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Papers by Nattapol Poomsa-ad

Acta Horticulturae

The objective of this research was to investigate the drying of turmeric (Curcuma longa) by heat ... more The objective of this research was to investigate the drying of turmeric (Curcuma longa) by heat pump dryer (HPD) under a closed loop system using air, nitrogen and carbon dioxide gas as drying media. The drying temperatures of 45, 50 and 55°C were applied. The velocity of drying media in the drying chamber was 0.5 m s-1. The initial moisture content of 81% wet basis was dried down to 10% wet basis within 3, 2 and 1.5 h at drying temperatures of 45, 50 and 55°C, respectively. The drying rate was increased with drying temperatures. The drying under different media had similar drying rate at a given temperature. The coefficient of performance of the heat pump was in the range of 2.149-2.919.

The purpose of this research was to study the kinetics of macadamia drying by a microwave dryer c... more The purpose of this research was to study the kinetics of macadamia drying by a microwave dryer combined with hot air. Macadamia nuts with shells were used in the experiment. The initial moisture content of the nut with shells in the range of 16-19% dry basis was dried until the final moisture content was less than 4% dry basis. Drying was done under different conditions to study the influences of hot air temperature (40, 50 and 60 degrees Celsius) and microwave power (300, 450 and 600 watts) on the appearance of the macadamias and energy consumption. The result indicated that the increase in microwave power could reduce moisture content of the macadamias more than the increase in the drying temperature. After drying and shelling, the microwave power of 300 watts at every temperature resulted in the most uniform color of the kernels. Considered in terms of energy consumption, the drying at 40 degrees Celsius combined with microwave power of 600 watts had the lowest energy consumptio...

Journal of Microwave Power and Electromagnetic Energy, 2020

The thin layer drying of Eri silkworm pupae using microwaves combined with hot air was conducted.... more The thin layer drying of Eri silkworm pupae using microwaves combined with hot air was conducted. Several empirical models simulating thin layer drying of Eri silkworm pupae were selected and analyzed. Microwave power between 100 and 200 W and drying temperatures between 50 and 70 C were used in the study. The comparison between experimental results and those of the models indicated that the Page's model was the best predictor for the thin layer drying of silkworm pupae. In addition color measurements showed that L Ã values increase with increased microwave power. The best drying condition of Eri silkworm pupae was also, found at microwave power of 200 W combined with the hot air at the temperature of 50 C.

Journal of Microwave Power and Electromagnetic Energy, 2018

We studied the microwave-assisted macadamia drying, using surface temperature control and without... more We studied the microwave-assisted macadamia drying, using surface temperature control and without surface temperature control as well as hot air drying, and assessed the drying time, drying rate, colour values, hardness and water activity of nuts and efficiency. The surface temperature of macadamia nuts was controlled between 60 and 80 C using a thermal radiation detector. For drying without the surface temperature control, drying temperatures in the range of 40-60 C and microwave power were controlled in the range of 1.6-4.4 Wg ¡1. We found that increase in microwave power and temperature had a positive effect with shorter drying time and increased drying rate. Microwave assisted hot air drying by surface temperature control led to a better quality product in respect of kernel brightness and suitable a w for storage, but a harder kernel. In addition, drying without surface temperature control had the highest energy efficiency followed by surface temperature control and hot air only. Considering quality, the recommended condition was drying by surface temperature control at 60 C with 60 C hot air combined with microwave.

Applied Thermal Engineering, 2016

h i g h l i g h t s 3D model effectively characterized a stepwise drying process. Step-up drying ... more h i g h l i g h t s 3D model effectively characterized a stepwise drying process. Step-up drying was the best mode with respect to energy saving and drying time. A critical point, 70%wb for carrot, was optimal intermediate moisture content. Step-up drying is an alternative method to conventional one.

