Postharvest Handling of Papaya The following is excerpted
from "Product Specifications and Postharvest Handling for Fruits,
Vegetables and Root Crops Exported from the Caribbean", by Dr. A.
Medlicott (Fintrac). Unauthorized duplication is prohibited.
Papaya Carica papaya L.
 Papaya Packed for Export
Chief Producers
Barbados
Season
Year-round
Quality Criteria
Papaya should be exported with the required size and stage of ripeness (as defined in the market specifications) with sufficient yellow peel and orange or red pulp colouration, free from bruises, blemishes, insect and spray damage and uniform in size and ripeness within each carton.
Variety
Solo type
POST-HARVEST HANDLING SYSTEM
Papaya fruits are sensitive to poor quality outturns and high post-harvest losses if harvesting, treatments and handling techniques are inadequate or inappropriate. From harvest, a shelf-life of four to six days under tropical conditions and up to three weeks at low temperature storage can be achieved with the correct harvest maturities, disease control measures, handling techniques and storage conditions.
Harvest Maturity
Papaya fruits should be harvested when the colour of the skin changes from dark green to light green and when one yellow streak begins development from the base upwards. Fruits in this condition will continue to ripen normally after harvest. Those fruits harvested before this stage will fail to show complete ripening, and those harvested after, are more susceptible to damage and bruising during handling.
Harvesting
Papaya are harvested manually depending on the size and age of the tree, using specialised tools, knives or by hand. When harvesting by hand or with knives, the peduncle is snapped or cut from next to the tree.. then immediately trimmed flush against the top of the fruit. The specialised implement for harvesting of fruit inaccessible by hand due to tree height, comprises of a long pole, a small circular hoop at the top, a small mesh bag attached to the hoop, and a horizontal blade above the hoop and the bag. The blade is positioned below the peduncle of the fruit and the pole moved upwards; the fruit is detached from the tree and then drops gently into the mesh bag below the hoop at the top of the pole.
After harvest, the fruit are placed in single layers into shallow, light coloured field crates, preferably containing a foam layer for cushioning. All stems should be trimmed after harvest to ensure that no stem to fruit rubbing occurs during transport to the packing facilities. Fruit should never be thrown or dropped. Field crates containing the fruit should be left in shaded conditions protected from the sun and rain, while awaiting collection for delivery to a packing facility. Mesh bags, sacks or baskets are unacceptable for papaya transport due to the high susceptibility to bruising. Care should be taken during transport in field crates to minimise the movement of fruit.
Export Grading and Packing
Grading should be carried out as soon as possible after harvest, and fruit left under ambient conditions to continue ripening or placed at 10° to 12°C for cooling and storage. On arrival in the packing facility, fruit should be washed in water to remove latex and debris, then treated in a 0.05% Thaibendazole solution for anthracnose control. Washing, treatment and grading can be carried out using mechanised or manual systems, depending on the volumes of fruits. Grading in each carton is required in terms of size, sex (shape) and stage of ripeness. Female and hermaphrodite fruit cannot be mixed in the same carton; all fruits must be of a similar size in each carton resulting in a range of counts, and separations must be made for the degree of ripeness. Carton net weight are dependent on the importer, ranging from 3.5 to 5 kg (8 to 11 lbs), and must not be overfilled during packing.
Packaging
Single layer, one-piece self-locking or two-piece full telescopic
fibreboard carton; bursting strength 200 to 250 lb/in2. Internal packaging material should include shredded paper in the base of the carton and individual tissue wraps for each or alternate fruit. Individual labels can be attached to the fruit for appearance and recognition.
Carton internal dimensions:
- 10.9 by 34 by 26.9 cm (4.3" by 13.4" by 10.6")
- 10.2 by 43.2 by 27.9 cm (4" by 17" by 11")
Storage and Transportation
Importers require fruit at specific stages of ripeness for optimum sales; this varies between 50 and 70% yellow colour depending on the importer, the market and the time of year. For fruit to arrive in the importing country at the correct colour stage, attention has to be paid to the maximum and minimum colour stages on departure from the packhouse, the length of the shipment period (24 hours when considering UK, Canada and USA, and 48 hours for Holland) and the temperature in the importing country. Thus, colour stages on departure from the packhouse for air shipment can vary from 20% to 50%, and the selections are generally more rigid during the summer months due to the rapid rates of ripening on arrival in importing countries. fruit exported too green (less than 20% yellow colour) will fail to ripen adequately when temperatures in importing countries are low, particularly in winter months.
Sea-shipment of papaya is possible when fruits are shipped at the optimum harvest maturity, with one or two yellow streaks. Shipments should be made at 10° to 12°C and 85 to 95% relative humidity, in refrigerated holds or reefer containers. Post-harvest disease control is critical with sea-shipment, particularly anthracnose and Phytophthora. Colour development during sea-shipment usually increases from 10% to 40% during 10 days at 12°C, and will develop further during the customs, clearance and delivery period on arrival.
