The effect of roasting on the total polyphenols and antioxidant activity of coffee

The total polyphenolic content and the antioxidant activity have been analyzed in ground beans of green, light, medium and dark roasted coffee by UV-VIS spectrometry. Water coffee extracts showed the highest levels of polyphenols in green and light roasted coffees where the total polyphenolic content (TPC) ranged from 49.19 ± 0.70 to 74.05 ± 0.28 and from 59.79 ± 1.45 to 38.34 ± 1.26 g GAE.kg^-1, respectively. In medium roast samples it ranged from 43.90 ± 3.07 to 74.05 ± 0.28g GAE.kg^-1 and in dark roast from 37.44 ± 0.63 to 47.41 ± 0.69 g GAE.kg^-1. The total antioxidant capacity (TAC) reached the highest values (DPPH inhibition ranging from 69.08 ± 1.33% to 78.55 ± 0.89%) in light roasted coffees. Dark roasted coffees showed both the lowest content of polyphenols as well as the total antioxidant capacity. In case of TPC, statistically significant differences (P˂0.001) have been identified between green coffee and other roasted degrees. Also, dark coffee showed statistically noticeable differences (P˂0.001) in TPC in relation to other roasted stages. Statistically important difference (P˂0.001) has been discovered between the total antioxidant capacity of dark roasted coffee and other roasting levels. The results demonstrated that roasting process affects both the oxidative activity as well as polyphenolic content.