Nondestructive analysis of packaged grape tomatoes quality using PCA and PLS regression by means of fiber optic spectroscopy during storage

The postharvest quality and shelf life of fruits and vegetables are controlled by maturity due to their cells which are still alive after harvest and continue to their physiological activity. The purpose of this study was nondestructive analysis of the physicochemical quality parameters of grape tomatoes during storage at (20 and 4 °C) for 20 and 40 days in polyvinyl chloride and high density polyethylene (PVC and HDPE) packaging films and without packaging. A miniature fiber-optic spectrometer system working in absorbance mode in the spectral region (360–1040 nm) was evaluated for this purpose. Partial least squares regression (PLSR) was used to estimate total soluble solids (TSS), titratable acidity (TA), and pH of the grape tomatoes. The PLSR calibration model with TSS during 40 days storage inside HDPE, gave the highest coefficient of determination (R2) = 0.91 and root mean squared error of prediction (RMSECV) = 0.042, while the lowest R2 with TA (0.74) at 20 °C inside HDPE packaging. TSS was changed at 4 °C inside packaging from 6.63°Brix to 6.43°Brix (for PVC) and 6.56°Brix to 5.6°Brix (for HDPE), respectively. Weight loss and moisture content at 20 °C in HDPE were changed from 0 to 2.24 and 91.17 to 89.46%, respectively. Results showed that principal component analysis had nondestructive high-performance in the category and separation of the product inside packaging and without packaging, so that products inside the packaging film (HDPE and PVC), mostly were in the PC1 > 0, while the product without packaging were in the PC1 < 0. The results showed that the physicochemical quality characteristics change significantly during storage of grape tomatoes and this is applicable in the field of postharvest.