Journal of Food Process Engineering, 2016

Biopolymer films are increasing in popularity due to its environmental friendly. The objectives o... more Biopolymer films are increasing in popularity due to its environmental friendly. The objectives of this work were to study the effect of drying temperatures and plasticizer types on the physical and mechanical properties of films. Konjac glucomannan (KGM) was used for base film forming. A heat pump dryer was used for drying films at temperatures from 30 to 50°C. Film properties were compared with those of films dried at ambient temperature. The film properties were evaluated by film thickness, tensile stress at yield, percent elongation at yield, elastic modulus, water vapor permeability (WVP), transparency, and microstructure of film. Glycerol, lemongrass (Cymbopogon citrates) essential oil and plai (Zingiber cassumunar) essential oil were used as plasticizers. The result found that thickness, percent elongation at yield and WVP were decreased with increased drying temperature. However, tensile stress at yield and elastic modulus were increased when the drying temperatures increased. Moreover, films with essential oil were thicker, lower tensile stress at yield and elastic modulus and higher WVP than film without essential oil. Films without essential oil were compact, smooth surface and uniform microstructure than the films with essential oil. Practical Applications This research was to study the effect of drying temperature and plasticizer types on property of film. Film was made from konjac flour and drying by a heat pump dryer. The application of the heat pump in the drying process is to control of the relative humidity and drying temperature of the process. Heat pump dryer provides low relative humidity and low temperature; reduce the drying time and faster than hot air drying. Also essential oil used as plasticizer combined with konjac flour as film-base could improve elasticity property and permeability of film were determined in order to produce packaging with good characteristics.

Applied Thermal Engineering, 2016

Abstract We discuss the drying performance and energy consumption of a closed system heat pump dr... more Abstract We discuss the drying performance and energy consumption of a closed system heat pump dryer for ginger drying at 50 °C within 200 minutes using air and nitrogen as the drying medium. The fresh ginger at moisture content of 777 was dried by air and nitrogen down to 132 and 89% dry basis. The gained heat at the internal condenser was 15.4 and 20.5 MJ, and rejected heat at evaporator was 18.6 and 22.9 MJ for air and nitrogen cycles, respectively. Heater provided 62.93 and 65.60% total input energy of refrigerant cycle while heat gained at external condenser were 37.92 and 28.79% output for air and nitrogen drying respectively. Air drying required total input energy of 11.6 compared to nitrogen of 12.5 MJ. Specific moisture extraction rate of ginger drying in air was 0.06, while nitrogen was 0.07 kg water/MJ. Specific energy consumption of air drying was 16.67 while nitrogen was 14.29 MJ/kg water.

International Journal of Food Agriculture and Environment, 2010

The effects of drying media and drying temperatures on drying kinetics, concentration of 2-acetyl... more The effects of drying media and drying temperatures on drying kinetics, concentration of 2-acetyl-1-pyrroline (2AP), milling quality and whiteness of Thai Hom Mali rice cv. Khao Dawk Mali 105 were investigated. Samples were dried in a heat pump dryer and were subjected to different drying media (hot air, carbon dioxide and nitrogen gas) and drying temperatures (40, 50, 60 and 70°C). Paddy samples dried at 40 and 70°C in all media were selected to be analyzed with regard to 2AP concentrations. The results showed that the moisture ratio of paddy dried under carbon dioxide or nitrogen gas at 40°C decreased faster than that of hot air. The effective diffusion coefficient was enhanced by drying temperature. The 2AP content had significantly decreased at 70°C. There was no interaction between drying media and drying temperature on head rice yield. The highest percentage of head rice yield was obtained in samples subjected to carbon dioxide gas and dried at 40°C. In addition, the whiteness of rice obtained from paddy dried at 40°C in all media had significantly highest values.

Journal of Medical and Bioengineering, 2014

The objective of this research was to study the effect of drying temperatures and glycerol concen... more The objective of this research was to study the effect of drying temperatures and glycerol concentrations on properties of edible film from konjac flour. Glycerol was used as plasticizer at the concentrations of 0 and 0.3% w/v for film forming. The drying process was done using heat pump dryer at various temperatures of 45, 50 and 55 C. Sample was dried until the final moisture content was down to 1% wet basis. Then, film samples were taken to determine various properties including, tensile strength, elongation, water vapor permeability and solubility. The results found that konjac film without glycerol had a higher tensile strength than that konjac film with 0.3% glycerol. Also, tensile strength was significantly increased with the increasing of drying temperature (p ≤ 0.05). For the elongation, water vapor permeability and solubility of film, these properties of konjac film with 0.3% glycerol were higher than that konjac film without glycerol. The elongation was significantly decreased when the drying temperature increased (p ≤ 0.05). Moreover, water vapor permeability and solubility were significantly difference at various drying temperature (p ≤ 0.05). The drying temperature at 50 C provided the lowest water vapor permeability and the highest solubility  Index Terms-edible film, konjac, drying, plasticizer, film properties Prayoon Jomlapeeratikul was born in Chiangmai, Thailand, Februarys 1978. He received his B.Eng. degree in Post-Harvest and Processing Engineering

