Application Research Of DMDC Pretreatment In Khoyo Ice Wine Brewing

Fermentation of ice wine is accomplished at low temperature and high sugar.Its fermentation process is easy to infect of miscellaneous bacteria and breeding of spoilage bacteria.Therefore,the grape mash should be pretreated to eliminate or reduce the contamination of bacteria.DMDC(dimethyl dicarbonate)is a safe,simple,rapid and low cost bactericide.It has been deeply researched in wine brewing,but its application in ice wine brewing and its research on color and quality are rarely reported.In this paper,useing kyoho grape as raw material to brew kyoho ice wine,the influence of DMDC pretreatment on the quality of grape vine,on the related physical and chemical indicators during the fermentation of kyoho ice wine and the sensory evaluation of wine,and on color and quality of kyoho ice wine brewing with kyoho grape and Vitis davidii Foex,were investigated.The main conclusions are as follows:The grape mash was pretreated by DMDC,sulfite and DMDC combined with sulfite at different temperatures.The grape mash was pretreated by DMDC,sulfite and DMDC combined with sulfite at different temperatures.The effects of these pretreatment methods on the physical and chemical indexes such as microbial colony number,anthocyanin,chromatic aberration value,total phenol,pH and volatile acid in grape mash were studied.The results showed that there was no significant effect on the bactericidal effect of the total number of colonies at 2 h,4 h and 6 h at the same temperature(p?0.05);compared with 4°C,the pretreatment at 25°C could achieve greater bacteriostatic effect in a shorter time,and had little effect on the physical and chemical indicators of grape mash.The antibacterial effect of 250 mg/L DMDC on the microorganisms in grape vines was significantly stronger than that in other pretreatment groups(p<0.05),especially for the total number of colonies,yeast and coliforms,which could reduce 2.05,2.47 and 1.89 Log CFU/mL,respectively.sulfite and DMDC combined with sulfite pretreatment can better retain the anthocyanin and polyphenol content,and play the role of acid reduction,but the bactericidal effect on microorganisms was not as good as that of DMDC pretreatment.In general,it is determined that 2 h is suitable treatment time,25 °C is suitable treatment temperature,and 25 0 g/L is suitable DMDC addition amount.In order to explore the effect of DMDC sterilization technology on fermentation process and quality of kyoho ice wine,concentrated grape pulp mash was pretreated with DMDC and sulfite respectively,and the two sterilization treatment methods were compared on physical and chemical indexes such as soluble solids,total sugar,reducing sugar,alcoholicity,pH,total acid,volatile acid,anthocyanin during fermentation and the influence of wine sensory evaluation.The results show that compared with sulfite pretreatment,DMDC pretreatment can not only improve the utilization of total sugar and reducing sugar,increase the yield of ethanol in fermentation broth,but also reduce the formation and accumulation of acid,reduce the content of volatile acid,and improve the taste of kyoho ice wine,but the retention of anthocyanin content is not as good as sulfite pretreatment.In general,DMDC pretreatment may be an effective way to control the quality of fermented kyoho ice wine.In order to improve the anthocyanin content of kyoho ice wine and improve its color,fresh grapes and Vitis davidii Foex are used as raw materials for ice wine.The effects of mixed fermentation of kyoho grape and Vitis davidii Foex on the physical and chemical indicators such as anthocyanin,total phenol,chromatic aberration value,total sugar,soluble solids,alcohol content,pH,total acid and volatile acid during fermentation and the sensory evaluation of wine were studied.The results showed that the content of anthocyanin,total phenol and chromatic aberration value in different proportions of Vitis davidii Foex mixed fermentation group were significantly higher than those in kyoho grape group(p<0.05),and the anthocyanin content of 1:1 mixture was 208.50 mg/L,at the same time,the chromatic aberration value and sensory score of kyoho grape and Vitis davidii Foex mixed fermentation reached the maximum at the ratio of 1:1,which were 17.16 and(78±2.79)score respectively.But there was no significant difference in the content of total sugar,total acid and volatile acid between different proportions of Vitis davidii Foex mixed fermentation group and kyoho grape group(p?0.05).In general,the mixing of Kyoho grape and Vitis davidii Foex in a ratio of 1:1 can improve the color and taste of kyoho ice wine,and develop the high quality kyoho ice wine.