THE EFFECT OF BREWING METHOD AND DIFFERENT ROASTING DEGREE ON PHYSICOCHEMICAL CHARACTERISTICS, TOTAL PHENOLIC CONTENT AND ANTIOXIDANT ACTIVITY OF ROBUSTA COFFEE (COFFEA CANEPHORA)

Coffee is one of the most consumed beverages in the world and an important commodity for the global market. Studies attribute many health benefits to coffee consumption, most of them linked to its antioxidant properties. However, several factors such as the cultivar, the degree of roasting and the method of preparation of the beverage influence the chemical composition and biological activity of the coffee. The aim of this study was to analyze the effect of roasting (light, medium, dark) and the brew methods (Hario V60, French Press, Clever, Aeropress, Espresso and Cold Brew) on physicochemical characteristics, total phenolic content and antioxidant activity of coffee beverage from Robusta beans (Amazonia, Brazil). Coffee beverages were prepared in a proportion of 1:20 and dilutions of 1:10, 1:40 and 1:60 were used to evaluate the color parameters (L*, a*, b*), browning index (BI= 100[x-0,31] /0,17, if x= a*+1,75xL*/ 5,645xL* + a*-0,30121xb*), dissolved soluble solids (TDS), pH and total phenolic content (Folin-Ciocalteau) and antioxidant activity (Ferric Ion Reducing Antioxidant Power, FRAP). French press coffees showed the lowest antioxidant activity among all methods (p<0.0001), in light, medium and dark roast, marked by lower concentration of darkened compounds, phenolic compounds (respectively, 1655,3±34,1; 1886,4±5,4; 1666,1±16,4 mg% gallic acid equivalents, GAE) and lower TDS and antioxidant activity (respectively, 6,23±0,05; 6,9±0,14; 6,4±0,07 mcmol Fe2SO4/mL), indicating that the isolated use of the infusion method is less efficient for the extraction of bioactive compounds from coffee. Suggesting that combined methods of infusion with percolation enhance extraction of phenolic compounds, as observed in the Aeropress (respectively, light: 3053,6±12,5; medium: 2920,6±3,1; dark: 3042±8,2 mg% GAE; p<0.001) and Clever (respectively, light: 3042,6±24,6; medium: 2583,9±25,0; dark: 2518,2±16,4 mg% GAE; p<0.001) methods. The Cold Brew extraction method also has low antioxidant activity (respectively, light: 7,17±0,02; medium: 7,47±0,04; dark: 7,50±0,05 mcmol Fe2SO4/mL; p<0.001). Using ice water extracts some compounds less effectively than using hot water. Among the extraction methods, Espresso dark roast showed the highest efficiency of extraction of phenolic compounds and antioxidant activity (respectively, 3220,2±49,7 mg% GAE and 7,50±0,05 mcmol Fe2SO4/mL; p<0.0001). However, the other roasting profiles (light and medium) of the espresso method, as well as the combined methods of Aeropress and Clever, showed high antioxidant activity in relation to the other preparation methods. The behavior of BI was similar, characterized by an increase in medium roasts and a decrease in dark roasts. It is generally considered an indirect measure of the dark-brown products formed from the Maillard reaction with typical aroma and functional properties, including antioxidant potential. However, higher values of antioxidant activity (such as the total phenolic content and FRAP) in some samples of dark roasts suggest that other substances, in addition to those produced during the non-enzymatic browning reaction, may be involved in the antioxidant potential of Robusta beans. In conclusion, these data suggest that the coffee roasting process associated with the brewing method should be considered to optimize extraction of antioxidants from coffee.