Spectral discrimination of kiwifruit with chilling injury from fruit with other types of tissue damage in high-speed grading applications

Chilling injury is a physiological disorder that can develop in kiwifruit during prolonged cool storage. At an early stage, symptoms are not visually apparent without cutting the fruit open. Development of non-destructive methods for early stage chilling injury detection has been a recent research focus. Using standard visible - near-infrared interactance spectroscopy - spectral characteristics of chill-damaged kiwifruit were investigated, particularly the spectral discrimination of chill-damaged fruit from fruit with visually similar tissue damage caused by impacts and rots. The initial expectation had been that the main visual damage symptom, in all cases internal water-soaked tissue, would dominate observed spectral characteristics. This proved not to be the case, the presence of tissues with a granular and/or corky appearance within chill-damaged fruit being a dominant feature. Compared with sound fruit, the spectral pattern changes of all damaged fruit looked different. While the spectral pattern differences of rotten and chill-damaged fruit appeared similar, those from impact-damaged fruit differed.