Kinetics of moisture uptake and soluble-solids loss by puffed breakfast cereals immersed in water

Breakfast cereals readily take up moisture when immersed in a liquid medium , leading to undesirable changes in texture. The mechanism of moisture upta ke is related to both the water movement within the cereal and the ability of the cereal to hydrate. In this work, the kinetics of moisture uptake and soluble-solids loss by puffed corn and peanut butter breakfast cereals imm ersed in water were experimentally measured under isothermal conditions cov ering a wide range of temperatures (5-55 degrees C). Different mathematical models, often reported in the literature to describe soaking processes, we re applied to the experimental data. Peleg, first-order, diffusion and Weib ull models were used. The fit provided by the first two models was clearly biased, and the best results were obtained with the Weibull model. The equi librium conditions were found to be independent of temperature, whereas the rate constants showed an Arrhenius-type dependency. The relaxation phenome na, which are related to the hydration of the cereal matrix, are probably t he main controlling step of the process. Furthermore, fat content appears t o play a major role in the ability of the cereal to hydrate, with fat hinde ring the process.