Interaction of Lupinus angustifolius L. α and γ conglutins with 13-hydroperoxide-11,9-octadecadienoic acid

Food proteins suffer losses of functional and nutritional value due to reaction with lipid peroxidation products. The seed globulins conglutin α and γ from Lupinus angustifolius L. have been incubated with 13-hydroperoxide-11,9-octadecadienoic acid at pH 9 as a model of the interactions between seed storage proteins and lipid peroxidation products during storage and processing of protein-based products. The incubation lead to fragmentation and/or polymerization of the conglutins as determined by chromatographic and electrophoretic analysis. Losses of tryptophan, methionine, cysteine, proline, valine and leucine were shown by amino acid analysis. In vitro digestibility assays did not show clear differences between the digestibilities of the native conglutins before and after incubation with the hydroperoxide. Nevertheless, it is concluded that reaction with 13-hydroperoxide-11,9-octadecadienoic acid lead to a decrease in the nutritional value of the conglutins because the losses of essential amino acids were substantial. In addition, fragmentation and polymerization reactions most likely have a detrimental effect in the functional properties of the conglutins. These results highlight the deleterious effects that lipid peroxidation products have on products such as protein concentrates, isolates and hydrolysates obtained from lipid-rich seeds.