Oscillatory water sorption test for determining water uptake behavior in bread crust.

In this work, water sorption kinetics of bread crust are described using an oscillatory sorption test in combination with a Langmuir type equation. Both kinetic and thermodynamic information could be obtained at the same time. An advantage of applying a Langmuir type equation for a quantitative description of the water uptake kinetics is that no prior knowledge is necessary with respect to shape and surface area of the sample. It was shown that adsorption and desorption of water to the bread crust particle surface is much faster than the experimental time used (15 min at minimum). From this, we may conclude that diffusion of water into the solid matrix is the rate-limiting step in the water sorption process. The method also allows one to calculate a Gibbs free energy. The method is suitable for use up to relative humidities of 60%.