ISHS Acta Horticulturae 367: VI International Symposium on Pear Growing
CONTROLLED ATMOSPHERE RECOMMENDATIONS FOR PEAR FRUITS AND STORAGE CHILLING SATISFACTION REQUIREMENTS FOR RIPENING WINTER PEARS. |
| Authors: | Daryl G. Richardson, D. Gerasopoulos |
| Abstract:
Although there are gaps in our knowledge of postharvest handling procedures for pears, nevertheless a considerable amount of information is available on maturity and controlled atmosphere conditions. We have compiled much of the world data, and have also added information on storage chilling duration requirements for sustainable ripening to occur in winter pear varieties. In contrast to summer pear varieties which need no chilling to ripen properly, winter pears are harvested at a maturity stage well in advance of the capability for ethylene biosynthesis which develops during cold storage. This paper summarizes air storage duration at 0°C needed by most pear varieties in order for autocatalytic ethylene synthesis to sustain ripening. The interactions of fruit ripening chilling requirement with stage of maturity, and fruit mineral nutrition status (particularly calcium) are discussed in relation to the methionine&rarrow; ACC&rarrow; ethylene pathways. Days from full bloom (DFFB) is often useful as a guide to predicting harvest, but is usually fine-tuned by using flesh firmness of pear fruits as a more accurate maturity index. Puncture force measurements are made using an 8 mm tip on peeled pear fruits, avoiding the sunblushed side. On average, summer pears lose firmness at about 0.15 kg/day, winter pears lose about 0.06 kg/day, but varietal differences and climate need to be considered. Fruit calcium concentration can play an important role in determining chilling requirement. Anjou pear fruits with normal calcium levels (7–10mg Ca per 100 g fresh weight) usually require about 60 days of chilling in order to sustainably produce enough internal ethylene to drive ripening. Low calcium fruits require much less time in cold storage to begin ripening. We have observed Anjou fruits which were very low in calcium(2–3 mg Ca/100 g) but harvested in the normal firmness range (6.8 kg) which had essentially no chilling requirement | |
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