Effect of Calcium on Ripening, Respiratory Rate, Ethylene Production, and Quality of Avocado Fruit

Abstract

The effect of Ca between 0.05 and 5.0 m on days to ripen, respiratory rates, rates of ethylene evolution, and external and internal quality of ‘Fuerte’ and ‘Hass’ avocado fruit at 20°C when placed directly at 20° or at 20° after 1, 3, and 5 weeks storage at 0° and 5° was determined. Dipping fruit in Ca solutions had no significant effect on these responses. The results discussed are for vacuum-infiltrated fruit. Days to ripen was increased and respiratory rates and rates of ethylene evolution were reduced as the Ca concentration increased. At 0.4 and 0.5 m Ca, no detectable climacteric occurred, essentially no ethylene was produced and the fruit failed to ripen. Exogenous ethylene or propylene exposure for 2 days resulted in typical stimulation of respiratory rates, ethylene production, and ripening of untreated fruit. Treatment with Ca reduced each response. Storage experiments indicated that Ca reduced internal chilling injury symptoms and increased external symptoms. Commercial Ca treatment of avocados to delay ripening and reduce chilling injury symptoms does not seem practical, because of the necessity to vacuum-infiltrate the Ca solution into the fruit and the adverse effect on external quality when ripened after storage.