Journal articles by Chung-Hung Chan
This work demonstrated the optimization and scale up of microwave-assisted extraction (MAE) and u... more This work demonstrated the optimization and scale up of microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) of bioactive compounds from Orthosiphon stamineus using energy-based parameters such as absorbed power density and absorbed energy density (APD-AED) and response surface methodology (RSM). The intensive optimum conditions of MAE obtained at 80% EtOH, 50 mL/g, APD of 0.35W/mL, AED of 250 J/mL can be used to determine the optimum conditions of the scale-dependent parameters i.e. microwave power and treatment time at various extraction scales (100-300 mL solvent loading). The yields of the up scaled conditions were consistent with less than 8% discrepancy and they were about 91-98% of the Soxhlet extraction yield. By adapting APD-AED method in the case of UAE, the intensive optimum conditions of the extraction, i.e. 70% EtOH, 30 mL/g, APD of 0.22 W/mL, AED of 450 J/mL are able to achieve similar scale up results.
A first-ever theoretical model describing the cell rupture mechanism for microwave-assisted extra... more A first-ever theoretical model describing the cell rupture mechanism for microwave-assisted extraction (MAE) of bioactive compounds from plant samples is presented. This model incorporates the microwave heating of intracellular moisture within the plant cells using Lambert's law. It then calculates the heating time and the intrinsic energy required to pressurize and stretch the plant cells until rupture using thermodynamic relations. The attainment of cell rupture is determined from elasticity theory for solids. The simulation requires the inputs of the effective shear modulus of the plant cell wall and the incident microwave irradiation flux entering the extraction mixture. The predicted cell rupture time by the intrinsic energy validated excellently against the optimum extraction time found in experiments. This model is generally applicable over a wide extraction parameters and microwave systems.
The impacts of various methods such as mechanical grinding, ultrasonic-assisted extraction (UAE),... more The impacts of various methods such as mechanical grinding, ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE), and also sample pretreatments using acid and alkali on the microstructure of plant sample were studied for the extraction of bioactive compounds from Orthosiphon stamineus leaf. From scanning electron microscopy (SEM) analysis of the extracted sample, UAE and MAE induced significant disruption on glandular trichomes structure, which is the main site for biosynthesis of plant secondary metabolites. This improves the diffusion of bioactive compound and resulted in approximately 86-95% of the total extraction yield quantified by conventional Soxhlet extraction. Chemical pretreatments generally imparted weaker microstructures disruption thus slight improvement on the extraction yields was observed. In this case, acid reagent is more suitable for the pretreatment as the presence of alkali decomposes the bioactive compounds. In a nutshell, the performance of an extraction strongly depends on its degree of disruption on the plant sample microstructure.
![Research paper thumbnail of Assessment of Cellulosic Biomass Saccharification by Molten Brönsted Acidic 1-Ethyl-3-Methylimidazolium Hydrogen Sulphate ([EMIM][HSO 4 ]) via Kinetic Studies](https://attachments.academia-assets.com/51891734/thumbnails/1.jpg)
Ionic liquids have been employed to deconstruct and fractionate lignocellulosic biomasses because... more Ionic liquids have been employed to deconstruct and fractionate lignocellulosic biomasses because of their capacity to dissolve cellulose. However, there is limited literature reporting the use of ionic liquids in biomass saccharification, which mostly involves the addition of acid or water that conceals the true action of ionic liquid in saccharification. This article assesses the performance of molten Brӧnsted acidic 1-ethyl-3-methylimidazolium hydrogen sulphate ([EMIM][HSO4]) in saccharifying three agricultural biomasses, namely sago hampas, sugarcane bagasse, and rice husk, via saccharification kinetics. At 100 °C, [EMIM][HSO4] saccharification of the biomasses achieved equilibrium reducing sugar yields at various durations (sago hampas, 3 h; sugarcane bagasse, 1 h; rice husk, 5 h). The kinetic rate constant was obtained from model fitting, indicated that [EMIM][HSO4] showed a preference for saccharifying less recalcitrant sugarcane bagasse (37.9%) than sago hampas (7.0%) and rice husk (1.1%). Compared to H2SO4 saccharification, reducing sugar yields of [EMIM][HSO4] were consistently lower. The difference in yields might be attributed to the hydrous/anhydrous state of reaction and limited availability of component ions of the ionic liquid for dissolution and saccharification. This study demonstrates the feasible technical aspects of applying [EMIM][HSO4] to saccharify agricultural biomasses, which may lead to economic feasibility, recyclability, and cost effectiveness of ionic liquids in saccharification.
