Modified Page Model Research Articles

Analysis of the interaction between airflow and high-voltage electric fields on drying characteristics of carrots using heat pump-electrohydrodynamics combined drying

The study investigates the drying characteristics of carrots under different coupling forms of airflow and high-voltage electric fields (parallel flow, PF, and cross flow, CF) using heat pump-electrohydrodynamics (EHD) combined drying. The results show that, compared to single heat pump drying, the combined drying under PF mode reduces carrot drying time by 13.33 %–31.58 %, increases effective moisture diffusivity (Deff) by 17.80 %–32.32 %, increases specific moisture extraction rate (SMER) by 12.25 %–34.26 %. While the combined drying under CF mode reduces carrot drying time by 12.5 %–18.18 %, increases Deff by 7.27 %–13.14 %, increases SMER by 4.64 %–12.58 %. The improvements in parameters under the CF mode are weaker than those under the PF mode. Additionally, the β-carotene content under PF mode is consistently higher than under CF mode. Based on the experimental results, the Modified Page model was improved, yielding an updated model MR = aexp(-(kt)^n), with an R2 value of up to 0.9999–1, which provides theoretical guidance for optimizing the heat pump-EHD combined drying process.

Experimental investigation and statistical analysis of the microwave drying process on the physical properties of Y2O3–Al2O3–ZrO2 composite ceramic powder

Y2O3–Al2O3–ZrO2 composite ceramic powders are an important structural and functional material. The agglomeration problem in the ceramic powder drying process must be resolved to prepare high-quality ceramic powder, and choosing the right drying techniques can significantly lessen ceramic powder agglomeration. Y2O3–Al2O3–ZrO2 ceramic powder was dried using microwave drying. The drying kinetics of the powders were examined with their initial mass, moisture content, and microwave power. As microwave power, beginning moisture content, and initial mass rose, the average drying rate also increased, according to the experimental data. To better characterize the microwave drying process, the drying data were fitted and analyzed using four thin-layer drying kinetic models, namely Quadratic Model, Modified Page, Wang and Singh, and Two-term exponential. The outcomes demonstrate the good fitting effect of the Modified Page model and the compliance of the fitting parameters with the law. The samples before and after drying were characterized by Fourier transform infrared spectroscopy. Calculating the diffusion coefficient by Fick's second law shows that the effective diffusion coefficient of Y2O3–Al2O3–ZrO2 composite ceramic powder is 5.6 × 10−11 m2/s when the initial moisture content is 5%, the microwave heating power is 560 W, and the initial mass is 25 g. The activation energy for microwave drying of Y2O3–Al2O3–ZrO2 ceramic powders was calculated to be 22.83 W/g according to the Arrhenius formula. This paper aims to provide a theoretical basis and rich experimental data for the study of microwave drying of Y2O3–Al2O3–ZrO2 composite ceramic powder.

Effect of microwave drying on TiO2–Y2O3–ZrO2 composite ceramics and drying kinetic study

TiO2–Y2O3–ZrO2 composite ceramics exhibit excellent abrasion resistance, corrosion resistance, and high-temperature resistance, making them vital structural-functional materials in ceramics and refractories. The key to preparing high-quality TiO2–Y2O3–ZrO2 ceramic powders lies in controlling the agglomeration rate, which can be optimized by choosing an appropriate drying method. This study utilized microwave drying techniques to dehydrate TiO2–Y2O3–ZrO2 ceramic powders. It was found that the average drying rate is proportional to initial masses, initial moisture contents and microwave heating powers. To describe the drying process, four models—the Quadratic, Wang and Singh, Modified Page, and Page—were employed. The best model for the drying process was the Modified Page model. The specimens were analyzed to assess the alterations in the samples pre and post-drying by scanning electron microscopy and Fourier transform infrared spectroscopy. The findings revealed that microwaves can hasten the drying process of TiO2–Y2O3–ZrO2 and enhance its spread. Utilizing Fick's second law, the effective diffusion coefficient was ascertained, showing an inverse proportionality to the sample mass, and a proportionality to the microwave heating power and initial moisture content. Using the Arrhenius exponential model, it was ascertained that the microwave drying process's activation energy stands at 13.81834 W/g. This paper demonstrates that microwave drying effectively achieves efficient drying and lays the theoretical and experimental groundwork for the microwave heating and drying of other powdered materials.

