Assessment of the optical properties with physicochemical properties and cell wall polysaccharides of 'Korla' pear flesh during Alternaria alternata-induced disease development.

Cell wall polysaccharides and physicochemical properties are the major quality characteristics of fruit, but they are significantly affected by the postharvest disease. In this study, the influence of Alternaria alternata-induced disease on the contents of cell wall polysaccharides and physicochemical properties in 'Korla' pear flesh during storage, as well as their relationships of the optical absorption (µa) and reduced scattering (µs') were explored. The infected pear had lower individual sugars, covalent-soluble pectin, cellulose and hemicellulose contents than the healthy ones. The successive decreases of µa and increases of µs' in pears were observed while the process of pathogen infection. Path-coefficient analysis indicated the ionic-soluble pectin was the main reason responsible for the change of µs' in infected pear at 675 nm and 980 nm. This study indicated the optical properties have the possibility to present the physicochemical characteristics and cell wall polysaccharides of pears during postharvest pathogen infection.

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

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.