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Performance comparison between gradient orifice and uniform orifice distributors in rotating fluidization for coated jasmine rice
(2026-04-01)
Prakotmak, Preeda
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Phothong, Watchama
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Rattanamechaiskul, Chaiwat
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Junka, Nittaya
A rotating fluidized bed coater offers an alternative technology in which particles are fluidized by balancing centrifugal, buoyant, and gravitational forces, thereby improving coating homogeneity and mass transfer. The coating performance between the gradient orifice distributor (GOD) and the uniform orifice distributor (UOD) was compared at rotational speeds of 20, 70, or 120 rpm. The experiment was set up to coat a turmeric-extract solution onto the surface of jasmine rice. The coating substance was sprayed from the nozzle at 35 or 40 mL/min at an air-atomization pressure of 1.5 bar for 6 or 8 min. Hot air (55 or 60 °C) flows were passed at an inlet velocity of 2.9 m/s, with 85 % by volume of the air recycled. The quality of the sample was evaluated based on its final moisture content, percentage of fissure kernels, head-coated rice yield, color, coating efficiency, total phenolic content, and antioxidant activity. Based on the results, GOD was a suitable distributor plate for producing turmeric-extract-coated rice. For optimal coating conditions, the jasmine rice should be coated at a drying temperature of 55 °C, using a coating solution spray rate of 35 mL/min, a rotational speed of 70 rpm, a spraying coating time of 6 min, and a drying time of 10 s after the spraying stage. Using these conditions, the coating efficiency was 84.2 % and the antioxidant activity of the coated rice was 30.53 % higher than that of the referent white rice.
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Enhancing biodiesel yield and purification with a recently developed centrifuge machine: A response surface methodology approach
(2024-04-15)
Limmun, Warunee
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Chungcharoen, Thatchapol
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Rattanamechaiskul, Chaiwat
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Phetpan, Kittisak
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Limmun, Wanida
Biodiesel production processes, such as gravity settling, have limitations in terms of biodiesel yield, purification efficiency, operating time in the separation process, and more extensive equipment. Therefore, this study has focused on using a recently developed centrifuge machine for biodiesel separation to address these challenges due to its compact design, high efficiency, and simplicity. Additionally, this study aimed to optimize the separation efficiency of glycerol from biodiesel using a centrifuge machine, employing response surface methodology (RSM) with central composite design (CCD). The optimum conditions for separating glycerol from biodiesel via centrifuge machine are a rotation speed of 1800 rpm, a mixture flow rate of 192.25 ml/min, and a temperature of 55 °C, respectively. In optimum conditions, 94.52% separation efficiency was achieved. Biodiesel production can be improved, leading to higher yields and greater purity. The utilization of RSM proved valuable in determining the optimum conditions for separation. Furthermore, the machine successfully separated the biodiesel to meet ASTM D6751 and EN 14,214 standards. The results highlight the potential of the centrifuge machine for efficient and reliable biodiesel production, contributing to the advancement of the biodiesel industry.
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Modeling and optimization of moisture diffusion of paddy and brown rice during thermal soaking
(2023-04-01)
Rattanamechaiskul, Chaiwat
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Junka, Nittaya
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Prakotmak, Preeda
In this study, a method involving soaking paddy and brown rice in hot water at different durations and temperatures is investigated. Data are acquired to develop a mathematical model to determine the most appropriate soaking conditions through simulation. Results show that higher soaking temperature at 60 °C yield higher moisture diffusion than lower temperature at 40 °C. The soaking times of paddy until the final moisture was attained at temperatures of 40 °C, 50 °C, and 60 °C were 10, 8, and 6 h, respectively. The dehusking process from paddy to brown rice can decrease soaking time to 7, 5, and 3 h, respectively, compared with that of paddy at the same temperature. The mathematical modeling can reveal the diffusion mechanism inside the grain and accurately predict the suitable soaking condition by brown rice at soaking temperature of 60 °C for 1.5 h. When this condition is used, the specific energy consumption of the soaking process can be reduced to 0.295 kWh kg−1 which is the lowest value in the scope of study. After steaming by commercial process, soaked brown rice is completely generated starch gelatinization as parboiled rice. Practical applications: Soaking is one of the most important procedures in the production of parboiled rice. It requires a significant amount of time as well as affects the specific energy consumption (SEC) and product quality at the final stage. Experiment results are used to develop a mathematical model to determine the most appropriate soaking condition. The shortest time possible to achieve the appropriate grain moisture while maintaining the lowest SEC is desired. Data are acquired to devise methods for reducing the time and energy required to produce parboiled rice.
