From the book
Fruits of Warm Climates
by Julia F. Morton
Papaya
Carica papaya
L.
CARICACEAE
The papaya, Carica
papaya
L., is a member of the small family Caricaceae allied to the
Passifloraceae. As a dual- or multi-purpose, early-bearing,
space-conserving, herbaceous crop, it is widely acclaimed, despite its
susceptibility to natural enemies.
Plate XLVII: PAPAYA, Carica
papaya
In some parts of the world,
especially Australia and some islands of the West Indies, it is known
as papaw, or pawpaw, names which are better limited to the very
different, mainly wild Asimina triloba Dunal, belonging to the
Annonaceae. While the name papaya is widely recognized, it has been
corrupted to kapaya, kepaya, lapaya or tapaya in southern Asia and the
East Indies. In French, it is papaye (the fruit) and papayer (the
plant), or sometimes figuier des Iles. Spanish-speaking people employ
the names melón zapote, lechosa, payaya (fruit), papayo or
papayero (the plant), fruta bomba, mamón or mamona, depending on
the country. In Brazil, the usual name is mamao. When first encountered
by Europeans it was quite naturally nicknamed "tree melon".
Description
Commonly
and erroneously referred to as a "tree", the plant is properly a large
herb growing at the rate of 6 to 10 ft (1.8-3 m) the first year and
reaching 20 or even 30 ft (6-9 m) in height, with a hollow green or
deep-purple stem becoming 12 to 16 in (30-40 cm) or more thick at the
base and roughened by leaf scars. The leaves emerge directly from the
upper part of the stem in a spiral on nearly horizontal petioles 1 to 3
1/2 ft (30-105 cm) long, hollow, succulent, green or more or less dark
purple. The blade, deeply divided into 5 to 9 main segments, each
irregularly subdivided, varies from 1 to 2 ft (30-60 cm) in width and
has prominent yellowish ribs and veins. The life of a leaf is 4 to 6
months. Both the stem and leaves contain copious white milky latex.
The
5-petalled flowers are fleshy, waxy and slightly fragrant. Some plants
bear only short-stalked pistillate (female) flowers, waxy and
ivory-white; or hermaprodite (perfect) flowers (having female and male
organs), ivory-white with bright-yellow anthers and borne on short
stalks; while others may bear only staminate (male) flowers, clustered
on panicles to 5 or 6 ft (1.5-1.8 m) long. There may even be monoecious
plants having both male and female flowers. Some plants at certain
seasons produce short-stalked male flowers, at other times perfect
flowers. This change of sex may occur temporarily during high
temperatures in midsummer. Some "all-male" plants occasionally bear, at
the tip of the spray, small flowers with perfect pistils and these
produce abnormally slender fruits. Male or hermaphrodite plants may
change completely to female plants after being beheaded.
Generally,
the fruit is melon-like, oval to nearly round, somewhat pyriform, or
elongated club-shaped, 6 to 20 in (15-50 cm) long and 4 to 8 in (10-20
cm) thick; weighing up to 20 lbs (9 kg). Semi-wild (naturalized) plants
bear miniature fruits 1 to 6 in (2.5-15 cm) long. The skin is waxy and
thin but fairly tough. When the fruit is green and hard it is rich in
white latex. As it ripens, it becomes light- or deep-yellow externally
and the thick wall of succulent flesh becomes aromatic, yellow, orange
or various shades of salmon or red. It is then juicy, sweetish and
somewhat like a cantaloupe in flavor; in some types quite musky.
Attached lightly to the wall by soft, white, fibrous tissue, are
usually numerous small, black, ovoid, corrugated, peppery seeds about
3/16 in (5 mm) long, each coated with a transparent, gelatinous aril.
Fig. 94: A healthy papaya (Carica
papaya) in Homestead, Florida, in 1946, when virus
diseases were not prevalent.
Origin and
Distribution
Though
the exact area of origin is unknown, the papaya is believed native to
tropical America, perhaps in southern Mexico and neighboring Central
America. It is recorded that seeds were taken to Panama and then the
Dominican Republic before 1525 and cultivation spread to warm
elevations throughout South and Central America, southern Mexico, the
West Indies and Bahamas, and to Bermuda in 1616. Spaniards carried
seeds to the Philippines about 1550 and the papaya traveled from there
to Malacca and India. Seeds were sent from India to Naples in 1626. Now
the papaya is familiar in nearly all tropical regions of the Old World
and the Pacific Islands and has become naturalized in many areas. Seeds
were probably brought to Florida from the Bahamas. Up to about 1959,
the papaya was commonly grown in southern and central Florida in home
gardens and on a small commercial scale. Thereafter, natural enemies
seriously reduced the plantings. There was a similar decline in Puerto
Rico about 10 years prior to the setback of the industry in Florida.
While isolated plants and a few commercial plots may be fruitful and
long-lived, plants in some fields may reach 5 or 6 ft, yield one
picking of undersized and misshapen fruits and then are so affected by
virus and other diseases that they must be destroyed.
In the
1950's an Italian entrepreneur, Albert Santo, imported papayas into
Miami by air from Santa Marta, Colombia, Puerto Rico and Cuba for sale
locally as well as shipping fresh to New York, and he also processed
quantities into juice or preserves in his own Miami factory.
Since
there is no longer such importation, there is a severe shortage of
papayas in Florida. The influx of Latin American residents has
increased the demand and new growers are trying to fill it with
relatively virus-resistant strains selected by the University of
Florida Agricultural Research and Education Center in Homestead.
Successful
commercial production today is primarily in Hawaii, tropical Africa,
the Philippines, India, Ceylon, Malaya and Australia, apart from the
widespread but smaller scale production in South Africa, and Latin
America.
Annual
papaya consumption in Hawaii is 15 lbs (6.8 kg) per capita, yet 26
million lbs (11,838,700 kg) of fresh fruits were shipped by air freight
to mainland USA in 1974, mainly direct from Hilo or via Honolulu.
Puerto Rican production does not meet the local demand and fruits are
imported from the Dominican Republic for processing.
The
papaya is one of the leading fruits of southern Mexico and 40% of that
country's crop is produced in the state of Veracruz on 14,800 acres
(6,000 ha) yielding 120,000 tons annually.
Fruits from bisexual
plants are usually cylindrical or pyriform with small seed cavity and
thick wall of firm flesh which stands handling and shipping well. In
contrast, fruits from female flowers are nearly round or oval and
thin-walled. In some areas, bisexual types are in greatest demand. In
South Africa, round or oval papayas are preferred.
Varieties
Despite
the great variability in size, quality and other characteristics of the
papaya, there were few prominent, selected and named cultivars before
the introduction into Hawaii of the dioecious, small-fruited papaya
from Barbados in 1911. It was named 'Solo' in 1919 and by 1936 was the
only commercial papaya in the islands. 'Solo' produces no male plants;
just female (with round, shallowly furrowed fruits) and bisexual (with
pear-shaped fruits) in equal proportions. The fruits weigh 1.1 to 2.2
lbs (1/2-1 kg) and are of excellent quality. When the fruit is fully
ripe the thin skin is orange-yellow and the flesh golden-orange and
very sweet.
