Acids in Brewed Coffee: Chemical Composition and Sensory Threshold &Nbsp;
Posted: 24 Aug 2023
Coffee brewed on light-roast coffee beans has emerged as a recent trend among specialty coffee drinkers. The acidity of such light-roast coffee, and coffee in general, is an important sensory characteristic, as there is a clear correlation between the roast level and perceived acidity in brewed coffee. The acidity is believed to be strongly linked to the content and composition of organic acids in coffee. Nevertheless, there is limited literature on acid content in brewed coffee and on the relevance of specific acid concentrations to sensory perception. In this study, we determined the concentrations of acids and sugars by chromatographic methods, and further determined 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). The concentration of all individual acids except one (formic) either significantly decreased (citric, malic, and chlorogenic acid) or increased (acetic, lactic, phosphoric, quinic, and glycolic acid) systematically with an increasing roast degree. The concentration of citric acid was found to be much higher for Brazil coffees. Only citric acid could be clearly detected in the threshold test in concentrations (<0.16g/L) above the measured concentrations (0.23-0.60g/L). In contrast, the sensory detection thresholds for malic, acetic, lactic, and phosphoric acid were determined to be around the actual concentration of said acids in the coffee, indicating that these compounds contribute to overall coffee acidity but are unlikely to individually be perceived in coffee. Furthermore, none of the five acids were correctly recognised and identified in coffee spiked with the average concentration found in brewed coffee by coffee experts. Combined, the results question the direct relation between individual organic acids and acidity in coffee and point towards a more complex understanding of perceived acidity.
Suggested Citation: Suggested Citation