Effects of superatmospheric oxygen levels on postharvest physiology and quality of fresh fruits and vegetables

Exposure to superatmospheric O-2 concentration may stimulate, have no effect, or reduce rates of respiration and ethylene production, depending on the commodity, maturity and ripeness stage, O-2 concentration, storage time and temperature, and concentrations of CO2 and C2H4 present in the atmosphere. In some plant organs, cyanide-resistant respiration is enhanced by elevated O-2 atmospheres. Ripening of mature-green, climacteric fruits was slightly enhanced by exposure to 30-80 kPa O-2, but levels above 80 kPa retarded their ripening and caused O-2 toxicity disorders on some fruits. High O-2 concentrations enhance some of the effects of ethylene on fresh fruits and vegetables, including ripening, senescence, and ethylene-induced physiological disorders (such as bitterness of carrots and russet spotting on lettuce). While superatmospheric O-2 concentrations inhibit the growth of some bacteria and fungi, they are much more effective if combined with elevated (15-20 kPa) CO2, which is a fungistatic gas. (C) 2000 Elsevier Science B.V. All rights reserved.