| Jujube distilled liquor has a long history of research with a typical aroma and soft taste.However,there are some problems such as high processing energy consumption,high methanol content,and no prominent characteristic flavor substances,which restrict its industrial production and market development.In this paper,the energy-saving jujube juice production process was firstly optimized,then the effect of molecular distillation on the removal of methanol in jujube juice was explored,and then the characteristics of pectinesterase in jujube was studied,and RVF technology was used to passivate pectinesterase to reduce methanol production,to minimize the methanol content in jujube juice before fermentation.Secondly,Saccharomyces cerevisiae with excellent performance was screened,the influence of different fermentation conditions on the flavor components of jujube wine was explored and the distillation process was controlled,and the characteristic flavor and formation mechanism of jujube wine with different distillation technology equipment were elucidated.Finally,the jujube distilled liquor process is transformed into the factory production.The main results of this paper are as follows:（1）The process of jujube pretreatment of rehydration and enzymolysis was improved.First,combined with the process matching degree and energy consumption analysis,the optimal rehydration conditions were obtained,namely,the rehydration temperature was 80℃and the material water ratio was 1:3.Secondly,pectinase with high juice yield and low methanol yield was screened,and the enzymolysis parameters were improved.The optimal enzymolysis process parameters were obtained as follows:enzyme addition was 0.35‰,enzymolysis temperature was 58℃,enzymolysis time was 170 min,and the actual juice yield was 81.20%.Compared with the traditional process,the juice yield of the improved process was increased by 17.89%,the sugar extraction rate was increased by 20.81%,and the unit energy consumption was reduced by 48.8%.Finally,molecular distillation technology was used to remove methanol from jujube enzymatic hydrolysate,and the methanol removal rate reached 82.11%after optimization.（2）Pectin esterase in jujube acts on pectin to produce methanol,the single-factor test and response surface design were used to optimize the extraction process of jujube pectinesterase.The optimum extraction conditions were determined as follows:Na Cl concentration was 1.9mol·L-1,extraction temperature was 28℃,extraction time was 22 h,p H 6.9.Under these conditions,the pectinesterase activity reached 0.495 U·m L-1.It provided a basis for the control of process conditions in the later stage.The technology of RF treatment was used to inactivate the enzyme of jujube.It was found that the RF heating rate was the best at the 90 mm distance between the plates.The inactivation efficiency of pectinesterase increased with the increase of RF time.The CD spectrum showed that the secondary structure of the enzyme changed after RF treatment,mainly as follows:β-Folding andβ-Corner directionα-Spiral and random crimp are transformed.The endogenous fluorescence spectra showed that the tertiary structure changed and the fluorescence intensity increased.At the same time,compared with the traditional water bath,RF has a better enzyme inactivation effect.（3）The flavoring substances and methanol content of 6 kinds of Saccharomyces cerevisiae fermented jujube wine were analyzed and studied,it was found that the methanol content in jujube wine increased after fermentation with 6 Saccharomyces cerevisiae,but the difference was not significant.The aroma active ingredients in jujube wine mainly consisted of 24 kinds of esters,8 kinds of alcohols,7 kinds of acids,and 4 kinds of other volatiles.Ethyl octanoate,ethyl decanoate,ethyl hexanoate,and phenyl ethyl acetate contributed more to the quality of jujube wine.The jujube wine produced by the BV818 strain had the strongest flavor,the best typicality,and the best flavor.（4）The methanol content and volatile aroma components in jujube wine were characterized and analyzed under different fermentation conditions.Under the condition of low p H fermentation,the methanol content in jujube wine was low,but the total amount and types of volatile aroma components were less.The total amount of volatile aroma components and the proportion of esters in jujube wine were the highest under natural p H（p H4.6）fermentation conditions.Different p H fermentation condition mainly affects the content of terpenoids,esters,and hydrocarbons in jujube wine.Fermentation temperature had no significant effect on methanol content.At a low fermentation temperature,the proportion of esters in the total volatile aroma components is low,while at a high fermentation temperature,the total volatile aroma components in jujube wine will decrease and the content of higher alcohols will increase.At 28℃,the types and total amount of volatile aroma components in jujube wine are the highest,and the proportion of esters is also the highest.Different fermentation temperature mainly affects the content of esters in jujube wine.The amount of yeast added to jujube wine had little effect on the methanol content,total number of volatile aroma components and the proportion of esters.However,the amount of yeast added to jujube wine would cause a significant decrease in the total amount of volatile aroma components.The amount of yeast added to jujube wine mainly affects the content of esters.（5）GC-MS was used to analyze the volatile aroma components in different jujube-distilled wines,and 67 aroma active substances were identified,including 38 esters.Principal component analysis and OPLS-DA can effectively distinguish jujube distilled liquor distilled by different distillation equipment,and the model has good adaptability and predictability.Volatile flavor substances,such as 3-furaldehyde,benzaldehyde,ethyl nonanoate,ethyl heptanoate,ethyl benzoate,ethyl caproate,ethyl hexadecane,ethyl benzoate,are the key aroma components to distinguish the aroma difference of jujube distilled liquor with different distillation equipment,and also the key substances that lead to the difference in flavor characteristics of jujube distilled liquor with different distillation equipment.The main key components and cyclic adenosine phosphate in industrial tower and pot distilled liquor and jujube distilled liquor obtained by permeable vaporization film were quantified.The methanol content of pot distilled liquor is 891.71 mg·L-1,which is 3.5 times that of tower distilled liquor.Meanwhile,the content of most higher alcohols and esters in pot distilled liquor are higher than that of tower distilled liquor,and the content of esters in pot distilled liquor is 13.6 times that of tower distilled liquor.The methanol content of pervaporation membrane jujube liquor was the lowest,which is 208.83 mg·L-1.In addition,most of the higher alcohols and esters in permeable vaporized film jujube liquor are lower than tower jujube distilled liquor and pot jujube distilled liquor,and the content of cyclic adenosine phosphate is 35.3 times and 30.8times that of tower jujube distilled liquor and pot jujube distilled liquor respectively,which shows that the preparation of jujube liquor by permeable vaporized film can better retain some functional components. |
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