Journal of Medical and Bioengineering, 2014

This research was to study the physical, mechanical and aerodynamic properties of sorghum. The mo... more This research was to study the physical, mechanical and aerodynamic properties of sorghum. The moisture contents of sample for 5 levels were in the range of 9.06 to 29.15 % wet basis. Each moisture content level, fifty grains were sampled. The results found that the increase in moisture content resulted in the increasing of grain width, length, thickness and geometric diameter which in the range of 3.86 to 4.16 mm, 4.45 to 4.65 mm, 2.49 to 2.72 mm and 3.50 to 3.75. mm, respectively. In addition, the sphericity, the thousand grains mass and surface area were in the range of 0.79 to 0.81, 23.37 to 28.58 g, and 38.44 to 44.07 mm 2 , respectively. The porosity and angle of repose were found to increase from 35.15% to 36.75%, and 20.04° to 26.82°, respectively. The bulk and true density decreased from 815.40 to 712.60 kg/m 3 , and 1257.33 to 1126.72 kg/m 3. The coefficient static friction on acrylic, wood, zinc and iron were in the range of 0.25 to 0.48, 0.40 to 0.48, 0.21 to 0.42 and 0.32 to 0.43, respectively. Terminal velocity and the drag coefficient were in the range of 8.54 to 9.73 m/s and 0.32 to 0.34. 

Food Chemistry, 2012

Soy isoflavones, which are well-known for their health benefits, could be affected by the techniq... more Soy isoflavones, which are well-known for their health benefits, could be affected by the technique and condition that are used to dry soybean prior to its use. In this study the drying kinetics of soybean as well as the inter-conversion and degradation of soy isoflavones during gas-fired infrared combined with hot air vibrating drying (GFIR-HAVD) at various temperatures (50, 70, 130 and 150°C) were investigated. Simple kinetic models for the evolutions of both moisture content and isoflavones were proposed and tested. The temperature dependency of the effective moisture diffusivity of soybean could be well described by the Arrhenius correlation with the activation energy of 13.88 kJ/mol. In terms of the evolutions of isoflavones the contents of 6 00-O-malonylgenistin (MGI) and 6 00-O-acetylgenistin (AGI) decreased, while genistin (GI) and genistein increased with an increase in the drying temperature and drying time. First-order kinetic models could be used to describe the changes of isoflavones. At all drying temperatures the conversion of MGI to GI exhibited the highest rate constant; this was followed by the conversion of AGI to GI. In addition, MGI had the highest degradation rate constant; this was followed, in descending order, by AGI, GI and GE. The activation energies of degradation were lower than those of inter-conversion among all forms of isoflavones.

Food and Bioproducts Processing, 2010

Thin layer solar drying experiments of silkworm pupae using a solar tunnel dryer were conducted u... more Thin layer solar drying experiments of silkworm pupae using a solar tunnel dryer were conducted under the tropical weather conditions of Mahasarakham, Thailand. The dryer consisted of a transparent glass covered flat-plate collector and a drying tunnel connected in series to supply hot air directly into the drying tunnel using a blower. During the experiments, silkworm pupae were dried to the final moisture content of 0.15 kg water kg −1 dry matter from 4.37 kg water kg −1 dry matter in 373 min at the corresponding air flow rate of 0.32 kg s −1. Ten different thin layer drying models were compared according to their coefficient of determination to estimate drying curves. The Midilli-Kucuk model precisely represents the solar tunnel drying behavior with the coefficient of determination (R 2) of 0.9982. The maximum drying rate and effective moisture diffusivity were 0.6723 kg water kg −1 dry matter h −1 and 2.7696 × 10 −10 m 2 s −1 , respectively, on the drying air flow rate of 0.32 kg s −1. A quality assessment shows that the lipid content of the dried silkworm pupae was not affected by the solar tunnel dryer. A slight decrease of polyunsaturated fatty acid (PUFA) was observed.

Drying Technology, 1999

This paper describes a strategy for reducing moisture in paddy by fluidized bed drying, tempering... more This paper describes a strategy for reducing moisture in paddy by fluidized bed drying, tempering and ambient air cooling. Experimental results showed that after the three processes, moisture content was reduced from 33 % to 16.5 % dry-basis within approximately 53 minutes. During the first process, a fluidized-bed dryer was used to reduce the moisture content of paddy down to

