PHYSIOLOGY OF CA TREATED PRODUCE

Abstract

Storage of fresh horticultural perishables within the optimum range of low oxygen and/or elevated carbon dioxide atmospheres for each commodity reduces their respiration and ethylene production rates. However, outside this range respiration and ethylene production rates can be stimulated indicating a stress response, which can contribute to incidence of physiological disorders and increased susceptibility to decay. Exposure to 30-80 kPa oxygen atmospheres stimulates respiration and ethylene production and action in some commodities. Carbon dioxide-enriched atmospheres inhibit activity of ACC synthase, while ACC oxidase activity is stimulated by low carbon dioxide and inhibited at high carbon dioxide and/or low oxygen concentrations. Ethylene action is inhibited by elevated carbon dioxide atmospheres. Optimum CA retard loss of chlorophyll, biosynthesis of carotenoids and anthocyanins, and biosynthesis and oxidation of phenolic compounds. CA reduce the activity of cell wall degrading enzymes that cause fruit softening and enzymes involved in lignification leading to toughening of vegetables. CA influence flavor quality by reducing loss of acidity, starch to sugar conversion, and biosynthesis of aroma volatiles, especially esters. Retention of ascorbic acid and other vitamins results in better nutritional quality, including antioxidant activity, of fruits and vegetables when kept in their optimum CA.