An apparatus for the measurement of adsorbed/entrapped oxygen held by dehydrated powdered products was developed and is described in detail.The method works on the principle of sample solubilization in deaerated water with compression of the liberated gases into a calibrated chamber containing an oxygen probe.When tested on nonfat dry milk, the coefficient of variation for the method is 20%.Kinetic studies using this apparatus were performed on a model system consisting of methyl linoleate dispersed on Avicel microcrystalline cellulose and nonfat dry milk at headspace oxygen concentrations of 0.52% -10.69%.Excellent correlation was found in the model system between diene conjugation values and oxygen uptake as measured by the apparatus.Correlation coefficients between the two methods were in the range .987 -. 997.Bimolecular kinetics were found to apply to both the model system and the milk-lipid system with KB's within the range expected from studies done by previous workers at higher 02 pressures.The KB's for the cellulose model system were found to be 5 to 6 times greater than those in the milk based system. This was due partly to encapsulation of lipids in the milk during preparation and partly due to smaller surface area in the milk-based system. Mathematical models for the oxidation rate constants as a function of headspace 02 concentrations were derived for the two systems.