| Huangjiu is a kind of nutrient-rich brewing wine.But there are still some harmful substances that pose health risks to human body in Huangjiu.In this study,the content of ethyl carbamate(EC)in Huangjiu was effectively reduced by adding raspberry extract(RBE)during fermentation process,and the quality of Huangjiu was optimized.Further,this study also explored to analyze the inhibitory mechanism of RBE on EC.The results of this study would provide reference for the effective inhibition and targeted regulation of EC formation in Huangjiu.The main results are as follows:1.Different plant extracts(raspberry extract,pyracantha fortuneana extract,bamboo leaf extract and sea buckthorn extract)rich in phenolic substances were added in the fermentation process of Huangjiu,and the influences of these extracts on the contents of harmful components in Huangjiu were analyzed.The results showed that the contents of EC(21.942 ± 6.895 μg/L),methanol(0.289 ± 0.088 mg/L)and urea(21.183 ± 2.365 mg/L)in the group added raspberry extract were the lowest,and the contents of methanol and urea were significantly lower than those in control group.Combined with the contents of fusel oil and polyphenols,it was considered that the addition of raspberry extract could inhibit the accumulation of EC or other harmful components in Huangjiu and had the potential to optimize Huangjiu quality based on our preliminary screening.2.Analyze the effects of RBE addition in Huangjiu fermentation on EC content,EC precursors contents,the key enzyme activities of arginine metabolism and Huangjiu quality.Gas chromatography-mass spectrometry(GC-MS)analysis showed that EC content in RBE group was significantly decreased compared with the control group.The contents of EC precursors(urea and citrulline)in RBE group were always lower than that in control group,while the content of arginine that was the upstream precursor of urea and citrulline was always higher than that in control group.In terms of enzyme activity,the activity of arginine deiminase(ADIase)in RBE group was always significantly stronger than that in control group,while the activity of ornithine transcarbamylase(OTCase)was always significantly weaker than that in control group.The results indicated that the degradation rate of citrulline was higher than the production rate in the fermentation process after adding RBE.In addition,the basic physicochemical indexes of RBE group were superior to those of control group,especially the alcohol content of RBE group was significantly higher than that in control group.Free amino acid analysis showed that the content of every free amino acid in RBE group was significantly higher than those in control group,except for proline.Furthermore,it was presented that the contents of volatile alcohols,esters and phenols in RBE group were higher than those in control group.3.Through adding RBE into the simulative culture system of Huangjiu,the regulation of RBE on arginine metabolism in Saccharomyces cerevisiae was analyzed,including the influence in arginine catabolism,arginine transport and the transcriptional expression of related genes.The results showed that RBE promoted the accumulation of arginine,but decreased the levels of urea and citrulline.In terms of enzyme activity,the activities of OTCase and urease in RBE group were higher than those in control group,but the activities of ADIase and arginase in RBE group were lower than those in control group,indicating that the degradation rate of citrulline and urea increased while the degradation rate of arginine decreased during the cultivation of simulative Huangjiu system supplemented with RBE.Besides,the results of q RTPCR analysis were consistent with the changes in enzyme activities.In RBE group,the expressions of ALP1 gene,CAN1 gene and GAP1 gene related to arginine transport were upregulated,while the expressions of VBA2 gene and CAR1 gene were down-regulated.The expressions of DUR1,2,DUR3 and DAL82 gene related to urea transport were up-regulated,while the expressions of DAL81 gene were down-regulated.And the expressions of ARG1 and CAR2 gene related to the catabolism of citrulline and ornithine were up-regulated,which suggested that RBE had a regulatory effect on arginine metabolism of in Saccharsaccharus cerevisiae at the transcriptional level. |
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