Targeted metabolomics study of ‘Braeburn’ apples during long-term storage

• The effects of various preharvest treatments with calcium, potassium and triazoles on the primary metabolites of ‘Braeburn’ apple were investigated.
• The ‘Braeburn’ apple primary metabolites were also studied during storage at browning-inducing controlled atmosphere conditions.
• No significant differences in the primary metabolites were observed between the different levels of the applied preharvest factors.
• During CA storage, some fruit developed browning, and this was correlated to a group of primary metabolites that either increased or decreased with time.
• Radial distribution of certain primary metabolites in the fruit tissue was also observed.

‘Braeburn’ is an apple cultivar susceptible to the occurrence of internal browning (Braeburn Browning Disorder; BBD) during storage. This physiological disorder is characterized by the development of brown spots inside the fruit, eventually resulting in the formation of cavities. The objective of this study was to investigate the effects of the preharvest application of calcium, potassium and triazole fungicides on the postharvest primary metabolites of ‘Braeburn’ fruit, and to offer a better understanding of the biochemical processes behind internal browning. The primary metabolites of ‘Braeburn’ fruit cortex samples at harvest and after 2 weeks, 4 weeks, 4 months and 8 months of storage at browning-inducing conditions were analyzed using GC–MS. No significant difference in the primary metabolites was observed between the different levels of the applied preharvest applications. Early during storage, fruit developed browning, with the severity increasing with storage duration. This was correlated with a group of primary metabolites that showed either an increase (e.g., alanine, galactose, mannitol, sorbitol, xylose) or a decrease (e.g., malate, sucrose) in concentration with time. Radial distribution of the metabolites in the fruit tissue was also observed; some metabolites (e.g., galactose, mannitol) were higher in concentration in the inner cortex, while the concentrations of other metabolites (e.g., mannose, sucrose) were higher in the outer cortex.