Effect of degree of methoxylation and particle size on compression properties and compactibility of pectin powders

Abstract

This study examines the effect of the degree of methoxylation (DM) and particle size on compression properties and compactibility of pectin powders. A powder classification system based on sequential handling of compression parameters was applied. A single size fraction (90–125 μm) of pectin powders with DM values ranging from 5–72% was studied. For DM 25%, the effect of different particle size fractions (180–250, 125–180, 90–125, 63–90, 45–63, <45 μm) were investigated. Compression parameters were derived based on time-resolved force-displacement data using Heckel, Kawakita and Shapiro equations. Volume-specific surface area was estimated for powders and tablets. Tablet tensile strength was determined. It was found that all pectin powders displayed low degrees of particle rearrangement and relatively low degrees of fragmentation (class IIA materials). Pectin particles were found to be relatively soft, with a tendency towards softer particles for pectins of higher DM. The overall variation in fragmentation and deformation behavior was limited. Both DM and initial particle size affected the tensile strength of pectin tablets. The difference in surface hydrophobicity caused by the DM was suggested as being responsible for the variation in the mechanical strengths. The study shows that pectin grades with DM ≤ 40% are potential direct compression excipients.

Keywords::

• Sequential handling of compression parameters
• particle rearrangement
• fragmentation propensity
• plastic deformation
• tensile strength

Acknowledgments

The authors would like to thank Ritter Pharma Technik, Germany, for donation of punches. We would also like to extend our gratitude to Merete Linchausen Skar, University of Tromsø, for measuring the bulk and tapped volumes, Wolfgang Schmid, Martin-Luther-University Halle-Wittenberg, Germany, for performing the X-ray powder diffraction measurements, and Camilla Olsson and Ingvild Klevan, Uppsala University, Sweden, for guidance and technical help concerning measurements of volume-specific surface areas of both powders and tablets.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.