By considering the absorbed power and energy based on heating power profile during extraction, a ... more 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).
Microwave-assisted extraction (MAE) is a promising technique for the extraction of flavonoid comp... more Microwave-assisted extraction (MAE) is a promising technique for the extraction of flavonoid compounds from plants. However, it is difficult to scale up due to the complex mass transfer involved. This has prompted the study of parameters for scaling up the system by considering energy-related parameters, i.e. the nominal power density and the absorbed power density (APD). Modeling of MAE of flavonoid compounds from cocoa (Theobroma cacao L.) leaves using the film theory model was performed for this purpose. Operating parameters such as the sample particle size, the solvent-to-feed ratio, and the microwave irradiation power were also included in the kinetic study. The APD exhibited its aptitude as scaling-up parameter as it can characterize both the extraction kinetics and the extraction yields of MAE. Furthermore, it can be used as a reference for predicting the optimum extraction time of MAE under various heating conditions.
The intrinsic microwave power and energy required for optimizing MAE was investigated for the ext... more The intrinsic microwave power and energy required for optimizing MAE was investigated for the extraction of active compounds from cocoa (Theobroma cacao L.) leaves at various extraction scales. To carry out this investigation, an optimization method based on absorbed power density (APD) and absorbed energy density (AED) were developed based on the extraction mechanism of MAE using sequential single factor experiments. The optimized results are consistent with those obtained by the conventional optimization method using response surface methodology (RSM) and also comparable with that of the optimized Soxhlet extraction. The main advantage of the method is that the intensive optimum conditions obtained at solvent to feed (S/F) ratio of 50 ml/g, APD of 0.3 W/ml and AED of 300 J/ml are capable of determining the specific optimum operating conditions (S/F ratio, power, time) of the MAE at various scales of 100–300 ml with great accuracy.
Batch solvent extraction techniques have been widely explored. On understanding its potential sig... more Batch solvent extraction techniques have been widely explored. On understanding its potential significance, this article aims to review kinetics and modeling of various extraction techniques which involve assisted means including microwave-assisted extraction (MAE), ultrasonic-assisted extraction (UAE), pulse electric field (PEF) and high voltage electrical discharge (HVED). This review includes a detailed discussion of the instrumental setup, extraction mechanisms and their distinct advantages and disadvantages. Additionally, the impact of the operating parameters on the extraction kinetics of the mentioned techniques are highlighted. The review also covers the mathematical modeling based on Fick's law, chemical rate law and empirical models. The established kinetic models of various extractions are also summarized to facilitate better understanding.
A modeling technique based on absorbed microwave energy was proposed to model microwave-assisted ... more A modeling technique based on absorbed microwave energy was proposed to model microwave-assisted extraction (MAE) of antioxidant compounds from cocoa (Theobroma cacao L.) leaves. By adapting suitable extraction model at the basis of microwave energy absorbed during extraction, the model can be developed to predict extraction profile of MAE at various microwave irradiation power (100–600 W) and solvent loading (100–300 ml). Verification with experimental data confirmed that the prediction was accurate in capturing the extraction profile of MAE (R-square value greater than 0.87). Besides, the predicted yields from the model showed good agreement with the experimental results with less than 10% deviation observed. Furthermore, suitable extraction times to ensure high extraction yield at various MAE conditions can be estimated based on absorbed microwave energy. The estimation is feasible as more than 85% of active compounds can be extracted when compared with the conventional extraction technique.
A study has been conducted with the aim to provide researchers with general information on anti d... more A study has been conducted with the aim to provide researchers with general information on anti diabetic extracts based on relevant research articles collected from 34 reliable medical journals. The study showed that Asian and African continents have 56% and 17% share of the worldwide distribution of therapeutic herbal plants, respectively. In Asia, India and China are the leading countries in herbal plants research, and there has been an increase in medicinal research on plants extract for diabetes treatment since 1995 in these regions. The information collected shows that plant leaves are about 20% more favorable for storing active ingredients, as compared to other parts of herbal plants. A brief review on the extraction techniques for the mentioned parts is also included. Furthermore, the acting mechanisms for the anti diabetic activity were described, and the related active ingredients were identified. The findings reveal that most of the anti diabetic research is focused on the alteration of glucose metabolism to prevent diabetes.
