Discrimination between Arabica and Robusta Coffees Using Hydrosoluble Compounds: Is the Efficiency of the Parameters Dependent on the Roast Degree?

Coffea arabica (arabica) and Coffea canephora (robusta) are the most important coffee species. Arabica has higher commercial value and, in general, more favorable sensory characteristics. After roasting, analytical methods are required to differentiate species. Blends with different proportions of arabica/robusta coffees, roasted at three degrees were studied. Color parameters and the levels of chlorogenic (5-CQA) and nicotinic acids, caffeine, and trigonelline were evaluated. Hydrosoluble compounds were analyzed by their efficiency to discriminate coffee species, considering different roast degrees. Caffeine was a good discriminator, regardless of roast degree. The roast degree influenced the efficiency of discrimination of the other hydrosoluble compounds. A model using color parameters and the variables Ratio (5-CQA/caffeine contents ratio) and Sum (sum of nicotinic acid and trigonelline contents) was proposed to the estimation of roasting degree. Considering the use of heat-labile compounds, the discrimination among coffee species should be carried out in two steps: first, the characterization of roasting degree, and subsequently the appropriate parameters are defined for each roasting degree. Thus, the combined use of color parameters and hydrosoluble compounds could be useful to help the differentiation of coffee species in blends of roasted samples