| Wine polyphenols play a significant role in the taste and color of red wine.The wine modern brewing industry usually adopts the method of impregnation to increase the content of phenolic acid.However,a series of industrial problems such as incomplete impregnation and long impregnation cycle still existed.In this study,the practical application of pulsed electric fields(PEF)in wine industry was investigated by using Muscat Hamburg grapes as raw materials.36 exponential attenuation pulses were set and the grape pulp residue before cold impregnation was pretreated with PEF of 1-3 k V/cm.The effects of different pulsed field pretreatment on the changes of polyphenols of grape juice during soaking and fermentation,and the changes of volatile aroma components in grape juice and after fermentation were investigated.Moreover,the influence of PEF pretreated on the stability of wine during storage were investigated based on thermodynamics analysis.The main results were as follows:1.PEF pretreatment showed a positive effect on grape juice polyphenol impregnation.The content of polyphenol gradually increased with the extension of the impregnation time and the increase of the treatment field strength.After 108 h of impregnation,the total phenol content of grape juice pretreated with 3 k V/cm was the highest(581.27 mg/L),the content of total anthocyanins,tannins,and flavonoids reached the highest vaues of 185.69 mg/L,1255.37mg/L,and 98.76 mg/L at 2 k V/cm,respectively,which were increased 16.81%,19.76%,21.65% compared with control group.After immersing for 84 h at 1 k V/cm pretreated,the total anthocyanin content was equivalent to the control group immersed for 108 h,suggesting that PEF pretreated could shorten the impregnation time of the grape juice impregnation time and improve the polyphenol impregnation efficiency.CIELAB color parameter analysis showed that PEF pretreatment caused a decrease in L*,b* values but an increase in a* value,resulting in darker grape juice color.Combined with HPLC analysis,the total amount of PEF pretreatment monomeric phenol increased significantly,which may be the main reason for the color change of grape juice.2.PEF pretreated did not change the alcohol fermentation kinetics,the content of polyphenol in wine was higher than the control group,and the antioxidant capacity of wine treated with different field strength was significantly higher than the control group,amongthem,2 k V/cm pretreated showed the highest antioxidant capacity.In terms of quality,the content of methanol and volatile acid decreased,while the content of tannin,catechin and ferulic acid increased in PEF pretreated wine,the content of dry extract in 2 k V/cm pretreated was the highest(23.37 g/L).Combined with sensory analysis,PEF pretreated enhanced the sense of convergence,made the color darker,and 2 k V/cm pretreated had the highest score of comprehensive sense and the best sense quality.3.GC-MS was used to analyze the main aroma components of rose-flavored grape juice and wine.A total of 26 aroma components were identified in the grape juice.Among them,the content of terpenoids was the most abundant,which was the characteristic variety of rose-flavored grape juice.The effect of PEF pretreated on the aroma of grape juice was mainly reflected in the number of volatile aroma compounds,which has a significant effect on the composition and content of terpenoid compounds.PEF pretreated grape juice added 9 new aroma components,including ?-linalool,2,6-dimethyl-7-octene and menthol-diene.Compared with grape juice,a total of 51 main aroma components have been identified in wine,esters and alcohols were the main aroma components,and the content of esters and alcohols in PEF treated wine were increased significantly.Meanwhile,the content of esters and alcohols in wines under the conditions of 1 k V/cm were the highest,which were23176.52 ?g/L and 4079.93 ?g/L,respectively.PEF pretreated added 18 aroma components to the wine.4.The stability of wine during storage pretreated with different field strengths was improved,the changes of polyphenols and colors were in line with the natural aging rules.The stability of wine anthocyanins during storage was enhanced,and PEF pretreatment anthocyanins induced color enhancement and red shift,indicating that PEF treatment was conducive to the anthocyanin co-pigmentation reaction.The results of thermodynamic analysis showed that the degradation rate of anthocyanins was accelerated with the increase of temperature,and the degradation constant of anthocyanins was reduced by PEF pretreated,and the half-life was prolonged.The calculated values of ?H and ?G were both greater than0,indicating that the reaction was a non-spontaneous endothermic reaction.Furthermore,the activation energy of PEF pretreated reaction increased,which further proved that PEF helps to improve the stability of wine anthocyanins during storage.Combined with sensory analysis,the storage capacity of 3 k V/cm pretreated wine is the best. |
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