EFFECT OF VARYING CONCENTRATIONS OF OXYGEN WITH AND WITHOUT CO2 ON SENESCENT CHANGES IN STORED McINTOSH APPLES GROWN UNDER TWO LEVELS OF NITROGEN FERTILIZATION

Abstract

McIntosh apples from trees having a high and low content of N as determined by leaf analysis were stored in modified atmospheres of zero, 5, or 7% CO2 in a range of O2 levels from 2.5 to 20%. Fruit from the low N trees was highly susceptible to core-browning in the presence of CO2 at all O2 concentrations above 2.5%, and in contrast the disorder appeared to be reduced by CO2 in the high N fruit. Firmness, soluble solids, and acids were higher with CO2 than without CO2. Low N apples softened significantly faster than high N fruit at all O2 concentrations. The presence of 5%, CO2 reduced the number of fungal rots. The reduction in O2 levels without CO2 had a marked beneficial effect in the control of fungal rotting.