Controlled Atmosphere and Antioxidant Effects on External CO2 Injury of `Empire' Apples

Abstract

The histology of external CO 2 injury of the skin of `Empire' apples and postharvest factors affecting occurrence of injury were investigated. Injury was greater in a 5% CO 2 /2% O 2 atmosphere than in 2% CO 2 /2% O 2 , but incidence was affected by orchard source. Susceptibility to injury was highest during the first 4 weeks of storage, while a postharvest treatment with diphenylamine prevented the disorder. Ethanol reduced injury, but ascorbic acid increased incidence of the disorder. Keeping fruit in air cold storage for 10 days before application of CO 2 markedly reduced incidence of CO 2 injury. Histological studies showed that external CO 2 injury begins at the hypodermis—cortex boundary and spreads outward into the upper hypodermis and inward into outer cortex cells, although the cuticle and epidermis appear unaffected and unbroken. Radial walls of affected cells collapse and become pleated, so that the skin surface sinks below nearby normal regions. Other cellular events include loss of cytoplasmic integrity, coagulation of the protoplast, loss of organelle structure, and cell wall separation. Nondigested starch can be found in cells of affected fruit at the hypodermis—cortex boundary. We conclude that several factors affect fruit susceptibility to CO 2 injury, including orchard, antioxidant treatment, and delays before application of CO 2 .