Effect of browning related pre- and postharvest factors on the ‘Braeburn’ apple metabolome during CA storage

• Metabolic differences induced by preharvest factors were identified.
• Metabolic differences induced by postharvest factors were identified.
• No browning-specific metabolites were identified.
• Spatial metabolic distribution in the fruit cortex was observed.
• No browning-related biomarker could be reliably identified.

‘Braeburn’ apple is susceptible to internal browning during controlled atmosphere (CA) storage which is responsible for large economic losses. The objective of this study was to investigate the effects of calcium and potassium fertilizers, triazole fungicides, harvest date, 1-MCP application, and O2 and CO2 levels on the metabolic profile of ‘Braeburn’ fruit; and to screen for metabolites as biomarkers for early prediction of browning. For this purpose, a gas chromatography coupled to mass spectrometry approach was used to quantify the polar metabolites involved in the central metabolism. This study identified the main metabolic changes (at harvest and after 182 d of CA storage) associated with the various pre- and postharvest factors, some of which could be correlated to the rate of cellular respiration and the stress state of the tissue. Internal browning was observed during CA storage as early as 14 d after harvest. A clear spatial distribution of certain metabolites between the inner and outer cortex was observed which was mainly attributed to at-harvest differences and gas gradients inside the fruit. The screening for potential browning biomarker metabolites did not identify any metabolite that could reliably predict the early incidence of the disorder.