Microwave-assisted extraction (MAE) is widely employed in the analysis and the extraction of acti... more Microwave-assisted extraction (MAE) is widely employed in the analysis and the extraction of active compounds from plants. This review summarizes the research done during the last decade on the MAE of active ingredients from plants. Advances and modifications to improve the performance of MAE are presented and discussed in detail. Modified MAE such as vacuum microwave-assisted extraction (VMAE), nitrogen-protected microwave-assisted extraction (NPMAE), ultrasonic microwave-assisted extraction (UMAE), dynamic microwave-assisted extraction (DMAE) and other advancements in MAE are also detailed in this article. In addition, the microwave extraction procedures and the important parameters influencing its performance are also included, together with the advantages and the drawbacks of each MAE techniques.
Conference Presentations by Chung-Hung Chan
Microwave-assisted extraction (MAE) is widely employed to extract active compounds from plants. H... more Microwave-assisted extraction (MAE) is widely employed to extract active compounds from plants. However, optimum operating conditions for MAE reported in literature are applicable only for specific scale of extraction and microwave system. This operational limitation was focused by taking into consideration the intrinsic power and energy required for optimizing the MAE in this study. Thus, the effects of absorbed microwave power density (APD) and absorbed microwave energy density (AED) on MAE of anti-diabetic compounds from cocoa (Theobroma cacao L.) leaves were investigated. This study suggests that APD addresses the real heating power of MAE and characterizes the extraction kinetics of MAE. Meanwhile AED can replace the extraction time to indicate the progress of MAE towards equilibrium extraction regardless of the heating conditions, i.e. solvent loading (100-300 ml) and microwave irradiation power (100-600 W). The optimum power and energy required for theMAE was 0.3 W/ml and 300 J/ml. respectively. They are independent of the extraction scales of 2-6 g sample and their extraction performances are comparable with that of Soxhlet extraction. In addition, structural analysis on plant sample illustrated the impact exerted by the microwave heating. This study highlights the implications and the significances of the energy-related parameters for MAE process.
A method was developed to predict the optimum extraction time for large scale microwave-assisted ... more A method was developed to predict the optimum extraction time for large scale microwave-assisted extraction (MAE) under various extraction conditions, i.e. solvent loading (100-300 ml) and microwave irradiation power (100-600 W). The method was established based on the correlation between optimum extraction time region and absorbed power density (APD) of the extraction system where APD is defined as the microwave power absorbed per unit solvent volume during extraction. This work provides an account on the procedure and the influencing factors amenable to the development of the proposed method. The predictive capability of the correlation was verified as the experimental optimum extraction time of MAE at various conditions and the predicted values are in good agreement
Microwave-assisted extraction (MAE) is a relatively new extraction method which is widely employe... more Microwave-assisted extraction (MAE) is a relatively new extraction method which is widely employed in the analysis and the extraction of active compounds from plants and lead to various discoveries of new medication and natural products. Due to localized microwave heating, the extraction can be performed efficiently and feasible in terms of solvent consumption and extraction time as compared to other conventional extraction methods such as Soxhlet Extraction, maceration and etc. Preliminary study was done to investigate the performance of MAE in the extraction of anti-diabetic active ingredient, quercetin 3-o glucoside from Gynura procumbens. Under optimized conditions, MAE required much shorter extraction time (5 minutes vs 3 hours) and gave better quercetin yield (1.60 mg/g vs 1.40 mg/g) as compared to Soxhlet extraction. For better recovery, the thermal degradation of active compounds should be minimized by incorporating temperature control to the extraction system. With that, a custom made temperature controlled extraction apparatus are currently developed and fabricated. The temperature control is achieved by controlling the microwave output with feedback from temperature sensor. The custom made systems is believed to give better control of the extraction process and a boost in the extraction yield.
Thesis by Chung-Hung Chan
Microwave-assisted extraction (MAE) is a promising plants extraction technique and it
has the po... more Microwave-assisted extraction (MAE) is a promising plants extraction technique and it
has the potential to be commercialized. However, due to limited significant parameters
to describe the MAE process, optimization and modeling of MAE for scaling up are
challenging and restricted. To resolve the problem, two intensive energy-related
parameters, i.e. absorbed power density (APD) and absorbed energy density (AED)
were introduced and they are respectively defined as the amount of microwave power
(W/ml) and energy (J/ml) absorbed in the solvent during the extraction. Following that,
three methods namely APD predictive method, AED modeling method and combined
APD-AED optimization method were developed to model and optimize MAE at
varying extraction scales. The methods developed in this work are based on the
extraction of anti diabetic compounds, i.e. isoquercitrin (0.13-3.51 mg/g), epicatechin
(0.23-2.91 mg/g) and rutin (0.30-7.07 mg/g) from cocoa (Theobroma cacao L.) leaves.
