2 Harvesting and Post-production operations
2.1 Harvesting
2.2 Packinghouse operations
2.3 Packing and packaging materials
2.4 Cooling system
2.5 Storage of fruits and vegetables
2.6 Transportation system
2.7 Processing

2 Harvesting and Post-production operations

Traditional and improved picking operations.

2.1 Harvesting

Pawpaws are harvested manually depending on the size and age of the tree, using specialized 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 specialized 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 colored 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 pawpaw transport due to the high susceptibility to bruising (Fig. 25 Pawpaw covered with paper in order to avoid bruising). Care should be taken during transport in field crates to minimize the movement of fruit (Medlicott, 2001).

Fig. 25 Pawpaw covered with paper in order to avoid bruising

2.1.1 Yield

A typical arrangement for the orchards would be that the trees are planted in a free-draining soil with a plant population of 792 to the acre and a spacing of 3 by 1.5 m. The expected yield is 100 to 140 export boxes per acre per week with each box containing 4 kg of fruit. (Lancashire, 2000) The following gross margin was based on a family unit growing pawpaw under good management. Yields in year 1 and 2 were 0.8 cartons/tree and 5 cartons/tree respectively. It was assumed pawpaw took 10 months to grow and was then picked for the following 14 months. Pawpaws were packed into 13kg cartons. A wholesale market price of $15 per carton was used. Then the gross margin= Total Income ($15/carton* x 6577 cartons) - Total variable costs (Seedlings, fertiliser, irrigation, cartons etc.). In this case, the gross margin for two years (crop cycle) was of $ 38,282 Trees were planted at a density of 1800/ha. As a general rule 10% of trees are non bearing male tees, and 30% of the remainder die, leaving a density of 1134 bearing trees/ha. (Queensland Government, 2000).

* Cartons per hectare over 14 months of harvest.
**   $ australian dollars.

In Mexico, the yield of pawpaw crop fluctuate between 40,000 kg and 85,000 kg/ha.

2.1.2   Grading: After pre-grading, washing, and fungicide treatment, the pawpaws are left to dry and then are graded for packing. Graders remove any fruit that shows signs of fresh mechanical damage or any of the conditions that qualify the fruit for rejection in the pre-grading stage. Remaining pawpaws are classified for packing based on size, stage of ripeness, and, if applicable, shape. Fruits of different shape may not be mixed in the same carton.

2.1.3   Packing. Fruit can be prepared for packing in two ways.

Single layer, one-piece self-locking or two-piece full telescopic fibreboard carton; bursting strength 200 to 250 lb/in ². 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. (Fig. 27 Pawpaws packing). Carton internal dimensions:

* 10.9 by 34 by 26.9 cm (4.3 in by 13.4 in by 10.6 in).
* 10.2 by 43.2 by 27.9 cm (4 in by 17 in by 11 in). (Medlicott, 2001).

Fig. 26 Pawpaws packing

The key packing processes followed in exporting pawpaws are shown below.

i) Pre-grading: Fruit that fail to meet export specifications (see Export Criteria above) should be removed before the washing and decontamination stages and packed later or in a different packing line. Failed fruit may be acceptable for sale on the domestic market.

A pawpaw can be rejected for export for the following reasons:

* Over-ripeness -fruit exhibits localized softening or has more than threeyellow stripes at its base.
* Under-ripeness -fruit has no yellow stripes.

Mechanical damaged fruit has been damaged by knives, harvesting poles, rubbing from the crate, and the like.

ii) Washing: Pre-graded fruit should be placed in a water tank to remove latex and debris. In larger operations, fruit is washed with water in a separate tank or with overhead sprays before being passed to the main wash tank. Normally pawpaws require no additional cleaning, but some may benefit from a careful wiping with a soft cloth. Fruit can also be cleaned with rotating brushes if the brushes are very soft, but simple movement through a water tank for 10 to 15 minutes generally suffices. (Fig. 28 Manual washing of pawpaws).

To help prevent disease and microbial build-up, sodium hypochlorite can be added to the water tanks at a rate of 100 parts per million, or 0.01 percent. Processing personnel should develop a timetable for re-administering the sodium hypochlorite and changing the water, based on the volume of fruit passing through the system.