'Kapoho Solo'
or 'Puna Solo' was discovered and became popular with growers on Kauai
before 1950. In 1955 a 'Dwarf Solo' (a back-cross of Florida's 'Betty'
and 'Solo') was introduced to aid harvesting, and this became the
leading commercial papaya on the island of Oahu. It was, up to 1974,
the only export cultivar. It is pear-shaped, 14 to 28 oz (400-800 g) in
weight in high rainfall areas, and has yellow skin and pale-orange
flesh.
'Waimanalo'
(formerly 'Solo' Line 77) was selected in 1960 and released by the
Hawaii Agricultural Experiment Station in 1968 and soon superseded Line
8 'Solo' on Oahu for the fresh fruit market because of its firmness and
quality, but there it is usually too large for export. It has long
storage life and is recommended for sale fresh and for processing.
Since 1974 this cultivar has been produced commercially on the
low-rainfall island of Maui where it ripens at a greener color than on
the island of Hawaii and is exported to cities in the northwestern and
central USA. The growers raised only bisexual plants; they say that the
fruits of female plants are too rough in appearance.
'Higgins'
(formerly Line 17A), the result of crosses in 1960, was introduced to
Hawaiian growers in 1974. It is of high quality, pear-shaped, with
orange-yellow skin, deep-yellow flesh, and averages 1 lb (0.45 kg) when
grown under irrigation. In and territory or seasons of low rainfall,
the fruit is undersized.
'Wilder'
(formerly Line 25) is a cultivar admired for its uniformity of size,
firmness and small cavity and it is now popular for export.
'Hortus Gold',
a South African cultivar, launched in the early 1950's, is dioecious,
early-maturing, with round-oval, golden-yellow fruits, 2 to 3 lbs
(0.9-1.36 kg) in weight. From 200 female 'Hortus Gold' seedlings
planted at the University of Natal's Ukulinga Research Farm in 1960,
selections were made of the plants showing the highest yield. Of these,
one clone having the best sugar content and disease resistance was
chosen and named 'Honey Gold' in 1976. This cultivar has a slight beak
at the apex, golden-yellow skin; is of sweet flavor and good texture
but becomes mushy when overripe. It averages 2.2 lbs (1 kg)
per
fruit except for those at the end of the season which are much smaller.
It does not reproduce true from seed and is therefore propagated by
cuttings. It is late in season and late-maturing (10 months from fruit
set to maturity) and therefore brings nearly double the price of other
cultivars.
'Bettina'
and
'Petersen', long-standing cultivars in Queensland, Australia, were
inbred for several generations to obtain pure lines. 'Bettina', a
hybrid of Florida's 'Betty' and a Queensland strain, is a low, shrubby,
dioecious plant producing well-colored, round-oval fruits weighing 3 to
5 lbs (1.36-2.27 kg).
'Improved Petersen',
of local origin, is dioecious, tall-growing, with fruits deficient in
external color and indifferent as to keeping quality but noted for the
fine color and flavor of the flesh. In 1947 'Bettina 100A' was crossed
with 'Petersen 170' to produce the superior, semi-dwarf 'Hybrid No. 5',
smooth, yellow, rounded-oval, 3 lbs (1.36 kg) in weight, thick-fleshed,
of excellent flavor and prized for marketing fresh and for canning. It
bore more heavily than either of its parents and remained a preferred
cultivar for more than 20 years. 'Solo' and 'Hortus Gold' are often
grown but most plantations are open-pollinated mixtures.
In Western Australia, after trials of 9 cultivars–'Hybrid No. 5', 'Petersen', 'Yarwun Yellow', 'Gold Cross', 'Goldy', 'Hong Kong', 'Guinea Gold', 'Golden Surprise' and
'Sunnybank'–only
'Sunnybank' and 'Guinea Gold' were chosen as having sufficient yield
and quality to be worth cultivating commercially. 'Sunnybank' fruits
average 1.39 lbs (0.63 kg), and ripen over 11 months. 'Guinea Gold'
averages 2.4 lbs (a little over 1 kg) and ripens over a period of 18
months.
The Universidad Agraria, La Molina, Peru, began to
assemble papaya strains in 1964, collecting 40 from various parts of
the country and introducing 3 from Brazil, 1 from Puerto Rico, 3 from
Mexico and 2 lines of 'Solo' from Hawaii, and embarked on an evaluation
and breeding program and the creation of a germplasm bank.
In
Ghana, dioecious cultivars such as 'Solo', 'Golden Surprise', 'Hawaii',
and 'No. 5595', were introduced and commonly cultivated by farmers but
they hybridized with local types and lost their identities after
several generations. A number of types were collected at the
Agricultural Research Station at Kade from 1966 to 1970 and classified
according to sex type, fruit form, weight, skin and flesh color, flesh
thickness, texture and flavor, number of seeds, and various plant
factors. It was determined that preference should be given female
plants with short, stout stems, early maturing, and bearing heavily all
year medium-size fruits of bright color, thick-flesh and with few seeds.
The
Instituto Colombiano Agropecuario, at Palmira, Colombia, began a papaya
breeding program in 1963 by bringing together Colombian-grown
cultivars–'Campo Grande',
'Tocaimera',
'Zapote', 'Solo',–with some
from Brazil–'Betty',
'Bettina'
and '43-A-3'–South
Africa–'Hortus Gold'–and
Puerto Rico, and representatives of related species: C. candamarcensis
Hook. F., C. pentagona
Heilborn, C. goudotiana
Tr. & Pl. (one type yellow with green peduncles and another red
with purple peduncles), C.
cauliflora Jacq. of Colombia and C. monoica Desf.
and Jacaratia
dodecaphylla A. DC. from Peru.
The first two of these species were not suited to conditions at Palmira.
The progeny of crosses with C.
caulfliora
were the only hybrids showing some virus resistance but they were
unfruitful when attacked. There were no viable seeds and 30% of the
fruits were seedless. C.
monoica
proved well adapted to Palmira, bore small, yellow fruits, but
succumbed to virus. The introductions from Brazil were by far the most
promising. 'Zapote', with rich, red flesh is much grown on the Atlantic
coast of Colombia.
In India, papaya breeding and selection work
has been carried on for over 30 years beginning with 100 introduced
strains and 16 local variations. A well-known cultivar is 'Coorg Honey Dew',
a selection from 'Honey Dew' at Chethalli Station of the Indian
Institute of Horticultural Research. There are no male plants; female
and bisexual occur in equal proportions. The plant is low-bearing and
prolific. The fruit is long to oval, weighs 4.4 to 7.7 lbs (2-3 1/2
kg); has yellow flesh with a large cavity, and keeps fairly well. 'Washington', popular
in Bombay, has dark-red petioles and yellow flowers. The fruits are of
medium size with excellent, sweet flavor. 'Burliar Long'
is prolific, bearing as many as 103 fruits the first year, mostly in
pairs densely packed along the stem down to 18 in (45 cm) from the
ground. Seedlings are 70% females and bloom 3 months after
transplanting.
'Co. 1' and 'Co. 2'
were developed at Tamil Nadu Agricultural University. Both are
dioecious and dwarf, the first fruits being borne 3 ft (1 m) from the
ground. 'Co. 1' is valued for eating fresh; 'Co. 2' is grown for table
use and for papain extraction. The fruits are of medium size–3.3
to 5.5 lbs (1 1/2-2 1/2 kg), with yellow, sweet flesh.
