The oxidative stability of an algal oil emulsion dispersed in water, or fluid milk of varying fat contents, was assessed from measurements of lipid hydroperoxide and propanal concentration. All of the milk samples, independent of their milk fat content, were stable compared to the aqueous samples. The extent of oxidation was unaffected when sodium azide (200 ppm) was added to inhibit microbial growth. Added iron (100 ppm) accelerated the oxidation rate in the aqueous samples, but had no effect on the milk samples. The antioxidant properties of milk were ascribed to the iron binding of casein. Added protein antioxidants (0.8 wt%) [i.e. sodium caseinate, whey protein isolate (WPI) and thermally denatured WPI] had minimal effects whereas EDTA and ascorbic acid (160 ppm) were effective antioxidants.
Bibliographical noteFunding Information:
This work was funded by a grant from the USDA-IFAFS program (2001-52102-11256). We are grateful to Bonnie Ford for assistance with the compositional analysis of the milk and to Laura Nattress for assistance with the sensory studies and statistical analysis. We are also grateful to Drs. Eric Decker, Julian McClements and Habibollah Faraji at the University of Massachusetts for many helpful discussions.
- Oxidative stability
- Sodium caseinate
- Whey protein
- ω-3 fatty acids