BROWNING OF APPLE CORTEX DURING CA STORAGE: A PROTEOMICS APPROACH

During long term storage of apple, physiological disorders may occur. One major group of internal disorders is characterized by flesh browning. The susceptibility to flesh browning is cultivar, batch and season dependent and is caused by a combination of pre- and postharvest factors. This can result in considerable economic losses with incidence levels up to 40%. ‘Braeburn’ and ‘Kanzi’ are commercial apple cultivars in Belgium that are prone to browning. An important influencing factor is the controlled atmosphere storage of apple. The final goal of this research project is to discover a biomarker for the development of browning in ‘Braeburn’. In this experiment we focus on how the proteome changes during storage. Apples were picked and samples were taken immediately after harvest and after two weeks, two months and four months of storage under an atmosphere and temperature combination known to induce browning. Proteins were extracted using a phenol extraction and quantified with a modified Bradford procedure. For each moment in storage the four least brown apples were sampled and after tryptic digestion, analysed using tandem mass spectrometry. Those measurements were run in 2 modes, one most suitable for identification of peptides and their corresponding proteins, the other one for quantitative analysis of the samples. To increase the identification rate of the samples ran in quantitative mode, a tool was developed to link database search results (gained from identification runs) with the less qualitative spectra of those samples ran in quantitative mode.