Study of lipid-protein interaction using pulsed NMR

Pulsed nuclear magnetic reasonance (NMR) measurements were made on freeze-dried emulsions containing fat and protein. It was demonstrated that this method can be used to determine the degree of lipid-protein interaction in the samples. Interaction is maximized near the isoelectric range of the protein, which supports the theory that hydrophobic interactions are predominant. Triglycerides and fatty methyl esters interact to nearly the same degree as do free fatty acids, which indicates that the carboxylate group plays a minor role in interaction. Degree of interaction increases when the emulsions are homogenized at higher pressures. There is an inverse relationship between interaction and foamability of the rehydrated emulsion suggesting that less protein is available for film formation after interaction. In addition, fat-protein interaction was shown to protect the protein from heat denaturation. These pulsed NMR measurements may represent an approach toward a better understanding of lipidprotein interactions in food systems.