IMAGE-ANALYSIS STUDIES OF WATER TRANSPORT AND DIMENSIONAL CHANGES OCCURRING IN THE EARLY STAGES OF HYDRATION IN CROSS-LINKED AMYLOSE MATRICES

The purpose of this work was to monitor and quantify water transport a nd dimensional changes occurring in the early stages of hydration in c ross-linked amylose (CLA) matrices using image analysis technique. Sam ples were prepared by direct compression of CLA-6 powder to obtain mat rices of 0.17 cm thickness and 1.295 cm in diameter. A surface gel lay er was formed quasiinstantaneously. The gel expansion was then constra ined and the material continuity caused the outer gel layer to be in a state of biaxial compression and the internal core in a state of biax ial tension. A diffusion front preceded the gel-glass interface even i n the early stages of hydration, A delayed stress-release occurred thr ough a radial expansion of the tablet interior. This relaxation coinci ded with the time at which the axial diffusion fronts met. The dimensi onal changes had a marked impact on the kinetics of water uptake in CL A-6 tablets in early stages of hydration. (C) 1998 Elsevier Science B. V.