Study On The Analysis Of Physical And Chemical Character And The Detection Adulteration In Orange Juices

Different juices have different physical and chemical character and different aroma compositions. In this paper, physical and chemical character of several varieties of orange juice in 2006 and 2007 were researched, also analysed the different commercial brands of different types of orange juice and Orange beverage . Aroma components of not from concentrated orange juice and refrigerated orange juice from concentrated were analysed by integrated using HS-SPME-GC-MS, and then distinguished them by SPSS. FOX 4000 electronic nose was used to distinguish the different orange juice and mandarin orange juice which come from one region, and also used to analyze adulterated orange juice qualitatively and quantitatively. In addition, we calculated the contents of raw orange juice by measuring buffer capacity and by the electronic nose technology. The main results of this paper are as follows.1. Analysis of physical and chemical characterThere was no significant difference in physical and chemical character of same species of orange juice between 2006 and 2007. PCA result showed that: pH, a~*, b~* , solid/acid ratio, glucose/total sugar ratio and content of soluble solids, total acid, sucrose, fumaric acid, VC, flavones, Cu, Fe, Mg, Mn, Zn have a higher load in the first principal component, and the first principal component is the comprehensive reflection of 16 indicators, and it is essential. The content of fructose, glucose, amino nitrogen, Cr and fructose/glucose ratio were remarkable higher in the second principal component. L~*and the content of Ca were remarkable higher in the third principal component. Over the three principal components accounted for physical and chemical character of orange juice for about 98.3% reliability. LDA result showed that: there were 9 kinds of physical and chemical parameters entered the gained discriminant functions, such as pH, L~*, a~* , b~* , solid/acid ratio and content of soluble solids, total acid, fructose, glucose. The gained discriminant functions can not only determine the unknown samples, but also can be determined from the known samples. The discriminant functions with 100% accuracy were constructed. Therefore, it was practical to make use of physical and chemical character to establish a scientific judgment of orange juice identification.2. Preliminary research on the identification of orange juice types by the use of aroma compositionsThe quantitative results showed that there were 127 aroma components in the 10 juice samples, and hydrocarbons, esters, alcohols, ketones, and aldehydes were the major constituents. With Chinese and foreign literature, 18 of which mainly contributed to orange juice aroma were analyzed by LDA, and established two Fisher linear discriminant function according to aroma compounds which quantified relatively. The gained discriminant functions can not only determine the unknown samples, but also can be determined from the known samples. The discriminant functions with 100% accuracy were constructed. Therefore, it was practical to make use of aroma compounds to identify the type of orange juice.3. Distinguish of orange juice and mandarin orange juice by electronic noseElectronic nose can identify different species of orange juice and mandarin orange juice effectively, and has a good sensitivity and repeatability. Therefore, we can establish the characteristics fingerprint of different varieties of orange juice to identify and protect varieties of orange juice effectively. Meanwhile, through detecting the different adulterated orange juice samples, PCA result showed that the trend of aroma fingerprint changed along with the proportion of mandarin orange juice to orange juice. PLS result is good, and the correlation coefficient is 0.9996. Therefore, electronic nose can detect adulterated orange juice qualitatively and quantitatively.4. Analysis of content of raw orange juiceCalculating the contents of raw orange juice by measuring buffer capacity is simple and rapid, and be appropriate for other non-professional testing organizations. But different orange juice maybe have different buffer capacity coefficient. This method may be extended to calculate the contents of other juice.Using electronic nose technology to detect samples which had different content of the raw orange juice, the result showed that the electronic nose sensor response signal increased along with the content of raw orange juice, and the sensitivity is good. With the built-in multivariate statistical analysis, the samples which had different content of the raw orange juice were analyzed by PLS. PLS result is good, and the correlation coefficient is 0.9996. It illuminated that using electronic nose to detect the content of the raw orange juice quantitatively was feasible.