Fig. 27 Manual washing of pawpaws

iii) Quarantine/fungicide treatment: Depending on the pawpaws' origin, some importing countries require that the fruits be treated for fruit flies. Treatments are determined by importing-country requirements, but may include long-exposure, hot-water dip treatment, or vapor heat treatment. Pawpaws that travel from Hawaii to Japan must undergo vapor heat treatment.

iv) Disease control: Disease control begins in the field. In some cases, and where permitted, postharvest treatments can be used to help prevent the development of anthracnose and phytophthora neck rot.

v) Grading: After pre-grading, washing, and fungicide treatment, the pawpaws are left to dry and then are graded for packing. Graders remove any fruit that shows signs of fresh mechanical damage or any of the conditions that qualify the fruit for rejection in the pre-grading stage. Remaining pawpaws are classified for packing based on size, stage of ripeness, and, if applicable, shape. Fruits of different shape may not be mixed in the same carton.

Because all the fruits in a carton must be similar in size, the counts across cartons can vary. A 4-kilogram carton, for example, can contain the following number of pawpaws, depending on fruit size:

* Small: 13 to 16 count (308 to 250 grams);
* Medium: 9 to 12 count (440 to 330 grams);
* Large: 6 to 8 count (666 to 500 grams).

Pawpaws are also separated according to degree of ripeness, normally as "one yellow stripe" (which is less than one-quarter ripe), "one-quarter ripe", and "one-half ripe". All fruit in a carton must be at the same stage of ripeness so as not to present problems during marketing. In this way, supermarket produce managers can easily identify which fruit are ready for display and which can be stored.

Because pawpaws produce ethylene when they ripen, they should not be stored or shipped with ethylene-sensitive produce. As noted earlier, pawpaws are particularly susceptible to postharvest losses because they are easily damaged and infected by disease. Measures pawpaw handlers can take to control fruit loss are shown below, by risk factor.

vi) Mechanical damage: Many factors contribute to pawpaw skin damage, including the harvesting tool used, dropping of fruit into crates, overfilling of crates, and jostling of fruit during field transportation. During ripening, bruised areas will develop into soft, dark regions that are susceptible to secondary microbial infection. Similar problems can result from poor handling during washing, grading, and packing.

Pawpaw handlers can minimize fruit damage by taking protective measures throughout all handling stages. Staff should be trained in proper harvesting techniques. As noted earlier, stems should be removed in the field to prevent puncturing or scratching of adjacent fruit, and fruit should never be thrown or dropped. In addition, transporters should drive slowly and carefully when taking fruit from the field to the packing house.

At the packing house, crates should include foam in their base and contain only one layer of fruit. In automated operations, all machinery should be padded where possible. Palletized systems are preferable for moving produce in both field crates and final packages.

vii) Pathological factors: Anthracnose is prevalent in pawpaws during long-term storage, particularly as a result of orchard humidity, inappropriate pre-harvest disease control, or other poor orchard management. The presence of the disease is characterized by small black or light-brown spots that gradually grow and may coalesce and sink.

Anthracnose (Fig. 29 Anthracnose in maradol pawpaw) can be controlled or reduced with pre-harvest sprays, which vary according to importer market. In operations that use pre-harvest sprays, postharvest control should consist of a cold-water dip or spray containing 0.05 percent thiabendazole solution and surfactant. (Before using any chemicals in the field or the packhouse on pawpaw for export, growers and packers should consult importing- and exporting-country legislation.).

Where no pre-harvest sprays are used and anthracnose is present in the orchard, the cold-water dip may be insufficient to disinfect the fruit. In that case, harvesters should use a hot-water treatment for 20 minutes at 46°C. Specialized equipment is needed during hot-water treatments to maintain proper temperature and water circulation. Regulation is necessary because temperature fluctuations will reduce the treatment's effectiveness and may damage the fruit.

Phytophthora can attack pawpaws during long-term storage at low temperatures if an orchard 's disease-control systems are not in operation. Phytophthora is characterized by circular, translucent lesions that develop with gray surface mycelia. The disease is particularly apparent around the fruit's peduncle (Market. A.G, 2002, Smith et al., 1992).

Fig. 28 Anthracnose in maradol pawpaw

2.1.4 Storage

Look for fruit with smooth skin. Avoid those with dark, sunken spots as it may affect the flesh of the fruit and spoil the flavor. You can gauge a pawpaw ripeness by touch and sight. The fruit is sent to market at various degrees of ripeness - 1/4, 1/2 and 3/4 ripe - with skin colours ranging from green to yellow-gree to yellow-orange. Pawpaw at its ideal stage of ripeness is 3/4 yellow or yellow-orange (depending on variety). Pawpaws are ripe when they emit a soft fruity aroma.