The Regional Research Station at Pusa has introduced some promising
selections:
'Pusa Delkious'
('Pusa 1-15')–medium size; flesh deep-orange, of excellent flavor;
female and hermaphrodite plants; high-yielding.
'Pusa Majesty'
('Pusa 22-3')–round, of medium size; flesh yellowish, solid;
keeps well and ships well; vinis resistant; hermaphrodite plants
higher-yielding than the female.
'Pusa Giant'
('Pusa 1-45V')–large fruits suitable for marketing ripe, or green
for use as a vegetable, also for canning. Plant dioecious,
fast-growing; tall; trunk thick, wind-resistant.
'Pusa Dwarf'
('Pusa 1-45')–fruit oval, of medium size. Plant is dwarf; begins
bearing fruit at 10 to 12 in (25-30 cm) above the ground. In much
demand for home and commercial culture; suitable for high-density
plantings.
In 1965, a program of papaya improvement was
undertaken in Trinidad and Tobago utilizing promising selections from
local types, including 'Santa
Cruz Grant',
a vigorous plant mainly bisexual (having both male and female flowers),
very large fruits weighing 10 to 15 lbs (4.5-6.8 kg), with firm, yellow
flesh of agreeable flavor. The fruit is too large for marketing fresh
but is processed both green and ripe. 'Cedro' is dioecious, rarely
bisexual, a heavy bearer and highly resistant to anthracnose. The
fruits weigh from 3 to 8 lbs (1.37-3.6 kg) but average 6 lbs (2.7 kg);
have firm, yellow, melon-like flesh and are suitable for sale fresh or
for processing.
In 'Singapore Pink',
the plants are mainly bisexual, producing cylindrical fruit. The
minority are female with round fruit. Average weight of fruit is 5 lbs
(2.27 kg) though there is variation from 2 to 7 lbs (1-3 kg). The flesh
is pink. The fruit surface is prone to anthracnose in rainy periods,
so, at such times, the fruits must be picked and sold in the green
state. Two smaller-fruited types, 2 to 3 lbs (1-1.37 kg) in weight,
with bright-yellow skin and thick, firm flesh, were selected for
marketing fresh.
The 'Solo'
of Hawaii has performed unsatisfactorily in Florida, producing low
yields of small fruits. Scott Stambaugh, a papaya specialist, began his
papaya breeding with a strain designated USDA Bureau of Plant Industry
#28533 obtained from the then Plant Introduction Station in Miami. From
offspring of this he made a selection which he named 'Norton'. When he
acquired seed of a type called 'Purplestem';
later 'Bluestem',
he crossed it with 'Norton' and the hybrid yielded fruits 10 lbs (4.5
kg) in weight and was named 'Big
Bluestem'. The latter was crossed with 'Solo' and the
hybrid was called 'Bluestem
Solo' or 'Blue
Solo'.
The 'Blue Solo' has been well regarded in Florida for its low growth,
dependable yields of good quality fruits, 2 to 4 lbs (1-2 kg) in
weight, orange-fleshed and rich in flavor.
'Cariflora'
is a new cultivar developed at the recently renamed Tropical Research
and Education Center of the University of Florida at Homestead. It is
nearly round, about the size of a cantaloupe, with thick, dark-yellow
to light-orange flesh; tolerant of papaya ringspot virus, but not
resistant to papaya mosaic virus or papaya apical necrosis virus. Yield
is good in southern Florida and warm lowlands of tropical America but
not at elevations above 2625 ft (800 m).
'Sunrise Solo'
(formerly HAES 63-22) was introduced from Hawaii into Puerto Rico. The
fruit has pink flesh with high total solid content. In Puerto Rican
trials, seeds were planted in mid-November, seedlings were transplanted
to the field 2 months later, flowering occurred in April and mature
fruits were harvested from early August to January. Recent selections
from Puerto Rican breeding programs are 'P.R. 6-65' (early), 'P.R.
7-65' (late), and 'P.R. 8-65'.
Venezuelan papayas are usually
long and large, ranging in weight from 2 to 13 lbs (1-6 kg) and mostly
for domestic consumption or shipment by boat to nearby islands.
Pollination
If
a papaya plant is inadequately pollinated, it will bear a light crop of
fruits lacking uniformity in size and shape. Therefore,
hand-pollination is advisable in commercial plantations that are not
entirely bisexual.
Bags are tied over bisexual blossoms for
several days to assure that they are self-pollinated. The progeny of
self-pollinated bisexual flowers are 67% bisexual, the rest being
female.
To cross-pollinate, one or 2 stamens from a bisexual
flower are placed on the pistil of a female flower about to open and a
bag is tied over the flower for a few days. Most of such
cross-pollinated blooms should set fruit. Resulting seeds will produce
1/2 female and 1/2 bisexual plants.
By another method, all but
the apical female flower bud are removed from a stalk and the apical
bud is bagged 1-2 days before opening. At full opening, the stigma is
dusted with pollen from a selected male bloom and the bag quickly
resealed and it remains so for 7 days.
Plants from female
flowers crossed with male flowers are 50-50 male and female. Bisexual
flowers pollinated by males give rise to 1/3 female, 1/3 bisexual and
1/3 male plants.
South African growers have long been urged to
practice hand-pollination in order to maintain a selected strain and,
in breeding, to incorporate factors such as purple stem, yellow flowers
and reddish flesh so that the improved selection will be
distinguishable from ordinary strains with non-purple stems, white
flowers and yellow flesh.
Climate
The
papaya is a tropical and near-tropical species, very sensitive to frost
and limited to the region between 32º north and 32º south of
the Equator. It needs plentiful rainfall or irrigation but must have
good drainage. Flooding for 48 hours is fatal. Brief exposure to
32º F (-0.56º C) is damaging; prolonged cold without overhead
sprinkling will kill the plants.
Soil
While
doing best in light, porous soils rich in organic matter, the plant
will grow in scarified limestone, marl, or various other soils if it is
given adequate care. Optimum pH ranges from 5.5 to 6.7. Overly acid
soils are corrected by working in lime at the rate of 1-2 tons/acre
(2.4-4.8 tons/ha). On rich organic soils the papaya makes lush growth
and bears heavily but the fruits are of low quality.
Propagation
Papayas
are generally grown from seed. Germination may take 3 to 5 weeks. It is
expedited to 2 to 3 weeks and percentage of germination increased by
washing off the aril. Then the seeds need to be dried and dusted with
fungicide to avoid damping-off, a common cause of loss of seedlings.
Well-prepared seeds can be stored for as long as 3 years but the
percentage of germination declines with age. Dipping for 15 seconds in
hot water at 158º F (70º C) and then soaking for 24 hrs in
distilled water after removal from storage will improve the germination
rate. If germination is slow at some seasons, treatment with
gibberellic acid may be needed to get quicker results.
To
reproduce the characteristics of a preferred strain, air-layering has
been successfully practiced on a small scale. All offshoots except the
lowest one are girdled and layered after the parent plant has produced
the first crop of fruit. Later, when the parent has grown too tall for
convenient harvesting the top is cut off and new buds in the crown are
pricked off until offshoots from the trunk appear and develop over a
period of 4 to 6 weeks. These are layered and removed and the trunk cut
off above the originally retained lowest sprout which is then allowed
to grow as the main stem. Thereafter the layering of offshoots may be
continued until the plant is exhausted.
