Hydratationseigenschaften von Zellwandmaterialien und Ballaststoffen

The knowledge of structure dependent hydration properties of cell wall materials and dietary fiber preparations plays an important role for their application as swelling and thickening agent and for their physiological effects. The hydration properties are influenced by the type of raw materials as well as by size, form, composition and physical state of the particles obtained during the manufacture of the materials. Furthermore, the hydration properties can be influenced by the plasticizing effect of the rehydration solution used and by temperature, time and external stress occurring during rehydration process. The efficient factors are not independent from each other, but they influence mutually and the relationships found are complex and multivariate. This complicates the prediction of hydration properties of cell wall materials and dietary fibers markedly. However, certain connections can be determined using model investigations carried out under simplified conditions. This way, the propability can be increased to prepare materials with tailor-made properties. It was found, that the predrying treatments play a key role at the preparation of materials with specific properties. Undesirable state transitions (shrinkage, aggregation etc.), occurring during drying, are often reversible by application of external stress during rehydration procedure. It can be recommended to characterize the hydration properties completely by determinations of swelling, water retention capacity and water uptake and, additionally, by using kinetic methods for the evaluation of swelling/water uptake and for water release under external stress.