Hyperspectral image analysis for the evaluation of chilling injury in avocado fruit during cold storage

Many vegetables and fruit are sensitive to storage at lower temperatures and experience chilling injury that can result in internal disorder, leading to postharvest waste and economic loss. Most tropical and subtropical fruit, such as avocado and mango, are sensitive to cold storage and can develop chilling injury with symptoms such as abnormal ripening, skin pitting, and darkening of the mesocarp. The severity of chilling injury symptoms is determined by various factors, including the cultivar, the storage temperature, and the length of cold exposure. The object of this study was to develop a method for estimation of internal chilling injury in avocado using hyperspectral imaging (HSI). Hyperspectral images of the avocado surface were obtained with a hyperspectral camera over the wavelength range of 400 nm to 1000 nm with 2 nm resolution. Using estimated functions of multiple instances (eFUMI) and hyperspectral unmixing approaches, we identified the spectra that correlated with areas of internal injured. By quantifying injured areas and fruit firmness, we showed the association between the internal and the external changes as detected by HSI, which implied that HSI has the potential to be used to monitor internal disorder of avocado. HSI technology opens the possibility of non-destructive determination of chilling injury and other internal quality attributes in horticultural and food products.