How harvested cherimoya should be stored
It is important to choose
cherimoya varieties that handle well, to make post-harvest handling easier. Rough handling, even of unripe fruit, leads to bruising and an off-flavour.
Cherimoya are sensitive to extremes of heat and cold and, like avocado, cant be chilled before they ripen. Experiments with storage temperatures of 12ºC and 22ºC (normal room temperature) have been done to see if the ripening process can be delayed. At 12ºC ripening was delayed but the fruit produced less acid (which is a delicate component of the cherimoyas flavour) and there was more starch present, which reduces sweetness. It seems that storing fruit at 22ºC is better for fruit quality although shelf life will be shorter, while 812ºC is the ideal temperature to actually store and hold cherimoya (where they can be stored for approximately 1428 days, depending on ripeness, variety and size). When ripe they can be refrigerated for up to 5 days. The optimum relative humidity for storage is 9095%.
Experiments have been done with post-harvest heat treatment for controlling fruit fly (this applies to countries where this is a problemnot in New Zealand) and showed some varieties were damaged less than others, so it may be worth looking at varieties that can better tolerate heat treatment if this is likely to affect you.
The ideal controlled atmosphere for storage is 35% oxygen and 510% carbon dioxide. Benefits from this type of atmosphere include delayed ripening, lower respiration and ethylene production rates, and firmness retention. Exposure to less than 1% oxygen and/or greater than 15% carbon dioxide can result in an off-flavour and uneven ripening. Cherimoya can be kept for up to 6 weeks at 10°C in 5% oxygen, then ripened at room temperature producing a good flavour. The freezing point of cherimoya is 2.2ºC.
Another new method being trialled is the use of carbon dioxide shock as a controlled atmosphere to extend cherimoya shelf life. Treatment with carbon dioxide retards ripening and potentially prolongs the useful commercial life of cherimoya.
Ethylene production and sensitivity
Cherimoya are climacteric fruit and produce high levels of ehylene (up to 100300µl/kg per hour, depending on variety) during ripening at room temperature. They are also sensitive to ethylene exposure, which will accelerate the ripening of mature fruits. Removal of other ethylene producing crops near the maturing fruit can help to delay ripening. Cherimoya should not be stored with crops that are sensitive to ethylene, produce ethylene, or need to be stored below 6ºC. Good ventilation also helps maintain the quality of stored fruit.
Physical and physiological disorders in storage
Control measures are needed when storing cherimoya to reduce disorders in the fruit. Good orchard sanitation to minimize sources of fungal spores, preharvest application of fungicides, careful handling to reduce physical damage, prompt cooling to 812°C and then maintaining the optimum temperature, and relative humidity all help.
Exposure of fruit to temperatures below 8ºC, depending on variety and ripeness, can result in chilling injury, with symptoms including darkening and hardening of skin, pitting, failure to develop full flavour, and mealy flesh.
In some varieties, fruit splitting occurs during advanced ripening stages and periods of increased ethylene production. Its possible that turgor changes, related to production of neutral sugars during ripening, force movement of water from the skin to the flesh receptacles, increasing their diameter and putting stress on the flesh and skin, which leads to fruit splitting.
Caused by Colletotrichum gloeosporioides, this appears as dark lesions and may produce pink spore-masses under high humidity conditions.
Caused by Phomopsis anonacearum, purple spots appear on fruit, which harden and crack, followed by the development of small black bodies containing spores.