Biosystems Engineering, 2008

The objective of this study was to conduct an experimental analysis to investigate the performanc... more The objective of this study was to conduct an experimental analysis to investigate the performance of a mixed mode type forced convection solar tunnel dryer (STD) which was used to dry silkworm pupae under tropical weather conditions of Mahasarakham, Thailand. The dryer consisted of a transparent glass covered flat-plate collector and a drying tunnel connected in series to supply hot air directly into the drying tunnel using a blower. The dryer was 6.2 m long and 1.8 m wide. The drying unit had a loading capacity of 30 kg of silkworm pupae. The effect of the drying air flow rate was examined. The drying time depended on the drying air flow rate and temperature. Moisture content of the silkworm pupae was reduced from 3.70 kg H 2 O kg À1 dry matter to 0.20 kg H 2 O kg À1 dry matter in 570 min at the corresponding air flow rate of 0.30 kg s À1 and it took 945 min in open sun drying; drying time was reduced by about 40%. A quality assessment shows that the lipid content of the dried silkworm pupae was not affected by the STD. A slight decrease of polyunsaturated fatty acid (PUFA) was observed. Maximum drying and overall efficiencies were 30.14% and 19.68%, respectively, at the air flow rate of 0.30 kg s À1. The economic analysis indicates that the payback period is 1.42 years. Due to its simplicity, the proposed system is relatively inexpensive. Therefore, commercial application seems to be viable.

Thermal Science, 2020

Konjac glucomannan (KGM) can be obtained from tubers (called corms) of various species within the... more Konjac glucomannan (KGM) can be obtained from tubers (called corms) of various species within the Amorphophallus genus. Among the most popular species for use in food industry is Buk Nuea Sai (Amorphophallus muelleri), a native species in Thailand. Drying process can be helpful in preserving KGM during long storage periods. However, the existing drying systems are often slow and lead to drying delays and subsequently quality reduction of the dried product. Given the economic importance of KGM, new, more efficient drying systems, have to be developed. The present study focuses on the drying kinetics of konjac dices in a fluidized bed, operating at a constant air velocity of 2.5 m/s and air temperatures of 50, 60, and 70?C. Six empirical mathematical models were selected to describe and compare the drying characteristics of konjac dices subjected to these conditions. The model coefficients were determined by non-linear regression analysis. Among the tested models used to describe the ...

The peel of dragon fruit is a byproduct left over after consuming. Normally, the use of plants as... more The peel of dragon fruit is a byproduct left over after consuming. Normally, the use of plants as antioxidant source must be dried before further process. Therefore, the aim of this study is interesting to dry the peel by heat pump dryer (45 ºC) and fluidized bed dryer (110 º C) compared with the sun drying method. The sample with initial moisture content of about 85-91% wet basis was dried down to about 10% wet basis where it took 620 and 25 min for heat pump dryer and fluidized bed dryer, respectively. However, the sun drying took about 900 min to dry the peel. After that, sample was evaluated antioxidant activity, -carotene and betalains contents. The results found that the antioxidant activity and betalains contents of dried peel obtained from heat pump and fluidized bed dryings were significantly higher than that sun drying (p 0.05). Moreover, the drying by heat pump provided the highest -carotene content.

Drying Technology, 2002

Drying and tempering models for paddy drying by a fluidised bed technique have been developed to ... more Drying and tempering models for paddy drying by a fluidised bed technique have been developed to describe the moisture movement inside a single paddy kernel. The grain shape was considered as a finite cylinder. The internal diffusion is an important contribution to control the drying rate of paddy. The dependence of effective diffusion coefficient on drying temperature can be adequately explained based on Arrhenius form. The parameters of this equation were evaluated in the range of temperatures between 110 o C and 170 o C by using the regression analysis with 189 experimental drying data. As compared with no tempering, the faster drying rate can be obtained by tempering treatment between drying stages, The effect of degrees of tempering on determining the moisture reduction in the second stage has also been explored. According to the simulation results, a prediction equation of the required tempering time for the tempering index of 0.95 has been established in which the drying air temperature, initial moisture content and drying time are taken into account. The tempering time for 35 min is recommended for the continuous fluidised bed dryers being operated in rice mills.

Journal of Stored Products Research, 2005

This analysis of the drying process is based on experiments and simulations of the influence of t... more This analysis of the drying process is based on experiments and simulations of the influence of temperature in the fluidised-bed dryer, moisture content and tempering period on head-rice yield, and operating time. A mathematical model incorporating the head-rice yield equation for predictions of the moisture content and the grain temperature in each drying stage and the final head-rice yield, is in good agreement with experimental data. The moisture content after first-stage drying and tempering have a dominant effect on head-rice yield and operating time in reducing high-moisture contents to a safe level. The simulation results recommend that the allowable temperature should be not higher than 150 °C for the first stage and the moisture content after first-stage drying should be not lower than 22.5% dry basis, with subsequent tempering for at least 25 min.