Hawaiian If you want to eat the fruit the same day make sure the pawpaw is 100% yellow. If you want to wait a couple of days before eating/serving, make sure your hawaiian pawpaw that have more green on the fruit. The more green on the fruit, the longer you can hold it. Store at room temperature unless they are completely ripe (100% yellow). If they are completely ripe, you can store in the refrigerator (40ºF) for 3 to 4 days. When you are ripening the fruit, turn it on the shelf everyday. This will ensure even ripening.

Sunrise Sunrise pawpaw is fully ripened when it is all yellow with small green speckles. If you want to wait a couple of days before eating/serving, make sure that sunrise pawpaw that have more green on the fruit. The more green on the fruit, the longer you can hold it.

Store at room temperature unless they are completely ripe (100% yellow with green speckles). If they are completely ripe, you can store in the refrigerator (40ºF) for 3 to 4 days. When you are ripening the fruit, turn it on the shelf everyday. This will ensure even ripening.

Maradol Maradol pawpaws turn completely salmon colour when they are fully ripe. When they are picked at mature green (not ripe at all) they have three little stripes. As the fruit ripens you will still see faint stripes.

If you want to wait a couple of days before eating/serving, make sure you maradol pawpaw that have more green on the fruit. The more green on the fruit, the longer you can hold it. Store at room temperature unless they are completely ripe (salmon colour). If they are completely ripe, you can store in the refrigerator (40º F) for 3 to 4 days.

When you are ripening the fruit, turn it on the shelf everyday. This will ensure even ripening. Relative humidity: more than 80% (Calavo Products, 2002).

2.2 Packinghouse operations

Before we begin the tour we must first understand how the fruit is harvested and delivered to the packinghouse. Field Managers are in contact with our Growers to schedule deliveries of fruit to meet market demands. Growers who want their fruit picked up in the groves will schedule transportation with the Field Manager. Many Growers elect to deliver the fruit to the packinghouse themselves.

The fruit is gradually pre-cooled before packing. This allows the fruit to cool down over a 12 hour period from the ambient temperature at delivery time, to 40-45 degrees before packing the next morning.

Packers have a built in system that allows full bins to be weighed before packing. Empty bins are then weighed so that the grower is given credit for every pound of fruit delivered to the packinghouse.

The fruit is placed on the packing line and graded. The fruit is then placed into tight fill cartons by Sizer machine. The fruit is labeled during the process. The sizer insures not only that the correct number of fruit is packed into the cartons by size, but also that the weight of the carton is correct.

All cartons of fruit are checked once more by a quality control person before the carton is sealed and placed in a cooler until shipment time. The cartons of fruit are stacked on pallets and these pallets are placed in a shipping cooler, where temperature is maintained between 40 and 42 degrees (Calavo Products, 2002).

a) Inspection
One the fruits are harvested at optimum mature, are transported to the packinhouse where are inspected and selected by size and mature grade.

b) Washing
Washing the fruits immediately after harvest is essential, as the sap, which leaks from the stem bums the skin of the fruit making black lesions, which lead to rotting.

c) Grading
Grading and packing should be carried out as soon as possible after harvest, normally within three hours, after which time the fruit should be kept at ambient tropical conditions (25°C to 28°C) to continue ripening, or cooled and stored at 10°C to 12°C.

Standard packing house design and operations apply for pawpaw grading and packing. Operations can be carried out with basic equipment, including water tanks, field crates, and grading tables, or with automated washing and weight-grading or separation systems. All tanks and grading tables should be covered with foam to protect fruit from exposed edges; the skin of the pawpaw is delicate, and scratches will result in latex exudation and staining. Similarly, if the fruit is dropped, it will easily develop bruises as it ripens (Market. A.G, 2002, Smith et al., 1992).

d) Hydrothermic process (rural installations and certification of automatic systems)
Hot water treatment: 30 minutes at 42°C (107.6°F) followed within 3 minutes by a 49°C (120.2°F) dip for 20 minutes (Kader, 2000).

e) Thermal disinfestations treatments
Pawpaw treated by vapor heat or forced hot air for export must be picked before the fruit is suitably ripe. Pawpaw is subjected to temperatures of 117°F for up to four hours. This results in premature wrinkling due to water loss.

Hot treatments are approved for insect disinfestations, but have demonstrated some commercial shortcomings. Vapor heat requires growers to harvest greener pawpaws, which more readily tolerate heat treatment than fruit at riper stages. Forced dry air has been shown to blacken lychee, while extended cold treatment of star fruit can render the fruit wilted and unmarketable. Dr Lyle Wong, Science & Public Policy Institute April, 1998.

