29B-33 |
The antioxidative stability of fish oil-in-water emulsions containing continuous phase protein |
H. FARAJI, D. J. McClements, and E. A. Decker. Dept. of Food Science, Univ. of Massachusetts, Amherst, Chenoweth Lab., Box 31410, Amherst, MA 01003-1410 Whey protein isolate (WPI), soy protein isolate (SPI) and sodium casenate (CAS) can be used to stabilized oil-in-water emulsions. However the impact of these proteins in the continuous phase of emulsions on oxidative stability of emulsions has not been defined. WPI-stabilized menhaden oil-in-water emulsions (pH 7) were prepared by high-pressure homogenization. In some experiments WPI was removed from the continuous phase of the emulsions through repeated (3x) centrifugation and resuspention of the emulsion droplets (washed emulsion). WPI, SPI and CAS were added back to the continuous phase of washed emulsion. The oxidative and physical stability of the emulsions were determined using lipid hydroperoxide, headspace propanal, particle size and zeta potential. WPI-stabilized emulsions were made using different protein concentrations (0.25-1.5 %). Continuous phase protein concentration increased with increasing WPI concentrations. In addition, increasing WPI concentrations increased the oxidative stability of emulsions. Unwashed emulsions were more oxidatively stable than washed emulsions suggesting that continuous phase proteins were antioxidative. When WPI was added back to the continuous phase of washed emulsions the oxidative stability of the emulsion were approximately equal to unwashed emulsions with similar continuous phase protein concentrations. Similarly, SPI and CAS added back to the continuous phase of washed WPI-stabilized emulsion resulted in inhibition of lipid oxidation. Oxidative stability of the emulsions with different continuous phase proteins was in order of SPI>CAS>WPI as determined by both hydroperoxide and headspace propanal formation. Zeta potential measurements showed that WPI, SPI and CAS were able to chelate and remove iron from surface of negatively charged BSA-stabilized emulsion droplets. This research shows the important role of proteins in the continuous phase of emulsion in the inhibition of lipid oxidation. Continuous phase proteins could potentially be used to protect omega-3 fatty acids, which are highly susceptible to oxidative deterioration.
Session 29B, Food Chemistry: Lipids, antioxidants and emulsifiers
|