29B-30 |
Physical and oxidative stabilities of different proteins-stabilized corn oil-in-water emulsions |
M. HU, D. J. McClements, and E. A. Decker. Dept. of Food Science, Univ. of Massachusetts, Amherst, Chenoweth Lab., Box 31410, Amherst, MA 01003-1410 Surface active proteins have been used as emulsifiers not only to form physically stable emulsions but also to increase oxidative stability of oil-in-water emulsions. However, differences in ability of different protein sources to produce emulsions with good physical and oxidative stabilities are not understood. Thus, the objective of this study was to investigate the physical and oxidative stability of corn oil-in-water emulsions stabilized with caseinate (CAS), whey protein isolate (WPI) and soy protein isolate (SPI) at pH 3. A coarse emulsion containing protein (0.2-1.5% CAS, or WPI, or SPI), acetate-imidazole buffer (pH 3) and corn oil (5%) was made by mixing with a polytron followed by homogenization. Particle size was measured to monitor physical stability, and lipid hydroperoxide and headspace hexanal were used to follow lipid oxidation. Physically stable, monomodel emulsions with 5% corn oil-in-water at pH 3 were made using 1.5% CAS, 0.5% WPI and 1.0 or 1.5% SPI, respectively. At pH 3, the oxidative stability of CAS stabilized corn oil-in-water emulsions was greater than that of emulsions made with WPI and SPI. For emulsion made with 0.5% CAS, lipid hydroperoxide concentrations were basically unchanged after 185 hr of incubation. Lipid hydroperoxides were not observed in the WPI- and SPI-stabilized emulsions after 24 hr of oxidation after which hydroperoxide concentrations increased to 113.2 and 205.5mmol/kg oil, respectively after 185 hr of storage. Hexanal formation in the emulsions stabilized with 0.5% protein exhibited similar trends with CAS-stabilized emulsions having no detectable headspace hexanal for up to 48 hr of storage while hexanal was detected in the WPI- and SPI-stabilized emulsions after 24 hr of storage. The result indicated that CAS is an excellent candidate to produce oil-in-water emulsions with both physical and oxidative stabilities. Key wards: caseinate, whey protein, soy protein, physical stability, lipid oxidation, antioxidant, emulsion.
Session 29B, Food Chemistry: Lipids, antioxidants and emulsifiers
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