This research aimed to evaluate the antioxidant properties of flour obtained from red alga Gelidium sp., which is underutilised nowadays in food applications. Thus, a model system consisting of minced mackerel (Scomber scombrus) muscle and aqueous flour extract was subjected to heating treatment (50 °C) for 11 days. Resulting levels on conjugated diene (CD) and triene (CT) contents, peroxide value, thiobarbituric acid index, and fluorescent compound and free fatty acid (FFA) formation were monitored at different heating times. As a result, the presence of the aqueous extract of the alga flour led to higher levels (p < 0.05) of primary lipid oxidation compounds (CD and CT assessment) and lipid hydrolysis (FFA content). Contrarily, alga flour addition led to lower (p < 0.05) fluorescent compound formation measured in the aqueous and organic fractions resulting from the lipid extraction of the fish muscle and in the supernatant medium corresponding to the heating reaction system. All effects were found to be more important (p < 0.05) with increased alga flour concentration and heating reacting time. According to the straight relationship between the interaction compound formation and nutritional and sensory values, this study opens the way to the quality enhancement of thermally treated seafood by the addition of flour extract from Gelidium sp.
Keywords: Gelidium sp.; aqueous extract; fish muscle; flour; fluorescent compounds; heating; hydrolysis; lipids; primary oxidation; secondary oxidation.