Extraction of Non-Volatile Chemical Compounds in High-Quality and Traditional Coffee

Abstract

Coffee contains different volatile and non-volatile compounds, which are responsible for its characteristic flavor and aroma attributes. The extraction of non-volatile compounds from high-quality and traditional coffee by different methods was evaluated to determine the chemical compounds that discriminate between coffees types. Standard methods of preparing the coffee drink by consumers were evaluated. Method A corresponded to boiling water with coffee, and method B to the strained coffee method. Extraction with different solvents did not distinguish the compounds chosen as markers for coffees. In addition to being non-toxic and low-cost, water was the most suitable solvent, conforming to the principles of green chemistry while enabling direct comparison with sensory analysis. The total dissolved solids, percentage extraction, and non-volatile compounds were quantified to select the most satisfactory extraction method. The TDS value ranged from 1.7 to 3 between methods and coffee types, and the extraction percentage ranged from 25 to 45%. Significant differences in the extracts obtained using methods A and B high-quality versus traditional coffees were detected using the Student’s t-test. Although method A extracted the chemical compounds in more substantial amounts, method B was also efficient in extracting the compounds and was easily executed given its similarity to the usual way of preparing coffee beverages used by consumers. The evaluated non-volatile compounds were identified in both high-quality and traditional coffee samples. In the chosen extraction method (method B), the average concentrations in mg 100 g-1 of the sample found for the compounds were: 5-hydroxymethylfurfural (11±0.5), 3,4-hydroxybenzoic acid (62±4), catechin (58±5), 4-hydroxybenzoic acid (58±2), caffeine (1152±44), chlorogenic acid (598±23), caffeic acid (0.7±0.1), and gallic acid (3±0.2).