Rooting of cuttings has
been practiced in South Africa, especially to eliminate variability in
certain clones so that their performance can be more accurately
compared in evaluation studies. Softwood cuttings made in midsummer
rooted quickly and fruited well the following summer. Cuttings taken in
fall and spring were slow to root and deficient in root formation. The
commercial cultivar 'Honey Gold' is grown entirely from cuttings. Once
rooted, the cuttings are planted in plastic bags and kept under mist
for 10 days, and then put in a shade house for hardening before setting
in the field.
Hawaiian workers have found that large branches 2-3 ft
(60-90 cm) long rooted more readily than small cuttings. Planted 1 ft
(30 cm) deep in the rainy season, they began fruiting in a few months
very close to the ground.
In budding experiments both Forkert
and chip methods have proved satisfactory in Trinidad. However, it is
reported that a vegetatively propagated selected strain deteriorates
steadily and is worthless after 3 or 4 generations.
In Hawaii,
'Solo' grafted onto 'Dwarf Solo' was reduced in vigor and productivity,
but 'Dwarf Solo' grafted onto 'Solo' showed improved performance.
In
recent years, the potential of rapid propagation of papaya selections
by tissue culture is being explored and promises to be feasible even
for the establishment of commercial plantations of superior strains.
Efforts
have been made to determine the sex of seedlings in the nursery, Indian
scientists making colorimetric tests of leaf extracts have had 87%
success in identifying seedlings as female; 67% in classifying
males/bisexuals grouped together.
Fig.
95: Papaya fruits vary in form, size, thickness, color and flavor of
flesh. Favored types have little, if any, muskiness of odor.
Variable
Season
Planting
may be done at any time of year and local conditions determine when it
is best for the crop to come in. Papayas mature in 6 to 9 months from
seed in the hotter areas of South Africa; in 9 to 11 months where it is
cooler, providing an opportunity to supply markets in the off-season
when prices are high. Seeds planted in early summer or midsummer will
produce the first crop in the second winter. Thereafter, the same
plants will mature fruit from spring to early summer.
Spring
fruits are apt to be sunburned because of winter leaf loss; are also
subject to fruit spot and have a low sugar content. Sunburn can be
avoided by advance whitewashing of sides exposed to the afternoon sun.
Some growers manipulate the harvest season by stripping off 6 of the
newly set fruits, thus forcing the plant to bloom again and produce
fruits 6 to 8 weeks later than they normally would.
In southern
Florida, plants set out in March or April will ripen their fruits in
November and December and have the advantage of a "tourist" market.
July plantings will be slowed down by winter and will not fruit for 10
months or more. Some growers advocate planting in September and October
so that the crop will be ready for harvest before the onset of the main
hurricane season. Further north in the state, papayas must be set out
in March or April in order to have the required growing season before
frost.
Spacing
Puerto
Rican trials have shown that papaya plants set in the field on 6 ft
(1.8 m) centers made stronger, stouter growth and were more fruitful
than those at closer spacings. Some growers insist on an 8 x 8 ft (2.4
x 2.4 m) area per plant. In India, 'Co. 1' and 'Co. 2' and 'Solo' are
set on 6 ft (1.8 m) centers; 'Coorg Honey Dew' and 'Washington' on 8 ft
(2.4 m) centers. Princess Orchards on Maui, Hawaii, plant in double
rows with an alley between each pair providing room for cultural and
harvesting operations. In Queensland, plants may be set only 3 ft (1 m)
apart on level ground and then thinned out by removal of unwanted
plants after flowering.
Culture
Seeds
may be planted directly in the field, or seedlings raised in beds or
pots may be transplanted when 6 weeks old or even up to 6 months of
age, though there must be great care in handling and the longer the
delay the greater the risk of dehydrated or twisted roots; also,
transplanting often results in trunk-curvature in windy locations.
Experiments
in Hawaii indicate that direct seeding results in deeper tap-roots,
erect and more vigorous growth, earlier flowering and larger yields.
In
Puerto Rico, it is customary to set 2 plants per hole. In El Salvador
planters place 5 to 6 seeds, separated from each other, in each hole at
a depth of 3/8 in (1 cm). When the plants bloom, 90% of the males are
removed, preferably by cutting off at ground level. Pulling up disturbs
the roots of the remaining plants. If the plantation is isolated and
there is no chance of cross-pollination by males, all the seed will
become female or hermaphrodite plants. Fruits should mature 5 to 8
months later.
In India, seeds are usually treated with fungicide
and planted in beds 6 in (15 cm) above ground level that have been
organically enriched and fumigated. The seeds are sown 2 in (5 cm)
apart and 3/4 to 1 1/8 in (2-3 cm) deep in rows 6 in (15 cm) apart.
They are watered daily and transplanted in 2 1/2 months when 6 to 8 in
(15-20 cm) high. Transplanting is more successful if polyethylene bags
of enriched soil are used instead of raised beds. Two seeds are planted
in each bag but only the stronger seedling is maintained. Transplanting
is best done in the evening or on cloudy, damp days. On hot, dry days,
each plant must be protected with a leafy branch or palm leaf stuck in
the soil. Except for 'Coorg Honey Dew' and 'Solo', the plants are set
out in 3's, 6 in (15 cm) apart in enriched pits. After flowering, one
female or hermaphrodite plant is retained, the other two removed. But
one male is kept for every 10 females. 'Coorg Honey Dew' and 'Solo' are
planted one to a pit and no males are necessary. Watering is done every
day until the plants are well established, but overwatering is
detrimental to young plants. Double rows of Sesbania aegyptiaca are
planted as a windbreak.
The installation of constant drip
irrigation (12 gals per day) has made possible papaya cultivation on
mountain slopes on the relatively dry island of Maui which averages 10
in (25 cm) of rain annually.
Papaya plants require frequent
fertilization for satisfactory production. In India, best results have
been obtained by giving 9 oz (250 g) of nitrogen, 9 oz (250 g) of
phosphorus, and 18 oz (500 g) potash to each plant each year, divided
into 6 applications.
Because of the need to expedite growth and
production before the onslaught of diseases, Puerto Rican agronomists
recommend treating the predominantly clay soil with a nematicide before
planting, giving each plant 4 oz (113 g) of 15-15-15 fertilizer at the
end of the first week, and each month thereafter increasing the dose by
1 oz (28 g) until the beginning of flowering, then applying .227 g per
plant as a final treatment. In trials, this program has permitted 6
harvests of green fruits for processing, each over 1 lb (1/2 kg) in
weight, spanning a period of 13 months. The roots usually extend out
beyond the leaves and it is advisable to spread fertilizer over the
entire root area.
In late fertilizer applications of a crop
destined for canning, nitrogen should be omitted because it renders the
fruit undesirable for processing. High nitrate content in canned papaya
(as with several common vegetables) removes the tin from the can. To
avoid nitrogen deficiency at the beginning of flowering for the next
crop, 1 or 2% urea sprays can be applied.
In southern Florida,
on oolitic limestone, experts have prescribed liquid fertilizer weekly
for the first 10 weeks and then 1 lb (1/2 kg) of 4-8-6 dry fertilizer
mixture (with added minor elements) per plant weekly until flowering.
Here a heavy organic mulch is desirable to conserve moisture, control
weeds, keep the soil cool, and help repel nematodes.
