Epicuticular changes and storage potential of cactus pear [Opuntia ficus-indica Miller (L.)] fruit following gibberellic acid preharvest sprays and postharvest heat treatment
1999
Schirra, M. | D'hallewin, G. | Inglese, P. | La Mantia, T.
Cactus pear [Opuntia ficus-indica Mill. (L.) cv. Gialla] fruit were treated 10 weeks after the second induced-bloom flush with 10 ppm gibberellic acid (GA3) or were heated at 37 degrees C for 30 h under saturated humidity after harvest. The two treatments were also combined before storage at 6 degrees C for 45 days plus 4 additional days at 20 degrees C to stimulate a marketing period (SMP). Fruit not treated with GA3 and unheated were used as controls. GA3 spray delayed fruit ripening as evaluated by peel colour change and scanning electron microscopic observations of epicuticular wax morphology, decreased ethanol levels in the flesh during storage and SMP, and reduced decay development during storage. Postharvest heat treatment (HT) reduced decay during storage and SMP, retained visual quality of fruit, prevented chilling injury and resulted in a higher ethylene production rate after SMP in comparison with untreated fruit. The combined treatments (GA3 + HT) did not produce any further beneficial effects in chilling injury and decay control or in maintaining fruit quality. Heat treatment caused a partial melting of the epicuticular wax layers. This caused the disappearance of platelets normally present on the skin surface of unheated fruit and sealed micro-wounds and cracks. The covering of wounds and cracks by melted wax following heat treatment was considered a contributing factor in protection against wound pathogens.
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