Acids in brewed coffee: Chemical composition and sensory threshold

Perceived acidity in brewed coffee is an important sensory characteristic and is believed to be linked to the organic acid content and composition. Nevertheless, there's limited literature on the acid composition in brewed coffee. In this study, we determined the concentrations of acids, the sensory detection threshold and recognition for selected acids in brewed coffee, using samples varying in roast degrees (light, medium, dark) and geographical locations (Brazil, Bolivia, Kenya). Our findings reveal either a significant systematic decrease (citric, malic, chlorogenic acid) or increase (acetic, lactic, phosphoric, quinic, glycolic acid) with an increasing roast degree. Citric acid was the only compound with a sensory detection threshold above measured concentration. In contrast, malic, acetic, lactic, and phosphoric acids exhibited sensory detection thresholds around their actual concentrations, suggesting their contribution to overall coffee acidity without individual recognition. None of the acids were significantly recognized in brewed coffee spiked with average concentrations found in brewed coffee. These results challenge the direct association between specific organic acids and perceived acidity, pointing to a more complex understanding. Our findings contribute to advancing the comprehension of coffee flavour complexity and pave the way for future investigations into the multifaceted nature of perceived acidity in coffee.