Mechanical cultivation between rows is apt to disturb the shallow
roots. judicious use of herbicides is preferable.
Overcrowded
fruits should be thinned out when young to provide room for good form
development and avoid pressure injury. Cold weather may interfere with
pollination and cause shedding of unfertilized female flowers. Spraying
the inflorescence with growth regulators stops flower drop and
significantly enhances fruit set. After the first crop, the terminal
growth may be nipped off to induce branching which tends to dwarf the
plant and facilitates harvesting. However, unless the plants are strong
growers, fruiting branches may need to be propped to avoid collapse.
Harvesting
Studies
in Hawaii have shown that papaya flavor is at its peak when the skin is
80% colored. For the local market, in winter months, papayas may be
allowed to color fairly well before picking, but for local market in
summer and for shipment, only the first indication of yellow is
permissible. The fruits must be handled with great care to avoid
scratching and leaking of latex which stains the fruit skin. Home
growers may twist the fruit to break the stem, but in commercial
operations it is preferable to use a sharp knife to cut the stem and
then trim it level with the base of the fruit. However, to expedite
harvesting of high fruits, most Hawaiian growers furnish their pickers
with a bamboo pole with a rubber suction cup (from the well-known
"plumber's helper") at the tip. With the cup held against the lower end
of the fruit, the pole is thrust upward to snap the stem and the
falling fruit is caught by hand. One man can thus gather 800-1,000 lbs
(363-454 kg) daily.
In Hawaii, it has been calculated that
manual picking and field sorting constitute 40% of the labor cost of
the crop (1,702 man-hours per acre to pick and pack). Therefore, in
1970, an experimental mechanical aid was tested and results indicated
that a machine with one operator and 2 pickers could harvest 1,000 lbs
(454 kg) of fruit per hour, the equivalent of 8 men hand-picking. Many
factors, such as investment, operation and repair costs, useful life,
and so forth must be considered before such a machine could be
determined to be feasible. On the island of Maui, harvesting is aided
by hydraulic lifts, each operated by a single worker. Picking starts
when the plants are 11 months of age and continues for 48 months when
the trees are 25 ft (7.5 m) high, too tall for further usefulness.
The
fruits are best packed in single layers and padded to avoid bruising.
The latex oozing from the stem may irritate the skin and workers should
be required to wear gloves and protective clothing.
Yield
In
the usual papaya plantation, each plant may ripen 2 to 4 fruits per
week over the fruiting season. Healthy plants, if well cared for, may
average 75 lbs (34 kg) of fruit per plant per year, though individual
plants have borne as much as 300 lbs (136 kg). In South Africa,
branched 'Honey Gold' plants set 20 ft (6 m) apart in rows 10 ft (3 m)
apart have produced 45 lbs (100 kg) of fruit each in their 4th year. A
field of 1,000 plants occupying 2 1/2 acres (1 ha) gave 30 tons of
fruit. In the Hilo area of the island of Hawaii, production averages 15
tons per acre (37 tons/ha). From 250 acres (100 ha), Princess Orchards
on Maui harvests 150,000 lbs (68,180 kg) weekly during the season.
In
the Kapoho region of the island of Hawaii, yields average 38,000
lbs/acre (roughly 38,000 kg/ha) the first year, 25,000 lbs (11,339 kg)
the second year. Papaya plants bear well for 2 years and then
productivity declines and commercial plantings are generally replaced
after 3-4 years. By that time they have attained heights which make
harvesting difficult.
Renovation of
Plantings
In
Trinidad and Tobago, plants that have become too tall are cut to the
ground and side shoots are allowed to grow and bear. In El Salvador,
after the 3rd year of bearing, the main stem is cut off about 3 ft (1
m) from the ground at the beginning of winter and is covered with a
plastic bag to protect it from rain and subsequent rotting. Several
side shoots will emerge within a few days. When these reach 8 in to 1
ft (20-30 cm) in height, all are cut off except the most vigorous one
which replaces the original top.
Postharvest
Treatment
Fruits
can be held at 85º F (29.64º C) and high atmospheric humidity
for 48 hours to enhance coloring before packing. Standard decay control
has been a 20-minute submersion in water at 120º F (49º C)
followed by a cool rinse. In India, dipping in 1,000 ppm of aureofungin
has been shown to be effective in controlling postharvest rots. In
Philippine trials, thiabendazole reduced fruit rot by 50%. In 1979,
Hawaiian workers demonstrated that spreading an aqueous solution of
carnauba wax and thiabendazole over harvested fruits gives good
protection from postharvest diseases and can eliminate the hot-water
bath.
In Puerto Rico, fruits of 'P.R. 8-65', picked green, were
ripened successfully by 6-7 days treatment with ethylene gas in
airtight chambers at 77º F (25º C) and 85 to 95% humidity,
following the hot-water bath.
Hawaiian papayas must be sanitized
before shipment to the mainland USA to avoid introduction of fruit
flies. Fruits picked 1/4 ripe are prewarmed in water at 110º F
(43.33º C) for about 40 min, then quickly immersed for 20 min at
119º (48.33º C). This double-dipping maybe replaced by
irradiation. One little-used method is a vapor-heat treatment following
dry heat at 110º F (43.33º C) and 40% relative humidity.
Fruits
that have had hot water treatment and EDB fumigation and then have been
stored in 1.5% oxygen at 55º F (13º C) for 12 days will have
a shelf life of about 3 1/2 days at room temperature. Fruits that have
had hot water treatment when 1/4 colored, followed by irradiation at
75-100 krad, and storage at 2-4% oxygen and 60º F (16º C) for
6 days will have a market life of 8 days. Those held for 12 days will
be saleable thereafter for 5 days.
In Puerto Rico, gamma
irradiation (25-50 krads) delayed ripening up to 7 days. Treatment at
100 krads slightly accelerated ripening in storage. Even at the lowest
level irradiation inhibited fungal growth. Carotenoid content was
unaffected but ascorbic acid was slightly reduced at all exposures.
Partly
ripe papayas stored below 50º F (10º C) will never fully
ripen. This is the lowest temperature at which ripe papayas can be held
without chilling injury.
'Solo 62/3' fruits harvested in
Trinidad at the first sign of yellow, treated with fungicide, placed in
perforated polyethylene bags and packed in individual compartments in
cartons, have been shipped to England by air (2 days' flight), ripened
at 68º F (20º C), and found to be of excellent quality and
flavor.
The same cultivar, similarly handled, withstood
transport in the refrigerated hold of a ship for 21 days. Immediately
ripened on arrival, the fruits were well accepted on the London market.
Sea shipment proved to be the more economical.
Hypobaric (low
pressure) containers have made possible satisfactory sea shipment
(18-21 days) of hot-water treated and fungicidal-waxed papayas from
Hilo, Hawaii, to Los Angeles and New York.
Pests
A major hazard to papayas in Florida and
Venezuela is the wasp-like papaya fruit fly, Toxotrypana curvicauda.
The female deposits eggs in the fruit which will later be found
infested with the larvae. Only thick-fleshed fruits are safe from this
enemy. Control on a commercial scale is very difficult. Home gardeners
often protect the fruit from attack by covering with paper bags, but
this must be done early, soon after the flower parts have fallen, and
the bags must be replaced every 10 days or 2 weeks as the fruits
develop. Rolled newspaper may be utilized instead of bags and is more
economical. India has no fruit fly with ovipositor long enough to lay
eggs inside papayas.
