Evolution of antioxidant activity in heated coffee brew

Coffee brew (CB) was prepared using a standard filter coffeemaker (24 g of ground roasted coffee, 400 mL of water). The glass flask containing CB was maintained in the coffeemaker hot-plate at 75 ºC. The antioxidant activity was monitored and assayed during 8 h by means of DPPH, FRAP, total phenols content, browning index and voltammetry. Antioxidant activity showed a fast increase during the first 1.0-1.5 h. Heating times longer than about 2 h produced nearly constant values for FRAP, total phenols and caffeine contents, but DPPH and oxidative capacity by voltammetry decreased probably due to the oxidation of antioxidant compounds by environmental stress. It was postulated that Maillard reactions products were formed in the heated CB, probably due to the degradation of CGAs that complexed with proteins/polysaccharides, giving way to potent antioxidants compounds such as melanoidins. The results of this work showed that the antioxidant activity increased with CB heating time.

Keywords: coffee brew, heating time, antioxidant activity, Maillard reactions products.