Papaya - pawpaw

The papaya Carica papaya is indigenous to the West Indies and central America. It was carried by the Spanish to Manila in the mid 1500's. From there it went to Malacca then India and reached Hawaii in 1800-1820's.
There are 45 species of papaya and the "trees" reach fruit bearing age when a year old, so are very fast growing.

The "Solo" type, with pink flesh was introduced to Hawaii from Barbados and Jamaica in 1911. Exports from Jamaica have been increasing slowly with 4062 tonnes shipped in 1995 and 4704 tonnes in 1996.

The largest grower of papaya in Jamaica is the Belvedere Estate, which is a joint venture between the Jamaica Flour Mills and the Jamaica Banana Producers. The acreage in papaya at Belvedere is expanding from 150 to 254 acres in 1997. The trees are planted in a free-draining soil with a plant population of 792 to the acre on a spacing of 3 by 1.5 metres. The yield has been 100 to 140 export boxes per acre per week and each box contains 4 kg of fruit.
40% of the fruit was destined for the US market, 33% for the UK and 27% for Canada.

Chemistry

Sugars

Much of the early work on the estimation of sugars in papaya is now known to be incorrect due to the presence of an invertase enzyme. A more recent evaluation which heated the samples in a microwave oven to deactivate the enzyme has given the distribution as follows:
sucrose (48.3% early reports suggested NONE), glucose (29.8%) and fructose (21.9%).

The total carbohydrate content has been found to be around 10 g per 100 g of edible portion.

Acids

The acid content of papayas is very low and the pH is generally between 5.5 - 5.9 and comes from almost equal amounts of citric and malic acid.

Pigments

The difference between yellow and red-fleshed papayas was first described in 1964 and the total carotenoid content was reported to be 3.7 mg/100 g and 4.2 mg/100 g respectively.
The major differences can be seen in the following table.

Percent composition of carotenoid pigments
pigment	yellow	red
beta-carotene	4.8	4.8
zeta-carotene cryptoxanthin	24.8	5.9
and monoepoxide	15.6	4.4
cryptoxanthin	38.9	19.2
lycopene	0.0	63.5
unresolved	15.9	2.2

Volatiles

106 volatile compounds were identified in 1977 using GC/MS techniques. The compound thought to have the odour that most closely resembled that of papayas was linalool. Benzyl isothiocyanate contributes a pungent off-odour and is present as a major component.

Papain and other enzymes

Several enzymes have been found in papayas of which papain is of commercial importance. 2/3 of the usage in the USA is as a meat tenderiser and it is used as a beer stabilising agent as well.
Papain is recovered by making scratches (tappings) in the latex. 6 tappings over 15 days has been recommended for optimum recovery of the enzyme. The scratches are made 0.2 cm deep at 1.25 cm apart and are best done on days 1,3,6,9,12 and 16. The yield is of the order of 180 lb per acre. The latex is either hyperallergenic or an irritant and so it is necessary to wear gloves. The scratches should not be made with a metallic knife although collection into aluminum trays is found to be OK.
Processing by 95% alcohol followed by acetone gives complete precipitation and dehydration. The 212 amino acid sequence has been determined.

References

"Tropical Fruit Processing", Edited by J. Jagtiani, H.T. Chan, Jr. and W.S. Sakai Food Science and Technology, A series of monographs, 1988, Academic Press, Inc., 1250 Sixth Avenue, San Diego, California, 92101.
"Food Flavourings", Edited by P.R. Ashurst, Blackie Academic & Professional, an imprint of Chapman & Hall, Wester Cleddens Road, Bishopbriggs, Glascow, G64 2NZ, UK. 2nd edit. 1995.
The Jamaica Gleaner, Farmers Weekly, Sat 14th June-97, page A 11.

Return to links to the chemistry of other Jamaican items, including spices and fruit and vegetables.