Quantum chemical descriptors in the formulation of pectin pellets produced by extrusion/spheronisation.
The objective of this study was to employ quantitative structure-activity relationships (QSAR) to relate calculated molecular descriptors of granulation liquid additives to improvements in the size of pectin pellets produced by extrusion/spheronisation. Quantum chemical descriptors were calculated for a large number of candidate additives. Based on a principal component analysis (PCA) of descriptors of the candidates, a few substances were selected. The most suitable concentration for each additive was found, and pellets were prepared by an extrusion/spheronisation process. Three pectin grades of different methoxy and amide substitution were tested and the quality of the pellets was evaluated based on size. PLS models were constructed to identify the molecular properties that were most important in producing short, nearly spherical pellets. The results show that quantum chemical descriptors can be a useful tool in the formulation of pectin pellets. Acceptable models relating additive properties and pellet size were achieved. Independent of the pectin grade, the two most important factors favouring formation of small spherical pellets were a small molecular size and a strong hydrogen bond forming ability of the additive molecules.