Consumers prefer fresh fruit. We are committed to fruit picked tree-ripened for sweetness and quality. Research shows repeat customer sales with Brix over 12.

Irradiation research performed by Dr. James Moy and Dr. Robert Paull at the University of Hawaii shows equal or superior retention of vitamins at allowable doses.

For many decades, chemical fumigants have been used to allow fruits, vegetables and grains to be transported across state lines and imported from foreign countries. But that era is coming to an end.

In 1984, ethylene dibromide was cancelled for further use. Now, with adoption of the international Montreal Protocol, methyl bromide, the primary fumigant used worldwide, will be phased our effective January, 2001.

These fumigants have been determined to present environmental hazards, including damage to the earth's ozone layer.

In 1997, USDA researcher Donald Thayer stated: "A safe, effective alternative to methyl bromide, irradiation has no harmful side effects."

That is why the list of endorsers for irradiation includes the U.S. Department of Health and Human Services, U.S. Public Health Service, American Medical Association, World Health Organization, United Nations Food & Agriculture Organization, the Institute of Food Technologists, and the international Codex Alimentarius Commission (Hawaii Pride, 2002).

Vapor heat treatment : Fruit temperature is raised by saturated water vapor at 44.4°C (112°F) until the center of the fruit reaches that temperature, and then held for 8.5 hours.

Forced hot air treatment: 2 hours at 43°C (109.4°F) + 2 hours at 45°C (113°F) + 2 hours at 46.5°C (115.7°F) + 2 hours at 49°C (120.2°F) (Kader, 2000).

The single hot-water dip (49 °C for 15 min) is the optimum heat treatment for disease control of pawpaw diseases with minimal detrimental impact on fruit quality. The additional disease control provided by a single hot-water dip before or after forced air dry heat (FADH) or vapor heat (VH) is about the same level provided by postharvest applications of the fungicide thiabendazole applied to FADH or VH treated pawpaw. (Nishijima, 1995).

White peach scale was collected for the first time in Hawaii in September 1997 from pawpaw. This scale insect is a threat to the pawpaw industry as a source of tree stress and fruit downgrading, and as a quarantine pest on fruit for export.

Pawpaws exported from Hawaii now receive a vapor heat quarantine treatment for fruit flies that involves heating the fruit core temperature to >117°F (47.2°C) in not less than 4 h. We conducted a study to test the effectiveness of this treatment against white peach scale. Pawpaws infested with all stages of the scale were treated under commercial conditions. The vapor heat treatment killed all the scales tested including 19,000 eggs, 27,000 crawlers, 13,000 immatures, 1000 pupae, and 5600 hardshells. White peach scale on pawpaws subjected to vapor heat treatment should pose no threat to quarantine security in export shipments (Follett, 2001).

2.3 Packing and packaging materials

Packaging practices
A package or packaging is the material used to protect, contain or transport a fruit. A package can also be a material that is physically attached to a product or its container for the purposes of marketing. Packing material is generally used to preserve, transport, inform about as an aid while using the fruit it contains.

Solo Sunrise pawpaw, the most popular variety, are packed in single-layer cartons, each with a net weight of 4 kilograms to 5 kilograms, depending on importer and importing-country requirements. Internal packaging materials can include shredded paper in the base of the carton and individual tissue wraps for each or every other fruit. Pawpaw may be individually labeled for appearance and easy recognition.

Pawpaws are best packed on their sides, in rows, with the stem ends at an angle; interlocking rows support one another. Pawpaws should not be packed on their bases because they soften from the base up. Packers should guard against overfilling the cartons.

Importers require pawpaws at specific stages of ripeness for optimal sales. Stages vary from 50 to 70 percent yellow depending on importer, market, and time of year. In order for fruit to arrive in the importing country at the correct colour stage, exporters must be aware of the fruit's maximum and minimum colour stages upon its departure from the packing house, the length of the shipment period (for air shipment, 24 to 48 hours), and the temperature in the importing country. Colour stages for air shipments can vary from 20 to 50 percent, with selections generally being more rigid during the summer months because of accelerated ripening rates on arrival in importing countries. Fruits that are exported at less than 20 percent yellow will fail to ripen adequately when temperatures in importing countries are low, particularly during winter (Hawaii Pride, 2002).

