Factors influencing the properties and the stability of spray-dried Sennae fructus extracts

Objective: The objective of this study was to characterize the properties of aqueous Sennae fructus extracts prepared by spray-drying at varying process conditions.

Significance: From an industrial point of view it is essential to develop a formulation which has a constant quality over the whole period of its specified shelf-life.

Method: Sennae fructus extracts were spray-dried with different atomizing gas pressures, pump feed rates, and inlet temperatures. The extracts were analyzed for their physical properties and stored at accelerated conditions. Sennoside degradation was monitored by HPLC analysis.

Results: An increase of the atomizing gas pressure had the most pronounced influence on the decrease of moisture content and particle size. An increase of the inlet temperature led to a decrease of moisture content and particle density, as well as an increase of smooth particle amount. An increase in the pump feed rate, increased the moisture content and resulted in stable hollow spheres. The different conditions also led to smooth or wrinkled particle surfaces, and to golfball, donut, and shard particle shapes. The chemical stability of the sennosides differed from each other after storage. Stability-reducing factors were the moisture content of the samples and their hygroscopicities, as well as different particle morphologies. These factors were influenced by the inlet temperature of the spray-drying process. High inlet temperatures led to a positive influence on dryness and particle morphology and therefore on the stability of the sennosides.

Conclusions: Variation of the process conditions affected the resulting particle properties and their storage stability of Sennae fructus extract.