Determination of surface energies of hot-melt extruded sugar–starch pellets

Abstract

Hot-melt extruded sugar–starch pellets are an alternative for commercial sugar spheres, but their coating properties remain to be studied. Both the European Pharmcopoeia 8.6 and the United States Pharmacopoeia 40 specify the composition of sugar–starch pellets without giving requirements for the manufacturing process. Due to various fabrication techniques, the physicochemical properties of pellets may differ. Therefore, the adhesion energies of three coating dispersions (sustained, enteric and immediate release) on different types of pellets were investigated. In this context, the surface energies of various kinds of corn starch (normal, waxy, high-amylose) and sucrose pellets were analyzed using the sessile drop method, whereas the surface tensions of the coating dispersions were examined using the pendant drop method. The adhesion forces were calculated from the results of these studies. Furthermore, sugar spheres were characterized in terms of particle size distribution, porosity and specific surface area. An increase of the pellets’ sucrose content leads to a more porous surface structure, which gives them an enhanced wetting behavior with coating dispersions. The adhesion energies of extruded sugar–starch pellets are similar to those of commercial sugar spheres, which comply with pharmacopeial requirements. Both types of pellets are equally suited for coating.

Keywords:

• Contact angle
• hot-melt extrusion
• sugar–starch pellets
• surface energy
• wetting

Acknowledgements

The authors would like to thank Leistritz Extrusionstechnik GmbH (Nuremberg, Germany) for kindly providing the extrusion equipment, Roquette Frères (Lestrem, France) and Südzucker AG (Mannheim, Germany) for supplying various starches and sucrose, and Krüss GmbH (Hamburg, Germany) for providing the Drop Shape analyzing system in Hamburg. The authors also would like to express thanks to Prof. Dr. Richard Süverkrüp (University of Bonn, Pharmaceutical Technology, Germany) for giving his opinions and support towards this study.

Disclosure statement

The authors report no declarations of interest.

Notes

1 The term surface energy is referred to both solids and liquids, whereas surface tension corresponds only to liquids.