Changes of backscattering imaging parameter during plum fruit development on the tree and during storage

• The LLBI technique was used for analyzing variations in quality-related optical properties during development of plums.
• There were negative correlations between FWHM532 and NAI and between FWHM785 and fruit firmness in fruit of both cultivars.
• The LLBI technique using 532 nm and 785 nm lasers can be feasible for non-destructive prediction of NAI and strength in plums.

Laser light backscattering imaging (LLBI) as a novel approach appears to be a promising technique for monitoring quality of horticultural products. The aim of this research was to investigate the feasibility of the non-destructive LLBI technique for the evaluation of plums quality indices during fruit development on tree and during storage. Plums of two cultivars were harvested four times during fruit development. At commercial harvest, fruit were stored at 2 ± 0.5 °C (90 ± 2% RH) for 28 days and 2 days at 20 °C with five measuring dates during storage. Experimental methods involved conventional measurements, i.e. fruit firmness, skin color, soluble solids content, dry matter content, and normalized anthocyanin index (NAI), and non-destructive LLBI at two wavelengths: 532 and 785 nm. The obtained backscattering images were characterized by variation of brightness of the backscattered light. As an objective measure full width at half maximum (FWHM) was calculated from these radial backscattering profiles. The reduction in FWHM532 was strongly correlated with the increase in anthocyanin content as indicated by NAI during fruit development. Furthermore, the increase in FWHM785 was strongly correlated with the decrease in fruit flesh firmness during fruit development on the tree and during storage. In conclusion, results suggest that the LLBI using appropriate wavelengths can be feasible for non-destructive prediction of NAI and firmness in plum fruit.