The effects of carbon dioxide and oxygen concentrations on superficial scald of Granny Smith apples

In the past, experiments on controlled atmosphere storage have tested specific combinations of carbon dioxide and oxygen, usually in a manner which precludes determination of the effect of change in concentration of these gases. The data from the series of trials discussed in this paper permitted an investigation of the effect of concentrations of carbon dioxide and oxygen on the incidence of scald with simple and multiple linear regression techniques. The method was applied to data from three types of controlled atmosphere storage: (1) Carbon dioxide 2.5–10% at 2.5% oxygen, (2) Oxygen 1.25–20%, at near zero carbon dioxide, (3) Carbon dioxide 3.3–10.9% oxygen 2.2–16%. The relation between scald (Y), carbon dioxide concentration (x), and the reciprocal of oxygen concentration (z), was described by the regression equation: Y = y + b(x – x) + c(z – z), which implies that scald is directly proportional to carbon dioxide concentration and indirectly proportional to oxygen concentration. The effects of changes in concentration of the gases, as estimated by the regression coefficients, were consistent for size of fruit, season, and orchard, but the effect for oxygen was dependent on the method of maintaining the atmosphere. Good control of scald was obtained with low oxygen atmospheres, even after storage for 6–7 months.