2.4 Cooling system

2.4.1 Low Temperature.

Storage of unripe pawpaw below temperatures of 10°C will result in chilling injury. The symptoms are indicated by surface pitting, discoloration of the peel and the flesh, incomplete ripening, poor flavor and increased susceptibility to disease incidence. Ripe pawpaws will store successfully at lower temperatures (Fig. 30 Refrigeration room), but transport of ripe fruit (more than 50% yellow colour) is not recommended due to the susceptibility to mechanical damage and bruising (Medlicott, 2001).

Fig. 29 Refrigeration room

2.5 Storage of fruits and vegetables

Recommended storage temperature for pawpaw is 10 ° C. Handling with care to reduce bruising, skin of the pawpaw is very delicate. Ripen at room temperature, fruit should be slightly soft to the touch and turned 3/4 yellow, approx. 2 to 3 days. Ripe pawpaw should be refrigerated to slow down the ripening process. Place ripe, whole fruit in a plastic bag in the refrigerator, and it should last about a week. (About, 2002).

Little is known about pawpaw fruit ripening and its response to standard fruit storage techniques. The fruit ripening is probably regulated by naturally produced ethylene similar to apple, tomato and banana. Furthermore, storage at 4 ° C for 4 weeks or more seems to delay ripening until removal to room temperature. Due to the nearly non-existent data about pawpaw ripening and postharvest storability, it is critical to develop appropriate storage practices in order to maintain fruit quality for both the fresh and processing markets. (Archbold, 2001).

2.5.1 Forced ripening

Among those treatments designed to accelerate the ripening process of fruit, the treatments commonly used include exposure to ethylene, acetylene ethephon (2-chloroethylphosphonic acid).

2.5.1.1 Controlled atmospheres treatment.

Ethylene effects: Exposure to 100 ppm ethylene at 20 to 25°C (68 to 77°F) and 90-95% R.H. for 24-48 h produces a rapid and uniform ripening (yellowing of peel and pulp softening, but a nill improvement in flavor) of pawpaws harvested between colour break to 1/4 yelllow (Kader, 2000).

Experiments carried out by our postharvest group (Instituto Tecnologico de Veracruz-UNIDA, Mexico), reported a reduction of the maturation time (three days) of maradol pawpaw fruits when were exposed with 500 ppm of ethylene, in modified atmospheres at ambient temperature (24-26°C and 85-95% HR). This fruits showed a better texture, taste and colour (Vela, 2002). (Fig. 30 Pawpaw ethylene treatment).

Fig. 30 Pawpaw ethylene treatment

2.5.2 Compatibility groups for storage of fruits.

The best storage environment for an individual fruit or vegetable depends on its unique requirements for temperature, relative humidity, and ethylene exposure. Most compatibility charts for mixing products during postharvest handling divide fruits and vegetables into eight groups. In practice it is very difficult to separate products into this many groups-very few wholesale or retail handling facilities, if any, have eight temperature-controlled rooms.

Researchers of UC Davis (Thompson, Kader and Sylva, 1999), have developed a three-group chart that is easier to use and still provides good product life (Table 5).

Group 3- Fruits
code thermometer 55-65 ° F, 13-18 ° C & 85-95% rh (relative humidity).

2.6 Transportation system

Based on the transit and storage life, a recommendation is made. Since many tropical products like pawpaw are high value and traded in small quantities, they are often shipped by air, even when surface transportation could be used. (USDA, 2002). (Fig. 26 Transportation of pawpaw fruits).

Although the UK market for pawpaw is expanding at a leisurely pace, efforts to increase it by shipping volumes by sea have proved unsuccessful due that the product doesn't respond well to this type of transit. (PGA, 1999).

Marketing and physical distribution of fresh produce inherently means moving the produce. The commodities are handled, either manually or mechanically, many times from harvest and through the distribution process before the consumer buys and prepares them to eat.

For domestic transportation the use of road vehicles offers substantial advantages of convenience, availability, flexibility permitting door-to-door delivery, and reasonable cost of transport. The use of road transportation for fresh produce is increasing and likely to increase in countries all over the world. Produce may be transported by pick-up, enclosed truck, open truck or refrigerated vehicle. (Harris, 1988).

