CHOLESTEROL OXIDATION IN WHOLE MILK POWDERS AS INFLUENCED BY PROCESSING AND PACKAGING

The effects of various spray-drying processes (direct-fired heating, h igh levels of oxides of nitrogen (NO(x)); direct-fired heating, low NO (x); indirect electrical heating) and packaging systems (polyethylene pouches and crimp-sealed glass vials, with and without oxygen absorber s) on the oxidative stability of lipids in whole milk powders during s torage were studied. Lipid oxidation, including the generation of chol esterol oxidation products, was greatest in samples processed by high NO(x) direct-fired driers. Oxygen absorbers effectively controlled cho lesterol oxidation during the six month storage period, even in those samples from the high NO(x) drying system. There was a positive correl ation (r = 0.89) between lipid oxidation and the concentration of chol esterol oxides in the samples. It was concluded that the stability of whole milk powders during storage can be improved by using low NO(x) d rying processes and by packaging in oxygen-impermeable packaging syste ms containing oxygen absorbers.