Compaction Properties of Three Types of Starch

A study has been made of the compaction properties of two experimental starches, namely yam starch obtained from Dioscorea rotundata and rice starch obtained from Oryza sativa and the mechanical properties of their tablets, in comparison with those of official corn starch. The influences of the physical and geometric properties of the starch particles on the compression properties of the starches were determined. Further analysis of the compaction properties was done using density measurements, and the Heckel and Kawakita equations. The mean particle diameter and the shape factor of the starches were directly related to the loose initial density (D_o) and rearrangement at low pressures (D_A) characteristics of the starches, but inversely related to the rearrangement of the particles in the early stages of compression (D_B). The packed initial relative density (D_I) was also directly related to the particle diameter and shape factor. The three starches deform mainly by plastic flow. The values of the mean yield pressures, which are inversely related to the onset of plastic deformation in the starches were in the rank order rice>corn>yam. Another pressure term, inversely related to the amount of plastic deformation during compression, was in the rank order yam>corn>rice. The ranking of the values of both the tensile strength and brittle fracture index of tablets made from the starches was rice>corn>yam, indicating that rice starch tablets exhibited the highest bond strength and brittleness while yam starch exhibited the lowest values. The compaction properties of the experimental starches as characterized compared well with those of official corn starch. The results obtained showed that in tablet formulations, yam starch would be more useful in minimizing the problems of lamination and capping while rice starch would be more useful when high bond strength of the tablet is desired. Thus, yam and rice starches could be useful in formulations to produce tablets with desired mechanical properties for particular purposes.