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Drying modelling of amylose fatty acid complex formation for reducing rapidly available glucose of geographical indication rice during high-temperature fluidisation
(2022-04-01)
Junka, Nittaya
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Rattanamechaiskul, Chaiwat
This study analysed changes in the available glucose of geographical indication rice, Sang Yod variety, from Thailand after drying through the fluidisation technique in the temperature range of 85–115 °C. When the rice with an initial moisture content of 33.3% dry basis was dried at temperature over 85 °C, starch gelatinisation occurred. As the starch underwent gelatinisation, the orderly structure of the starch granules was partially disrupted. Thus, amylose leached out of the granules and simultaneously formed fatty acids in the rice. This created amylose fatty acid complexes (AFCs). This change was detected from the A and V type crystallinity patterns of the starch and complexes using X-ray diffractometry. When drying the rice at 115 °C, the formation of AFCs resulted in rapidly available glucose of dehulled rice decreasing from a medium-high level to a medium-low level; the slowly available glucose value also increased. The drying modelling was developed based on experimental data to explain the observed changes. The developed mathematical model could predict changes in A type crystallinity with the R2 value and average of relative root mean square error of 0.9855 and 6.34%, while those of the V type changes were 0.9879 and 4.64%, respectively. This data can explain the mechanism underlying the available glucose response observed during drying.
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Optimization modeling of fluid bed drying and coating technique to control fungal growth and aflatoxin content in paddy
(2022-01-01)
Junka, Nittaya
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Rattanamechaiskul, Chaiwat
Fluid bed drying with temperatures of 70–130°C, together with a coating system based on a zinc oxide nanoparticle (n-ZnO) solution, was investigated for control of fungal growth in paddy before storage. A mathematical model to find suitable conditions for this process was developed. The installation of the coating system into the drying system was possible and the amount of n-ZnO in paddy, as detected by an X-ray diffractometer, related to the operating time. Total phenolic content decreased by 9.4% when a hot air temperature of 130°C was used. The percentage of fungal growth decreased with an increase in hot air temperature and operating time. This decrease could be expressed by a first-order rate reaction. Specific energy consumption decreased to 72.5% as hot air temperature increased. The mathematical model could predict suitable process conditions to completely control fungal growth and aflatoxin content while maintaining total phenolic content. Novelty impact statement: Sangyod rice is a high-value variety of rice cultivated in Thailand, which is abundant in total phenolic content, including anthocyanins. However, since this species can only be cultivated once a year, the rice is stored in storehouses for long durations of time, where there is the risk of fungal infection. This study reports a novel coating method adapted for the fluid bed drying technique, and its optimization using both experiments and mathematical modeling. The data obtained from this research will have applications for the rice industry.
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Mathematical modelling to control fungal growth in paddy dried using fluidisation
(2021-04-01)
Junka, Nittaya
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Rattanamechaiskul, Chaiwat
Fungi can infect paddy from the planting process through to storage. Contaminating fungi can produce aflatoxins that can persist in the paddy and in storage until it is used to make other products. In the interests of food safety, in this study, we aimed to control the growth of fungi in paddy during storage using mathematical modelling of a drying method that uses fluidisation at temperatures of 70–150 °C. We found experimentally that an increase in the drying rate was related to an increase in the drying temperature. Drying paddy at a high temperature hardened the texture of rice when cooked, owing to the starch gelatinisation. Drying could decrease fungal growth (FG) and aflatoxin content during storage; however, it also resulted in a decrease in the antioxidant properties of paddy. Mathematical modelling and a proposed FG equation were applied to predict a suitable drying condition. The optimal drying condition reduced the risk of FG in stored paddy by ~50% without affecting antioxidant properties.
