Peroxyl radical scavenging activity of soluble high molecular weight fraction from coffee brews

Roasting process of coffee beans affects the final composition of coffee brew. While the presence of some of its antioxidant compounds (phenolic acids) decrease throughout the treatment, melanoidins are formed during the thermal process. Recent research into nutritional, physiological and functional properties of melanoidins has suggested that they have antioxidant activity. Instant coffees produced from roasted coffee beans were obtained from a company coffee in three different roasting degrees: light (CTn 110), medium (CTn 85) and dark (CTn 60). Melanoidins of high molecular weight (> 10 000 Da) were obtained from each coffee, as well as pure melanoidins by incubation in 2M ClNa and ultrafiltration. CGA contained in extractes of different melanoidins (1 mg/ml) was measured by HPLC. Peroxyl radical scavenging activity of melanoidins and pure melanoidins were tested using a procedure to inhibite the peroxidation of linoleic acid. Antioxidant efficiency (AE50, ml/min/mg) was calculated as the slope of the time of inhibition at 50% (min) against concentration (mg/ml). No significant differences were found between melanoidins and pure melanoidins in the different roasting degrees. Peroxyl radical scavenging activity of melanoidins from coffee brew is mainly due to the chelated compounds by ionic binds.