| Purple sweet potato(Ipomoea batatas L.Poir)has extremely high nutritional value and extensive planting resources,which have become a research hotspot in the fields of medicine,food,cosmetics and so on.In this study,a kind of purple sweet potato glutinous rice beverage with unique flavor,low alcohol and high nutritional value was developed.The beverage will meet the current people's pursuit of health concept,and suitable for the majority of people to drink.The research and development of the fermented beverage is divided into two parts,which are the pretreatment technology of purple sweet potato juice and the key technology of fermentation of purple sweet potato glutinous rice beverage wine.The main research contents and results are as follows:(1)High intensity pulsed electric fields(PEF)was used to pretreat purple sweet potato juice.With the dissolution rate of antioxidant active components in purple sweet potato juice as the index,the ratio of beating material to liquid,treatment time,electric field in-tensity,electric field frequency and duty cycle were optimized by single factor and re-sponse surface box-Behnken experimental design,and the optimal process formula was determined.The research shows that the purple sweet potato juice processed under the conditions of material liquid ratio of 1:3,processing time of 50 s,electric field intensity of8.2 k V/cm,pulse frequency of 19.9 k Hz,and duty ratio of 31.9%.The total phenol con-tent and anthocyanin content of the samples without PEF treatment were significantly in-creased(P<0.05),and the total phenol content was 425.618±2.275 mg/kg,and anthocyanin content was 155.590±4.527 mg/kg,which was 29.17%and 29.17%higher than that of the samples without PEF.(2)The samples(PEF,NO PEF)were analyzed by GC-MS,LC-MS/MS and FTIR.GC-MS was used to determine phenol,olefin,alkyne,acid,ester and alkane.The total vol-atile content of sample PEF was 191.342 mg/L,which was higher than that of NO PEF(177.693 mg/L).Among them,2,2'-methylene-bis-(4-methyl-6-tert-butylphenol)in phenols is the main component,which is 16.231 mg/L in PEF sample and 13.831 mg/L in NO PEF.The contents of 8 anthocyanins(4 Peonidins and 4 Cyanidins,respectively)in purple sweet potato juice were determined by LC-MS/Ms.the content of the main substances was sig-nificantly higher than that of the samples without PEF treatment(P<0.05).Pe-onidin-3-sophoroside-5-glucoside was 14.989 mg/L(PEF)and 8.506 mg/L(NO PEF);Pe-onidin-3-p-hydroxybenzoyl sophoroside-5-glucoside was 21.277 mg/L(PEF)and 14.453mg/L(NO PEF);Cyanidin-3-p-hydroxybenzoylsoph-5-glucoside 9.474 mg/L(PEF)and5.602 mg/L(NO PEF).The characteristic functional groups in the juice were measured by FTIR.Edge angle vibration and other functional groups were measured,including the benzene ring skeleton vibration peak(1610.42 cm-1),the phenol hydroxyl stretching vibra-tion peak(3360.24 cm-1),and the hydrocarbon bond(2931.25 cm-1).It was preliminarily determined that the phenol dissolution rate in the purple potato juice increased significantly.It was further verified that GC-MS and LC-MS/MS were used to determine the compo-nents in the juice of purple sweet potato,and PEF technology had a significant effect on the pigment dissolution of purple sweet potato cells.(3)A kind of low alcohol precision purple sweet potato and glutinous rice beverage wine was prepared by mixed fermentation of purple sweet potato juice and glutinous rice.The better saccharification conditions(Sweet Wine Koji)and commercial yeast were se-lected,and the physical and chemical properties,sensory evaluation and aroma compo-nents of fermented products were used as evaluation indexes.In the process of saccharifi-cation,the mixture of cooked glutinous rice and purple sweet potato juice in the ratio of1:2(m/V)and 1:3(m/V)could significantly increase the content of reducing sugar in the system(P<0.05),and reached the highest level in the 5-6 days.The highest reducing sugar in the experimental group was 32.311±0.333 g/L when the ratio of material to liquid was1:2.The highest reducing sugar in the experimental group was 29.474±0.609 when the ratio of material to liquid was 1:3.The experimental group can provide energy and nutri-ents for later fermentation.The analysis of Aroma White,D254,RW,Red Fruit and EC1118 was discussed,which about the Growth characteristics of yeast and sensory evaluation,physical and chemical properties,sensory evaluation,antioxidant capacity and volatile aroma components of fermented beverage wine.Finally,EC1118 was selected as the optimal experimental group after 6 days fermentation,which characteristics are as fol-lows:the yeast has moderate fermentation capacity(the fermentation accuracy reaches4.7%vol).After fermentation,the sugar and acid content of alcoholic beverages is moder-ate,the sensory quality is optimal,and the aroma components are prominent(the alcohol content of 3-methyl-1-butanol reaches 15.043%,the phenol content of2,5-di-tert-butylphenol reaches 4.062%,the ester content of sulfurous acid,butyl tridecyl ester reaches 2.212%).(4)Optimization of main fermentation process by single factor orthogonal method,through single factor and orthogonal experiments,it is found that the main fermentation process:the ratio of raw materials of 1:2,yeast addition amount 6%,fermentation temper-ature of 18?,low alcohol content purple sweet potato beverage prepared under these conditions,the sensory score of 85.50,total phenol 406.02 mg/kg,anthocyanin 121.71mg/kg,ABTS 77.66%,DPPH 92.82%,total Acid 13.48 g/L,total sugar 84.74 g/L,reduc-ing sugar 13.48 g/L,soluble solids 17.0%,alcohol content 3.5%vol.Compared with the fermentation product without PEF treatment(refer to the optimal fermentation process),its antioxidant activity was significantly improved(P<0.05).It is a low alcohol content purple sweet potato beverage with rich nutritional value and excellent taste. |
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