Respiration Rate and Ethylene Production of Ackee (Blighia sapida Köenig) Fruit Harvested at Different Stages of Maturity

Within the Caribbean communities in southern Florida, ackee (Blighia sapida) trees are popular as part of the home landscape. The fruit is widely consumed as a cooked item. The consumption of raw ackee has recently gained popularity among food enthusiasts, particular in raw vegan cuisine. Immature ackee fruit are known to contain toxic levels of hypoglycine A; but upon reaching maturity the level of toxicity is considerably reduced, making the fruit safe for consumption. The objective of this study was to determine the respiratory pattern, ethylene production, color change, and weight loss of ackee fruit harvested at five maturity stages and stored for 72 hours at 20 °C. The maturity stages were based on the progression of dehiscence and color change from; 1) small in size green unopened pods; 2) medium sized, yellow immature unopened pods; 3) full size unopened pods, red in color, can be rack ripened; 4) slightly dehisced pods, aril and seed visible, edible; and 5) fully dehisced pods with seed and aril clearly visible, edible. The respiration rates for stages 4 and 5 were significantly higher, at 64.6 and 97.9 mL/kg/h CO₂, respectively, than the respiration rates for stages 1, 2, and 3, at 43.3, 49.1, and 52.5 mL/kg/h CO₂, respectively. Stage 5 had the highest rate of ethylene production at 12.4 µL/kg/h C₂H₄, followed by stages 4, 1, 3, and 2 with rates of 7.24, 6.62, 3.93, and 3.25 µL/kg/h C₂H₄, respectively. There were no significant changes in hue angle (H*) of the pericarp surface during storage of ackee fruit. However, a decrease of 59.5% was observed in H* from stages 1 to 5, corresponding to a change from greenish yellow to scarlet red. Weight loss during storage increased from 8.79% to 15.65% for stages 2 to 5. The maturity stage at which the ackee fruit were harvested significantly affected the physiological parameters investigated in this experiment. The RRCO₂ and ethylene production were elevated upon ripening, coinciding with dehiscence, suggesting that the ackee fruit follows a climacteric pattern of ripening.