Ripening-induced chemical and antioxidant changes in bell peppers as affected by harvest maturity and postharvest ethylene exposure

Greenhouse-grown bell pepper (Capsicum annuum L. 'Robusta') were harvested at five stages of maturation (10% red to full red) in early winter 2002 (Expt. 1) and at two stages (10% red and full red) in early Spring 2002 (Expt. 2). The fruit were subsequently stored at 20 degrees C in a continuous-flow chamber consisting of either 100 mu L center dot L-1 ethylene (balance air) or air-only (control) at 90% relative humidity (RH). Individual fruit were removed from the chambers upon reaching full red color, and stored at -30 degrees C until physicochemical analyses were conducted. Harvest maturity, and ethylene exposure had no appreciable effect on pulp soluble solids content, total titratable acidity or pH. Exposure to ethylene hastened ripening time compared to the air control but was independent of fruit maturity at harvest. Fruit exposed to ethylene reached full-red color 6.4 days (Expt. 1) and 4 days (Expt. 2) earlier than air-only fruit, respectively. There were no significant phytochemical and antioxidant differences noted for total carotenoids, total ascorbic acid, and soluble phenolics at various maturity stages due to ethylene exposure. Appreciable differences were observed between the two experiments for phytochemicals and antioxidants, as bell peppers from the latter experiment contained at least twice the concentrations of phytochemicals and antioxidant capacity as those from the first experiment. Differences in these parameters between experiments were attributed to environmental factors such as average temperature, day length, and light intensity. Ethylene was demonstrated to be an effective postharvest treatment for accelerating color change in this bell pepper cultivar, permitting earlier harvest without altering phytochemical synthesis rates.