| Citrus juice is loved by consumers because of its unique flavor,color and nutritional components,among which flavor is one of the most important characteristics that affect the quality of juice.The flavor of citrus juice largely depends on the type,content and proportion of its aroma components.Although there are many studies on the aroma components of orange juice,there are great differences in the research materials,extraction and analysis techniques of aroma components,data statistics methods and so on reported in the past,so it is difficult to systematically compare the aroma components of different kinds of orange juice.Therefore,the study on the aroma components of orange juice is not only helpful to understand the aroma quality of domestic characteristic citrus varieties,but also to provide more information for the research field of citrus fruit flavor.In this study,different kinds of orange juice were used as the research object,and GC-MS combined with multivariate statistical method was used to study the overall aroma profile and characteristic aroma components of orange juice.Meanwhile,the wide skin citrus varieties with better flavor quality were selected as the experimental objects,and three new processing technologies,ultra-high pressure technology,ultrasonic wave technology and microwave technology,were explored to process the aroma components,nutritional components and sensory products The influence of quality provides reference information for the application of new processing technology in citrus juice industry.The specific research results are as follows:1.To define the overall aroma profile of all kinds of citrus juice,including the content and types of important aroma components and all kinds of aroma components,and to compare the differences of 13 varieties of citrus juice aroma components and their unique aroma components.Based on the analysis and summary,the following conclusions are drawn: 65 kinds of volatile components were determined by HS-SPME/GC-MS,among which the most alkenes,followed by alcohols,esters and aldehydes,and the least phenols.In all the aroma components of citrus juice,olefins account for a large proportion in both types and contents,of which the highest percentage is 95%.The kinds and contents of aroma components of three kinds of wide peel citrus were lower than those of Ehime 38 and most of the oranges,and the content of aroma components of Ehime 38 was significantly lower than that of most of the oranges.The main aroma components of alcohol are linalool,α-terpineol and 4-terpenol.N-heptanol is the unique aroma component of Jiang’an summer orange.The aldehydes are mainly trans-2-hexenal,nonanal and decanal.Hexanal and α-methylcinnamaldehyde are the aldehydes of Ehime 38.Carvone,geranyl acetone and β-ionone,as the main ketone aroma components,have no significant difference in the distribution of citrus,Miscanthus and orange,while nocardione only exists in orange fruits.As a kind of important aroma compounds,esters in sweet orange are significantly higher than those in broad skinned and mixed citrus.Limonene,laurene and Valencia tangerine are the main aroma components of olefins,among which limonene is the highest.2.OAV method was used to identify the characteristic aroma components in 13 varieties of citrus juice.Sensory experiments were carried out to evaluate the aroma quality.PCA and PLSR were used to study the correlation among the samples,sensory attributes and characteristic aroma components.Through the experiment of aroma recombination and omission,the contribution of characteristic aroma components to the whole flavor was further verified.The results are as follows: there are 37 aroma components with OAV > 1 in 13 kinds of citrus juice,8,6,4,6,11 and 2 kinds of alcohols,aldehydes,ketones,esters,terpenes and phenols,respectively.Among them,the aroma components with higher OAV value are linalool,nonaldehyde,decanal,β-ionone,ethyl butyrate,ethyl crotonate,laurene and limonene.Among them,the most characteristic aroma components are Ham Lin orange and Jiangjin long leaf orange,and the least are three kinds of wide skin citrus.The sensory evaluation results showed that sweet and fruity aroma had the highest score,and the aroma was more prominent.The highest scores of sweet,flower,green and fruit were Ponkan,Nanfeng,Natal late maturing and Jiangjin Changye,respectively.Multivariate statistical analysis can clearly distinguish three kinds of wide skinned citrus,nine kinds of orange and one kind of hybrid orange,and can also specifically divide the varieties of wide skinned citrus and orange.The sweet properties of wide skinned citrus are more prominent,and the characteristic aroma components with positive effects are ethyl caproate and ethyl crotonate;Xinqishi orange,Jiangjin Changye orange and Olympia orange have a greater correlation with the aroma,while Natal late maturing sweet orange and Fengjie navel orange have a significant correlation with the aroma,but no significant correlation with the aroma and woodiness is found;Natal late maturing sweet Orange has obvious correlation with green fragrance and skin sensation,while the positive correlation components with green fragrance are ethyl butyrate,n-octanol,etc.The results show that OAV analysis can effectively screen out the aroma components that contribute to the flavor of the samples.The omission of the experimental results shows that alcohols and terpenes have a very significant impact on the aroma,followed by ketones,phenols and esters have the lowest contribution.Linalool is the most important aroma substance,followed by limonene,decanal,citronellol also has a significant impact on the overall aroma of Ponkan juice.3.Compared and analyzed the influence of processing technology on the physical and chemical indexes,active components and volatile components of Ponkan orange juice,identified the potential advantages of new processing technology instead of heat treatment,which is of great significance to the quality improvement and production improvement of wide peel orange juice.The conclusion is as follows: pasteurization has the most significant effect on the content and types of aroma components.Compared with pasteurization,ultra-high pressure,ultrasound and microwave have stronger ability to maintain the aroma components,and can promote the conversion of terpenes,alcohols and aldehydes into esters,so as to improve the overall aroma.All processing technologies will not affect the basic sour and sweet taste of Ponkan juice,but the new processing technology can maintain the original color,VC,total carotenoids and total phenol content of Ponkan juice to a greater extent than the traditional pasteurization. |
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