Acta Horticulturae

The objective of this research was to investigate the drying of turmeric (Curcuma longa) by heat ... more The objective of this research was to investigate the drying of turmeric (Curcuma longa) by heat pump dryer (HPD) under a closed loop system using air, nitrogen and carbon dioxide gas as drying media. The drying temperatures of 45, 50 and 55°C were applied. The velocity of drying media in the drying chamber was 0.5 m s-1. The initial moisture content of 81% wet basis was dried down to 10% wet basis within 3, 2 and 1.5 h at drying temperatures of 45, 50 and 55°C, respectively. The drying rate was increased with drying temperatures. The drying under different media had similar drying rate at a given temperature. The coefficient of performance of the heat pump was in the range of 2.149-2.919.

The purpose of this research was to study the kinetics of macadamia drying by a microwave dryer c... more The purpose of this research was to study the kinetics of macadamia drying by a microwave dryer combined with hot air. Macadamia nuts with shells were used in the experiment. The initial moisture content of the nut with shells in the range of 16-19% dry basis was dried until the final moisture content was less than 4% dry basis. Drying was done under different conditions to study the influences of hot air temperature (40, 50 and 60 degrees Celsius) and microwave power (300, 450 and 600 watts) on the appearance of the macadamias and energy consumption. The result indicated that the increase in microwave power could reduce moisture content of the macadamias more than the increase in the drying temperature. After drying and shelling, the microwave power of 300 watts at every temperature resulted in the most uniform color of the kernels. Considered in terms of energy consumption, the drying at 40 degrees Celsius combined with microwave power of 600 watts had the lowest energy consumptio...

Journal of Microwave Power and Electromagnetic Energy, 2020

The thin layer drying of Eri silkworm pupae using microwaves combined with hot air was conducted.... more The thin layer drying of Eri silkworm pupae using microwaves combined with hot air was conducted. Several empirical models simulating thin layer drying of Eri silkworm pupae were selected and analyzed. Microwave power between 100 and 200 W and drying temperatures between 50 and 70 C were used in the study. The comparison between experimental results and those of the models indicated that the Page's model was the best predictor for the thin layer drying of silkworm pupae. In addition color measurements showed that L Ã values increase with increased microwave power. The best drying condition of Eri silkworm pupae was also, found at microwave power of 200 W combined with the hot air at the temperature of 50 C.

Journal of Microwave Power and Electromagnetic Energy, 2018

We studied the microwave-assisted macadamia drying, using surface temperature control and without... more We studied the microwave-assisted macadamia drying, using surface temperature control and without surface temperature control as well as hot air drying, and assessed the drying time, drying rate, colour values, hardness and water activity of nuts and efficiency. The surface temperature of macadamia nuts was controlled between 60 and 80 C using a thermal radiation detector. For drying without the surface temperature control, drying temperatures in the range of 40-60 C and microwave power were controlled in the range of 1.6-4.4 Wg ¡1. We found that increase in microwave power and temperature had a positive effect with shorter drying time and increased drying rate. Microwave assisted hot air drying by surface temperature control led to a better quality product in respect of kernel brightness and suitable a w for storage, but a harder kernel. In addition, drying without surface temperature control had the highest energy efficiency followed by surface temperature control and hot air only. Considering quality, the recommended condition was drying by surface temperature control at 60 C with 60 C hot air combined with microwave.

Applied Thermal Engineering, 2016

h i g h l i g h t s 3D model effectively characterized a stepwise drying process. Step-up drying ... more h i g h l i g h t s 3D model effectively characterized a stepwise drying process. Step-up drying was the best mode with respect to energy saving and drying time. A critical point, 70%wb for carrot, was optimal intermediate moisture content. Step-up drying is an alternative method to conventional one.

