Submitted to: Postharvest Biology and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/25/2011
Publication Date: 5/29/2011
Citation: Felicetti, E., Mattheis, J.P., Zhu, Y., Fellman, J.K. 2011. Dynamics of ascorbic acid in ‘Braeburn’ and ‘Gala’ apples during on-tree development and storage in atmospheres conducive to internal browning development. Postharvest Biology and Technology. 61:95-102. Interpretive Summary: High concentrations of carbon dioxide (CO2) can cause browning of internal tissues in many apple varieties. Why some apples are CO2 sensitive and some are not is unclear, but for the sensitive ones control of CO2 during storage prior to marketing is critical to avoid fruit damage and loss of marketability. Vitamin C, the same compound important for human health, is thought to provide resistance to CO2 injury in apple fruit. Scientists at the USDA, ARS Tree Fruit Research Laboratory in cooperation with Washington State University, examined how amounts of vitamin C in apple fruit change in relation to fruit development on the tree and during high CO2 storage conditions. Vitamin C content in two varieties sensitive (‘Braeburn’) and tolerant (‘Gala’) of CO2 were similar prior to harvest. ‘Braeburn’ had more vitamin C during storage than ‘Gala’ indicating factors other than vitamin C content may be important for CO2 tolerance in apple fruit.
Technical Abstract: The underlying causes as well as chemical and biochemical alleviation for CO2-induced browning in apple fruit are poorly understood. Ascorbic acid (AsA) dynamics in ‘Braeburn,’ a susceptible cultivar, and ‘Gala,’ a resistant cultivar, were evaluated during on-tree development and storage at 0.5' C in air or controlled atmospheres (CA) containing 1 kPa O2 and 1, 3 or 5 kPa CO2. ‘Braeburn’ fruit treated with diphenylamine (DPA) was also stored for 1m to determine effects on browning incidence and AsA concentration. ‘Braeburn’ apples had significantly higher (P = 0.05) AsA quantity compared with ‘Gala’ during on tree development and storage. No correlation between AsA and maturity/ripening indices for ‘Braeburn’ or ‘Gala’ was apparent. Histochemical localization of fruit AsA showed a staining intensity consistent with the quantity analytically determined and that AsA is diffusely distributed throughout the cortex in both cultivars during on-tree development. During storage, AsA was localized to the periphery of brown tissue in ‘Braeburn’ and to the coreline and cortex proximal to the peel in ‘Braeburn’ and ‘Gala’ tissues. DPA decreased browning development during storage, however, no correlation between DPA treatment and AsA quantity in healthy or brown cortex tissue was observed. The results indicate AsA quantity alone is not an indicator of CO2 sensitivity in these two cultivars.