Effects Of Ultra-high Pressures Treatment On The Quality Of Xinjiang Junzao Juice And Microbial Community During Storage

Xinjiang jujube has a large planting area and good product quality,which is one of the main producing areas in China.However,due to the short storage period of fresh jujube,most researchers focus on the extraction of functional components from jujube at present,which poses great challenges in processing and application.Ultra-high pressure technology is a new food cold sterilization technology,which is widely used in food industry.Jujube juice is an important part of deep processing,so it is necessary to improve the quality of jujube juice by ultra-high pressure technology.In this study,the quality of Junzao juice treated by ultrahigh pressure was studied,and then the mechanism of flavor components was analyzed based on metabonomics.High-throughput sequencing technique was used to analyze the microorganisms of Junzao juice treated by ultra-high pressure during storage and deterioration at 25℃.At the same time,the ultra-high pressure of 100 MPa～500 MPa was selected to pretreat jujube juice,and Lactiplantibacillus plantarum was inoculated for fermentation.Compared with heat-treated jujube juice,the preliminary work was verified and the feasibility of ultra-high pressure technology in fermenting jujube juice was discussed.The results are as follows:(1)Using electronic bionics technology,it is found that the color of Junzao juice after ultra-high pressure treatment is red and yellow,and its brightness increases,which has no effect on its soluble solids and taste,but can significantly improve its flavor and increase the content of aromatic components,while the content of sulfide,methane,ethanol,nitrogen oxides and other harmful substances decreases,especially when Junzao juice is treated under ultra-high pressure of 330 MPa.(2)By HPLC,it was found that the content of organic acids in Junzao juice increased obviously under the ultra-high pressure of 0 MPa～300 MPa,but decreased under the pressure of 330 MPa～630 MPa.The main organic acids in Junzao juice are malic acid,succinic acid and tartaric acid.The results showed that there were 9 volatile substances with VIP >1 in Junzao juice samples,namely ethyl acetate,hexanal,methyl acetate,3-methylbutyraldehyde,methyl hexanoate,benzaldehyde,2-methylbutyraldehyde,acetic acid and furfural.Among them,methyl acetate and methyl caproate were significantly higher in the 330 MPa ultrahigh pressure treatment group.(3)The results of high-throughput sequencing showed that the bacteria and fungi that caused the spoilage of Junzao juice during storage can be divided into three clusters.According to the bacteria,samples P0～P330 can form a cluster,samples P360～P450 can form a cluster,and samples P480～P630 can form a cluster,while fungi have no obvious pressure law.The main bacteria causing spoilage in Junzao juice are mainly Lactobacillus before 480 MPa,while after 480 MPa,there are some spoilage bacteria such as Nocardia,Achromobacter,Pseudomonas,Mesorhizobium and Rhodococcus.The dominant fungi genera causing the spoilage of Junzao juice are mainly yeasts and molds.In addition,LEf Se analysis showed that the spoilage bacteria groups causing significant differences between 360 MPa～450 MPa and 480 MPa～630MPa were mainly Lactobacillus,Achromobacter,Enterobacter and Pseudomonas.However,the main spoilage fungi in Junzao juice are Torulaspora,Lodderomyces,Wickerhamomyces and Fusarium.(4)Ultra-high pressure pretreatment has no effect on the number of viable bacteria in fermented jujube juice,which can make the color of the product reddish and yellowish.Although it has no effect on the taste quality,it can improve its flavor quality.And when using 400 MPa ultra-high pressure to pretreat jujube juice,it has no effect on the thermal stability and ethanol stability of the product,but it can improve its aging stability.Using 400 MPa ultra-high pressure treatment can obviously improve the quality of fermented jujube juice.