The role of Maillard reaction products isolated from barley malt by gel permeation chromatography and ultrafiltration on the antioxidant potential of pale, melano80 and black malts was evaluated. The roasting process is responsible for the polymerisation of early formed lower molecular weight compounds (<10 kDa) into high molecular weight melanoidins (>300 kDa). Melanoidins showed 3-fold higher capacity to scavenge radicals than the lower molecular weight colorants by the metmyoglobin assay. However, a significant decrease of the capacity of black malt and high molecular weight melanoidins to inhibit Fenton induced hydroxyl degradation of deoxyribose was observed. As the high molecular weight fraction, isolated from the black malt extract, exhibited 4-fold higher reducing power than the lower molecular weight fraction, our results support a pro-oxidant effect due to the catalytic formation of hydroxyl radicals in the presence of ferric ions.
Keywords: Antioxidants; Kilning; Maillard reaction products; Malt; Melanoidins; Pro-oxidants; Roasting.
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