Journal of Food Process Engineering, 2016

Biopolymer films are increasing in popularity due to its environmental friendly. The objectives o... more Biopolymer films are increasing in popularity due to its environmental friendly. The objectives of this work were to study the effect of drying temperatures and plasticizer types on the physical and mechanical properties of films. Konjac glucomannan (KGM) was used for base film forming. A heat pump dryer was used for drying films at temperatures from 30 to 50°C. Film properties were compared with those of films dried at ambient temperature. The film properties were evaluated by film thickness, tensile stress at yield, percent elongation at yield, elastic modulus, water vapor permeability (WVP), transparency, and microstructure of film. Glycerol, lemongrass (Cymbopogon citrates) essential oil and plai (Zingiber cassumunar) essential oil were used as plasticizers. The result found that thickness, percent elongation at yield and WVP were decreased with increased drying temperature. However, tensile stress at yield and elastic modulus were increased when the drying temperatures increased. Moreover, films with essential oil were thicker, lower tensile stress at yield and elastic modulus and higher WVP than film without essential oil. Films without essential oil were compact, smooth surface and uniform microstructure than the films with essential oil. Practical Applications This research was to study the effect of drying temperature and plasticizer types on property of film. Film was made from konjac flour and drying by a heat pump dryer. The application of the heat pump in the drying process is to control of the relative humidity and drying temperature of the process. Heat pump dryer provides low relative humidity and low temperature; reduce the drying time and faster than hot air drying. Also essential oil used as plasticizer combined with konjac flour as film-base could improve elasticity property and permeability of film were determined in order to produce packaging with good characteristics.

Applied Thermal Engineering, 2016

Abstract We discuss the drying performance and energy consumption of a closed system heat pump dr... more Abstract We discuss the drying performance and energy consumption of a closed system heat pump dryer for ginger drying at 50 °C within 200 minutes using air and nitrogen as the drying medium. The fresh ginger at moisture content of 777 was dried by air and nitrogen down to 132 and 89% dry basis. The gained heat at the internal condenser was 15.4 and 20.5 MJ, and rejected heat at evaporator was 18.6 and 22.9 MJ for air and nitrogen cycles, respectively. Heater provided 62.93 and 65.60% total input energy of refrigerant cycle while heat gained at external condenser were 37.92 and 28.79% output for air and nitrogen drying respectively. Air drying required total input energy of 11.6 compared to nitrogen of 12.5 MJ. Specific moisture extraction rate of ginger drying in air was 0.06, while nitrogen was 0.07 kg water/MJ. Specific energy consumption of air drying was 16.67 while nitrogen was 14.29 MJ/kg water.

International Journal of Food Agriculture and Environment, 2010

The effects of drying media and drying temperatures on drying kinetics, concentration of 2-acetyl... more The effects of drying media and drying temperatures on drying kinetics, concentration of 2-acetyl-1-pyrroline (2AP), milling quality and whiteness of Thai Hom Mali rice cv. Khao Dawk Mali 105 were investigated. Samples were dried in a heat pump dryer and were subjected to different drying media (hot air, carbon dioxide and nitrogen gas) and drying temperatures (40, 50, 60 and 70°C). Paddy samples dried at 40 and 70°C in all media were selected to be analyzed with regard to 2AP concentrations. The results showed that the moisture ratio of paddy dried under carbon dioxide or nitrogen gas at 40°C decreased faster than that of hot air. The effective diffusion coefficient was enhanced by drying temperature. The 2AP content had significantly decreased at 70°C. There was no interaction between drying media and drying temperature on head rice yield. The highest percentage of head rice yield was obtained in samples subjected to carbon dioxide gas and dried at 40°C. In addition, the whiteness of rice obtained from paddy dried at 40°C in all media had significantly highest values.

Journal of Medical and Bioengineering, 2014

The objective of this research was to study the effect of drying temperatures and glycerol concen... more The objective of this research was to study the effect of drying temperatures and glycerol concentrations on properties of edible film from konjac flour. Glycerol was used as plasticizer at the concentrations of 0 and 0.3% w/v for film forming. The drying process was done using heat pump dryer at various temperatures of 45, 50 and 55 C. Sample was dried until the final moisture content was down to 1% wet basis. Then, film samples were taken to determine various properties including, tensile strength, elongation, water vapor permeability and solubility. The results found that konjac film without glycerol had a higher tensile strength than that konjac film with 0.3% glycerol. Also, tensile strength was significantly increased with the increasing of drying temperature (p ≤ 0.05). For the elongation, water vapor permeability and solubility of film, these properties of konjac film with 0.3% glycerol were higher than that konjac film without glycerol. The elongation was significantly decreased when the drying temperature increased (p ≤ 0.05). Moreover, water vapor permeability and solubility were significantly difference at various drying temperature (p ≤ 0.05). The drying temperature at 50 C provided the lowest water vapor permeability and the highest solubility  Index Terms-edible film, konjac, drying, plasticizer, film properties Prayoon Jomlapeeratikul was born in Chiangmai, Thailand, Februarys 1978. He received his B.Eng. degree in Post-Harvest and Processing Engineering

