Ethyl carbamate in foods and beverages: a review

Abstract

Food and beverages contain many toxic chemicals that raise health concerns. Ethyl carbamate (EC) or urethane is the ethyl ester of carbamic acid. It occurs at low level, from ng/L to mg/L, in many fermented foods and beverages. Ethyl carbamate is genotoxic and carcinogenic for a number of species such as mice, rats, hamsters and monkeys. It has been classified as a group 2A carcinogen, “probably carcinogenic to humans”, by the World Health Organization’s International Agency for Research on Cancer (IARC) in 2007. The benchmark dose lower limit of ethyl carbamate is 0.3 mg/kg bw per day and the mean intake of ethyl carbamate from food is approximately 15 ng/kg bw per day. Those levels were calculated for relevant foods including bread, fermented milk products and soy sauce. Alcoholic beverages were not included in this calculation. However, high levels of ethyl carbamate can be found in distillated spirits at concentrations ranging from 0.01 to 12 mg/L depending on to the origin of spirit. Alcoholic drinks should thus be considered as a source of ethyl carbamate. Ethyl carbamate is produced by several chemical mechanisms: first, from urea and various proteins like citrulline produced during the fermentation step and second from cyanide, and hydrocyanic acid, via ethyl carbamate precursors such as cyanate. A large panel of ethyl carbamate formation mechanisms is described from simple ethanolysis of urea in homogeneous liquid phase to photochemical oxidation of cyanide ion or complex heterogeneous gas/solid catalytic reactions. Determination of ethyl carbamate in foods and beverages involves various strategies according to the material, food or beverage, solid or liquid, and according to the concentration, from ng/L to mg/L. Usually, adapted extractive techniques and pre-concentration step are followed by analysis by gas chromatography coupled to mass spectrometry (GC–MS of GC–MS–MS). High performance liquid chromatography (HPLC) and semi-quantitative spectroscopic methods (infra-red) are also proposed as valuable alternatives to the classical but time-consuming GC–MS. Various preventing methods are developed and used in some cases at industrial scale to lower ethyl carbamate levels in food. Two types of preventing methods are described. First, adapted and optimised practices in all step of the chain of foods’ (or beverages) production lead in general to low ethyl carbamate level. Second, the abatement of ethyl carbamate precursors can be done by adapted enzymatic, physical chemical or chemical methods according to the natures of raw materials and conditions of their production processes.