Prior to the evaluation of the developed methods, the optimization and modeling of
MAE were performed conventionally using response surface methodology (RSM) and
Patricelli model, respectively. The optimum MAE conditions are 85% (v/v) aqueous
ethanol at 50 ml/g (2g), 156 W, and 18 min, and its performance are similar to that
obtained in Soxhlet extraction but with lesser solvent (50 ml/g vs. 100 ml/g) and shorter
extraction time (18 min vs. 6 hr). From the modeling study, the washing step of MAE is
strongly affected by the size of plant sample while the diffusion step is influenced by
both the solvent to feed ratio (S/F) and microwave power (P).
The findings obtained from the proposed methods suggest that the APD predictive
method is able to predict the optimum extraction time for large scale MAE between
100-300 ml under various microwave power based on the correlation established
vi
between the optimum extraction time region and the APD of the extraction system. By
conducting MAE at the predicted optimum extraction time region, more than 85% of
equilibrium extraction yields can be achieved and the prediction is valid at solvent to
feed ratio varying from 20 to 80 ml/g. Besides that, AED modeling method enables the
prediction of overall extraction curves of MAE. By adapting suitable extraction model
i.e. film theory model at AED basis, a predictive model can be developed. The AED
extraction model is accurate in capturing the experimental extraction profile of MAE at
various microwave power (200-600 W) and solvent loading (100-300 ml) with R-square
value > 0.87. In addition, APD-AED optimization method standardizes the optimization
of MAE based on three mechanisms, i.e. penetration of solvent, disruption of plant cell
and elution of active compounds. According to this method, the optimization can be
performed using sequential single factor experiments based on APD and AED and the
result obtained was similar to those obtained from the optimization using RSM. Most
importantly, the intensive optimum MAE conditions (S/F = 50 ml/g, APD = 0.3 J/ml,
AED = 300 J/ml) determined from this method can be used to determine the optimum
operating parameters (S/F, Power, Time) of MAE at varying extraction scale (100-300
ml).
Papers by Chung-Hung Chan
Journal of Food Engineering, 2016
A first-ever theoretical model describing the cell rupture mechanism for microwave-assisted extra... more A first-ever theoretical model describing the cell rupture mechanism for microwave-assisted extraction (MAE) of bioactive compounds from plant samples is presented. This model incorporates the microwave heating of intracellular moisture within the plant cells using Lambert's law. It then calculates the heating time and the intrinsic energy required to pressurize and stretch the plant cells until rupture using thermodynamic relations. The attainment of cell rupture is determined from elasticity theory for solids. The simulation requires the inputs of the effective shear modulus of the plant cell wall and the incident microwave irradiation flux entering the extraction mixture. The predicted cell rupture time by the intrinsic energy validated excellently against the optimum extraction time found in experiments. This model is generally applicable over a wide extraction parameters and microwave systems.
Uploads
Journal articles by Chung-Hung Chan
Conference Presentations by Chung-Hung Chan
Thesis by Chung-Hung Chan
has the potential to be commercialized. However, due to limited significant parameters
to describe the MAE process, optimization and modeling of MAE for scaling up are
challenging and restricted. To resolve the problem, two intensive energy-related
parameters, i.e. absorbed power density (APD) and absorbed energy density (AED)
were introduced and they are respectively defined as the amount of microwave power
(W/ml) and energy (J/ml) absorbed in the solvent during the extraction. Following that,
three methods namely APD predictive method, AED modeling method and combined
APD-AED optimization method were developed to model and optimize MAE at
varying extraction scales. The methods developed in this work are based on the
extraction of anti diabetic compounds, i.e. isoquercitrin (0.13-3.51 mg/g), epicatechin
(0.23-2.91 mg/g) and rutin (0.30-7.07 mg/g) from cocoa (Theobroma cacao L.) leaves.
Prior to the evaluation of the developed methods, the optimization and modeling of
MAE were performed conventionally using response surface methodology (RSM) and
Patricelli model, respectively. The optimum MAE conditions are 85% (v/v) aqueous
ethanol at 50 ml/g (2g), 156 W, and 18 min, and its performance are similar to that
obtained in Soxhlet extraction but with lesser solvent (50 ml/g vs. 100 ml/g) and shorter
extraction time (18 min vs. 6 hr). From the modeling study, the washing step of MAE is
strongly affected by the size of plant sample while the diffusion step is influenced by
both the solvent to feed ratio (S/F) and microwave power (P).
