Analysis Of Cyanide In The Fermentation Of Chinese Rice Wine

Ethyl carbamate(EC)is a potential carcinogen in Huangjiu(Chinese rice wine).The studies on the mechanism of EC formation and its precursors are important to solve the problem in Huangjiu.Urea and cyanide are widely known as precursors for EC formation.Many researches were carried out on the pathway of EC formation from urea in Huangjiu,however,little attention was paid to cyanide.In this study,cyanides in Huangjiu and relevant raw materials were analyzed using a new method established for the determination of trace cyanide in Huangjiu.Based on the method,the relationship between cyanide and EC formation during fermentation were investigated.This work provided an efficient analytical method and a basis for further studying the relationship between ethyl carbamate and cyanide in Huangjiu.The main results were as follows:(1)A sensitive and convenient device was developed for derivatization of cyanide,and a LC-MS/MS method was established for the determination of cyanides based on the derivating reaction.It could be used to determine the cyanides,including free cyanide and total cyanide,in Huangjiu and its raw materials.The method had a good linearity with correlation coefficient greater than 0.99,the LOD was 0.01 μg·L-1,recovery rate was 89.7%~106.0% and precision was less than 5.0%(RSD).It was suitable for the determination of trace cyanides in Huangjiu.(2)Through the established method,we analyzed cyanides in Huangjiu and its raw materials.The results showed the existence of trace cyanides in Huangjiu and raw materials.The cyanide concentration was low in rices.A rather higher concentration of cyanides was detected in the raw material wheat Qu,with a concentration range of 20.35~93.73 μg·kg-1 for the free cyanide and 98.09~1032.03 μg·kg-1 for the total cyanide.Free cyanide and total cyanide in Huangjiu were lower than 15 μg·L-1 and 30 μg·L-1,respectively.This result suggested that cyanide might not be an important factor on the formation of ethyl carbamate during the storage and sale of Huangjiu.(3)To better understand the relationship among EC,urea and cyanide in the fermentation of Huangjiu,we compared two fermentation processes with different addition of wheat Qu,typical traditional production and mechanized production.The results showed that the addition of Wheat Qu caused the increase of cyanide in both broth and mash during fermentation.As the fermentation went on,the cyanide in mash could transfer to the broth.Total and free cyanide in broth were consumed and EC increased gradually.Furthermore,we studied the contribution of urea and cyanide on the formation of EC in simulated solution under different condition.The results showed that the formation of EC was related with cyanide,but little with urea during the fermentation.Cyanide,especially free cyanide,could be an important precursor of EC during the fermentation.