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Drying and mathematical modelling for the decelerated rancidity of treated jasmine brown rice using different drying media
(2021-01-01)
Junka, Nittaya
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Rattanamechaiskul, Chaiwat
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Wongs-Aree, Chalermchai
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Soponronnarit, Somchart
Jasmine brown rice (JBR) attains a rancid odour because of lipid deterioration, which reduces its shelf life. This study focused on preserving JBR's stability through drying in a fluidised bed at 100–150 °C using different drying media: hot air (HA), humidified hot air (HHA), and superheated steam (SHS). The JBR and the rancid odour caused by thiobarbituric acid (TBA) were analysed. A mathematical model was developed for the drying process, and associated equations were formulated to predict the mechanism underlying changes in TBA during 180 days of storage. The dried samples became harder owing to gelatinisation of starch and decrease in 2-acetyl-1-pyrroline volatility. Changes in JBR quality were correlated to the drying temperature and drying media used. SHS drying at 150 °C decelerated TBA formation the most. The proposed mathematical model and associated equations can predict changes in TBA during storage accurately and be applied to JBR under most drying conditions.
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Modeling of fragment formation of parchment coffee beans for rapid heat and mass transfer during fluidization drying
(2020-08-01)
Rattanamechaiskul, Chaiwat
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Junka, Nittaya
Fluidization drying technique allows fluidized coffee beans to float, resulting in rapid heat and mass transfer, which have been directly associated with an increase in the moisture gradient, creating bean stress. Bean quality is determined by the degree of bean fragmentation caused by drying, an important standard considered in purchasing and selling. We have modeled the drying process to explain the kinetics of bean fragmentation. Drying temperature affected the drying rate and fragmentation of parchment coffee beans. Specific energy consumption varied with the drying rate. Comparing the experimental results for the predicted average moisture content and the predicted bean fragment formation, using a first-order equation, yielded satisfactory results. Modeling enabled the prediction of drying conditions with the lowest possible specific energy consumption, while the final moisture content and bean fragment percentage met commercial standards. Practical applications: The advantage of fluidization drying is rapid heat and mass transfer between material and hot air. In spite of this advantage, a rapid reduction of moisture during fluidization may cause stress to the material, resulting in bean fragmentation. Fragmentation is a physical measurement of bean quality after undergoing the drying process; it is one of the standards that is taken into consideration by buyers and sellers. We have developed a model to explain and predict the kinetics of bean fragmentation during the complex drying process. The predictions of our model can be used as guidelines for drying parchment coffee beans by the fluidization technique.
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Drying guideline to control colour quality of para rubber sheet by computation method
(2018-12-01)
Junka, Nittaya
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Rattanamechaiskul, Chaiwat
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Prachayawarakorn, Somkiat
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Soponronnarit, Somchart
Colour is one of the most important basic physical characteristics of dried para rubber sheets. This characteristic is used to determine the standards and trading prices. In this research, a mathematical model and a colour change equation were developed for para rubber sheet drying in a hot air oven, with the yellowness index (YI) as an indicator. The results show that the mathematical model provides validation of the moisture change and that the first-order rate reaction equation gives a satisfactory prediction of the colour change. The determination coefficient for every drying condition is between 0.9080–0.9742 and 0.9273–0.9813. Suitable drying conditions were used in the simulation using the model and equation, and the shortest drying time was applied in the study. Moreover, the colour value of the simulated para rubber sheet is not higher than that of the reference Unsmoked Sheet (USS) whose moisture is decreased by sun drying and is still in the best standard range.
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Modeling the improved textural properties of purple waxy rice dried through fluidization
(2018-07-04)
Rattanamechaiskul, Chaiwat
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Junka, Nittaya
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Prachayawarakorn, Somkiat
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Soponronnarit, Somchart
This study developed a mathematical model and gelatinization kinetic equation for drying rice through fluidization. This model was then applied to improve the softness and stickiness of non-milled waxy rice (NWR) to be comparable to those of milled waxy rice (MWR). The results demonstrate that the hardness value decreased and that the stickiness value increased with an increasing degree of starch gelatinization. The model and equation were validated based on their satisfactory R2 values and were then used to predict the suitable degree of starch gelatinization and to recommend drying conditions. Compared to MWR, the simulated NWR had an equal hardness value and a larger stickiness value.

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