| Sweet potato is one of the most important food and cash crops in China.Studies have shown that sweet potato has the function of antioxidation,free radical scavenging,anti-mutagenic,anti-cancer,lowering blood fat and cholesterol.Malt contains a variety of hydrolytic enzymes and extractable substances.Malt has a variety of pharmacological activity,can help digestion,lower blood sugar,free radicals,protect the liver,et al.The sweet potato starch was saccharified with malt can avoid the bitter sense of industrial glucoamylase and the toxins of microbial,reduce the content of higher alcohols and methanol in finished wine,give the wine of unique malt flavor and increase its health functions.The materials and brewing characteristics of sweet potato in different regions were studied.The fermentation technology including starch liquefaction and saccharification conditions,sweet potato wine fermentation conditions and strains selected were optimized by orthogonal and response surface experiments.And also the distillation process to reduce higher alcohol and methanol content were studied,aims to provide theoretical basis and technical supports for developing the sweet potato wine with a healthy and unique flavor.The main conclusions were as follows:(1)Based on the comparative study on the basic composition and brewing characteristics of fresh sweet potato in six areas,it was found that the basic components of sweet potato in different regions were significantly different,and the contents of starch,soluble protein and Vc in the sweet potato of Chongqing were higher.Based on the analysis of basic ingredients and sensory evaluation of sweet potato wines,it is concluded the brewing characteristics of sweet potato in Chongqing were better and sensory quality was the best.The flavor components of sweet potato wines were extracted and analyzed.The results showed that 68 aroma compounds were identified and the aroma substances in sweet potato wines of Anhui,Hebei,Henan,Sichuan,Chongqing and Shandong were 45,47,37,44,51 and 43,respectively.Their common aroma components were 28 and the main aroma compounds were Hexanoic acid,ethyl ester,Octanoic acid,ethyl ester,Acetic acid,phenethyl ester,Decanoic acid,ethyl ester,Dodecanoic acid,ethyl ester,Butanoic acid,ethyl ester,Dodecanoic acid,ethyl ester,Isopentyl alcohol,Phenylethyl alcohol and Linalol,but the density were different.There were also some unique aroma substances in sweet potato wines.These same and different aroma substances and content together constitute the similar and unique style of sweet potato wines.Based on the analysis of the quality characteristics of fresh sweet potato and fermented wines and the flavor substances of sweet potato wines,the sweet potato in Chongqing was determined as the raw material of this experiment.(2)Based on the result of single factor and orthogonal experiments,the best conditions of enzymatic hydrolysis of sweet potato liquid has been determined.The gelatinized sweet potato after beating,were liquefied by the ?-amylase in the condition of ?-amylase addition 0.25%,pH 6.5,hydrolysis temperature 60°C and hydrolysis time 3.0 h.And saccharified by malt in the condition of saccharification temperature 60°C,hydrolysis time 3.0 h,malt addition 18% and pH 6.0.The DE value in the final hydrolysis was 64.32±1.17%.(3)Compared with the comparison of seven kinds of yeasts and two kinds of fermentation methods.The results showed that the appropriate brewing yeast was the highly active dry yeast of rice wine,the fermentation time of the yeast is short,fermentation speed is fast,yield is high and the sensory evaluation result is better than others.The best way of fermentation was fermentated with slag,the wine fermented with slag was more thoroughly and alcoholic,total ester content and sensory score were higher than juice fermentation.(4)Based on the results of single factor test and the response surface experiments,the best fermentation technical parameters of sweet potato wine was determined,which was fermentation temperature 21.5°C,addition of yeast 0.15%,pH 4.0.Under these conditions,the alcohol and total esters content was 14.25±0.18 %vol and 372.41±3.82 mg/L.The color of the wine is golden,clear and transparent,the aroma is coordinated and the taste is mellow and plump.(5)Through the study on the fermentation process and its regularity of sweet potato wine.Results showed that during the fermentation process,the alcohol content increased gradually and the growth rate slowed down and stabilized on the fifth day.The total ester content increased rapidly in the first 5 days,and reached the maximum at the fifth day,then decreased slightly.The soluble solids content decreased rapidly in the early stages of fermentation,and then slow down and almost no change at the beginning of sixth days.The total acid content also showed a trend of increased first and then decreased and reached the maximum value at fifth days.(6)The first distillation method was determined by analyzing the physical and chemical indexes,sensory and flavor substances of sweet potato wine in the first distillation of solid and liquid.And finally the liquid distillation was determined as the first distillation method.In the second distillation,condensing loading volume,the amount of head wine and tailing wine were selected as parameters of single factor experiments and orthogonal experiments.The optimal conditions of the second distillation were confirmed: the amount of head wine was 2.5% of liquid volume,cut off the tail when the alcoholicity was 45 %vol and the loading volume was 70%.The main quality indexes of the sweet potato wine prepared under the optimal conditions and had three mouths of aging process were as follows: alcoholicity was 45.37±0.22 %vol,higher alcohols content was 351.15±4.73 mg/L,total ester content was 411.68±2.62 mg/L and the methanol content was 342.04±3.05 mg/L. |
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