Microcrystalline cellulose-water interaction - A novel approach using thermoporosimetry

Purpose. To study the physical state of water in microcrystalline cellulose (MCC) and in silicified microcrystalline cellulose wet masses and the effe ct of granulation on different water fractions. Methods. Thermoporosimetry, together with the solute exclusion technique, w as used to measure different water fractions and pore size distributions of wet granules. To understand the effect of granulation on the physical stat e of water, both ungranulated and granulated wet masses were studied. In ad dition, dynamic and isothermal step melting procedures were compared. Results. Four distinct fractions of water (nonfreezing, freezing bound, fre e, and bulk water) could be detected in MCC wet masses. Granulation decreas ed the volume of bulk water and increased the volume of freezing bound and free water. Consequently, granulated wet masses were able to hold more wate r inside the particles compared to ungranulated wet masses. Thus, granulati on had a similar effect on MCC as beating has on cellulose fibers in the pa permaking process. Conclusions. Thermoporosimetry and solute exclusion increased the understan ding of MCC-water interaction and showed how the physical state of water in MCC wet masses changes during granulation.