Study On The Production Technology Of Blackened Jujube(Ziziphus Jujuba Mill.)Vinegar

Blackened jujube vinegar(BJV)is made of jujube as raw material which is after the temperature and humidity control ripening process(blacking process)through fermentation by Acetobacter aceti,its color,aroma,taste,shape and nutritional value have new changes.Response surface methodology(RSM)was used to optimize the fermentation factors of blackened jujube vinegar(BJV)on the basis of single factor experiment.Fermentation temperature,Acetobacter aceti inoculation amount,initial alcohol content affecting the one-step fermentation process of blackened jujube vinegar with the total acid content as the index,and the optimum fermentation conditions were obtained.Compared with the fermented dried jujube vinegar under the same conditions,the contents of total acid,cAMP(cyclic adenosine phosphate),polysaccharide and 5-HMF(5-hydroxymethylfurfural)in the fermentation process were analyzed.The antioxidant activity was detected by the antioxidant test.The sensory characteristics of jujube vinegar and jujube vinegar were obtained through sensory evaluation.The aroma composition and relative content were determined by the volatile gas composition.(1)The processing technology of blackened jujube vinegarThe primary fermentation process of BJV was adopted,and the optimal fermentation parameters were obtained by analyzing the fermentation temperature,inoculation amount and initial alcohol content with the total acid content as the index through single factor experiment and response surface optimization.the fermentation temperature was 30.44?,the acetic acid bacteria inoculation amount was 15%,and the initial alcohol content was 6.45%vol.Under the optimized conditions,the total acid content of fruit vinegar was 5.16 g/100 m L,which was in good agreement with the prediction model.(2)Sensory evaluation of blackened jujube vinegar and dried jujube vinegar.By sensory evaluation of blackened jujube fruit vinegar and dried jujube fruit vinegar,the color,aroma,taste and morphology were evaluated.The sensory characteristics of the two kinds of fruit vinegar were compared.The results showed that the total score of jujube fruit vinegar was 88 and that of jujube fruit vinegar was 79,the aroma and taste of jujube fruit vinegar was better than that of jujube fruit vinegar.(3)Main changes of bioactive substances during fruit vinegar fermentationThe contents of total acid,crude polysaccharide,cAMP and 5-HMF in fermentation were determined by acid-base titration,phenol-sulfuric acid colorimetry and HPLC,respectively The results showed that the rising rate of acidity of BJV was lower than that of RJV,and the total acid yield was higher than that of RJV.The contents of cAMP in BJV and RJV were6.60±0.04 ?g/m L and 1.86±0.01 ?g/m L,respectively,and the content of cAMP in BJV was3.5 times of that in red,which was significantly higher than that in RJV.In the fermentation process,the BJV decreased slightly in the late fermentation period,and RJV had an increasing trend in the middle fermentation period The content of crude polysaccharides in BJV and RJV decreased significantly with the fermentation time and the change trend was basically the same.After the fermentation,the content in BJV and RJV was 21.52±0.23 mg/m L and21.95±0.85 mg/m L,which made the two kinds of fruit vinegar maintain some physiological activities of polysaccharides The content of 5-HMF in blackened jujube vinegar decreased rapidly from 360.67± 1.67 ?g/m L at the beginning of fermentation and reached 9.94±0.26?g/m L at the end of fermentation,while the content of 5-HMF in dried jujube vinegar remained low at 1.50±0.37 ?g/m L.(4)Determination of antioxidant capacity of blackened jujube vinegar and dried jujube vinegar.By comparing the scavenging activities on ABTS+ and DPPH and the reducing activity of FRAP of BJV and RJV under the same conditions,the results showed that the DPPH scavenging ability of BJV and RJV were 0.15±0.02 mg Trolox/m L and 0.10±0.1 mg Trolox/m L,but the scavenging ability of ABTS+ and the reducing ability of FRAP were0.52±0.03 mg Trolox/m L,0.18±0.01 mg Trolox/m L,1.23±0.02 mg Trolox/m L and 0.35±0.01 mg Trolox/m L,respectively.The BJV was significantly higher than RJV.In vitro antioxidant level of BJV was significantly higher than that of RJV(P<0.05).(5)Volatile components of blackened jujube vinegar and dried jujube vinegar during fermentation.The main acids,esters,alcohols,aldehydes,ketones and a few other volatile components in blackened jujube vinegar and dried jujube vinegar were detected by SPEM-GC /MS.The proportions of various types in BJV were acids(72.91%),esters(19.11%),alcohols(7.43%),aldehydes(0.41%),ketones(0.14%)and others(0.065%).That of RJV were acids(81.15%),esters(9.28%),alcohols(4.27%),aldehydes(1.91%)and ketones(4.27%).It showed that there were no significant differences in the categories and quantities of volatile components between BJV and RJV,but there were significant differences in their constituent proportions and relative contents.In BJV,acid class material in proportion(72.91%)is less than that in RJV(81.15%),esters proportion in BJV(19.11%)was higher than that in RJV(9.28%).consequently,the sensory of BJV was softer,richer ester fragrance,yet the RJV was more stimulating.In addition,3-Hydroxy-2-butanone is 3.93% in RJV,which is another reason that made the RJV stimulating.In the fermentation process,the relative content of acids increases,and the relative content of esters increases first and then decreases.Acids and esters are the main aroma components of fruit vinegar.A small amount of ketones,aldehydes and other small amount of compounds are also indispensable parts of the aroma of fruit vinegar.These volatile components give the vinegar its distinctive flavor.