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 effect of granulation on different water fractions. Methods. Thermoporosimetry, together with the solute exclusion technique, was used to measure different water fractions and pore size distributions of wet granules. To understand the effect of granulation on the physical state of water, both ungranulated and granulated wet masses were studied. In addition, dynamic and isothermal step melting procedures were compared. Results. Four distinct fractions of water (nonfreezing, freezing bound, free, and bulk water) could be detected in MCC wet masses. Granulation decreased the volume of bulk water and increased the volume of freezing bound and free water. Consequently, granulated wet masses were able to hold more water inside the particles compared to ungranulated wet masses. Thus, granulation had a similar effect on MCC as beating has on cellulose fibers in the papermaking process. Conclusions. Thermoporosimetry and solute exclusion increased the understanding of MCC-water interaction and showed how the physical state of water in MCC wet masses changes during granulation.