Effects of Controlled Atmosphere Storage on Specific Biochemical Changes in Apricot and Peach Fruits

The effects of controlled atmosphere storage vs conventional refrigerated storage on the metabolism of Moorpark and Large Early Montgamet apricot and Elberta peach fruits were studied. The controlled atmospheres studied were 0.0 percent CO2-5.0 percent O2; 2.5 percent CO2-5.0 percent O2; 5.0 percent CO2-2.5 percent O2; 7.5 percent CO2-5.0 percent O2; as compared to conventional refrigerated storage. Nitrogen percent was assumed to be the difference between the total CO2 and O2 content minus 100. Fruits were periodically removed from the storage and analyzed for firmness, fleshy pericarp color, total pectins, pH, titratable acidity, total and free reducing sugars, tannins, organic acids, and amino acids. Controlled atmosphere storage had both beneficial and detrimental effects on stored apricot and peach fruits. The general retardation of the respiration rate and consequent delay of the climateric rise due to controlled atmosphere are important in prolonging the storage life of the fruit. Apricot fruits stored in 2.5 to 5.0 percent CO2 and 2.5 to 5.0 percent O2 maintained superior quality for 15 to 30 days longer than did conventionally refrigerated fruit. Moorpark fruit could be stored longer than Large Early Montgamet fruit, mainly because of mesocarp browning in the latter variety of fruit. The results indicated that the storage life of Elberta peach fruits were not substantially increased in controlled atmosphere storage. Apricot fruit stored in controlled atmosphere treatments ripened at a reduced rate and produced less yellow pigments of the fleshy pericarp tissue than the conventional refrigerated fruit. There was a retardation of the de-greening processes of the fruit stored in CO2 concentrations higher than atmospheric air. It appeared that high concentrations of CO2 had an inhibitory effect on chlorophyll degradation. Succinic acid coupled with high tannin concentrations, induced by CO2, apparently caused browning of the mesocarp tissue of the fruit in controlled atmosphere storage at a more rapid rate than conventional refrigerated stored fruit. The organic and amino acids of peach and apricot fruits had a variable response to control atmosphere treatment. The organic acids, particularly malic acid, were reduced in concentration, while succinic acid accumulated. Succinic acid accumulation was dependent upon the concentration of CO2 in the atmosphere. It was suggested that CO2 had a toxic or inhibitory effect on the succinic oxidase enzyme system which resulted in succinic acid accumulation. The accumulated succinic acid, thereby, may have had a toxic effect on the mesocarp tissue of the fruit and caused part of the browning. Aspartic acid decreased in concentration under higher CO2 treatments, while alanine and glutamic acid increased. Total sugar concentration was generally not effected by controlled atmosphere storage. The metabolism of free reducing sugars in higher CO2 treatments was markedly reduced in the apricot fruit. The beneficial aspects of controlled atmosphere on stored fruit appeared to be the increased length of the storage period for apricot fruit, as well as a reduced rate of metabolism. The storage life of apricot fruit was extended 15 to 30 days in the appropriate atmosphere. The adverse effects of controlled atmosphere storage of apricot and peach fruit appeared to be: the inhibitory or toxic effect of CO2 on certain enzyme systems; the accumulation of certain metabolites, which may have been toxic to the fruit tissue; the increased rate of tissue browning, the inhibitory effect of CO2 on the de-greening and color development mechanisms