Scaling up of the processes for the production of optimized eurycoma longifolia extracts using dimensional analysis

Abstract

Eurycoma longifolia (EL) extract has attracted a lot of consumer interests. However, the production of EL extract has long been affected by issues of low yield and weak quality assurance. Two main processing units in EL extraction that are solidliquid extraction and spray drying, became the main focus of this research work. A study on the optimization of both processes followed by scaling up using dimensional analysis and similarity study were conducted to increase the extract yield and improve the quality of EL extract. Crude EL extract yield of 8.8 ± 0.6% (w/w) was obtained under the following optimal conditions at laboratory scale: 53 minutes of extraction, solvent to raw material ratio of 12.5:1 and raw material particle size of 0.5 to 1.0 mm. Process efficiency of 39.6% was achieved following the optimization of the spray drying process (without carrier agent) which was conducted under the following optimal conditions: air inlet temperature of 137 oC, air pressure of 8 psi and feed flow rate of 2.3 ml/min. The quality of EL extracts before and after spray drying was analysed. Spray drying resulted in loss of all marker compounds with protein being the highest at 87.7%. To improve the retention of marker compounds, microencapsulation of the extracts using a carrier agent was considered. Microencapsulation with scleroglucan (sclg) at laboratory scale resulted in the best retention of compounds with the highest process efficiency of 72.3%, which was achieved under the following optimum conditions: air inlet temperature of 185 oC, feed flow rate of 4.5 ml/min, air pressure of 8 psi and sclg concentration of 3.8% (w/w). Spray drying at the optimized air inlet temperature resulted in final product yield of 4.54% (w/w) when drying without using carrier agent and 45.0% (w/w) with sclg, respectively. To scale up the extraction process, a dimensionless number denoted as ShSc-1 number was proposed based on best fitted data. Using data at laboratory scale, ShSc-1 number of 0.0312 was obtained at optimized EL extraction conditions. Taking into account the scale up rule of P/V being constant and the scale-up factor of 7.6, pilot scale works at ShSc-1 number of 0.0376 (the closest to lab-scale value) satisfactorily produced EL extract yield of 8.65% (w/w) with an error of 0.06%. Due to the dissimilarity in the physical conditions of both spray dryers, scale up of the spray drying process was performed based on air inlet temperature only. Spray drying at the optimized air inlet temperature at lab-scale resulted in final pilot-scale product yield of 2.5% (w/w) and 29.2% (w/w) when drying without using carrier agent and with sclg, respectively. Microencapsulation process efficiency at pilot scale was 71.7%, and the quality of extracts after spray drying (with the exception of polysaccharides) were quite consistent with the quality obtained at laboratory scale. The outcome of this research work demonstrated that useful scale-up knowledge of the production of EL extract from laboratory scale to pilot scale had been successfully obtained.