An important and widespread pest is the papaya web-worm, or fruit
cluster worm, Homolapalpia
dalera,
harbored between the main stem and the fruit and also between the
fruits. It eats into the fruit and the stem and makes way for the
entrance of anthracnose. Damage can be prevented if spraying is begun
at the beginning of fruit set, or at least at the first sign of webs.
The tiny papaya whitefly, Trialeuroides
variabilis,
is a sucking insect and it coats the leaves with honeydew which forms
the basis for sooty mold development. Shaking young leaves will often
reveal the presence of whiteflies. Spraying or dusting should begin
when many adults are noticed. Hornworms (immature state of the sphinx
moth–Erinnyis obscura
in Jamaica, E. ello
in Venezuela, E. alope
in Florida) feed on the leaves, as do the small, light-green
leafhoppers.
Mention is made later on of the aphids that transmit virus diseases and
other infections.
Other pests requiring control measures in Australia include the red
spider, or red spider mite, Tetranychus
seximaculatus,
which sucks the juice from the leaves. In India and on the island of
Maui, plant and fruit infestation by red spider has been a major
problem. This pest and the cucumber fly and fruit-spotting bugs feed on
the very young fruits and cause them to drop. In Hawaii, the
red-and-black-flat mite feeds on the stem and leaves and scars the
fruit. The broad mite damages young plants especially during cool
weather.
In the Virgin Islands scale has been most troublesome,
apart from rats and fruit-bats that attack ripe fruits. In Australia, 5
species of scale insects have been found on papayas, the most serious
being oriental scale, Aonidiella
orientalis, which occurs on both the fruit and the stem.
So far, it is confined to limited areas. In Florida, the scale insects Aspidiotus destructor
and Coccus hesperidium
may infest bagged fruit more than unbagged fruit. Another scale, Philaphedra sp.,
has recently been reported here.
Indian scientists have observed that immature earthworms, Megascolex insignis,
are attracted by and feed on rotting tissue of papaya plants. They
hasten the demise of plants afflicted with stem rot from Pythium aphanidermatum
and may act as vectors for this fungus.
Root-knot nematodes, Meloidogyne
incognita acrita,
and reniforin nematodes, Rotylenchulus
reniformis, are detrimental to
the growth and productivity of papaya plants and should be combatted by
pre-planting soil fumigation if the nematode population is high.
Diseases
Hawaii,
partly because of its distance from other papaya-growing areas, is less
afflicted with disease problems than Florida and Puerto Rico, but still
has to combat a number of major and minor maladies. Most serious of all
is the mosaic virus, on plant and fruit, which is common in Florida,
Cuba, Puerto Rico, Trinidad, and first seen in Hawaii in 1959. It is
transmitted mechanically or by the green peach aphid, Myzus Persicae, and
other aphids including the green citrus aphid, Aphis spiraecola,
in Puerto Rico. Two forms of mosaic virus are reported in Puerto Rico:
the long-known "southern coast papaya mosaic virus", the symptoms of
which include extreme leaf deformation, and the relatively recent
"Isabela mosaic virus" on the northern coast which is similar but
without leaf distortion. Both forms occur in some northcoast
plantations. There is no remedy, but measures to avoid spread include
the destruction of affected plants, control of aphids by pesticides,
and elimination of all members of the Cucurbitaceae from the vicinity.
Mosaic is sporadic and scattered and not of great concern in Queensland.
Papaya
ringspot virus, prevalent in Florida, the Dominican Republic and
Venezuela, is occasionally serious in the Waianae area on the dry
leeward side of Oahu. It is transmitted by the same vectors. Mosaic and
ringspot viruses are the main limiting factors in papaya production in
the Cauca Valley of Colombia.
In Florida, virus diseases were
recognized as the greatest threat to the papaya industry in the early
1950's. The first signs are irregular mottling of young leaves, then
yellowing with transparent areas, leaf distortion, and rings on the
fruit. If affected plants are not removed, the condition spreads
throughout the plantation. Fruits borne 2 or 3 months after the first
symptoms will have a disagreeable, bitter flavor.
At the
Agricultural Research and Education Center of the University of Florida
in Homestead, the late Dr. Robert Conover established a test plot of
papayas grown from seed of 95 accessions from a number of countries and
94 collections in Florida in the hope of finding some virus-free
strains. Most of the introductions were highly susceptible to papaya
ringspot virus; local strains showed some resistance. Highest tolerance
was shown by a dioecious, round-fruited, yellow-fleshed strain brought
from Colombia by Dr. S.E. Malo several years ago. The fruits weigh 3-5
lbs (1.36-2.27 kg).
It is thought that at least 3 virus diseases
are involved in papaya decline in East Africa and it has been suggested
that the diseases are spread in part by the tapping of green fruits for
their latex (the source of papain).
Bunchy top is a common, controllable mycoplasma disease transmitted by
a leafhopper, Empoasca
papayae in Puerto Rico, the Dominican Republic, Haiti, and
Jamaica; by that species and E.
dilitara
in Cuba; and by E. stevensi in Trinidad. Bunchy top can be
distinguished from boron deficiency by the fact that the tops of
affected plants do not ooze latex when pricked.
In the
subtropical part of Queensland, but not in the tropical, wet climate of
northern Queensland, papaya plants are subject to die-back, a malady of
unknown origin, which begins with shortening of the petioles and
bunching of inner crown leaves. Then the larger crown leaves quickly
turn yellow. Affected plants can be cut back at the first sign of the
disease and if the cut stem is covered to avoid rotting, the top will
be replaced by healthy side branches. The problem occurs mainly in the
hot, dry spring after a season of heavy rains.
Anthracnose, which usually attacks the ripe fruits and is caused by the
fungus Colletotrichum
gloeosporioides,
was formerly the most important papaya disease in Hawaii, Mexico and
India, but it is controllable by spraying every 10 days, or every week
in hot, humid seasons, and hotwater treatment of harvested fruits. A
strain of this fungus produces "chocolate spot" (small, angular,
superficial lesions). A disease resembling anthracnose but which
attacks papayas just beginning to ripen, was reported from the
Philippines in 1974 and the causal agent was identified as Fusarium solani.
A major disease in wet weather is phytophthora blight. Phytophthora parasitica
attacks and rots the stem and roots of the plant and infects and spoils
the fruit surface and the stem-end, inducing fruit fall and
mummification. Fungicidal sprays and removal of diseased plants and
fruits will reduce the incidence. P.
Palmivora
has been identified as the chief cause of root-rot in Hawaii and Costa
Rica. In Hawaii, the strains, 'Waimanalo-23' and -24, 'Line 8' and
'Line 40', are resistant to this fungus. 'Kapoho Solo' and '45-T22' are
moderately resistant, and 'Higgins' is susceptible.
Root-rot by
Pythium
sp. is very damaging to papayas in Africa and India. P. ultimum
causes trunk rot in Queensland. Collar rot in 8- to 10-month old
seedlings, evidenced by stunting, leaf-yellowing and shedding, and
total loss of roots, was first observed in Hawaii in 1970, and was
attributed to attack by Calonectria sp. Collar rot is sometimes so
severe in India as to cause growers to abandon their plantations.