Fruit harvested and placed to ripen at the recommended harvest stage (one yellow stripe) will ripen to 60 to 70% yellow colouration within four to six days under ambient tropical conditions (25° to 28°C). Fruit transferred to low temperature storage (10° to 12°C), when harvested at the one-stripe stage, will store successfully for 14 to 21 days if post-harvest disease incidence can be controlled. When harvested at more advanced stages of ripening, the storage life will be significantly reduced.
Potential Post-harvest Losses
 Post-harvest loss in Papaya
Papaya is particularly susceptible to post-harvest losses as a result of high susceptibility to bruising and disease infection. Careful handling must be employed during harvesting, handling and shipping, and the relevant disease control measures employed.
Mechanical Damage
Damage to the skin immediately after harvest, as a result of the harvesting implement, dropping into crates, over-filling of crates and excess movement of fruit during in-field transport, will result in latex staining, punctures, scars and bruises. During ripening, bruised areas will develop into dark soft regions which become affected by secondary microbial infection. Similar effects can occur as a result of poor handling during washing, grading and packing. Damage can be reduced by taking protective measures throughout the handling procedures. Staff should be trained with harvesting techniques, foam should be included in the base of field crates and crates should contain only one layer of fruit. Stems are to be removed in the field to prevent puncturing or scratching of adjacent fruit. Vehicles used to transport the fruit from the field to packhouse should be driven slowly and with care. During handling in the packhouse, fruits should never be thrown or dropped and in automated operations, all machinery should be padded where possible.
Palletised systems of produce movement in packhouse operations are preferable, both with field crates and with the final packed product.
Pathological Factors
Anthracnose (Colletotrichum gloespoirides L.) disease is prevalent during long term storage and with humid orchard conditions, inappropriate pre-harvest disease control or poor orchard hygiene. The presence of the disease is characterised by small black or light brown spots which gradually enlarge and may coalesce and sink. Anthracnose can be controlled or reduced by pre-harvest sprays. Post-harvest control where pre-harvest sprays are in operation should include a cold-water dip or spray containing 0.05% Thaibendazole and surfactant. Changing of chemical is required each four to five tonnes of fruit. Where no pre-harvest control is in operation and the disease is present in the orchard, the cold water treatment may have to be replaced with a hot-water Thaibendazole treatment. A treatment time of 20 minutes at 46°C is required. Specialised equipment for temperature maintenance and water circulation is necessary as fluctuations in temperature will reduce the effectiveness of the treatment and may damage the fruit.
Phytophthora: the disease can be prevalent during long-term storage at low temperature if orchard control systems are not in operation. Phytophthora is characterised by circular translucent lesions which develop with grey surface mycelium, and is particularly apparent around the peduncle. Post-harvest control is achieved by treatment with 0.1% Previncur N.
Low Temperature
Storage of unripe papaya below temperatures of 10°C will result in chilling injury. The symptoms are indicated by surface pitting, discolouration of the peel and the flesh, incomplete ripening, poor flavour and increased susceptibility to disease incidence. Ripe papayas will store successfully at lower temperatures, but transport of ripe fruit (more than 50% yellow colour) is not recommended due to the susceptibility to mechanical damage and bruising.
Papaya Specifications - Summary
Markets
UK, Holland, Canada, USA.
Varieties
Solo type
Characteristics
Yellow/green peel, deep orange/yellow flesh. Hermaphrodite fruit should be pear-shaped and female fruit uniformly round; all fruit should appear fresh with no shrivelling, discolouration or non-uniform ripening.
Size
Different sized fruit are separated and packed according to weight, resulting in different "counts". The following weight range is used for a 4 kg net weight carton, both for female and hermaphrodite fruit:
- small: 12 to 15 count (260 to 330 g)
- medium: 8 to 12 count (360 to 500 g)
- large: 4 to 8 count (570 to 1000 g)
Condition
- no latex stains or surface debris
- no wounds from harvesting or handling, including punctures, scratches and bruises
- no scars or residues from insect or spray damage
- no fruit above the required colour stage for shipment
Market Requirements
All markets: small and medium hermaphrodite fruit are preferred with 50 to 70% yellow colouration on arrival at the importer. Small female fruit are acceptable to some importers.
Selected markets and importers require medium and large fruit, particularly for ethnic or catering markets. Hermaphrodite fruit are preferred due to the large cavity size and susceptibility to damage shown with large female fruits.
Handling in Importing Countries
For the maximum marketing period of papaya, the fruit should be stored at 10° to 12°C. Temperatures below this range will cause chilling injury and rapid deterioration in fruit quality. To develop ripening in papaya, fruits should be stored at 18° to 25°C and treated with ethylene gas at 100 ppm (0.01%) for 24 hours. Unripe papaya are sensitive to ethylene and will commence ripening if stored with ethylene-producing commodities. Similarly, ripe papaya produce ethylene and will cause deterioration in ethylene-sensitive crops.
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