Testing of a VIS-NIR System for the Monitoring of Long-Term Apple Storage

The development of diseases during long-term storage of apples is a well-known issue causing loss of product for warehouses. Non-destructive characterization of fruit can be helpful in order to reduce waste and maximize apple quality. The aim of this study was to evaluate the applicability of visible and near-infrared (VIS-NIR) spectroscopy to monitor and manage lots of apples during long-term storage in a cold room. A bench-top VIS-NIR apparatus (600-1200 nm) was used to classify apples from two different cultivars, Golden Delicious and Red Delicious, based on their total soluble solids content (TSS). The evolution of the originally created classes was analyzed during 7 months of storage by monitoring TSS and firmness (peak force and penetration energy), and the estimation ability of the VIS-NIR device was evaluated. The results indicate that the spectroscopic technique allows for an accurate estimation of chemical-physical parameters for non-destructive classification of apples in homogeneous lots. Regarding the estimation ability of the compact VIS-NIR spectrophotometer, the results show good prediction ability both for total soluble solids content and firmness indices. The use of the instrument for on-line selection and classification of fruits is therefore desirable. This can lead to better management of postharvest storage and the destination of lots, with a consequent reduction in fruit wastage. This approach is important to plan the opening sequence of storage rooms during the winter season, providing the market with the best available products all year round.