| Apple juice is a main product of fruit processing with a large sales in the world,and apple juice quantity is about 17%of the total sales of fruit and vegetable juices in the world.China is an important country of apple producer and trader in the world,and the industrial processing of apple juice is developing rapidly in China.At present,research on improving the quality of Chinese NFC apple juice can play a role in increasing the value-added of apple juice products,which is conducive to further occupying international market share of apple juice in the world and improving the economic benefits of fruit juice processing enterprises in China.In this paper,red Fuji apple was used as raw material to prepare the NFC apple juice.Firstly,on the basis of ensuring microbial safety and juice quality,the research literature was studied and analyzed to select the ultra-high pressure sterilization treatment and high temperature short-time sterilization treatment conditions.The changes of microbial,physical and chemical indicators and aroma components of NFC apple juice during storage after ultra-high pressure and high temperature short-time sterilization treatment were studied.The main results were as follows:1.On the basis of self-made NFC apple juice and analysis of its various indexes,400 MPa and 15 min were selected for ultra-high pressure treatment of juice;98?and 50s for high-temperature short-time sterilization treatment by comparing literature and experimental equipment conditions.2.The effects of the two treatments on the sensory and physical and chemical indicators of NFC juice during storage were as follows:HTST-treated NFC apple juice had superior physical and chemical indicators during the first week and storage period.In the first week,compared with the control,the changes of pH,TSS and TA were not significant,and the L*value of the juice treated by HTST decreased slightly.The L*value of the NFC apple juice after UHP treatment was closer to the control sample.HTST can kill the endogenous enzymes of NFC apple juice.The UHP treatment enzyme activity is higher than the control sample.The total phenolic content of the juice after the two treatments is lower than that of the control sample.The content of chlorogenic acid is higher than that of the control sample,and the HTST treated juice.The total phenolic and chlorogenic acid content is higher than the UHP treated juice.The antioxidant activity of HTST treated juice was higher than that of UHP treated juice and control samples.During storage,the TSS values of HTST and UHP treated juices did not change much,the acidity increased less,the pH value decreased by 0.02%,the L*value decreased by 0.06%and 0.11%,respectively,and the juice color became darker.The juice enzyme activity of UHP treatment decreased slightly.The chlorogenic acid content was degraded from 113.96,98.99 ?g/mL to 97.93 and 97.58 ?g/mL,the epicatechin decreased by 33%and 53%,respectively.The total antioxidant capacity of FRAP in NFC apple juice remained at 76%and 73%,respectively.DPPH free radical scavenging rates were maintained at 77%and 76%,respectively.NFC apple juice after HTST and UHP treatment can better maintain the sensory quality of the juice.3.The effect of the two treatments on the aroma components of NFC juice during storage is that during storage,HTST treatnent can better maintain the aroma components.After HTST treatment,except for the slight increase of 2-methyl-1-butanol,hexyl acetate,hexanal and 2-methylbutyrate,the main aroma substances were reduced.The retention rate of 18 characteristic aroma substances was 52%,and the aroma component content of apple juice after UHP treatment was closer to the control sample.During the storage period,the aroma components of the apple juice treated at high temperature for a short time remained stable,only decreased by 0.09%,while the aroma components of the ultra-high pressure treated NFC apple juice decreased by 26.13%,and the change was remarkable.4.The effect of the two treatments on the microbial index of NFC juice during storage was that the quality of the NFC apples stored for 4 weeks and 9 weeks at 4?was basically unchanged after UHP and HTST-treated in the case of microbiological safety,the shelf life of HTST-treated NFC apple juice was doubled.For the characteristics of UHP and HTST which can not completely kill microorganisms,the bacterial phase analysis of fruit juices with different storage time is carried out.Analysis of the initial sample found that in the control sample,the dominant genus was Unidentified rickettsia,Pseudomonas and Unidentified oxyphotobacteria;The advantage of UHP treatment of juice belongs to the Unconfirmed rickettsia and Unidentified oxy-photobacteria;the advantage of HTST-treated juice is Unconfirmed rickettsia,Pseudomonas,Microbacterium,unidentified Oxyphotobacterium and Sphingomonas.At the 4th week and the 5th week of storage,the advantage of UHP-treated apple juice belongs to the Unidentified rickettsia genus,Unidentified oxy-photobacteria and Pseudomonas.At the 7th week of storage,the advantage of HTST-treated apple juice is Unidentified rickettsia,Unidentified oxy-photobacteria,Pseudomonas,Sphingomonas,Fusarium.At the 10th week of storage,the advantage of HTST-treated apple juice was Unidentified rickettsia,Unidentified oxy-photobacteria,Pseudomonas,Sphingomonas,and Bacillus,Ralstonia,and Bacteroides.This study found that compared with ultra-high pressure treatment,high-temperature short-time sterilization treatment can better maintain the physical and chemical indicators and aroma components of NFC apple juice,and the shelf life is doubled,and the high-temperature short-time sterilization technology can be applied to the commercial production of NFC apple juice.This will help the circulation of the NFC apple juice market and enhance the market competitiveness of apple juice.The content of this study laid the foundation for the subsequent prediction of the shelf life of NFC apple juice by modeling. |
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