Study on the oxidation process of tomato juice during storage by near-infrared spectroscopy

Near-infrared (NIR) transmittance spectroscopy combined with several chemometrical techniques was investigated to study the oxidation process during storage in tomato juices. A total of 100 tomato juice samples were used for NIR spectroscopy analysis at 800-2400 nm using FT-NIR spectrometer. The spectrum of each tomato juice was collected twice: the first time as soon as the tomatoes were squeezed, centrifuged, filtered and the tomato juice had not undergone any oxidation process and the second measurement was taken after a month. Principal component analysis (PCA) and partial least squares discriminant analysis (PLSDA) were applied to discriminate between the two groups of spectra. The results show that differences between tomato juices before and after the storage period do exist attributed to changes in certain compounds of juice and excellent classification can be obtained after optimizing spectral pretreatment.