For perishable products, however, the increased speed of handling and reduced transport costs that came with containerization were not enough. Ocean transport of cooled and frozen cargo received a substantial boost with development of mobile refrigerated cargo ships that lack this flexibility. Controlled atmosphere (CA) technologies allow operators to lower the respiration rate of produce by monitoring oxygen, carbon dioxide ans nitrogen levels within a reefer. In this way, CA can slow ripening, retard discoloration, and maintain freshness of pawpaw. Although it is likely that container ships will dominate the perishable trade between North America, East Asia and Europe, conventional refrigerated vessels can serve many smaller ports, especially in the developing world, that are unable to handle large container vessels. Thus, in north-south trade and in certain niche markets, conventional refrigerated ships may have a brighter future, but even here, competition from container vessels is bound to increase as cost decline (Agricultural Outlook, 1999).

Fig. 31 Transportation of pawpaw fruits

2.7 Processing

Essentially a prime table fruit, pawpaw pulp (Table 6) is perfectly suited for conversion to juices Fig. 32 Processing of freeze pawpaw juice, nectars, drinks, jams, fruit cheese, concentrates (Fig. 33 Process for pawpaw concentrate) or to be had by itself or with cream as a superb dessert. It can also be used in puddings, bakery fillings, and fruit meals for children, flavors for food industry, and also to make the most delicious ice cream and yoghurt. While the raw fruits are utilized for products like chutney, pickle, sauce. pawpaw beverage, etc. ripe ones are used in making pulp, juice, nectar (Table 6), squash, leather, slices, etc. Major export products include dried and preserved vegetables, jams, fruit jellies, canned fruits and vegetables, dehydrated vegetables, frozen fruits, vegetables and pulps (Table 7) and freeze dried products.

Ripe pawpaw may be frozen whole or peeled, sliced and packed in sugar (1 part sugar to 10 parts pawpaw by weight) and quick-frozen in moisture-proof containers. The diced flesh of ripe pawpaw, bathed in sweetened or unsweetened limejuice, to prevent discoloration, can be quick-frozen. Half-ripe or green pawpaws are peeled and sliced as filling for pie, used for jelly, or made into sauce.

Fig. 32 Processing of freeze pawpaw juice

Fig. 33 Process for pawpaw concentrate

2.7.1 Fresh consumption and processing.

For long distance marketing, fruit should be harvested after the colour of blossom end has changed; but for local consumption pick up fruits at half way change in green colour. Size grade, treat with hot vapors of ethylene bromide to kill fruit fly, if required, wrap in newspapers and pack in boxes before shipping. For table use and processing, prefer pawpaw harvest at 3/4 ripe stage indicated by 75 % colour change to yellow. Such wrapped fruits will ripen completely to total yellow colour at room temperature within 2-4 days. Fruit harvested at 3/4 ripe stage will store successful at 7°C for 21 days. Ideal storage temperature is 13-16°C. Unripe fruit if stored at 12°C suffers from chilling injury. Fresh ripe pawpaw is consumed as `it is' after peeling and slicing, often with added salt, spices, sugar or lime juice. (Fig 34 Peeling of maradol ripened pawpaw).

Fig 34 Peeling of maradol ripened pawpaw

It is preferred breakfast and dessert fruit. Pawpaw is quite nutritious having many therapeutic and medicinal uses. It is rich source of many vitamins and minerals. Use early drop unripe green pawpaw for the preparation of curried or dry vegetable, raita, burfey, pickle or chutney.

a) Vegetable
Wash, peel, halve, remove seed, slice, rewash and cook like other. For large scale consumption of early fallen green fruits, supply them in bulk to community kitchens of hostels, dhabas, hotels, restaurants and langers of religious places for use as vegetable and raita.

b) Raita
Boil grated pulp of peeled green pawpaw with equal amount of water. Press to squeeze out water. Mix curd with laddle. Add grated boiled pieces and mix. Mix edible salt and spices (cumin, black pepper, coriander, etc.) according to taste and serve.

c) Drying
Prepare slices (6 mm thick) after washing, peeling, cutting and removal of seeds. Sulfuring of slices is done for 2 h by burning 3 g sulfur/kg slices in a closed chamber. Dry at 60-65°C in a drier with occasional turning, or sun dry. Pack in polyethylene bags. (Fig. 35 Dried pawpaw product and dryer).

