Extrusion/spheronization of pectin-based formulations. II. Effect of additive concentration in the granulation liquid

The aim of this study was to improve the formation of spherical pectin pellets by investigating the effect of additive concentration in the granulation liquid on the shape and size of the products as well as by identifying an optimal additive concentration.

High-methoxylated, low-methoxylated, and amidated low-methoxylated pectin types were evaluated in combination with different concentrations of methanol, ethanol, citric acid, lactic acid, and calcium chloride. Pellets were prepared in a power-consumption-controlled twin-screw extruder, then spheronized and dried. The moisture content of the extrudate was determined, and the final products were characterized by image analysis and sieving analysis. A cloud point test was employed for the identification of an optimal additive concentration.

The concentration of additive in the granulation liquid affected the moisture content of the extrudate and the shape, size, and mechanical stability of the pectin pellets. Improvements in the pellet characteristics are dependent on the pectin type employed. The 2 low-methoxylated pectins were more sensitive to concentration changes than was the high-methoxylated type. Above a certain threshold concentration, the quality of the pellets are improved. This additive concentration differs according to type of pectin and type of additive.

It was demonstrated that there is a concentration-dependent interaction between pectin and substances added to the granulation liquid that can be utilized to improve the formation of spherical pectin pellets.