Interactions of autoxidizing lipids with proteins in model food systems

Abstract

The reactions of peroxidizing lipids with proteins may be important biologically either because they result in toxic or otherwise biologically active compounds in food; or because there is a actual peroxidation in vivo. In order to help understanding the interactions of autoxidizing lipids with proteins, especially to know the contribution of hexanal to these interactions as a secondary product and to find the correlation between the reactions, two model systems were constructed as follows: One model system (H system) consists of model foods with hexanal supplemented in the dessicator. Model food is a freeze dried emulsion composed of lysozyme chloride and linoleic acid (1:1 w/w). Model foods and 10 ml of hexanal in 50 ml flask were incubated in a dessicator which was adjusted to Aw of 0.75 at 37℃ in the dark chamber for 10 days. The other system (N system) was a control without hexanal. In a dark chamber two dessicators (H system, N system) were incubated concurrently. The results from the scanning of slab gels after electrophoretic separation show that the protein polymerization in H system was accelerated than control. In the light of lower values of fluorescence production by malonaldehyde cross-linking, POV and TBA values, it was certain that the protein polymerization through free radical mechanism by volatile secondary product (hexanal) and hydroperoxide was more critical in model foods rather than cross-linking by the malonaldehyde. Also in both systems it was found that TBA values and fluorescence production could be correlated with browning and/or enzyme inactivation for the first three days. And the unidentified hydroperoxide was detected in H system by the TLC.