Direct sunlight influences postharvest temperature responses and ripening of five avocado cultivars.
Woolf, A. B.; Wexler, A.; Prusky, D.; Kobiler, E.; Lurie, S.;
Journal of the American Society for Horticultural Science Year: 2000 Vol: 125 Issue: 3 Pages: 370-376 Ref: 25 ref.
2000
บทคัดย่อ
Effect of direct sunlight on the postharvest behaviour of 5 avocado (Persea americana) cultivars (Ettinger, Fuerte, Hass, Horshim and Pinkerton) was examined. Probes placed 6-7 mm under the peel showed that the temperature an the side exposed to the sun could be as much as 15-20 deg C higher than the temperature of shade fruits, while the nonexposed side of the fruit was approx equal to 5 deg C higher than the shade fruit. With the exception of Ettinger, sun fruits, and especially the exposed side, were found to be most tolerant to postharvest 50 and 55 deg C hot water treatments. Similarly, storage of fruits at 0 deg C for 3-6 weeks caused severe chilling injury to shade fruits, with less effect on sun fruits. Furthermore, there was little or no damage on the exposed side of the sun fruits. During postharvest ripening at 20 deg C, sun fruits showed a delay of 2-5 days in their ethylene peak compared with shade fruits. The exposed side of the sun fruits was generally firmer than the nonexposed s
ide, and the average firmness was higher than that of shade fruits. Activities of polygalacturonase and cellulase were similar in shade and sun fruits of similar firmness. After inoculation with Colletotrichum gloeosporioides [Glomerella cingulata], the appearance of lesions on sun fruits occurred 2-3 days after shade fruits. Levels of heat-shock proteins were examined using western blotting with antibodies for Class I and II cytoplasmic heat-shock proteins. Class I reacted with proteins from the exposed side of sun fruits and Class II with proteins from both sides of sun fruits. Thus, it is clear that preharvest exposure of fruits to the sun can result in a wide range of postharvest responses.