Study On Brewing Technology And Flavor Substances Of Seeding-watermelon Beer

Seeding-watermelon is rich in vitamin B1,vitamin B2,calcium,iron,zinc and other nutrients,and has a unique flavor.At present,the main use of seeding-watermelon is to process seeding-watermelon seeds,but the pulp of seeding-watermelon has not been well developed and utilized,resulting in a great waste of resources.In this study,seeding-watermelon beer being of special flavor and rich nutritional value was produced using seeding-watermelon juice,malt,hops as raw materials The development of seeding-watermelon beer can not only promote the plant of seeding-watermelon,but also enrich the market of melon processing and beer products,which has broad development prospects and good economic and social benefits.In this experiment,the biological characteristics and fermentation properties of top-fermenting yeast SM1 and bottom-fermenting yeast XM1 were studied.Then,the brewing process of two type seeding-watermelon beer was determined by single factor test and response surface test method,and the comparative analysis was made.The main findings were as follows:(1)The optimum pH values for SM1 and XM1 growth were 4.5 and 4.0,and the optimum temperatures were 26℃.The lowest tolerable pH and temperature were 2.0 and 10℃ respectively.They had strong tolerance to SO2,ethanol and glucose.Through comparison,it was found that the tolerance of XM1 to SO2 was stronger than SM1,while the tolerance to glucose and ethanol was lower than SM1.Fermentation experiments showed that for SM1,the rate of CO2 weight loss,speed of sugar decreasing,ability of ethanol producing,fermentation degree and ability of reducing diacetyl were all higher than that of XM1.(2)the optimal fermentation conditions of top-fermenting seeding-watermelon beer was determined by single factor test and response surface test:20%of seeding-watermelon juice addition,2.5%of SM1 addition,initial pH4.0,and main fermentation temperature of 19℃.The sugar content of the beer was 3.5°Brix,alcohol content was 3.7.%vol,pH was 3.7,and the diacetyl content was 0.091 mg/L.(3)the optimal fermentation conditions of bottom fermentation seeding-watermelon beer was determined by single factor test and response surface test:20%of seeding-watermelon juice addition,3.5%of SM1 addition,initial pH4.8,and main fermentation temperature of 10℃.The sugar content of the beer was 3.5°Brix,alcohol content was 3.2%vol,pH was 4.2,and the diacetyl content was 0.097mg/L.(4)Comparing the sensory characteristics and flavor substances of the top and bottom fermenting seeding-watermelon beer the results were showed:①Through the analysis of electronic tongue,it was found that the overall taste of the top and bottom beer was salty,fresh and sweet,and full.According to the comparison of response values,the acidity value,bitterness value,bitter aftertaste value,umami value,and saltiness value of the top seeding-watermelon beer were higher.However the astringency,astringency aftertaste,and sweetness value of the bottom seeding-watermelon beer were higher.Through electronic nose detection and analysis,the principal component analysis method and load analysis method of electronic nose were suitable for evaluating the odor of beating seeding-watermelon beer.The odor profiles of the two types beer were similar,but there existed differences.②The content of organic acids in beating seeding-watermelon beer was rich,and the total amount of organic acids in top-fermenting beer(338.28mg/L)is higher than that of bottom-fermenting one(288.15mg/L).Among them,the succinic acid,citric acid and malic acid in the top beating beer were significantly higher than those in the bottom fermenting beer.The differences in oxalic acid,α-ketoglutarate,L-pyroglutamic acid,tartaric acid and lactic acid were less.