356 Starch-protein-lipid interaction in a model system.

G., Zhang and B. R. Hamaker. Department of Food Science, Purdue University, West Lafayette, IN 47907.

Starch-protein-lipid interaction in a model system that was composed of sorghum starch, whey protein and free fatty acids was studied. A Rapid Visco-Analyzer (RVA) was used to examine the paste viscosity profile changes. A viscosity peak formed during the RVA cooling stage when starch, whey protein and free fatty acid were present together in the system. Normal corn starch behaved similarly. The cooling peak viscosity increased in the order of palmitic acid, oleic acid, linoleic acid and lauric acid when protein was present in the system. The degree of syneresis of sorghum starch was also affected by starch-protein-lipid interaction. When protein was present in the system, palmitic acid, oleic acid and linoleic acid increased the degree of syneresis by 7, 5, 0.5 times while lauric acid decreased it by 1.2 folds. DSC results showed that whey protein decreased the enthalpy of the starch-lipid complex by 20–30% except when linoleic acid was used. X-ray diffraction data showed more pronounced V-type crystal pattern of starch-lipid complex when protein was present. Complex index (CI) experiments also showed less complexations between starch and all free fatty acids tested when whey protein was present. Starch-protein-lipid interaction not only affected formation of the starch-lipid complex, but the functionality of starch was changed in terms of paste and gel properties.