Changes of ethyl carbamate and its precursors in maesil (Prunus mume) extract during one-year fermentation

• Ethyl carbamate, cyanide, and ethanol in maesil extracts were determined for one year.
• Ethyl carbamate was detected from day 150.
• The contents of EC, cyanide, and ethanol were higher in the extracts fermented at 25 °C compared with those at 15 °C.
• Soaking of maesil after day 90 is not critical for determining cyanide content in the maesil extract.
• Ethyl carbamate contents had a higher positive correlation with the cyanide contents than ethanol contents.

The contents of ethyl carbamate (EC), cyanide, and ethanol were determined in maesil extracts that are liquids generated from fermentation of maesil fruit and brown sugar at 25 °C or 15 °C for one year. EC was detected from day 150 with a maximum value of 9.7 μg/kg. The cyanide levels increased with prolonged soaking time of maesil and decreased at day 150 where EC was firstly detected, indicating that cyanide is a precursor of EC. Ethanol slowly increased at 25 °C, while it fluctuated at 15 °C. The contents of EC, cyanide, and ethanol were higher in the extracts fermented at 25 °C compared with those at 15 °C. EC contents had a higher positive correlation with cyanide contents (R = 0.658) than ethanol contents (R = 0.351). These results indicate that fermenting temperature gave a rise of EC precursors and consequently led to the increase of EC in the maesil extract.