POSTHARVEST RIPENING AND RIPE FRUIT QUALITY OF DURIAN
SCIENTIFIC NAME: Durio zibethinus
FAMILY: Bombacaceae
Limited postharvest experimental work was carried out in March 1986 at Walkamin Research Station on durian fruit. Eight mature unripe fruit were obtained from Kamerunga Horticultural Research Station. Two fruit were stored at each of 4 ripening conditions:
1. storage in air at 15°C.
2. storage in air at 25°C.
3. storage under 100 ppm ethylene at 15°C.
4. storage under 100 ppm ethylene at 25°C.
During storage, each fruit was examined daily and assessed for general appearance (hedonic scale 1- 9), skin colour (1- green to 6-fully yellow colour); skin discolouration (0-nil to 4-severe); and aroma (0-nil to 4-extremely strong).
Each fruit was judged to have reached an eating ripe condition by:
(i) an increase in aroma.
(ii ) a detectable softening (by manual finger pressure) of the body of the fruit.
( iii) splitting of the base of the fruit body.
At eating ripe, each fruit was removed from storage and placed at 8°C for 12 hours to facilitate removal of pulp from the skin shell. Pulp from fruit stored at 25°C in air and under ethylene was recovered in whole segments (complete with seed), packed into plastic punnets, over-wrapped with PVC clingwrap plastic film then stored at 4°C and -15°C for up to 4 weeks. At intervals of 1, 3, 7, 14, 21 and 28 days, pulp samples were removed from storage and assessed for flavour, texture, general acceptability (hedonic scale 1-9), and pulp discolouration (0-nil to 4-severe) and aroma (0-nil to 4-extremely strong). After 21 days of storage, samples of frozen pulp in punnets were air freighted to the Hamilton laboratory for assessments by European and Asian tasters.
Results and Discussion
The results indicated that 15°C is not an appropriate temperature for ripening durian fruit in air or under ethylene, although the ripening process under ethylene appeared to be more rapid with less apparent loss of fresh appearance. Fresh appearance was maintained better at 25°C and the fruit ripened faster. Controlled ripening with ethylene at 25°C further reduced the ripening time.
Percent weight loss during ripening at both temperatures was high (up to 40% at 15°C), although this was reduced by more rapid ripening under ethylene.
These results indicated that mature, unripe durian fruit may respond to controlled ripening with ethylene gas, and that the fruit should be stored under high humidity to reduce dehydration and consequent weight loss.
The results indicated that the eating quality of pulp was maintained for up to 28 days equally well at 4°C or at -15°C. That is, chilled durian pulp retained eating quality as well as frozen pulp. The pulp from fruit ripened under ethylene also retained equal equality when chilled or frozen, but this pulp lost fresh quality progressively after about 1 week. Controlled ripening with ethylene may therefore adversely affect the subsequent eating quality of chilled or frozen pulp.
Taste panel assessments at Hamilton by two 10-member panels (European, Asian) on frozen pulp samples, indicate distinct ethnic differences in panel scores. Thawed samples of pulp were presented to each panel, and in each case there was a preference for pulp from fruit ripened in air rather than in ethylene. However the Asian tasters, who were familiar with durian fruit and considered it a delicacy, rated both pulp samples (air-ripened and ethylene-ripened pulp) much higher than the European panel, which generally disliked the aroma (described as sulphurous, like rotting onions, nauseating) and rated the eating quality of the pulp barely acceptable.
Consumer education, fruit presentation and careful selection of the market will be necessary in any attempt to market this fruit commercially in Australia. Durian fruit may well have better prospects for selected export markets in Asia, provided the market is supplied with the type and quality of product in demand.
DATE: September 1991
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