Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2012
Publication Date: 6/1/2012
Citation: Lee, J., Mattheis, J.P., Rudell Jr, D.R. 2012. Antioxidant treatment alters metabolism associated with internal browning in ‘Braeburn’ apples during CA storage. Postharvest Biology and Technology. 68:32-42. Interpretive Summary: Internal browning provoked by high carbon dioxide levels in storage economically cullable defect of many apple fruit varieties, especially ‘Braeburn’. The disorder is characterized by moderate to severe, patterned browning of the flesh tissue. Very little is known about chemical changes that coincide with the injury or may provoke the injury. We used untargeted metabolic profiling to link changes in apple flesh chemistry caused by conditions that both reduce and/or provoke this injury. We found diverse compounds were linked with conditions and or actual injury and changes in the overall chemistry occurred prior to symptom development. Results indicate that monitoring a particular set of metabolites related to fermentation may be a good way of detecting whether injury is developing within a particular storage room.
Technical Abstract: ‘Braeburn’ apple (Malus × domestica Borkh.) fruit can develop internal browning (Braeburn breakdown disorder; BBD) and pitting during hypoxic cold storage in elevated levels of CO2. Pre-storage treatment with the antioxidant diphenylamine (DPA) can prevent this disorder. To evaluate disorder-related metabolism, we employed untargeted metabolic profiling using GC-MS and LC-MS to characterize metabolism in cortex tissue of ‘Braeburn’ apple fruit treated with 2 g L-1 DPA or left untreated and stored under high CO2, hypoxic controlled atmosphere (CA) storage of 1.5 kPa O2/3 kPa CO2 at 0.5 degrees C for up to 12 weeks. Partial least squares regression (PLSR) was employed to define metabolomic differences developing between untreated and DPA-treated fruit during storage and identify metabolites linked with treatments, storage duration, and BBD. Control and DPA-treated cortex metabolomes began to diverge after 4 weeks of storage, which accompanied increased flesh browning only in untreated fruit. Flesh browning was associated with increased acetaldehyde, ethanol, and ethyl esters. DPA treatment reduced the levels of these and other volatile compounds. DPA treatment also reduced flesh content of many amino acids. These results indicated that metabolism is altered by DPA treatment after 4 weeks of CA storage and these metabolic changes may be related to tissue integrity.