Fig. 35 Dried pawpaw product and dryer

d) Papain
Unripe green but fully mature fruits are lanced with a knife. Give four cuts at equal distance on single fruit. Collect latex in a suitable vessel of glass or porcelain. Latex hardens within 15 min. Sundry it as crude papain. To obtain high quality papain, precipitate it with alcohol followed by washing with acetone. Dry under sun or in an over or preferably under vacuum oven sulfuric acid at room temperature. Small amount of sodium sulfate may be added during latex collection to obtain better quality product. Extract papain from the green fruits after collecting latex as pawpaw fruit contains 10 % papain on dry weight basis.

e) Pectin
Unripe green fruits otherwise unsuitable for product making or fruits after obtaining latex may be used for pectin extraction. Green pawpaw is rich in pectin, containing 10% of it on dry weight basis. Pectin has extensive applications in food and medicinal industries. Pectin can also be extracted from peel waste of green pawpaw.

f) Pulp
Pulp of fully mature and ripe pawpaw is used for the preparation of nectar and mixed ready-to serve beverages. Unripe fruits may be sorted out from the bulk lot and ripened at room temperature by keeping them wrapped in newspaper. Combine in the ratio of 1:1 pectin rich slightly unripe fruit with full ripe pawpaw having fully developed yellow colour and flavor for pectin requiring products such as chutney, sauce, jam and jelly (Fig. 36 Maradol pawpaw pulp). For pulping, fruits are thoroughly washed, peeled and halved with stainless knives. Peeled halves are pulped with mechanical fruit crusher or home mixer. Filter or sieve the pulp to remove fibrous material. Use fresh pulp for the preparation of different products. However, for long distance marketing, pulp is usually concentrated, frozen or canned.

Fig. 36 Maradol pawpaw pulp

g) Pickle
Blanch 1 kg slices of peeled green pawpaw in boiling water for 3 minutes. Drain and sprinkle 100 g salt and dry under shade. Mix spices i.e. 10 g each of powdered red chillies, cardamom, large cumin and black pepper. Fill in jars. Cover with vinegar (>250 ml). Close with airtight lids. Curing will be completed within 2-3 weeks.

h) Chutney
Cook 1 kg of pulp of ripe firm peeled and grated pawpaw with chopped onion (100g) and 50g salt till soft. Add 50g ginger and 15g garlic after chopping and 10g each of the powdered aniseed, red chillies, cumin, large cardamon, cinnamon, black pepper, and 2g headless cloves. Cook gently to desired consistency. Add sugar (3/4kg). Cook again to thick consistency. Add vinegar (200ml) Cook for 5min. Fill hot into previously cleaned dry jars followed by capping.

i) Sauce
Concentrate 1 kg strained pulp containing 20 g sugar to 1/3 of its original volume in the presence of suspended spice bag containing 50 g chopped onion, 5 g garlic and 50 g ginger, 10 g powdered spices and 5 g red chillies. Press out spice bag occasionally and squeeze it out finally to obtain maximum spice extract. Add 15 g salt and remaining 40 g sugar and cook to thick consistency. Add 450 ml vinegar and cook again to end point. Add and mix preservative after dissolving in minimum quantity of water. Heat to boiling and hot pack.

j) Jam
Boil 1 kg pulp of ripe firm peeled fruit with 100 ml water and 3 g citric acid. Add 3/4 kg sugar and cook to thick consistency. End point is confirmed by sheet test. Boiling mass is allowed to fall after cooking from a serving spoon, which will flow in the form of a sheet. Pack hot in clean dry glass jars.

k) Jelly
Mix 1 kg grated pulp of fully mature peeled but somewhat raw fruits with ripe pawpaw pulp (1 kg), 2.5 l. water and 10 g citric acid. Boil for 30 min, cool and allow to settle for 2 hours. Separate the supernatant (upper layer) and filter. Test for pectin quality. Formation of single clot with small quantity of ethyl alcohol added to test samples indicates high pectin content. Concentrate further, if necessary to obtain single clot. Cook gently the extract with equal quantity of sugar to obtain the end point indicated by the formation of sheet. Pack hot. Cover with a layer of melted wax and close the lid.

l) Burfi
Boil the grated pulp of peeled green pawpaw for 5 min. Press out excess water. Fry in equal amount of animal mil-fat. Add sugar equal to the grated material. Mix and heat for 2 min. Spread it in the form of 1 to 2 cm thick uniform layer on aluminum/steel tray smeared with fat. Allow to dry. Cut pieces of suitable size.

m) Preserve and candy
Cut rectangular slices (4x1 cm) or suitable sized cubes from the fully mature ripe washed peeled fruits after removing seeds. Puncture with a stainless steel fork. Keep in 1.5 % limewater for 3-4 hours. Drain and wash 3-4 times in plain water. Dissolve 400 g sugar in 600 ml hot water and filter. Boil pieces in sugar syrup and keep overnight. Next day drain the syrup, raise its Brix to 50. Add slices, boil and keep again. Repeat this process every day, until Brix reaches 70-75°. Keep for a week. Drain the syrup, fill the pieces in dry jars and cover slices with freshly prepared sugar syrup of 70°Bx.

