Agriculture Reference
In-Depth Information
more colour on the skin. Foam mesh sleeves, foam padding on the bottom
of the carton or paper wrapping prevent abrasion injury, which is a major
problem in fruits still having green areas of skin.
Room cooling and forced air cooling are most commonly used to pre-cool.
Hydro-cooling is possible; however, rapid cooling after insect disinfestation
treatments can lead to skin scalding. Storage recommendations are in the
range of from 7 to 13°C and from 90 to 95% RH. At 7-10°C, storage life is
limited by chilling injury, while at 10-13°C ripening slowly occurs (Chen and
Paull, 1986). Papaya fruit at colour-turning (break) stage can be stored at 7°C
for 14 days and will ripen normally when transferred to room temperature
(Fig. 5.3). Chilling injury symptoms include skin scald, hard lumps in the
pulp around the vascular bundles and water-soaking of fl esh. Fruits become
progressively less susceptible to chilling stress as they ripen, and the symptoms
occur after 14 days at 5°C for mature green fruit and 21 days for 60%
yellow fruit. Skin scald can be induced in colour-break fruit after chilling at
1°C for 24 h.
Shelf-life extension of 1-1.5 days was obtained when papaya were
stored at 12°C in 1-1.5% oxygen for 6 days. Low oxygen (1.0-5%), with or
without high CO
2
(2-10%), reduces decay and delays ripening. High CO
2
(30%) adversely af ected internal colour, aroma and fl avour, while there is
no residual ef ect of 10% CO
2
on decay control, though skin degreening is
delayed. At 10°C, fruit could be stored for 36 days in 8% CO
2
, 3% O
2
and still
have 5 days at 25°C for retail. Ethylene removal prior to storage has shown
variable results. Controlled atmosphere has not shown dramatic improvement
in storage life and the economic cost of the treatment needs to be balanced
against the improvement in fruit storage life and quality.
The optimum temperature for fruit ripening is between 22.5 and 27.5°C,
with fruit taking 10-16 days to reach full skin yellowing from the colour-break
stage (An and Paull, 1990). Severe weight loss and external abnormalities
become signifi cant at temperatures higher than 27.5°C. Fully ripe fruit at the
edible stage can be held at 1-3°C. Loss of
ca.
8% of initial weight from colour-
break papaya produces 'rubbery', low-gloss, unsaleable fruit.
Marketing
Most papayas produced in the tropics are consumed locally, due to long
distances to markets and the dii culty in handling the large fruit size.
Marketing standards for trade are normally set by agreement between the
shipper and the wholesale or retail buyer. In Hawaii, standards for Hawaiian-
grown papaya have been developed. Fruit must conform to the 'Solo' type,
with similar cultivar characteristics as to size and shape, must be mature
with a defi nite tinge of yellow at the blossom end, must be clean, well-formed
and meet the total soluble solids standards, averaging not less than 11.5%
