MID-INFRARED SPECTROSCOPY AS A RAPID AND CONVENIENT TOOL FOR THE CHARACTERISATION OF TOMATO PUREES

Abstract

1. The quantitative determination of quality traits requiring spectral and classical data. In the work, the accuracy of the mid-infrared spectroscopy was investigated to predict internal quality traits in purees of fresh tomatoes. In a first time, the models of prediction were established using 50 representative samples and then these models were used to evaluate the quality traits of a large diversity of tomatoes through an experiment. Mid-infrared spectroscopy showed a good ability to estimate not only soluble solids (error of 4%) and titratable acidity (error of 5%) but also individual compounds such as glucose, fructose and citric acid (error of 4%). For malic acid, the high error of prediction (20%) was probably in relation with its low level in the studied tomatoes. Using these models, the tomato quality has been shown to depend on the following factors listed in descending importance as field/greenhouse cultivation > genotype > harvesting date > post-harvest duration. 2. The discrimination of different processed tomato matrices by the direct exploitation of spectral data. The analyses of principal components (PCA) performed on some specific spectral areas allowed the sample discrimination. A clear separation was shown between tomato purees prepared at 20, 40 and 70°C from those prepared at 90°C. An important change happened at around 70°C.