Powdery mildew, caused by Oidium
caricae
(the imperfect state of Erysiphe
cruciferarum the source of mildew in
the Cruciferae) often affects papaya plants in Hawaii and both plants
and fruits elsewhere. Sulfur, judiciously applied, is an effective
control. Powdery mildew is caused by Sphaerotheca humili
in Queensland and by Ovulariopsis
papayae in East Africa. Angular leaf spot, a form of
powdery mildew, is linked in Queensland to the fungus Oidiopsis taurica.
Corynespora
leaf spot, or brown leaf spot, greasy spot or "papaya decline"
(spotting of leaves and petioles and defoliation) in St. Croix, Puerto
Rico, Florida and Queensland, is caused by Corynespora cassiicola,
which is controllable with fungicides.
A
new papaya disease, yellow strap leaf, similar to YSL of
chrysanthemums, appeared in Florida during the summer in 1978 and 1979.
Black spot, resulting from infection by Cercospora papayae,
has plagued Hawaiian growers since the winter of 1952-53. It causes
defoliation, reduces yield, blemishes the fruit, and is unaffected by
the hot-water dip. It can be prevented by field use of fungicides.
Rhizopus
oryzae
is most commonly linked with rotting fruits on Pakistan markets. R.
nigricans is the usual source of fruit rot in Queensland.
Injured
fruits are prone to fungal rotting caused by R. stolonifer and Phytophthora palmivora.
Stem-end rot occurs when fruits are pulled, not cut, from the plant and
the fungus, Ascochyta
caricae,
is permitted entrance. This fungus attacks very young and older fruits
in Queensland and also causes trunk rot. In South Africa, it affects cv
'Honey Gold' which is also subject to spotting by Asperisporium caricae
on the fruits and leaves. Both of these diseases are controllable by
fungicidal sprays.
Infection at the apex by Cladospoiium
sp. is manifested by internal blight. A pre-harvest fruit rot caused by
Phomopsis
caricae
papayae is troublesome in Queensland and was announced from India in
1971. A new disease, papaya apical necrosis, caused by a rhabdovirus,
was reported in Florida in 1981.
Papayas
are frequently blemished by a condition called "freckles", of unknown
origin; and mysterious hard lumps of varying size and form may be found
in ripe fruits. Star spot (grayish-white, star-shaped superficial
markings) appears on immature fruits in Queensland after exposure to
cold winter winds. In Uttar Pradesh, an alga, Cephaleuros mycoidea,
often disfigures the fruit surface.
In Brazil, Hawaii and other areas, a fungus, Botryodiplodia theobromae,
causes severe stem rot and fruit rot. Trichothecium rot (T. roseum) is
evidenced by sunken spots soon covered by pink mold on fruits in India.
Charcoal rot, Macrophomina
phaseoli, is reported in Pakistan.
Young papaya seedlings are highly susceptible to damping-off, a disease
caused by soil-borne fungi–Pythium
aphanidermatum, P. ultimum, Phytophthorap palmivora, and Rhizoctonia sp.,
especially in warm, humid weather. Pre-planting treatment of the soil
is the only means of prevention.
Papayas generally do poorly on land previously planted with papayas and
this is usually the result of soil infestation by Pythium aphanidernwtum
and Phytophthora
palmivora.
Plant refuse from previous plantings should never be incorporated into
the soil. Soil fumigation is necessary before replanting papayas in the
same field.
Food
Uses
Ripe
papayas are most commonly eaten fresh, merely peeled, seeded, cut in
wedges and served with a half or quarter of lime or lemon. Sometimes a
few seeds are left attached for those who enjoy their peppery flavor
but not many should be eaten. The flesh is often cubed or shaped into
balls and served in fruit salad or fruit cup. Firm-ripe papaya may be
seasoned and baked for consumption as a vegetable. Ripe flesh is
commonly made into sauce for shortcake or ice cream sundaes, or is
added to ice cream just before freezing; or is cooked in pie, pickled,
or preserved as marmalade or jam. Papaya and pineapple cubes, covered
with sugar sirup, may be quick-frozen for later serving as dessert.
Half-ripe fruits are sliced and crystallized as a sweetmeat.
Papaya
juice and nectar may be prepared from peeled or unpeeled fruit and are
sold fresh in bottles or canned. In Hawaii, papayas are reduced to
puree with sucrose added to retard gelling and the puree is frozen for
later use locally or in mainland USA in fruit juice blending or for
making jam.
Unripe papaya is never eaten raw because of its
latex content. [Raw green papaya is frequently used in Thai and
Vietnamese cooking.] Even for use in salads, it must first be peeled,
seeded, and boiled until tender, then chilled. Green papaya is
frequently boiled and served as a vegetable. Cubed green papaya is
cooked in mixed vegetable soup. Green papaya is commonly canned in
sugar sirup in Puerto Rico for local consumption and for export. Green
papayas for canning in Queensland must be checked for nitrate levels.
High nitrate content causes detinning of ordinary cans, and all papayas
with over 30 ppm nitrate must be packed in cans lacquered on the
inside. Australian growers are hopeful that the papaya can be bred for
low nitrate uptake.
A lye process for batch peeling of green
papayas has proven feasible in Puerto Rico. The fruits may be immersed
in boiling 10% lye solution for 6 minutes, in a 15% solution for 4
minutes, or a 20% solution for 3 minutes. They are then rapidly cooled
by a cold water bath and then sprayed with water to remove all softened
tissue. Best proportions are 1 lb (.45 kg) of fruit for every gallon
(3.8 liters) of solution.
Young leaves are cooked and eaten like
spinach in the East Indies. Mature leaves are bitter and must be boiled
with a change of water to eliminate much of the bitterness. Papaya
leaves contain the bitter alkaloids, carpaine and pseudocarpaine, which
act on the heart and respiration like digitalis, but are destroyed by
heat. In addition, two previously undiscovered major D1-piperideine
alkaloids, dehydrocarpaine I and II, more potent than carpaine, were
reported from the University of Hawai'i in 1979. Sprays of male flowers
are sold in Asian and Indonesian markets and in New Guinea for boiling
with several changes of water to remove bitterness and then eating as a
vegetable. In Indonesia, the flowers are sometimes candied. Young stems
are cooked and served in Africa. Older stems, after peeling, are
grated, the bitter juice squeezed out, and the mash mixed with sugar
and salt.
In India, papaya seeds are sometimes found as an
adulterant of whole black pepper. Collaborating chemists in Italy and
Somalia identified 18 amino acids in papaya seeds, principally, in
descending order of abundance, glutamic acid, arginine, proline, and
aspartic acid in the endosperm; and proline, tyrosine, lysine, aspartic
acid, and glutamic acid in the sarcotesta. A yellow to brown, faintly
scented oil was extracted from the sundried, powdered seeds of unripe
papayas at the Central Food Technological Research Institute, Mysore,
India. White seeds yielded 16.1% and black seeds 26.8% and it was
suggested that the oil might have edible and industrial uses.
