Effect of milk fat and total solids concentration on the kinetics of moisture uptake by ready-to-eat breakfast cereal

When immersed in milk, breakfast cereal easily take up moisture, lose their brittle texture and become soggy. Earlier comparative analysis of the moisture sorption by breakfast cereal immersed in water and milk indicated that milk solids might play an important role on the sorption kinetics. In this work, the moisture uptake by ready-to-eat corn breakfast cereal immersed in milk solutions, reconstituted from whole and skimmed milk powder, was measured under isothermal conditions at 5, 30 and 55 degrees C. Dilutions between 0.25 and 1.5 were tested, with the factor of dilution 1 corresponding to the standard recommended by the milk powder manufacturer. The Weibull probabilistic model adequately fitted the experimental data by appropriate choice of its variable parameters. The dependence of the model parameters on temperature and total solids concentration was assessed for both skimmed and whole milk. Fat was found to play a major role on the process mechanism, which was attributed to the deposition of a fat layer at the solid matrix surface, hindering water and solids uptake. Yet, for short times, moisture uptake proceeded at a similar rate both in skimmed and whole milk.