Opinion of the Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food (AFC) on hydrocyanic acid in flavourings

Please note that this opinion replaces the earlier version which contained an error in the 'conclusion and recommendation' section on page. 23. SUMMARY The Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food is asked to evaluate substances used as flavourings or present in flavourings or present in other food ingredients with flavouring properties. In particular, the Panel is asked to advise the Commission on the implications for human health of hydrocyanic acid (HCN) in the diet. The Panel noted that cyanogenic glycosides present in plants, as sources of hydrocyanic acid, are relatively non-toxic until HCN is released. This can occur as a result of enzymatic hydrolysis by β-glucosidases following maceration of plant tissue, or by the gut microflora. Depending on the specific glycosides the hydrolysis products can be, besides sugar moieties and HCN, benzaldehyde (for amygdalin, prunasin, sambunigrin,), p-hydroxybenzaldehyde (for dhurrin) and acetone (for linamarin). The potential toxicity of a cyanogenic plant depends primarily on its capacity to produce HCN. The Panel noted further that: 1. Following oral administration, HCN is readily absorbed and rapidly distributed in the body via the blood. 2. HCN absorbed from the gut is metabolically converted to the less toxic thiocyanate. Other detoxification pathways include combination with vitamin B 12 or some sulphur-containing amino acids. Acute toxicity results when the rate of absorption of HCN is such that the metabolic detoxification capacity of the body is exceeded. 3. Cases of human intoxication and chronic neurological effects have occurred from the ingestion of processed plants. This is particularly apparent when processing practices change as a result of trading practices or uncertain food supply. 4. The cyanide ion inhibits enzymes associated with cellular oxidation and causes death through energy deprivation. The symptoms, which occur within a few minutes, may include constriction of the throat, nausea, vomiting, giddiness, headache, palpitations, hyperpnoea then dyspnoea, bradycardia, unconsciousness and violent convulsions, followed by death. 5. The occurrence of intoxication symptoms depends upon the rapidity of the increase in HCN concentration in the tissues. In the case of cyanogenic glycosides, the route of exposure, the nature of the cyanogenic compound, the dose, and the ability of the organism to detoxify cyanide determine the symptoms. HCN 2 6. The available toxicity data show that cyanogenic glycosides from certain plants could produce acute toxic effects. Thus fatalities have occurred from e.g. consumption of stone fruit kernels. 7. The …