Optimization and kinetic modelling of total water extracts and water soluble proteins in root extracts of Eurycoma apiculata by microwave assisted extraction

Abstract

Tongkat Ali is a well-known plant for its’ various bioactivities for human health. However, Tongkat Ali processing suffer from low yields and time consumption. Therefore, this study had been done to investigate the water soluble extracts (WSE) and water soluble proteins (WSP) in water extracts of Eurycoma apiculata that were obtained by microwave assisted extraction (MAE) to accomplish increases in the yields with high efficiency and less time consumption. The study was based on a circumscribed composite central design (CCCD) based on four factors, namely the radius of particle size (P), temperature (T), microwave power (W) and irradiation time (i). The CCCD was successful in identifying the optimal condition for E. apiculata extraction by MAE. Results illustrated that the optimum conditions for obtaining the maximum WSE yield (6.932 ± 1.002%) were (P: 0.0254 mm, T: 61 °C, W: 430 W and i: 19 min) while for the maximum yield of WSPs (15.853 ± 0.697%) were (P: 0.0254 mm, T: 46 °C, W: 270 W and i: 19 min). Kinetic investigations were based on the comparison the second order extraction rate, Peleg and the two site kinetic model for the WSPs. Results revealed that the best empirical models to represent the kinetic characteristics of extraction process were the second order extraction rate and Peleg models with an R2 = 0.9714. The capability of the two site kinetic model represent the extraction was enhanced by the insertion of the degradation factor (kD) which was illustrated by the increase of R2 from 0.9296 to 0.9997. The study concluded that the MAE process is a more efficient extraction process than the one-step conventional extraction method, therefore it was nominated for the upscaling of extracting proteins from E. apiculata roots in pilot and industrial scales.