Journal of Medical and Bioengineering, 2014

This research was to study the physical, mechanical and aerodynamic properties of sorghum. The mo... more This research was to study the physical, mechanical and aerodynamic properties of sorghum. The moisture contents of sample for 5 levels were in the range of 9.06 to 29.15 % wet basis. Each moisture content level, fifty grains were sampled. The results found that the increase in moisture content resulted in the increasing of grain width, length, thickness and geometric diameter which in the range of 3.86 to 4.16 mm, 4.45 to 4.65 mm, 2.49 to 2.72 mm and 3.50 to 3.75. mm, respectively. In addition, the sphericity, the thousand grains mass and surface area were in the range of 0.79 to 0.81, 23.37 to 28.58 g, and 38.44 to 44.07 mm 2 , respectively. The porosity and angle of repose were found to increase from 35.15% to 36.75%, and 20.04° to 26.82°, respectively. The bulk and true density decreased from 815.40 to 712.60 kg/m 3 , and 1257.33 to 1126.72 kg/m 3. The coefficient static friction on acrylic, wood, zinc and iron were in the range of 0.25 to 0.48, 0.40 to 0.48, 0.21 to 0.42 and 0.32 to 0.43, respectively. Terminal velocity and the drag coefficient were in the range of 8.54 to 9.73 m/s and 0.32 to 0.34. 

Food Chemistry, 2012

Soy isoflavones, which are well-known for their health benefits, could be affected by the techniq... more Soy isoflavones, which are well-known for their health benefits, could be affected by the technique and condition that are used to dry soybean prior to its use. In this study the drying kinetics of soybean as well as the inter-conversion and degradation of soy isoflavones during gas-fired infrared combined with hot air vibrating drying (GFIR-HAVD) at various temperatures (50, 70, 130 and 150°C) were investigated. Simple kinetic models for the evolutions of both moisture content and isoflavones were proposed and tested. The temperature dependency of the effective moisture diffusivity of soybean could be well described by the Arrhenius correlation with the activation energy of 13.88 kJ/mol. In terms of the evolutions of isoflavones the contents of 6 00-O-malonylgenistin (MGI) and 6 00-O-acetylgenistin (AGI) decreased, while genistin (GI) and genistein increased with an increase in the drying temperature and drying time. First-order kinetic models could be used to describe the changes of isoflavones. At all drying temperatures the conversion of MGI to GI exhibited the highest rate constant; this was followed by the conversion of AGI to GI. In addition, MGI had the highest degradation rate constant; this was followed, in descending order, by AGI, GI and GE. The activation energies of degradation were lower than those of inter-conversion among all forms of isoflavones.

Food and Bioproducts Processing, 2010

Thin layer solar drying experiments of silkworm pupae using a solar tunnel dryer were conducted u... more Thin layer solar drying experiments of silkworm pupae using a solar tunnel dryer were conducted under the tropical weather conditions of Mahasarakham, Thailand. The dryer consisted of a transparent glass covered flat-plate collector and a drying tunnel connected in series to supply hot air directly into the drying tunnel using a blower. During the experiments, silkworm pupae were dried to the final moisture content of 0.15 kg water kg −1 dry matter from 4.37 kg water kg −1 dry matter in 373 min at the corresponding air flow rate of 0.32 kg s −1. Ten different thin layer drying models were compared according to their coefficient of determination to estimate drying curves. The Midilli-Kucuk model precisely represents the solar tunnel drying behavior with the coefficient of determination (R 2) of 0.9982. The maximum drying rate and effective moisture diffusivity were 0.6723 kg water kg −1 dry matter h −1 and 2.7696 × 10 −10 m 2 s −1 , respectively, on the drying air flow rate of 0.32 kg s −1. A quality assessment shows that the lipid content of the dried silkworm pupae was not affected by the solar tunnel dryer. A slight decrease of polyunsaturated fatty acid (PUFA) was observed.

Drying Technology, 1999

This paper describes a strategy for reducing moisture in paddy by fluidized bed drying, tempering... more This paper describes a strategy for reducing moisture in paddy by fluidized bed drying, tempering and ambient air cooling. Experimental results showed that after the three processes, moisture content was reduced from 33 % to 16.5 % dry-basis within approximately 53 minutes. During the first process, a fluidized-bed dryer was used to reduce the moisture content of paddy down to

