Abstract

Early season ‘Hass’ avocado fruit are susceptible to chilling injury (CI); and thus, develop poor peel colour during ripening which reduces market value. Therefore, this study was conducted during early-season (April) of 2018 at Agricultural Research Council - Tropical and Subtropical Crops (ARC-TSC), South Africa to evaluate the use of hot water treatment (HWT) dips to mitigate chilling injury (CI) and thereby, enhancing early-season harvested 'Hass' avocado fruit peel colour during ripening. The trial was laid down in completely randomized design with four hot water treatments: fruit with no treatment (control), 38°C for 30 minutes, 42°C for 25 minutes and 46°C for 20 minutes. Thereafter, fruits were stored at commercial shipping temperature (5.5°C) for up to 28 days. After removal from cold storage, fruits were ripened at ambient temperature (±25°C) and evaluated every after 2 days for weight loss, firmness loss, objective colour parameters (lightness-L*, chroma-C* and hue angle-h°), subjective colour (eye colour) and ripening percentage. However, CI and electrolyte leakage (EL) were evaluated immediately after removal from cold storage. The results showed that HWT significantly (P < 0.05) increased weight and firmness loss during ripening. Furthermore, HWT reduced EL and external chilling injury (ECI) of ‘Hass’ avocado fruit during cold storage. In addition, the results exhibited that HWT had a significant effect (P < 0.05) on colour parameter L* and eye colour rating but did not affect (P > 0.05) chromatic C* and h°. Avocado ‘Hass’ fruit subjected to HWT at 42°C for 25 minutes and 46°C for 20 minutes developed purple colour (eye colour rating 4.47 and 4.36, respectively) during ripening when compared with HWT at 38°C for 30 minutes and control fruit. This study demonstrated that postharvest HWT effectively mitigated chilling injury and improved peel colour development of early-season 'Hass' avocado fruit during ripening.