Study On Detection & Analysis Methods Of Orange Juice Quality Based On PTR-TOF-MS

The proton transfer time-of-flight mass spectrometry(PTR-TOF-MS)is a volatile organic compounds(VOCs)detection technique which has been developing fast in recent years and has wider detection range,higher mass resolution and shorter response time than the commonly used quadrupole MS.In the field of VOCs detection,it has great advantages.VOCs released by orange juice are the main component of orange juice aroma and one of important indicators of orange juice quality.In this paper,the methods of PTR-TOF-MS and multivariate statistical analysis are used to test the quality of orange juice.The conclusions are listed as follow:1.Research on detection of VOCs in orange juice by PTR-TOF-MS.The effects of E/N value,sample temperature and orange juice flesh content on the detection of VOCs in orange juice are considered.The results show that E/N=140~150Td is selected for the inhibition of cluster ion generation and the generation of ionic debris.The increase of sample temperature leads to the increase of masses related to some compounds,which affects the flavor of orange juice.The flesh content has different effects on different masses related to the main compounds contained in pulp.Qualitative and quantitative analysis are made on PTR-TOF-MS data of orange juice.By fragmentation patterns observed for PTR-TOF-MS measurement of pure substances and on the basis of relative documents,36 of the mass peaks are tentatively identified by predicting the sum formula.2.Identification of adulterated orange juice by PTR-TOF-MS.Single factor variance(ANOVA)is used to analyze the data of six groups of orange juice with different percentage of citrus juice.The results show that there are significant differences of 37 masses in different groups(p<0.01).Principal component analysis results can reflect the classification of the sample information.With the help of the first three main components,different groups of samples can be separated.The results show that the established partial least squares regression model can distinguish with 100% accuracy all samples with different adulteration proportion,and can accurately predict the percentage of incorporation.The margin of error is less than 5%.3.Study on the discrimination of the origin of orange juice by PTR-TOF-MS.The discriminant analysis of orange juice of 6 provinces and 4 counties in Chongqing is conducted by using partial least squares discriminant analysis(PLS-DA)and Fisher discriminant analysis respectively.The results show that PLS-DA is able to distinguish orange juice samples from 6 provinces and 4 counties respectively.Fisher discriminant function is established to identify different samples of different provinces and counties with 100% accuracy.The results show that PTR-TOF-MS could be used for rapid detection of VOCs in orange juice,which has great practical value in orange juice quality testing.