Browning Disorders and DA Meter Readings in ‘Gala’ Apples

Consumer demand for ‘Gala’ [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] is high thanks to its desirable texture and flavor characteristics. Increasingly, however, stem end browning (SEB), senescent breakdown and core browning has been found in stored fruit. As a result, fresh cut and whole fruit sales are affected and significant economic losses have occurred. We have investigated the effects of fruit maturity, storage temperature and conditioning on quality of controlled atmosphere (CA) stored fruit. The Delta Absorbance (DA) meter was used to categorize fruit into 7 different I_AD classes at harvest. Fruit were stored in CA storage (2%O₂ + 2%CO₂) at either 0.5 ^oC or 3 ^oC directly or after one week of conditioning at 10 ^oC. Internal ethylene concentrations, soluble solid concentrations and starch pattern indices increased as I_AD values decreased (less chlorophyll), but flesh firmness or titratable acidity were not affected by maturity. After 6 months of storage, SEB incidence and severity was not affected by conditioning, but was higher in lower I_AD classes in 0.5 ^oC, and in higher I_AD classes in 3 ^oC. Senescent breakdown was higher in the lower I_AD classes and higher storage temperature. Core browning was observed only in fruit from the 0 I_AD class at 3 ^oC with conditioning. Greasiness was greater in the lower I_AD classes, the higher storage temperature, and with the addition of a conditioning treatment. Separation of maturity using I_AD classes is a valuable method to investigate variation of responses within a population of fruit.