Study On Ethyl Carbamate And The Related Precursors In Hakka Rice Wine

Hakka rice wine is an important branch of yellow rice wine in China, mainly mainly distributed in Meizhou, Heyuan and Huizhou area in Guangdong province. Hakka rice wine is a kind of nutritional health winewhich contains a variety of of nutrients and functional ingredients. Ethyl carbamate(EC) is a well-known carcinogen which occurs naturally in many fermented foods. The existence of EC in Hakka rice wine may bring some food safety issues and significantly restricts the development of Chinese rice wine industries.The research results are as follow:(1) The measurement of ethyl carbamate content in Hakka rice wine by solid-phase extraction combined with GC/MS internal standard method had been was improved.N-butyl carbamate was used as internal standard, and the parameters of ethyl carbamte extraction in Hakka rice wine were optimized by use of solid phase extraction column(Chem Elut,50 m L).The optimum measurement conditions were summed up as: the adsorption time of the sample in the column was 20 min, the use level of dichloromethane was 150 m L. Results showed that the standard curves of ethyl carbamate was linear over the quality range of10~1000μg/L,the correlation coefficient R2 were 0.9992. The recovery of ethyl carbamte was 91.86%~98.16%, RSD was 3.2%.Base on this method to determine EC content in Hakka rice wine during traditional fermentation process: before fried the liquor,the content of EC was 14.56~26.72 ug/ L, after fried the liquor, the content of EC was 62.15 ug/ L, after2 years of aging, the content of EC was 113.46 ug/ L.(2) The content of EC,total sugar, total acid, urea, alcohol, and amino acids in Hakka rice wine were determined and analyzed.The results showed that EC and urea, arginine,ornithine existed significant correlation(P<0.05),the correlation coefficient were 0.656、-0.651,0.743;EC and citrulline existed significant correlation(P<0.01), the correlation coefficientwas-0.836.Through linear regression analysis, which takes EC as the dependent variable, urea, arginine,arginine, ornithine as independent variables, the linear regression equation was Y=404.286-5.777X1-6.101 X2+1.448 X3+0.231 X4(Y for the content of EC, X1 as urea content, X2 as citrulline content, X3 as citrulline content, X4 as ornithine content);The dynamic equations of the formation of EC in the modle wine system was establish to predict the values of EC in the real Hakka rice wine sample. In fact, the predicted values are only 70.9% to 87.5% of the measured values in the raal Hakka rice wine sample. It suggests that the urea is not the only one precursor of ethyl carbamate in Hakka rice wine,from the view of kinetics.(3) Based on the arginine metabolism, the effect of exogenous additives(L-ornithine hydrochloride, urease) on the content of EC and precursors related in Hakka rice wine during fermentation were analyzed. The results show that: the addition of L-ornithine hydrochloride in Hakka ricewine during fermentation process, the content of urea decreased, citrulline content reduced, less influence on arginine and ornithine; the addition of urease inin Hakka rice wine during fermentation process, the content of urea decreased, content of arginine reduced, less influence on citrulline and ornithine.L-ornithine hydrochloride and urease inhibits formation of EC L- ornithine hydrochloride and urease has certain inhibitory effect on the formation of EC during fermentation.