Influence of spray-drying operating conditions on Rhamnus purshiana (Cascara sagrada) extract powder physical properties

The aim of this work was to study Rhamnus purshiana (Cascara sagrada) extract spray-drying in order to obtain powders with good rheological properties for direct compression (DC) and stability attributes. The experiments were carried out in a Buchi B-290 Mini Spray Dryer using colloidal silicon dioxide as carrier agent. A 2(5-1) fractional factorial statistical design was used to find adequate spray-drying operating conditions to produce Cascara sagrada powders with good flow, good compactability properties, high process yield, low moisture content, low hygroscopicity, and caking tendency. Morphology, size, structural and thermal properties of the particles were also evaluated. The operating variables studied were air inlet temperature, atomization air flow rate, pump feed rate, aspiration capacity, and feed solids concentration. The 2(5-1) factorial experimental design used was a good strategy to establish spray-drying operating conditions to produce Cascara sagrada extract powders with good properties for direct compression and high process yields. Colloidal silicon dioxide was an effective drying adjuvant. Its use in relatively high concentrations together with low atomization air flow rates improved powder flowability, increased the product's glass transition temperature, and decreased its moisture content and hygroscopicity. (C) 2010 Elsevier B.V. All rights reserved.