We found an effective roasting method that enhances the effects on various radical scavenging activities of polysaccharide (alginic acid) derived from the marine brown alga Lessonia trabeculata. These enhancing effects were observed by a roasting treatment under relatively high temperature conditions (160ºC and 180ºC), which were measured by (i) a stable radical compound diphenylpicrylhydrazyl (DPPH), (ii) a hydroperoxide generating system of linoleic acid autooxidation, and (iii) an opsonized zymosan (Opz)-induced oxygen radical generating system in human blood neutrophils. Although a significant enhancing effect of the roasting treatment on the radical scavenging activity of the alginic acid itself was not detected under relatively low temperature conditions (100ºC and 130ºC), the roasting treatment of a mixture of alginic acid and several specific amino acids caused considerable radical scavenging activities under the same roasting conditions. When alginic acid was roasted at relatively high temperatures (160ºC or 180ºC), the mixture of the alginic acid and specific amino acids exhibited much higher radical scavenging activities than did the alginic acid alone. The significance of this finding is discussed from the viewpoint of healthy food science.
Keywords: alginic acid; amino acid; radical-scavenging activity; roasting treatment.