ETHYL CARBAMATE FORMATION IN GRAIN BASED SPIRITS: PART I: POST-DISTILLATION ETHYL CARBAMATE FORMATION IN MATURING GRAIN WHISKY

Abstract

Distilled spirits are subject to post-distillation ethyl carbamate formation in the presence of appropriate precursors. Freshly distilled grain whisky, produced by the continuous distillation Coffey still process, normally contains ethyl carbamate concentrations not exceeding 20 ppb (normalized to 43% v/v alcoholic strength). Further ethyl carbamate formation, dependent upon the presence of trace anionic precursors such as cyanate, cyanide, and copper cyanide complexes, may take place during normal maturation in oak casks. Related but different mechanisms may induce ethyl carbamate formation under normal daylight and artificial light in the laboratory. Ethyl carbamate precursors convert into ethyl carbamate during the initial three months of maturation and are not detectable in the final bottled product. Thus the final ethyl carbamate concentration in spirit is dependent upon the initial ethyl carbamate level measured after distillation plus ethyl carbamate formed from precursors. It is important during process control to monitor not only the ethyl carbamate level in freshly distilled spirit but also the spirit's potential to form ethyl carbamate from precursors with the objective of minimizing these components in the freshly distilled and maturing spirit. A scheme for predicting final ethyl carbamate concentrations from precursor concentrations in freshly distilled spirit is presented.