Detection of Alternaria alternata infection in winter jujubes based on optical properties and their correlation with internal quality parameters during storage

Abstract

In this work, a single integrating sphere system was applied to characterize the optical absorption (μa) and reduced scattering (μs′) properties (550 – 1050 nm) in winter jujube flesh infected by Alternaria alternata during storage at 4 and 20 °C, respectively. Meanwhile, physical (L*, a*, weight loss) and biochemical characteristics (soluble solids content, titratable acids, chlorophyll, total phenolic, and ascorbic acid) of winter jujubes were measured. Among them, chlorophyll, weight loss and ascorbic acid were highly correlated with μa at 680 nm, 690 nm, while chlorophyll and a* had the best correlations with μs′ at 700 – 920 nm. These optimal optical properties were proved efficiently contributed to the disease detection of winter jujubes after 12 days at 4 °C and 3 days at 20 °C during storage, with satisfactory discrimination accuracies (acc > 93.75 %). Consequently, optical properties in Vis-NIR region were available to detect the postharvest disease in winter jujubes.