Enhancing Flowability and Compactibility of Glutinous Rice Starch Through Co-Precipitation: A Central Composite Design Approach

Abstract

Purpose

Flowability and compactibility are essential properties for excipients in direct compression tablet formulations. Native starches often exhibit limitations in these aspects. They exhibit poor flow characteristics due to their small particle size and high moisture sensitivity, and their limited plastic deformation leads to low compactibility. This study aimed to optimize a co-precipitation method to enhance the flow and compaction properties of glutinous rice starch (GRS), providing an alternative excipient for direct compression. The influence of key formulation parameters on the physicomechanical properties of modified starch was investigated, and optimal conditions for achieving superior performance were established.

Methods

Co-precipitated GRS (cpGRS) was prepared by swelling native starch in an alkaline sodium hydroxide solution, followed by incorporation of excipients (polyvinylpyrrolidone K30 (PVP K30) and calcium carbonate), and subsequent acid neutralization to precipitate modified starch granules. A Central Composite Design (CCD) was employed to systematically evaluate the effects of sodium hydroxide concentration, mixing time, endpoint pH, PVP K30, and calcium carbonate concentration on the flowability and compactibility of cpGRS. The modified starch was characterized in terms of yield, Carr’s Index, Hausner Ratio, tensile strength, and disintegration time.

Results

Higher sodium hydroxide concentrations and calcium carbonate levels significantly improved flowability and compactibility, while endpoint pH influenced particle size distribution. The optimized conditions (0.43 M sodium hydroxide, 95 min of mixing, endpoint pH 6.97, 7.09% w/w PVP K30, and 14.02% w/w calcium carbonate) produced cpGRS with a tensile strength of 3.05 MPa, a disintegration time of 222.95 s, a yield of 68.80%, and improved flow properties (Carr’s Index 17.16, Hausner Ratio 1.21).

Conclusion

This optimized co-precipitation approach effectively enhances the functional properties of GRS, making it a viable excipient for direct compression tablet formulations. This study provides a novel starch modification strategy that broadens the application of rice-derived excipients in pharmaceutical sciences.