Changes in ATP, ADP and pyridine nucleotide levels related to the incidence of physiological disorders in 'Conference' pears and 'Jonagold' apples during controlled atmosphere storage

The effects of four controlled atmosphere (CA) storage conditions on ATP and ADP levels, and the concentrations of NAD(H) and NADP(H) were investigated in relation to the incidence of physiological disorders of 'Conference' pears and 'Jonagold' apples during six months at 0 degrees C (+/-0.5 degrees C). ATP concentrations in apple and pear fruits stored in CA were lower than those in air-stored fruits but their reduction was lowest for 'Conference' pears stored in 1.5% CO2 + 1.5% O-2 'Jonagold' apples showed a sharp decrease followed by a slight increase in the ATP levels at the beginning of the second month of storage. The concentrations of NADH and NADPH in the tissues of 'Conference' pears and 'Jonagold' apples increased in both CA- and air-stored fruits. In contrast, the oxidized nucleotides, NAD and NADP, generally decreased with storage time and no significant differences between the treatments were found. Only 'Conference' pears, when stored in 6% CO2 + 0.5% O-2, exhibited a strong decline in NADP levels, which was associated with the low metabolic activity due to the high incidence of disorders. No physiological disorder was noted in 'Jonagold' apples during the six months of storage time, while 'Conference' pears exhibited disorders such as flesh browning, brown heart and cavities in all CPI-storage conditions. Severity of these disorders depended on CA-conditions and length of storage. For 'Conference' pears the CA-combination of 1.5% CO2 + 1.5% CO2 seemed to be most promising since it resulted in very low percentage of damaged fruits. A probable relationship between energy level expressed by ATP concentrations, ATP:ADP ratios and pyridine nucleotides and the development of these disorders is discussed.