QUALITY OF PINK LADY ® BRAND APPLE
Apple (Malus domestica Borkh, ‘Pink Lady ® brand’) fruit were harvested from one California orchard in 2002, 2003 and 2004 at two or three different maturity stages each year. Fruit were evaluated for background color, firmness, fruit size, percentage of blush, starch index (CTIFL chart), soluble solids, titratable acidity and carbon dioxide (CO2) production and immediately stored at 33 oF in air or in controlled atmosphere (CA). In 2003, additional treatments included 1 ppm of SmartFresh ® (1-MCP) or 2200 ppm of diphenylamine (DPA). Firmness, CO2 production, external condition and internal browning were determined after storage in CA or air and 5 days at 68 oF. Fruit stored in CA conserved higher firmness and produced less CO2. Internal browning was not seen in fruit stored in air, but appeared in fruit after two months storage in CA. The incidence did not increase after longer storage times. SmartFresh ® worked as well as CA in conserving the quality of the fruit. It did not affect the incidence of internal browning, but DPA inhibited internal browning completely. When comparing similar storage atmospheres for all three seasons, the incidence of internal browning was significantly different, being much higher in 2002 and 2004. A mineral analysis of the apple flesh showed differences among the seasons. Concentrations of calcium (Ca), boron (B) and magnesium (Mg) were significantly higher in 2003, corresponding with a lower incidence of internal browning.
Superficial Scald, Carbon Dioxide Injury, and Changes of Fermentation Products and Organic Acids in 'Cortland' and 'Law Rome' Apples after High Carbon Dioxide Stress Treatment
Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] were either nontreated or treated with the inhibitor of superficial scald development, DPA, and exposed to air or CO 2 (40 or 45 kPa) in air at 2 o C for up to 12 days. Fruit exposed to air or 45 kPa CO 2 were sampled during treatment, and peel and flesh samples taken for fermentation product and organic acid analyses. After treatment, fruit were air stored for up to 6 months at 0.5 o C for evaluation of disorder incidence. ‘Cortland’ apples were most susceptible to external CO 2 injury and ‘Law Rome’ to internal CO2 injury. DPA treatment markedly reduced incidence of both external and internal injury. Fermentation products increased in peel and flesh of both cultivars with increasing exposure to CO 2, but the extent of the increase was cultivar dependant. Acetaldehyde concentrations were about 10 times higher in peel and flesh of ‘Law Rome’ than that of ‘Cortland’ apples. Ethanol concentrations in the flesh were similar in both cultivars, but were about twice as high in ‘Cortland’ than in ‘Law Rome’ peels. Neither acetaldehyde nor ethanol concentrations were affected consistently by DPA treatment. Succinate concentrations, often regarded as the compound responsible for CO 2 injury, increased with CO2 treatment, but were not affected by DPA application. Citramalate concentrations were reduced by CO 2 treatment in ‘Law Rome’ peel, but other acids were not consistently affected by CO 2. Results indicate that acetaldehyde, ethanol or succinic acid accumulation are not directly responsible for CO 2 injury in apples. Chemical name used: diphenylamine (DPA).
Development of ACC oxidase activity during maturation and ripening of ‘Paulared’, ‘Empire’ and ‘Law Rome’ apples
Abstract The development of ACC oxidase activity was investigated in three cultivars of apple ( Malus domestica Borkh.), ‘Paulared’, ‘Empire’ and ‘Law Rome’, as typifying early, mid-season and late cultivars, respectively, during maturation and ripening. Fruits were selected at progressive stages of development of the autogenous ethylene climacteric during maturation and ripening on the tree. The level of 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene was used as a relative measure of the activity of ACC synthase and the ability of fruit tissue to convert ACC to ethylene was used as a measure of the activity of ACC oxidase, the ethylene forming enzyme. ‘Paulared’ fruits accumulated high levels of ACC as the autogenous ethylene climacteric began and this was associated with slow development of ACC oxidase activity. ‘Law Rome’ apples showed ACC oxidase activity early in the development of the ethylene climacteric but this was associated with accumulation of low levels of ACC in fruits. ‘Empire’ fruits were found to be intermediate between the early and late cultivars. ACC oxidase activity of fruits of the three cultivars was found to increase concurrently with or subsequent to the accumulation of ethylene to ca. 0.1 μl 1 −1 in the internal atmosphere of the fruit. Thus, the ACC content of the fruit was found to be a function of the development of ACC synthase activity as well as the relative activity of ACC oxidase. The levels of these activities were cultivar dependent. Differential sequestering of ACC into malonyl ACC by malonyl Co A-ACC transferase among the three cultivars may also account for the wide disparity in changes in ACC content with maturation but this was not investigated.