Biosystems Engineering, 2008

The objective of this study was to conduct an experimental analysis to investigate the performanc... more The objective of this study was to conduct an experimental analysis to investigate the performance of a mixed mode type forced convection solar tunnel dryer (STD) which was used to dry silkworm pupae under tropical weather conditions of Mahasarakham, Thailand. The dryer consisted of a transparent glass covered flat-plate collector and a drying tunnel connected in series to supply hot air directly into the drying tunnel using a blower. The dryer was 6.2 m long and 1.8 m wide. The drying unit had a loading capacity of 30 kg of silkworm pupae. The effect of the drying air flow rate was examined. The drying time depended on the drying air flow rate and temperature. Moisture content of the silkworm pupae was reduced from 3.70 kg H 2 O kg À1 dry matter to 0.20 kg H 2 O kg À1 dry matter in 570 min at the corresponding air flow rate of 0.30 kg s À1 and it took 945 min in open sun drying; drying time was reduced by about 40%. A quality assessment shows that the lipid content of the dried silkworm pupae was not affected by the STD. A slight decrease of polyunsaturated fatty acid (PUFA) was observed. Maximum drying and overall efficiencies were 30.14% and 19.68%, respectively, at the air flow rate of 0.30 kg s À1. The economic analysis indicates that the payback period is 1.42 years. Due to its simplicity, the proposed system is relatively inexpensive. Therefore, commercial application seems to be viable.

Thermal Science, 2020

Konjac glucomannan (KGM) can be obtained from tubers (called corms) of various species within the... more Konjac glucomannan (KGM) can be obtained from tubers (called corms) of various species within the Amorphophallus genus. Among the most popular species for use in food industry is Buk Nuea Sai (Amorphophallus muelleri), a native species in Thailand. Drying process can be helpful in preserving KGM during long storage periods. However, the existing drying systems are often slow and lead to drying delays and subsequently quality reduction of the dried product. Given the economic importance of KGM, new, more efficient drying systems, have to be developed. The present study focuses on the drying kinetics of konjac dices in a fluidized bed, operating at a constant air velocity of 2.5 m/s and air temperatures of 50, 60, and 70?C. Six empirical mathematical models were selected to describe and compare the drying characteristics of konjac dices subjected to these conditions. The model coefficients were determined by non-linear regression analysis. Among the tested models used to describe the ...

The peel of dragon fruit is a byproduct left over after consuming. Normally, the use of plants as... more The peel of dragon fruit is a byproduct left over after consuming. Normally, the use of plants as antioxidant source must be dried before further process. Therefore, the aim of this study is interesting to dry the peel by heat pump dryer (45 ºC) and fluidized bed dryer (110 º C) compared with the sun drying method. The sample with initial moisture content of about 85-91% wet basis was dried down to about 10% wet basis where it took 620 and 25 min for heat pump dryer and fluidized bed dryer, respectively. However, the sun drying took about 900 min to dry the peel. After that, sample was evaluated antioxidant activity, -carotene and betalains contents. The results found that the antioxidant activity and betalains contents of dried peel obtained from heat pump and fluidized bed dryings were significantly higher than that sun drying (p 0.05). Moreover, the drying by heat pump provided the highest -carotene content.

Drying Technology, 2002

Drying and tempering models for paddy drying by a fluidised bed technique have been developed to ... more Drying and tempering models for paddy drying by a fluidised bed technique have been developed to describe the moisture movement inside a single paddy kernel. The grain shape was considered as a finite cylinder. The internal diffusion is an important contribution to control the drying rate of paddy. The dependence of effective diffusion coefficient on drying temperature can be adequately explained based on Arrhenius form. The parameters of this equation were evaluated in the range of temperatures between 110 o C and 170 o C by using the regression analysis with 189 experimental drying data. As compared with no tempering, the faster drying rate can be obtained by tempering treatment between drying stages, The effect of degrees of tempering on determining the moisture reduction in the second stage has also been explored. According to the simulation results, a prediction equation of the required tempering time for the tempering index of 0.95 has been established in which the drying air temperature, initial moisture content and drying time are taken into account. The tempering time for 35 min is recommended for the continuous fluidised bed dryers being operated in rice mills.

Journal of Stored Products Research, 2005

This analysis of the drying process is based on experiments and simulations of the influence of t... more This analysis of the drying process is based on experiments and simulations of the influence of temperature in the fluidised-bed dryer, moisture content and tempering period on head-rice yield, and operating time. A mathematical model incorporating the head-rice yield equation for predictions of the moisture content and the grain temperature in each drying stage and the final head-rice yield, is in good agreement with experimental data. The moisture content after first-stage drying and tempering have a dominant effect on head-rice yield and operating time in reducing high-moisture contents to a safe level. The simulation results recommend that the allowable temperature should be not higher than 150 °C for the first stage and the moisture content after first-stage drying should be not lower than 22.5% dry basis, with subsequent tempering for at least 25 min.