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Advances in practical management of pear ripening capacity and postharvest decay

Publication . Sugar, David; Basile, Sally R.; Nunes, Carla

Most pear (Pyrus communis) cultivars are harvested when mature but do not have the capacity to ripen to a buttery-juicy texture without further postharvest conditioning, either with cold temperatures (“temperature conditioning”), ethylene exposure (“ethylene conditioning”) at 20 °C, or a combination of the two. It has been assumed that the length of temperature conditioning required to induce ripening capacity is characteristic of the cultivar, and that temperature conditioning is most efficient at normal storage temperatures (0 to -1 °C). At these temperatures, ‘Beurré Bosc’ pear is expected to need 15 days (d) of conditioning, ‘Doyenné’ du ‘Comice’ 30 d, and ‘Beurré d’Anjou’ 60 or more days. We found that as fruit maturity in the orchard advances, the length of conditioning needed at -0.5 °C decreases linearly. Furthermore, temperature conditioning is satisfied more rapidly as conditioning temperature is increased, up to 10 °C. Combining ethylene exposure and temperature conditioning at 10 °C allows rapid development of ripening capacity, facilitating early marketing of pears with excellent eating quality. With respect to postharvest decay of pears, we have found that postharvest fungicide or biocontrol treatments are relatively inefficient when applied more than 3 weeks after fruit wounding which occurs at harvest, yet pears are typically stored for longer periods before postharvest treatment. Enhancement of fruit calcium through foliar applications during the growing season can reduce the rate of increase in decay risk with delay in postharvest treatment. Application of fungicides regarded as “reduced-risk” by US EPA in the 1-3 weeks before harvest can further reduce decay increase with postharvest treatment delay, and the combination of calcium enhancement plus pre-harvest fungicide treatment can substantially reduce decay risk.

2010Book part

Open access

Sugar variation in healthy, blue mold infected and aureobasidium pullulans treated ‘rocha’ pear

Publication . Ramalho, J. C.; Pais, Isabel P.; Silva, M. J.; Nunes, Carla

Soluble sugars variation in ‘Rocha’ pear was studied in healthy, infected with Penicillium expansum (blue mold) and treated with the antagonist Aureobasidium pullulans fruits. Pears from four pickings were analyzed after 1, 3 and 5 months of cold storage (-0.5 ºC, 95% RH). For each storage period fruits were inoculated and kept at room temperature (ca. 20 ºC) for 5 d and analyzed. After 1 month of cold storage sucrose increased from the first to the last picking, while fructose, glucose and sorbitol were stable in healthy fruits. After 5 d at room temperature non-inoculated fruits presented fructose and glucose rises and sorbitol decreases for the 4 harvest dates, while sucrose increased in earlier yielded fruits but decreased in the last two pickings. After infection with P. expansum, in general, was observed a tendency to decrease in all sugars. The application of the antagonist A. pullulans partly reverses such tendency. The antagonist alone causes lower disturbances in sugar contents, except in glucose that may present slight decreases. Considering only the fruits of the commercial harvest date (DC3), sugars tend to increase along cold storage (except sucrose), particularly in healthy fruits and for most cases of both blue mold and antagonist inoculated fruits. On the other hand, the tendency for sugar decrease in P. expansum infected fruits, reported for 1 month of cold storage, is still detectable for glucose and sucrose after 3 months, and glucose, fructose and sorbitol after 5 months. After 3 and 5 months of storage, the maintenance of sugar content in fruits of the DC3 inoculated with both blue mold and the antagonist was not as clear as for 1 month. Data suggested that cold storage was beneficial for sugar increase of healthy fruits, except for sucrose. In the DC3 fruits, sugar loss caused by P. expansum was higher after 1 month of storage, but the use of the antagonist A. pullulans partly reverses that tendency.

2010Book part

Open access