Kinetics of fluorescence formation in whole milk powders during oxidation

Changes in the fluorescence and peroxide value of whole milk powders were studied during storage at 37, 50, 60 and 70°C. The fluorescence of oxidized whole milk powders showed an excitation maximum at 350 nm and an emission maximum at 440 nm. The fluorescent compounds were soluble in the organic phase of chloroform–methanol (2:1, v/v), and the intensity increased in proportion to both storage time and temperature. Fluorescence kinetics of whole milk powder oxidation showed a zero-order increase, and the rate followed an Arrhenius relationship with activation energies in the range of 50–70 kJ/mol. Experimental kinetic equations were derived to predict the fluorescence intensity in whole milk powders due to oxidation at different times and temperatures.