The findings obtained from the proposed methods suggest that the APD predictive
method is able to predict the optimum extraction time for large scale MAE between
100-300 ml under various microwave power based on the correlation established
vi
between the optimum extraction time region and the APD of the extraction system. By
conducting MAE at the predicted optimum extraction time region, more than 85% of
equilibrium extraction yields can be achieved and the prediction is valid at solvent to
feed ratio varying from 20 to 80 ml/g. Besides that, AED modeling method enables the
prediction of overall extraction curves of MAE. By adapting suitable extraction model
i.e. film theory model at AED basis, a predictive model can be developed. The AED
extraction model is accurate in capturing the experimental extraction profile of MAE at
various microwave power (200-600 W) and solvent loading (100-300 ml) with R-square
value > 0.87. In addition, APD-AED optimization method standardizes the optimization
of MAE based on three mechanisms, i.e. penetration of solvent, disruption of plant cell
and elution of active compounds. According to this method, the optimization can be
performed using sequential single factor experiments based on APD and AED and the
result obtained was similar to those obtained from the optimization using RSM. Most
importantly, the intensive optimum MAE conditions (S/F = 50 ml/g, APD = 0.3 J/ml,
AED = 300 J/ml) determined from this method can be used to determine the optimum
operating parameters (S/F, Power, Time) of MAE at varying extraction scale (100-300
ml).
Papers by Chung-Hung Chan
has the potential to be commercialized. However, due to limited significant parameters
to describe the MAE process, optimization and modeling of MAE for scaling up are
challenging and restricted. To resolve the problem, two intensive energy-related
parameters, i.e. absorbed power density (APD) and absorbed energy density (AED)
were introduced and they are respectively defined as the amount of microwave power
(W/ml) and energy (J/ml) absorbed in the solvent during the extraction. Following that,
three methods namely APD predictive method, AED modeling method and combined
APD-AED optimization method were developed to model and optimize MAE at
varying extraction scales. The methods developed in this work are based on the
extraction of anti diabetic compounds, i.e. isoquercitrin (0.13-3.51 mg/g), epicatechin
(0.23-2.91 mg/g) and rutin (0.30-7.07 mg/g) from cocoa (Theobroma cacao L.) leaves.
Prior to the evaluation of the developed methods, the optimization and modeling of
MAE were performed conventionally using response surface methodology (RSM) and
Patricelli model, respectively. The optimum MAE conditions are 85% (v/v) aqueous
ethanol at 50 ml/g (2g), 156 W, and 18 min, and its performance are similar to that
obtained in Soxhlet extraction but with lesser solvent (50 ml/g vs. 100 ml/g) and shorter
extraction time (18 min vs. 6 hr). From the modeling study, the washing step of MAE is
strongly affected by the size of plant sample while the diffusion step is influenced by
both the solvent to feed ratio (S/F) and microwave power (P).
The findings obtained from the proposed methods suggest that the APD predictive
method is able to predict the optimum extraction time for large scale MAE between
100-300 ml under various microwave power based on the correlation established
vi
between the optimum extraction time region and the APD of the extraction system. By
conducting MAE at the predicted optimum extraction time region, more than 85% of
equilibrium extraction yields can be achieved and the prediction is valid at solvent to
feed ratio varying from 20 to 80 ml/g. Besides that, AED modeling method enables the
prediction of overall extraction curves of MAE. By adapting suitable extraction model
i.e. film theory model at AED basis, a predictive model can be developed. The AED
extraction model is accurate in capturing the experimental extraction profile of MAE at
various microwave power (200-600 W) and solvent loading (100-300 ml) with R-square
value > 0.87. In addition, APD-AED optimization method standardizes the optimization
of MAE based on three mechanisms, i.e. penetration of solvent, disruption of plant cell
and elution of active compounds. According to this method, the optimization can be
performed using sequential single factor experiments based on APD and AED and the
result obtained was similar to those obtained from the optimization using RSM. Most
importantly, the intensive optimum MAE conditions (S/F = 50 ml/g, APD = 0.3 J/ml,
AED = 300 J/ml) determined from this method can be used to determine the optimum
operating parameters (S/F, Power, Time) of MAE at varying extraction scale (100-300
ml).