| Black rice Huangjiu is rich in various amino acids,organic acids,vitamins and minerals,and its nutritional value is much higher than that of traditional Huangjiu.At present,there are a series of problems that need to be solved during the brewing process of black rice Huangjiu.For example,anthocyanin is an important physiologically active substance in black rice Huangjiu.The traditional black rice Huangjiu raw material pretreatment methods caused the loss of nutrients in black glutinous rice,which affected the nutritional value of the liquor.The traditional rice Huangjiu koji has a long koji making process and the open koji making process makes the koji quality unstable.At the same time,the roasting black rice Huangjiu brewing process parameters and the research on physiologically active substances need to be further improved.Therefore,studying the effect of different pre-treatment methods on the quality of black rice Huangjiu,and optimizing the pure strain koji and main fermentation process have important practical significance for improving the quality of black rice Huangjiu.This study takes black glutinous rice as raw material,and compares the effects of different pretreatment methods on the quality of brewed black rice Huangjiu.At the same time,optimized the optimum process conditions for koji making by two strains with high enzyme production ability which were selected from Xiecun Huangjiu koji.On the basis of previous experiments,the main fermentation process of black rice Huangjiu was optimized.At last,compared the effects of different pretreatment methods of raw materials and koji on the antioxidant activity of black rice Huangjiu in vitro.The main research contents and results are as follows:?1?Using physical and chemical indicators and brewing sample quality as evaluation indicators,the researcher compared the effects on the suitability of black rice Huangjiu brewed with black glutinous rice which was pretreated by roasting,microwave expansion,and traditional steamed.The results showed that three treated black glutinous rice could be used to brew black rice Huangjiu,and the changes of chemical indexes of the three types of wine were consistent.The difference is the degree of gelatinization of the black glutinous rice after the traditional rice steamed rice treatment,the wine yield and alcohol content are the highest,which were 92.18±0.17%,29.43±0.92%and 14.31±0.09%vol respectively.but the functional factor anthocyanin content is only 180.37±2.39 mg/L,as the lowest.And the gelatinization degree of black glutinous rice after the roasting treatment,the wine yield and alcohol content are the lowest,which were 84.06±0.23%,25.37±0.06%and 13.34±0.16%vol.but the anthocyanin content was increased by about 36.60%compared with the traditional method,which was 284.50±1.58 mg/L.By analyzing the free amino acids in the three wines,there were significant differences in the total free amino acids content in different liquors?p<0.05?.Among them,the content of free amino acids in microwave puffed rice wine was the highest,followed by roasted rice wine and traditional rice wine.HS-SPME-GC-MS was used to analyze the volatile components in the wine.Alcohols and esters were the main aroma components of black rice Huangjiu.The volatile flavor substances were the most abundant in roasted rice wine,with 40 species detected;37 and 34 species were detected in traditional rice wine and microwave puffed rice wine.?2?The 16 strains of fungi selected from Xiecun Huangjiu Koji which was provided by Shaanxi Provincial Engineering Research Center for Edible and Medicinal Fungi were used as starting bacteria,the saccharifying enzyme activity was used as an indicator,using the transparent circle method with experiment of single strain cooked wheat koji,two strains with excellent enzyme-producing performance were screened out,namely M33?Saccharomycopsis fibuligera?and M9?Aspergillus niger?.According to the experiments on the effects of different ratios of M33 and M9 on the combined enzyme production,it was determined that when M33:M9 was 4:6,the enzyme production capacity was the optimal.Using saccharifying enzyme and protease activity as indicators,the single-factor experiment and orthogonal experiment were used to optimize the feed-water ratio,inoculation amount,culture temperature,and culture time,and the best koji-making process parameters were:feed-water ratio of 1.0:0.8,The inoculation amount is 2.50%,the culture temperature is 30?,and the culture time is 5 d.Under these conditions,the activity of saccharifying enzyme produced by compound koji was up to 2735.18±6.14 U·g-1,the activity of protease was up to 1856.24±9.08U·g-1,and the activity of amylase was up to 257.06±3.69 U·g-1.Compared with Xiecun Huangjiu wheat Qu,the activities of saccharifying enzyme and protease were enhanced,and the preparation process was easy to control and the quality was stable.?3?Using roasted black rice and pure strain compound koji as raw materials,with alcohol content and anthocyanin content as indicators,through single factor experiments and orthogonal experiments,the fermentation process parameters of black rice Huangjiu,including ratio of material to liquid,amount of koji and yeast,rewing temperature and time were optimized.The results showed that the optimal conditions were:solid-liquid ratio of1.0:3.0,the amount of koji was 10%,and the amount of yeast was 0.20%,fermentation temperature of 30?,fermentation time of 6 d.Under these conditions,the alcohol content of black rice Huangjiu was up to 13.49±0.45%vol,and the anthocyanin content was up to306.36±1.02 mg/L.?4?Detected the total phenol,total flavonoids,anthocyanin content and antioxidant activity in vitro of black rice Huangjiu produced by different raw materials and processing methods:roasted rice with pure strain koji,roasted rice with Xiecun wheat koji,steamed rice with pure strain koji,steamed rice with Xiecun wheat koji.Results shows that reducing capacity and the ability to scavenge DPPH,FRAP,ABTS radicals and of four black rice Huangjiu was positively correlated with its content of total phenol,total flavonoids and anthocyanin.The order was:roasted rice with pure strain koji group>roasted rice with Xiecun wheat koji group>steamed rice with pure strain koji group>steamed rice with Xiecun wheat koji group,and roasting treatment had significant effect on antioxidant activity of black rice Huangjiu?p<0.05?. |
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