| In this study,colored pomelo was used as the raw material to evaluate the processing characteristics of different pomelo varieties.The effects of different treatment conditions on the microorganism and key quality of pomelo juice were studied,and the new HPP processing technology of pomelo juice was developed.At the same time,the process of extracting pectin from HPP was also studied.HPP was used as the pretreatment condition and the model was established.We also compared the characteristics of pectin extracted by different extraction method.The main conclusions were as follows:(1)There were significant differences in sugar,acid,total phenol,color and volatile component among the eleven varieties of pomelo,and there was no difference in the content of glucose and fructose.Pinghe pomelo and Majia pomelo were suitable for processing.(2)Terpene,aldehydes,alcohols,phenols,ketones,esters,aromatic hydrocarbons and other substances were the main volatile components of eleven pomelo varieties.There were significant differences in the variety and content of volatile substances among different varieties.The quantitative results of GC-MS showed that the volatile components were dominated by terpenes;the results of DFA showed that there were 38 kinds of aroma active ingredients in eleven varieties.The aroma properties were mainly divided into balsam,pine,wood,citrus,grass,flower and mint.According to the result of PC A and PLS-DA,all the pomelo varieties could be seperated.(3)HPP and HTST treatments could effectively kill microorganisms in pink pomelo juice.The changes of carotenoids,sugar and flavonoids were not significantly changed in the two varieties of pomelo juice after HPP treatment,the content of phenolic acids and total phenols decreased,with a slight decrease of antioxidant activity(DPPH,FRAP).The antioxidant activity and some related antioxidant substances of Majia pomelo were higher than those of Pinghe pomelo,which also remained relatively high after HPP and HTST treatments.(4)During the storage period,after HPP and HTST treatment,the total number of colony in pomelo juice was less than 3 log,and the mold and yeast was less than 2 log.The microbiological safety of pomelo juice could be ensured by HPP and HTST treatment.There was no significant change in the content of flavonoids,phenolic acids and total phenols in pomelo juice after HPP and HTST treatment.After storage at 4 and 25?,the antioxidative and related antioxidants were reduced.The value of DPPH and FRAP were decreased,as well as the content of phenols.The content of sugar was not changed significantly after HPP and HTST treatment.With the prolongation of storage time,the content of sucrose and total sugar were gradually decreased,but the content of glucose and fructose were not changed significantly.(5)Compared with the storage of 250C,two varieties of pink pomelo juice had better quality in the storage of 4?.Therefore,it is suggested that the pink grapefruit juice should be preserved under 4?.In addition,the quality pomelo juice treated by HPP was better than that of HTST treatment group in the storage condition of both 4 and 25?.Therefore,HPP processing will be a better choice.(6)HPP was used as a pretreatment assisted with temperature to extract pectin and establish a model.This model was fitted well with experimental data with little error.Comparison of different processing methods of pomelo pectin showed that pectin had the highest extraction rate,lower esterification degree and higher galacturonic acid content by HPP assisted extraction.The content of galacturonic acid was lowest by ultrasonic treatment. |
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