For the preparation of candy, raise the Brix of syrup to 75°, and keep it for a week. Drain and dry the pieces under shade. Dip pieces in boiling water to remove adhering sugars. Drain, dry and pack.

n) Toffee
Concentrate 1 kg sieved pulp to 1/3 volume and cook with added sugar (600 g), glucose (100 g) and hydrogenated fat (100 g) till a speck of the product put into water forms compact solid mass. Make thick paste of 100 g skim milk powder in minimum quantity of water and mix with the boiling mass. Spread 1-2 cm thick layer of the cooked mass over /SS trays smeared with fat. Add flavouring material at this stage, if necessary. Allow cool. Cut and wrap in butter paper.

ñ) Leather
Mix thoroughly powdered sugar (50-75 g) citric acid (0.5 g) and KMS (Sulphite Mono Potassium) (3 g). Smear /steel tray with fat and spread the above mixture in 1cm thick layer. Dry in a home drier at 55-60°C. Roll the dry leathery product for storage as slab or cut it into pieces of suitable size.

o) Canning
Cut slices (2.5 x 4 cm) or cubes of suitable size from fully developed ripe firm washed, peeled fruits after removing seeds. Pack slices in plain cans. Cover with hot sugar syrup (33°Brix). Exhaust at 90°C for 5 min. Seam and process in boiling water. Cool, label and store (Indiaagronet.com, 2000).

p) Papain from pawpaw
Papain is prepared from pawpaw Latex, which is viscous and milky. It has good protein hydrolysis properties.

In the year 1987 world production of pawpaw was 34.54 ton. India's contribution was 3.4 ton. which has increased considerably during past years due to its increasing use in food industry, pharmaceuticals, leather tanning, beer industry, textiles, etc.

The pawpaw fruit has got a wide spectrum of applicability both in the form of raw and ripe fruit. Some of the important applications has been shown below:

At present there is production of more than 100 tonnes of papain in the country of which 35 t. is BPC (British Pharmacopoiea Commission) grade and the rest is pure Papain. BPC grade papain is used in the country and 90% of pure papain is exported. For marketing of papain entrepreneur could contact pharmaceutical, beer plants, food & tanning industry, meat & cheese processing industry, etc. They can also contact Agricultural Process Food Export Promoter Agency, Bikajee Camp Place, New Delhi for export of Papain.

q) Latex
Tropical and sub-tropical climate is suitable for cultivation of pawpaw and it is widely grown in India. Fertile soil having good water retention quality is suitable for pawpaw cultivators. Tamil Nadu Agriculture University, Coimbatore has developed CO2, and CO5 varieties which are suitable for obtaining good latex production. Generally papain manufacturers grow pawpaw to cater to their needs or else they could collect from nearby farmers. For obtaining 50-60 kg. of latex per day for 300 days there is need for cultivation on 25 acres of land. The land is divided into 3 sections the plantation is done in one section at a time in a cycle of 3-4 months so as to make availability of latex round the year (Timeis, 2000).

Pawpaw fruits on the trees itself are launched by giving 1/2 in deep 4-6 longitudinal cuts with a stainless steel knife or razor blade fitted in a curved wooden frame with a handle. The latex is collected in suitable stainless steel or trays or polyethylene sheet held below the tapped fruit. Five to six tappings in the course of 30 days have been found to be sufficient for the purpose. At the end of each tapping, the latex coagulated on the surface is scrapped and added to the batch.  The collected latex is passed through 50 mesh sieve to remove dirt. It is mixed with 0.5% potassium metabisulphite and spread on stainless steel or aluminum trays (0.5-1 lb/ft ² of tray area) and dried in a vacuum shield drier at a temperature of about 55°C for 4-5 hours. Vacuum dried product is superior in quality and is easier to remove from the trays due to its porous structure.

The dried product is packed in air-tight containers and stored in a cool dry place. It is advisable to keep the product in flake form as powdering decreases the stability of the product during storage. In pilot plant trial, the average yield of wet latex was about 20-25% of the tapped fruits. The yield of the dry papain was 20-25% of the wet latex collected. The yield of papain thus obtained was about 80 BPC units per gram. The dried flakes are powdered and blended with a dilutent to the desired concentration just before the dispatch of the consignment. It is preferable to have a dehumidifier in the powdering and packing rooms (Timeis, 2000).

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