Kinetics of browning during accelerated storage of sweet whey powder and prediction of its shelf life

Sweet whey powder (SWP) of different pH was prepared by exposing native SWP to acetic acid vapors in a desiccator. Samples were subjected to accelerated browning at temperatures of 40, 60 and 80 °C in sealed vials and the rate of color formation was measured. Sample lightness decreased over time and the rate of decrease was faster at higher temperature and lower pH. Results were modeled using a pseudo-first-order reaction kinetic equation. The shelf life of SWP was estimated using a time–temperature plot. Increasing the temperature and decreasing the pH strongly decreased the shelf life from greater than 2 years at 53 °C for native SWP (pH∼6.3) to 5.2 days at 60 °C for intermediate acid SWP (pH∼5.0). A time–temperature–tolerance approach involving the practical storage life was used to predict the impact of temperature abuse during manufacture, transportation or storage.