The Effect Of Urea On Ethyl Carbamate Formation During Rice Wine Storage And Its Removal By Resin Adsorption

Ethyl Carbamate(EC) is a carcinogen mainly produced by urea during frying and storage in Chinese rice wine, especially during storage. So it is very important to reduce the concentration of urea for EC control. There’s no limitation on the level of urea in rice wine. And some methods had been used for urea reduction with some problems for application.In this research, the change of EC with urea during the storage of rice wine, built the dynamic model and calculated the maximum concentration of urea before storage. Some adsorption materials were screened for removing urea in Chinese rice wine. and an adsorption resin was obtained with effective adsorption of urea. This work provided a safe and effective approach for the removal of urea in Chinese rice wine. The main results are as follows:(1) The determination of urea and EC in Chinese rice wine. Optimized high-performance liquid chromatography with fluorescence detection(HPLC-FLD) and headspace solid-phase microextraction and gas chromatography-mass spectrometry(HS-SPME-GC-MS) with deuterium isotope-labeled EC-d5 as internal standard.can detect urea and EC accurately.(2)The change of EC with urea in rice wine and model rice wine, it can be concluded that the similarity of model rice wine and rice wine was no less than 80%. Considering the degradation of urea and EC formation from urea, the activation energy of urea degradation(Ead) and EC formation from urea(Eau) were calculated 100.44 kJ?mol-1 and 85.88 kJ?mol-1, respectively. The dynamic model equation, which involved urea content, temperature, time, and ethanol, was established. Using the equation to verify the rice wine with a perfect result. The limitation of urea in rice wine before storage can be predicted by the equtaion.When the initial concentration of EC is zero, if the content of EC in rice wine with 10% ethanol after 3 years storage under 20℃ was no more than 200 μg·L-1, the content of urea must be reduced less than 4.5 mg·L-1 before storage.(3) Adsorption materials were screened for removing urea in rice wine, and an adsorption resin was selected for the effective adsorption of urea. The optimized adsorption conditions by the resin were as follows: the addition of resin was 10%(v?v-1), the temperature was 40℃, the adsorption time was 24 h. Under the treatment conditions, the removal efficiencies of urea were 32~49% for different samples with different concentration of urea. For the rice wines with higher urea concentration(>15 mg?L-1), the concentration of urea can be reduced to less than 4.0 mg?L-1 after several adsorption treatments. Moreover, significant changes of main flavor components in the wines were not founded after multi-adsorption treatments.