal dosage of cyanide in humans is estimated to be around 1.52 mg per kilogram of body weight, with 0.56 mg per kilogram of body weight being the lowest recorded (although this lowest figure was obtained from a historical case when the measurements taken may not have been accurate) <ref>[http://www.atsdr.cdc.gov/toxprofiles/tp8.pdf Toxicology Profile for Cyanide. Agency for Toxic Substances & Disease Registry. July 2006. Pg 42. Retrieved 08/25/2016.]</ref>. High exposure can cause light-headedness, nausea, vomiting, stomach cramps, diarrhea, convulsions, harm to the brain and heart, comas, and death. Exposure to 0.05 mg of cyanide per kilogram of body weight per day for 15-364 days is considered to be the minimum accumulative cyanide exposure by the US CDC. Accumulative exposure can cause health risks, such as reproductive, respiratory, neurological, thyroid, and gastrointestinal issues <ref>[http://www.atsdr.cdc.gov/toxprofiles/tp8.pdf Toxicology Profile for Cyanide. Agency for Toxic Substances & Disease Registry. July 2006. Pg 21. Retrieved 08/25/2016.]</ref>. In some foods, such as marzipan and persipan (made from bitter apricot seeds), the processing of this food destroys the natural beta-glucosidase enzyme (which denatures at 75°C), leaving the flora in the human gut to break down the cyanogenic glycosides. Even if an abnormally large portion of marzipan or persipan is ingested, the lack of beta-glucosidase along with the high calories in the food acts as a slow release of cyanide into the human body which the body can deal with <ref>[http://link.springer.com/article/10.1007%2Fs00204-015-1479-8 Bioavailability of cyanide after consumption of a single meal of foods containing high levels of cyanogenic glycosides: a crossover study in humans. Klaus Abraham, Thorsten Buhrke, Alfonso Lampen. 2015.]</ref>.
Upon learning about cyanogenic glycosides, brewers often question the toxicity of ingredients such as cherry pits or apricot kernels in beer. Cherry pits have traditionally been used in [[lambic]] kriek beers in Belgium. However, the dilution of HCN from cherry pits in beer results in benign levels. Assuming full breakdown of these glycosides, and that none of the HCN boils off (25.6°C boiling temperature), levels of HCN introduced from cherry pits are too low to cause harm to adult humans. The EU regulates that alcoholic beverages cannot exceed 1 mg of HCN per ABV percentage (v/v%) per liter <ref>[http://ec.europa.eu/food/fs/sfp/addit_flavor/flav09_en.pdf COUNCIL DIRECTIVE of 22 June 1988 on the approximation of the laws of the Member States relating to flavourings for use in foodstuffs and to source materials for their production (88/388/EEC). The European Food Commission, Food Safety. Retrieved 08/26/2016.]</ref>. Luk Daenen, a glycoside researcher, calculated that for a 4% ABV alcohol beer, 4 mg of HCN per liter is allowed. With 200 grams of cherries per liter, and the pits being 10 - 14 grams of that weight, there is 22 - 30.8 mg amygdalin per liter of beer. Around 6% of the weight of amygdalin is converted into HCN. Assuming maximum extraction of HCN from the amygdalin glycoside, which is unlikely because the pits are not ground up when used in beer, this equates to 1.3 - 1.82 mg of HCN per liter of beer. This amount is less than the 4 mg of HCN per liter that the EU regulation states. Considering that ~42 mg of HCN is required to kill a person that weighs 70 kilograms (154 pounds), that person would need to drink around 23 liters of beer <ref name="daenen">[https://www.uclouvain.be/cps/ucl/doc/inbr/documents/presentation-luk-daenen.pdf "Use of beta-glucosidase activity for flavour enhancement in specialty beers," slideshow by Luk Daenen. 2012. Retrieved 08/26/2016.]</ref>. Considering that 350 mL of pure alcohol would kill a 70 kilogram adult <ref>[http://www.alcohol.org.nz/alcohol-its-effects/health-effects/alcohol-poisoning "Alcohol Poisoning". NZ Health Promotion Agency. Retrieved 08/26/2016.]</ref>, the amount of 4% ABV beer required to kill a 70 kg adult from alcohol poisoning is around 8.75 liters. Alcohol would kill such a person far before cyanide poisoning would become a concern. In general, the potential cyanide in most plants will become too dilute to have any health problems when added to beer in normal amounts, however there might still be plants that are extremely high in HCN content that should be avoided in beer (see the table below). If there is a concern that an ingredient containing potentially high levels of HCN could reach unhealthy levels in beer, the beer should be sent for lab analysis so that the HCN levels can be determined before being consumed.
Some cyanogenic foods can have their cyanogenic glycosides reduced by cooking them at 230°C for 15 minutes (flaxseed, for example) <ref name="Chaouali"></ref><ref name="flax"></ref>, however some amygdalin based cyanogenic plants may have their amygdalin content reduced to about 25% by cooking alone (apricot seeds, for example; only the cooking temperature of 100°C was tested <ref name="tuncel"></ref>). Fermentation by certain species of microbes can have a greater effect on reducing amygdalin to HCN than cooking alone. Microbes that have been shown to break down amygdalin include some species of lactic acid bacteria including ''Lactobacillus plantarum'', and fungi such as ''Endomyces fibuliger'', ''Pichia etchellsii'', and ''Hanseniaspora valbyensis''. Some strains of ''Brettanomyces'' that have high beta-glucosidase activity might be able to break down amygdalin by around 64%, and some strains of ''S. cerevisiae'' might be able to break down up to around 10% of amygdalin, but this needs to be verified by science. Once the amygdalin is broken down into HCN, the HCN can then be volatilized off by cooking in a ventilated space <ref>[http://link.springer.com/article/10.1007/BF00151870 Simple screening procedure for microorganisms to degrade amygdalin. L. Brimer, G. Tunçel, M. J. R. Nout. 1993.]</ref><ref>[http://www.ncbi.nlm.nih.gov/pubmed/7710917 Microbial degradation of amygdalin of bitter apricot seeds (Prunus armeniaca). Nout MJ, Tunçel G, Brimer L. 1995.]</ref><ref name="Daenen1"></ref>. In normal brewing procedures, however, the beer is not cooked nor ventilated, so any HCN that is produced by the breakdown of cyanogenic glycosides should be presumed to remain in the beer.