Potential for improvement of mango skin colour during storage

Abstract

External fruit colour is a major determinant of consumer appeal in mango. Mangoes are generally harvested at the hard, green preclimacteric stage, with ripening occurring after harvest. The optimum ripening temperature for cv. Kensington Pride, the main Australian mango cultivar, is 18–24°C. These conditions generally allow parallel skin yellowing and flesh softening. Prolonged mango storage (e.g. at 13°C) or ripening at 30°C desynchronises these two ripening processes, so that fruit generally soften but retain some of the green skin colour. In addition, some mango cultivars develop a red blush prior to harvest but this is often limited by reduced fruit exposure to light due to shading during growth, subtropical seasonal haze and too high temperatures. Therefore, there is a need for a postharvest method to improve mango skin colour.
To test the potential for postharvest illumination to improve mango skin colour at ripe fruits of cvs. Kensington Pride and Tommy Atkins at commercial maturity were exposed soon after harvest to cool-white fluorescent illumination at 13°C and 20°C (temperatures recommended for mango storage and ripening in Australia, respectively). Two levels of photon fluency rate (135 μmol/m2.s and 175 μmol/m2.s) were tested. In both cultivars the response to illumination was greater at 20°C than at 13°C. Both levels of illumination provided similar improvements in skin colour at ripe. Illumination of ‘Kensington Pride’ for 5 and 48 hrs at both low and high light intensity, resulted in significantly more yellow and red colour on the skin at ripe. Low intensity light exposure for 1 hr was not effective. Twenty four hours illumination of ‘Tommy Atkins’ fruit with low intensity illumination increased both the yellow and red colour of the skin at ripe.