Effects Of High Pressure Processing Treatment On The Quality Of Fertile Orange Juice

As one of the most productive citrus varieties in Guangxi,fertile orange is different from sweet oranges,which are commonly used for juice production.At present,it is mainly sold fresh and lacks the necessary deep processing forms.In recent years,with the increasing market demand for orange juice,the domestic market mainly relies on imports to make up for the lack of orange juice varieties.As a variety with high juicing rate and large yield,fertile orange has the potential to be used as a new raw material for citrus juice.At present,most of the orange juice processing at home and abroad adopts non-thermal processing sterilization mode.Among them,high pressure processing technology is a new type of new technology that is relatively mature in research and has entered industrial application,but it is easily affected by various factors such as raw materials,oxygen,light,temperature,etc.,especially when the variety of raw materials is different,the processing parameters will have different effects on its quality and flavor.In this study,fertile orange juice was taken as the research object to explore the effects of different high pressure treatment parameters on the physicochemical indexes,nutritional indexes and taste changes of juice,and sensory evaluation,GC-MS and GC-IMS were used to analyze the volatility of fertile orange juice.The change rules of components,main aroma components and characteristic aroma components provide some theoretical understanding for understanding the high pressure processing characteristics of fertile orange juice,realizing large-scale industrial application,and extending the fertile orange industry chain.The main findings are as follows:1.Through the high pressure processing at different pressures and times,the changes of the physicochemical properties,nutritional indexes and taste of the fertile orange juice were evaluated.When350～550 MPa high pressure processing treatment for 0～10 min of fertile orange juice,the p H value,soluble solids and total acid content of the juice did not change significantly;It increased by 41.8% at 7 min of treatment;the retention rate of ascorbic acid after high pressure processing treatment was above 92%;the content of total phenols increased significantly,and the highest at 450 MPa for 3 min,increased by 64.95%;the content of total flavonoids increased significantly,The highest at 350 MPa for 7 min,with an increase of 29.95%;the total amount of free amino acids increased by 6.59-29.99%.After the analysis of taste amino acids and electronic tongue,after high pressure processing treatment,the proportion of sweet amino acids increased significantly,and the proportion of sour,bitter and umami amino acids decreased by0.14%,7.09% and 1.97%,respectively.2.Sensory evaluation and gas chromatography-mass spectrometry were used to analyze the volatile components,main aroma components and characteristic aroma components of fertile orange juice,and principal component analysis,cluster analysis and orthogonal partial least squares discriminant analysis were used to evaluate the high pressure processing effects of treatments on aroma components and overall aroma type of fertile orange juice.The sensory evaluation experiment defined the flavor of fertile orange juice as long-lasting,fresh,fruity,sweet,citrus and grassy.With the increase of pressure and the prolongation of time,the fertile orange juice showed the regularity that the long-lasting taste was enhanced,and the fresh,fruity,sweet,citrus and grassy tastes were weakened,but the 350 MPa treatment showed the opposite rule;Compared with the original juice of fertile orange without high pressure processing treatment,the juice has a significant difference in sensory.There are five main categories of volatile components in freshly squeezed fertile orange juice,with a total of 53 substances,namely olefins,esters,alcohols,ketones and aldehydes,of which olefins are the most abundant,with 18 species,including D-Characteristic aroma components such as limonene,methyl butyrate,alpha-pinene and myrcene.Combined with OAV analysis,it can be seen that after high pressure processing the main aroma components methyl butyrate,ethyl butyrate,β-ionone,myrcene,p-cymene,heptanal and nonanal have increased aroma activity,2-Ethyl methylbutyrate,α-pinene and D-limonene have decreased aroma activity,but are still active aroma components,and the main aroma components such as ethyl acetate andβ-phellandrene appear at the same time;With the increase of treatment pressure and the prolongation of time,the aroma components are different.High pressure processing treatment can strengthen the fresh flavor of fertile orange juice,but when the pressure is increased to 450 MPa and the duration is longer than 5 min,the characteristic aroma components decrease,and fertile orange juice the typical style disappears,so the treatment time of 3 min at 450 MPa is the appropriate high pressure processing treatment parameter.The correlation analysis of sensory and aroma components with OAV>1 shows that ethyl2-methylbutyrate and linalool are positively correlated with long-term taste,and heptanal is positively correlated with fresh taste;while nonanal and D-Limonene has a strong positive correlation with citrus taste;methyl butyrate has a strong positive correlation with fruity taste;and hexyl butyrate has a negative correlation with grassy taste.3.Qualitative and quantitative analysis of volatile components in fertile orange juice was carried out by GC-IMS,and it was expected to establish an evaluation method for the aroma change of fertile orange juice during high pressure processing.The identified volatile components were divided into five categories like GC-MS,with a total of 43 species,including 29 components such as propionaldehyde and n-butyraldehyde,which were detected by GC-IMS.At a lower pressure of 350 MPa,the treatment time was prolonged,the content of aldehydes decreased significantly,and the content of ketones,esters,and olefins increased,which was consistent with the detection results of GC-MS;The content of the substance did not change significantly.Through the analysis of principal components and clustering heat map,the volatile components of fertile orange juice treated with different high pressure processings can be divided into three categories.The second category is the orange juice treated with 350 MPa for 5 and 7 min,450 MPa for 5 and 7 min,and 550 MPa for 1 min,and the third category is the orange juice under other treatment conditions,and the results can be compared with the analysis of GC-MS.The results complement each other and also reflect the overall change law of fertile orange juice in high pressure processing,which proves that GC-IMS can be used as another evaluation method for the flavor characteristics of fertile orange juice,and the optimal high pressure processing parameters screened by this method are: 450 MPa for 3 min,consistent with the results of GC-MS analysis.