EARLY DETECTION OF ABNORMAL SKIN RIPENING CHARACTERISTICS OF KENSINGTON MANGO (MANGIFERA-INDICA LINN)

Changes in skin colour and chlorophyll fluorescence of 'Kensington' ma ngoes were measured daily on fruit harvested at the green mature stage and stored at 22 degrees C until ripe. Fruits were sourced from two s ites, 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 fluores cence parameters, F-0 (minimal fluorescence) and the F-v/F-m ratio (th e ratio of variable fluorescence to maximum fluorescence, where F-v = F-m - F-0), were measured. Fruit from the Eumundi orchard ripened norm ally with skin colour increasing from green to yellow following an app roximate sigmoidal pattern. The F-0 parameter followed skin colour dev elopment closely, but the F-v/F-m ratio remained constant for 7 days, before declining, Fruit from the Gin Gin orchard were considered 'gree n ripe' as the fruit did not degreen fully in parallel with the soften ing associated with fruit ripening. With these fruit, the F-0 values r emained higher than with Eumundi fruit and did not decline as rapidly during storage at 22 degrees C. Regression analyses revealed a high li near correlation between the subjective skin colour rating and the obj ective measurements of reflectance, chroma, hue angle and F-0 for both Gin Gin and Eumundi fruit. Because of its rapid measurement time, F-0 shows potential as a commercial nondestructive measurement for scanni ng 'Kensington' mangoes early in the postharvest handling chain to det ect and separate any fruit that have the potential to 'green ripen', t hus minimising losses in the market through unsalsable fruit. (C) 1993 Elsevier Science B.V.