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Separation and Purification Technology, Volume 143, 25 March 2015, Pages 152-160.
Chung-Hung Chan, Jian-Jiun Lim, Rozita Yusoff, Gek-Cheng Ngoh.
Centre for Separation Science and Technology (CSST), Department of Chemical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia.
Abstract
By considering the absorbed power and energy based on heating power profile during extraction, a generalized model with washing coefficient (b), diffusion coefficient (k) and predictive parameter namely absorbed power density (APD) was developed for microwave-assisted extraction (MAE) at any operational heating modes. To study the model, MAE of flavonoids from cocoa (Theobroma cacao L.) leaves was conducted using the heating modes (constant-power, two-steps-power, intermittent-power and constant-temperature) at various microwave power (100–300 W) and extraction temperature (50 °C and 70 °C). The results shows that the model (b = 0.5595 and k′ = 0.01279 mL/J) is able to predict the normalized extraction yields of MAE at any heating modes, heating power, microwave system, extraction scale and batch of plant sample with less than 4% discrepancy. The accuracy of the prediction relies on particle size of sample (0.25–0.60 mm), type of extraction solvent (85% aqueous ethanol) and solvent to feed ratio (50 mL/g).
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Significance statement
Microwave-assisted extraction (MAE) technique is known to be efficient to extract bioactive compounds from plants in terms of extraction time and solvent consumption. However, the technique is yet to be industrialized due to lack of reliable model to predict the extraction behavior. Empirical model incorporated with energy-related parameters such as absorbed power density (APD) and absorbed energy-density (AED) exhibits predictive capability as these intrinsic parameters are able to characterize the extraction kinetics of MAE and its progress to reach equilibrium state, respectively. By analyzing the APD and AED values based on the heating power profile during the extraction, a generalized MAE model can be developed to predict the normalized extraction yield profiles at any heating modes, heating power, microwave extractor, extraction scale and batch of plant sample. Calibration of the model parameters using one extraction profile is required when applying the model for different species of plant, extraction solvent, solvent-to-sample ratio and particle size of sample. This generalised model is useful for scaling up and optimization of the MAE process.
Figure legend
Steps required to develop generalized energy-based MAE model.
