The effects of different amounts of sugar addition on the aroma and aroma-active compounds of Turkish coffee

In this study, the effects of different levels of sugar addition on the aroma compounds, aroma-active compounds, total phenolic content, and antioxidant activity of Turkish coffee were investigated. For this purpose, Turkish coffee samples were prepared using 100% Brazil-origin medium-roasted Arabica coffee beans with four different sugar concentrations: unsweetened (0 g), low sugar (2 g), medium sugar (4 g), and high sugar (8 g), combined with 5 g of ground coffee and 75 mL of water. Aroma compounds were extracted using the Solvent-Assisted Flavor Evaporation (SAFE) method and identified by Gas Chromatography-Mass Spectrometry (GC-MS). Aroma-active compounds were determined through Aroma Extract Dilution Analysis (AEDA), and sensory evaluations were conducted by a trained panel of seven individuals. As a result of the analyses, a total of 63 aroma compounds were identified, 25 of which exhibited aroma-active properties. The identified aroma compounds were classified into 14 different chemical groups, including pyrazines, furans, ketones, lactones, pyrroles, phenols, alcohols, acids, furanones, pyridines, pyrrolidines, aldehydes, pyranones, and indoles. Among them, pyrazines (e.g., 2-methylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine), furans (e.g., 2-furanmethanol, furfural), ketones (e.g., 2,3-butanedione), lactones (e.g., γ-butyrolactone), and pyranones (e.g., maltol) were found to be the most dominant and characteristic aroma compounds. As the sugar content increased, the concentrations of these key compounds and their odor dilution (OD) factors determined by AEDA decreased. This reduction was attributed to the increase in matrix viscosity caused by sugar and the limitation of volatility due to physical interactions (e.g., hydrogen bonding, aroma-sugar complexes) between sugar and aroma compounds. Sensory analysis results indicated that characteristic aromas of coffee such as "roasted/cooked", "nutty", "fruity/flowery", and "burnt/smoky" were perceived more intensely in unsweetened and low-sugar samples. In addition, a significant decrease in total phenolic content and antioxidant activity was observed with increasing sugar levels. In conclusion, the addition of sugar to Turkish coffee has been found to have significant effects on the aroma profile, as well as on aroma-active and bioactive compounds; plain coffee and coffee with a low level of added sugar were determined to be more favorable in terms of both sensory quality and aromatic characteristics.