Acidity in coffee: a flavoromics approach comparing multiple extraction methods

This PhD thesis investigates coffee acidity through a multidisciplinary approach combining chemical analyses and sensory evaluation. Four main experiments were carried out. In experiment 1, a new analytical method using solid-phase extraction (SPE) and HPLC-DAD was developed and validated to quantify organic acids, chlorogenic acids and caffeine in espresso coffee. The method was applied to C. arabica samples with different roasting levels (light, medium, dark) to study chemical changes due to roasting. Experiment 2, part of the Pure Brew project, explored how different filter coffee brewing methods affect the composition of volatile and non- volatile compounds. Eight coffee brewing methods were compared, focusing on the influence of filter material, shape and brewing parameters. In experiment 3, two novel malic acid derivatives (2-IPMA and 3-IPMA) were identified and quantified using HPLC-MS/MS in green, roasted and espresso coffee. The study highlighted the role of postharvest processing (natural, washed, honey) in influencing their concentration and proposed 2-IPMA as a potential marker of fermentation. While experiment 4 applied an untargeted flavoromics approach to identify chemical drivers of perceived acidity. Thirteen C. arabica samples with different origins and postharvest methods were analyzed by a trained panel and profiled using HPLC-QToF-MS. Multivariate statistical models revealed compounds related to acidity intensity. Overall, this research provides new insights into the chemical basis of coffee acidity and how it is influenced by processing and brewing practices.