| Aroma has long been known to be one of the most important quality attributes of citrus juices.Encompassing the central task of aroma component of orange juice,aroma components were systematically analyzed focused on pomelo juice and lemon juice by integrated using Gas-Chromatogram and Mass-Spectrum(GC/MS) in this paper.Through analyzing and comparing the distilling method for aroma components,integrated using Solvent Extraction, Simultaneous Distillation-Extraction and Solid Phase Microextraction resulted the three methods have advantages in different aspects.In this study,the aroma components of pomelo (GuanXi honey pomelo,Gongshui pomelo,Shatian pomelo) and lemon(Youlinke,Taxiti,Feimi Nailao) were studied, of which the differents of basic physical and chemical indexes, the aroma components and contents were analyzed.Take Guanxi honey pomelo and Youlike lemon as representation,the change of aroma components, basic physical and chemical indexes during processing and storage were qualitatively and quantitatively analyzed.Through the studies above,conclusions were made as follows.1.Comparative study of distilling method for aroma components75 aroma components were extracted by three kinds of methods in pomelo juice,while 83 aroma components were extracted in lemon juice.29 aroma components were extracted by SE in pomelo juice,while 43 aroma components in lemon juice; 54 aroma components were extracted by SDE in pomelo juice,while 21 aroma components in lemon juice; 15 aroma components were extracted by SPME in pomelo juice,while 38 aroma components in lemon juice;Some low-octane aroma components wre extracted by SDE in pomelo juice,making distilling impact better than other methods,while SPME best extracted in lemon juice.it is necessary to choose different methods to distilling the aroma components from different material in order that making full use of advantages of the methods.2.Aroma components analysis of citrus juice for different cultivars98 aroma components were identified in three cultivars pomelo juice.18 aroma components were identified in Guanxi honey pomelo,37 aroma components were identified in Gongshui pomelo,60 aroma components were identified in Shatian pomelo. 3-Methyl-3-hexene, y-Terpinene and D-Limonene were identified in all three kinds of pomelo.The aroma contents of Shatian pomelo is the highest,in which the hydrocarbons and alcohols are the main components.125 aroma components were identified in three cultivars lemon juice.44 aroma components were identified in Youlike,75 aroma components were identified in Taxiti,67 aroma components were identified in Feimi Nailao.22 aroma components were identified in all three kinds of lemon,in which 18 hydrocarbons,3 alcohols,1 esters.The aroma contents of Taxiti is the highest,in which the hydrocarbons and alcohols are the main components.Besides,the soluble solid, pH value,the total acid,TSS/TA and VC contents were different in analyzed citrus juices. TSS/TA of Gongshui is moderate, VC contents in Shatian and Taxiti were highest in pomelo or lemon respectively,the lum and yellow value all highest,the color value best.3. Effects of key processing unit operations on aroma components in citrus juicesAfter pasteurization, homogenizing and concentrating, changes of trace aroma components of the juice leaded different degrees effects on original flavor, detected a total 45 aroma components were identified in the pomelo juice in Three key processing units, in which 17 kinds of pasteurized juice,21 species of homogeneous juice,20 types of concentrated juice and two same materials. And in the lemon juice, a total of 78 aroma components were identified in three processing units, which of them were 44 kinds of pasteurized juice,42species of homogeneous juice,24 types of concentrated juice and 13 same materials.After pasteurization, contents of hydrocarbons, alcohols, aldehydes, esters and other substances in pomelo juice were decreased, but contents of ketones was increased. While contents of alcohols and ketones in lemon juice increased through pasteurization, and several other substances were had different degrees of loss, in which the total content of hydrocarbons decreased by 51.2%.After homogenizing, contents and types of hydrocarbons, ketones in pomelo juice were increased, yet several other substances had different degrees of loss, in which the loss of alcohol is a maximum and its loss rate was 97.1%. During the same homogenizing processing, alcohols, aldehydes, ketones, esters and other aroma components in lemon juice were increased and the loss of hydrocarbons is visible.As the result of concentration, contents of hydrocarbons, esters and similar substances in pomelo juice were increased, other substances were reduced. Concentrated lemon juice got a sharp decline in aroma substances contents, in which hydrocarbons was reduced to 8.217μg/ml from 238.559μg/ml, and the loss rate was 96.6%, alcohols loss rate was as high as 99.3%.In addition, three key processing operation had different effects on the basic physical and chemical indexes of two citrus juices, in which the VC content and color had a relatively big influence.4.Research on changes of aroma components in citrus juice during storageFresh and processed juice of these two kinds of citrus juices were stored at 4℃for qualitative and quantitative analysis of aroma, so that can get a variation pattern. With the extension of storage, the aromatic substances of four types juice samples were firstly increased and then decreased, contents increased slightly during the storage of five days, then decreased gradually, after that the aroma was significantly increased after fifteen days, but the raise of fresh juice and processed juice have the different range. |
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