The Effects Of Ultrasonic And Ultra-high Pressure Treatment On Color And Flavor In Blueberry Vinegar

Objective:The newly fermented blueberry vinegar,which is unsuitable for drinking since its rough taste and pungent smell,needs to be aged for a further promotion on the flavor,color and feelings.Therefore,it has always been a goal to shorten the aging process of blueberry vinegar.As significant nonthermal processing methods,ultrasonic?US?and ultra-high pressure?UHP?are applied in the wine and vinegar processing with a tremendous potential,based on their capacity to reduce aging time and cost-effectiveness.In this paper,we treated blueberry vinegar with ultrasonic and ultra-high pressure separately and discussed the effects of ultrasonic with different power and processing time and ultra-high pressure with different pressure and processing time on the color and flavor in blueberry vinegar.Methods:Besides an untreated group,the newly fermented blueberry vinegar was treated with ultrasonic and ultra-high pressure under different conditions.These samples were in storage for 4weeks,out of which a certain amount was taken to have a test on related indices.?1?We first tested the CIELAB color characteristics.?2?Ultra-Performance Liquid Chromatography/Tandem Mass Spectrometry?UPLC-MS/MS?was used for quantitatively and qualitatively analysis on the anthocyanins in the blueberry vinegar.We also measured the color values of anthocyanins in blueberry vinegar to explore the changes in content of free anthocyanins,co-pigmental anthocyanins and polymeric anthocyanins under different treatment during the storage period.?3?We used the principal component analysis?PCA?on color indices and the related indices of anthocyanins to investigate the relationship between the color and anthocyanins and estimate the effect on the overall color of the blueberry vinegar under ultrasonic or ultra-high pressure treatment,providing a further description of the mechanism on how ultrasonic and ultra-high pressure influence the color in blueberry vinegar.?4?We determined the total value of acids and esters in the blueberry vinegar.?5?The volatile aroma components were analyzed by Gas Chromatography-Mass Spectrometry?GC-MS?to study how ultrasonic and ultra-high-pressure treatment under diverse conditions effect the flavor of blueberry vinegar during the storage period.Results:?1?After the US treatment and 4-week storage,the color characteristics of blueberry vinegar were more stable.US could remarkably increase the value of L^*,a^*,b^*,h_ab and decline the value of?E,while could promote the formation of co-pigmental anthocyanins and anthocyanin derivatives.The content variation of 12 kinds of anthocyanins in the blueberry vinegar,which is determined by UPLC-MS/MS,was consistent with the color characteristics variation of blueberry vinegar.Analyzing correlation between the color characteristics and the12 kinds of anthocyanin in blueberry vinegar,a remarkable correlation showed in the US system.It was noticed that,there were distinct differences of color and anthocyanins between US groups and untreated group.And the color of blueberry vinegar was affected more by US power than treatment time.Among these samples,the most stable color of blueberry vinegar was obtained at the optimum condition at 45 W and 20 min.?2?During the storage period,the effect of UHP treatment on the color of blueberry vinegar was not significant.There was no significant difference in CIELAB color characteristics between the majority of the UHP group and the untreated group.Only at 600MPa and 10 min,UHP could promote the transformation of monomeric anthocyanins into co-pigmental anthocyanins.After the storage period,the scores of 1,2 and 3 of the principal components about PCA in the UHP group and the untreated group were similar,which indicated that there was no remarkable difference in the color and anthocyanin between the UHP group and the untreated group during the storage period.?3?By analyzing the content change of the total acid and ester in the blueberry vinegar,there was no significant difference between the US group and the untreated group during the storage period.GC-MS was used to analyze the volatile components of blueberry vinegar.The results showed that US treatment had no obvious effect on the volatile acids,alcohols and terpenes,but promoted the formation of volatile aldehydes and ketones,and weakened the volatile esters.This might be due to the heat brought by the US effect,which made the esters with low boiling point volatilize.Overall,US had no significant effect on the flavor of blueberry vinegar.?4?After storage for 4 weeks,the total ester content of blueberry vinegar treated with UHP increased significantly,and there was no significant difference between the UHP group and the untreated group in total acid.The highest total ester content of blueberry vinegar was obtained by ultra-high pressure treatment of 450 MPa and 5 min.Through the qualitative and quantitative analysis of the volatile components of blueberry vinegar by GC-MS,it was found that UHP treatment could promote the esterification reaction in the blueberry vinegar,resulting in lower acids and alcohols,and more esters,while aldehydes and ketones were not affected.Overall,the UHP treatment could remove impurities and increase aroma components and make the blueberry vinegar tasted softer and the sensory quality improved.Conclusion:US treatment could make the color of blueberry vinegar more stable than ultra-high pressure treatment,and promote the formation of co-pigmental anthocyanins and anthocyanin derivatives in blueberry vinegar,while ultra-high pressure treatment was better in flavor.After UHP treatment and storage,the ester substances and other aroma substances of blueberry vinegar increased significantly,which made the taste of blueberry vinegar better.Therefore,the two methods had their own advantages in color and flavor.The results of this study will provide theoretical basis for the application of US and UHP technology in the aging process of blueberry vinegar.