Epicuticular Wax Changes in Grapefruit as Affected by Hot Water Dip and Postharvest Relevance

Grapefruit cv 'Marsh seedless' were used to study the effect of hot water dip as a postharvest treatment to prevent decay, chilling injury and quality loss during cold storage. A 2 min dip of half of the fruit was performed at 50 °C (HWT) and the remaining at 20°C. Then, when dry fruit was placed in boxes and stored at 9°C for 11 weeks. Following cold-storage fruit were moved at 20°C (control) for one additional week in order to simulate the marketing conditions (SMC). A monthly survey of fruit-rind disorders and decay was performed. Chemical analysis (TSS, TA) of fruit juice took place at harvest, at the end of storage and SMC. Also juice off-flavour was monitored by GC head-space analysis. At all inspection times three fruit were used for SEM observations of the rind. During the first period of cold-storage (5 weeks) HWT fruit had a significantly lower incidence of decay and chilling injury in comparison to control fruit. While, as storage proceeded decay rose but remained lower until after the SMP. HWT significantly contaned chilling injury and did not increased the off-flavour nor the other chemical parameters analysed. TheSEM observations evidenced a clear re-modelling of the epicuticular wax with a change from cristalline to amorpheus structure .