Early detection of abnormal skin ripening characteristics of 'Kensington' mango (Mangifera indica Linn)

Abstract

Changes in skin colour and chlorophyll fluorescence of `Kensington' mangoes were measured daily on fruit harvested at the green mature stage and stored at 22°C until ripe. Fruits were sourced from two sites, Gin Gin and Eumundi, within the one production region, southeast Queensland. The skin colour parameters of colour rating (1–6 scale), reflectance, chroma and hue angles, as well as the chlorophyll fluorescence parameters, F0 (minimal fluorescence) and the Fv/Fm ratio (the ratio of variable fluorescence to maximum fluorescence, where Fv=Fm−F0), were measured. Fruit from the Eumundi orchard ripened normally with skin colour increasing from green to yellow following an approximate sigmoidal pattern. The F0 parameter followed skin colour development closely, but the Fv/Fm ratio remained constant for 7 days, before declining. Fruit from the Gin Gin orchard were considered `green ripe' as the fruit did not degreen fully in parallel with the softening associated with fruit ripening. With these fruit, the F0 values remained higher than with Eumundi fruit and did not decline as rapidly during storage at 22°C. Regression analyses revealed a high linear correlation between the subjective skin colour rating and the objective measurements of reflectance, chroma, hue angle and F0 for both Gin Gin and Eumundi fruit. Because of its rapid measurement time, F0 shows potential as a commercial nondestructive measurement for scanning `Kensington' mangoes early in the postharvest handling chain to detect and separate any fruit that have the potential to `green ripen', thus minimising losses in the market through unsaleable fruit.