Food Value
The
papaya is regarded as a fair source of iron and calcium; a good source
of vitamins A, B and G and an excellent source of vitamin C (ascorbic
acid). The following figures represent the minimum and maximum levels
of constituents as reported from Central America and Cuba.
| Food
Value Per
100 g of Edible Portion |
|
Fruit |
Leaves* |
| Calories |
23.1-25.8
|
|
| Moisture |
85.9-92.6
g |
83.3% |
| Protein |
.081-.34
g |
5.6% |
| Fat |
.05-.96
g |
0.4% |
| Carbohydrates |
6.17-6.75
g |
8.3% |
| Crude
Fiber |
0.5-1.3
g |
1.0% |
| Ash |
.31-.66
g |
1.4% |
| Calcium |
12.9-40.8
mg |
0.406%
(CO) |
| Phosphorus |
5.3-22.0
mg |
|
| Iron |
0.25-0.78
mg |
0.00636% |
| Carotene |
.0045-.676
mg |
28,900
I.U. |
| Thiamine |
.021-.036
mg |
|
| Riboflavin |
.024-058
mg |
|
| Niacin |
.227-555
mg |
|
| Ascorbic
Acid |
35.5-71.3 |
mg
38.6% |
| Tryptophan |
4-5
mg |
|
| Methionine |
1
mg |
|
| Lysine |
15-16
mg |
|
| Magnesium |
|
0.035% |
| Phosphoric
Acid |
|
0.225% |
*Analyses made in Malaya. |
|
Carotenoid
content of papaya (13.8 mg/100 g dry pulp) is low compared to mango,
carrot and tomato. The major carotenoid is cryptoxanthin.
Papain
The
latex of the papaya plant and its green fruits contains two proteolytic
enzymes, papain and chymopapain. The latter is most abundant but papain
is twice as potent. In 1933, Ceylon (Sri Lanka) was the leading
commercial source of papain but it has been surpassed by East Africa
where large-scale production began in 1937.
The latex is
obtained by making incisions on the surface of the green fruits early
in the morning and repeating every 4 or 5 days until the latex ceases
to flow. The tool is of bone, glass, sharp-edged bamboo or stainless
steel (knife or raxor blade). Ordinary steel stains the latex. Tappers
hold a coconut shell, clay cup, or glass, porcelain or enamel pan
beneath the fruit to catch the latex, or a container like an "inverted
umbrella" is clamped around the stem. The latex coagulates quickly and,
for best results, is spread on fabric and oven-dried at a low
temperature, then ground to powder and packed in tins. Sun-drying tends
to discolor the product. One must tap 1,500 average-size fruits to gain
1 1/2 lbs (0.68 kg) of papain.
The lanced fruits may be allowed
to ripen and can be eaten locally, or they can be employed for making
dried papaya "leather" or powdered papaya, or may be utilized as a
source of pectin.
Because of its papain content, a piece of
green papaya can be rubbed on a portion of tough meat to tenderize it.
Sometimes a chunk of green papaya is cooked with meat for the same
purpose.
One of the best known uses of papain is in commercial
products marketed as meat tenderizers, especially for home use. A
modern development is the injection of papain into beef cattle a
half-hour before slaughtering to tenderize more of the meat than would
normally be tender. Papain-treated meat should never be eaten "rare"
but should be cooked sufficiently to inactivate the enzyme. The tongue,
liver and kidneys of injected animals must be consumed quickly after
cooking or utilized immediately in food or feed products, as they are
highly perishable.
Papain has many other practical applications.
It is used to clarify beer, also to treat wool and silk before dyeing,
to de-hair hides before tanning, and it serves as an adjunct in rubber
manufacturing. It is applied on tuna liver before extraction of the oil
which is thereby made richer in vitamins A and D, It enters into
toothpastes, cosmetics and detergents, as well as pharmaceutical
preparations to aid digestion.
Papain has been employed to treat
ulcers, dissolve membranes in diphtheria, and reduce swelling, fever
and adhesions after surgery. With considerable risk, it has been
applied on meat impacted in the gullet. Chemopapain is sometimes
injected in cases of slipped spinal discs or pinched nerves.
Precautions should be taken because some individuals are allergic to
papain in any form and even to meat tenderized with papain.
Folk Uses
In
tropical folk medicine, the fresh latex is smeared on boils, warts and
freckles and given as a vermifuge. In India, it is applied on the
uterus as an irritant to cause abortion. The unripe fruit is sometimes
hazardously ingested to achieve abortion. Seeds, too, may bring on
abortion. They are often taken as an emmenagogue and given as a
vermifuge. The root is ground to a paste with salt, diluted with water
and given as an enema to induce abortion. A root decoction is claimed
to expel roundworms. Roots are also used to make salt.
Crushed
leaves wrapped around tough meat will tenderize it overnight. The leaf
also functions as a vermifuge and as a primitive soap substitute in
laundering. Dried leaves have been smoked to relieve asthma or as a
tobacco substitute. Packages of dried, pulverized leaves are sold by
"health food" stores for making tea, despite the fact that the leaf
decoction is administered as a purgative for horses in Ghana and in the
Ivory Coast it is a treatment for genito-urinary ailments. The dried
leaf infusion is taken for stomach troubles in Ghana and they say it is
purgative and may cause abortion.
Antibiotic
Activity
Studies
at the University of Nigeria have revealed that extracts of ripe and
unripe papaya fruits and of the seeds are active against gram-positive
bacteria. Strong doses are effective against gram-negative bacteria.
The substance has protein-like properties. The fresh crushed seeds
yield the aglycone of glucotropaeolin benzyl isothiocyanate (BITC)
which is bacteriostatic, bactericidal and fungicidal. A single
effective does is 4-5 g seeds (25-30 mg BITC).
In a London
hospital in 1977, a post-operative infection in a kidney-transplant
patient was cured by strips of papaya which were laid on the wound and
left for 48 hours, after all modern medications had failed.
Papaya Allergy
Mention
has already been made of skin irritation in papaya harvesters because
of the action of fresh papaya latex, and of the possible hazard of
consuming undercooked meat tenderized with papain. It must be added
that the pollen of papaya flowers has induced severe respiratory
reactions in sensitive individuals. Thereafter, such people react to
contact with any part of the plant and to eating ripe papaya or any
food containing papaya, or meat tenderized with papain.
Related
Species
The mountain papaya (C. candamarcencis
Hook. f.), is native to Andean regions from Venezuela to Chile at
altitudes between 6,000 and 10,000 ft (1,800-3,000 m). The plant is
stout and tall but bears a small, yellow, conical, 5-angled fruit of
sweet flavor. It is cultivated in climates too cold for the papaya,
including northern Chile where it thrives mainly in and around the
towns of Coquimbo and La Serena at near-sea-level. The fruit (borne all
year) is too rich in papain for eating raw but is popular cooked, and
is canned for domestic consumption and for export. The plant grows on
mountains in Ceylon and South India; does well at 1800 ft (549 m) in
Puerto Rico. Its high resistance to papaya viruses is of great interest
to plant breeders there and elsewhere.
The babaco, or chamburo (C.
pentagona
Heilborn), is commonly cultivated in mountain valleys of Ecuador. The
plant is slender and no more than 10 ft (3 m) high, but the 5-angled
fruits reach a foot (30 cm) in length. Usually seedless, or with only a
few seeds at most, the fruits are locally eaten only after cooking. The
plant is not known in the wild and botanists have suggested that it may
be a hybrid. It is propagated by cuttings and is grown on a small scale
in Australia and New Zealand primarily for export.
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