Drying kinetics and energy efficiency of soot ash of smelting silicon manganese alloys under microwave heating

When smelting silicon manganese alloy in an industrial electric furnace, it will produce smoke and dust waste gas, which can be utilized again back to the furnace and improve the utilization rate of raw materials after a particular trapping device and collection treatment. However, at higher moisture levels, they are prone to explode. Effects of various initial masses, initial moisture contents, and microwave output powers on the soot ash of smelting silicon manganese alloy were studies. The findings indicate that the microwave drying rate increases with all three variables. The time for complete microwave drying is directly proportional to the sample's initial moisture content and the sample's initial mass, and the time for complete microwave drying is inversely proportional to the microwave output power. The results demonstrate that the Modified Page model can accurately describe the microwave drying process. The experimental data were fitted experimentally by drying kinetic models. Microscopic characterization of soot ash from refining silico‑manganese alloys before and after drying was carried out using FTIR and SEM. Through FTIR characterization, the peak value of the -OH absorption peak decreases upon drying, and SEM results in no agglomeration caused by microwave drying and better dispersion of the soot ash of the dried smelted silica‑manganese alloys, all of which proved that microwaves could effectively remove water. It was discovered that the diffusion coefficient increased gradually with increasing power when it was computed using Fick's second law. The diffusion coefficient increases and then decreases as the moisture content increases. The diffusion coefficient decreases as the initial mass increases. Activation energy of microwave drying of soot ash from the refining of silicomanganese alloys was calculated to be −1.4467 W/g. Its purpose is to offer a detailed guide for the industrial drying of soot ash from silicomanganese alloy refinement using microwave drying technology.

Drying characteristics and thin layer drying model of semi-mature rice paper

Abstract The effects of different hot air speeds and temperatures on the drying characteristics of half-ripe rice paper were investigated by hot air convection drying experiments. The thin-layer drying experiments were carried out at three different combinations of air speeds of 1.97 m/s, 3.00 m/s, and 3.90 m/s and temperatures of 85 °C, 100 °C and 115 °C. The results show that among the 10 drying kinetic models selected, the Modified Page model is the most suitable model to describe the drying characteristics of the thin layer of half-ripe rice paper; the whole drying process exists obvious ascending, constant and descending processes; the effective moisture diffusion coefficient of half-ripe rice paper is in the range of 1.52656 × 10−9 m2/s–3.15816 × 10−9 m2/s, whose size increases with the increase of the hot wind speed and temperature. Its magnitude increases with the increase of wind speed and temperature; the drying activation energy of half-ripe rice paper is 6.55 kJ/mol calculated by Arrhenius equation.

Physico-chemical and Functional Properties of Drumstick Leaf Powder

The study was conducted to analysis of physico-chemical properties of drumstick leaf powder. Drumstick leaf were dried in a convective hot air dryer at 30oC, 40oC and 50oC. The air velocity inside the dryer was 2-3 m/s, the drying process takes 6 hrs, 27hrs, and 19 hrs time to dry the product at 30⁰C, 40⁰C, and 50⁰C.
 The experimental drying data of drumstick were applied to six Moisture ratio models, namely, the Newton model, modified Page model, Henderson and Pabis, Logarithmic, Two term and Exponential Model was found to be the best for explaining the drying characteristics of drumstick leaf. The effective moisture diffusivity varied from 3.651 ×10-11, 4.503×10-11 and to 7.343×10-11 over the temperature range studied, with activation energy of 28.281 kJ/mol for drying of drumstick leaf. The drumstick leaf powder contains moisture 10.85 to 15.56 %, protein 22.88 to 23.979 %, fat 1.80 to 2.42 %, fibre 11.53 to 12.16 %, ash 3.69 to 4.93 %, carbohydrate 40.94 to 849.25% The flour had average water absorption capacity (3.081to 4.22l g/cc), bulk density (3.081 to 0.445 g/cc) were recorded.

Some Aspects of the Modelling of Dried Red Beets Rehydration Process

Some dehydrated products must be rehydrated before consumption or further industry processing. Optimization of the rehydration process needs mathematical models of the process. Despite the widespread use of computers and their associated software, empirical equations are still widely used in view of their simplicity and ease of computation. The mathematical description of the kinetics of mass gain, volume increase, dry matter loss, and moisture content increase and changes of rehydration indices during the rehydration of dried red beets was investigated. The effects of drying air temperature (Td), drying air velocity (vd), characteristic dimension (L), and rehydration temperature (Tr) on model constants were also examined. Red beets cubes (10 mm) and slices (5 and 10 mm) were dried in natural convection (vd = 0.01 m/s), forced convection (vd = 2 m/s), and fluidization (vd = 6 m/s) at Td = 50, 60, and 70 °C. The rehydration was conducted in distilled water at Tr = 20, 45, and 70 °C. The kinetics of rehydrating dried red beets was modelled applying five empirical models: Peleg, Lewis (Newton), Henderson–Pabis, Page, and modified Page. Equations were developed to make the model constants dependent on Td, vd, L, and Tr. Artificial neural networks (ANNs) (feedforward multilayer perceptron) were adopted to condition the rehydration indices on Td, vd, L, and Tr. The following models can be recommended as the most acceptable: (1) the modified Page model for mass gain (RMSE = 0.0236–0.0897) and for volume increase (RMSE = 0.0213–0.0972), (2) the Peleg model for dry mass loss (RMSE = 0.0161–0.610), and (3) the Henderson–Pabis model for moisture content increase (RMSE = 0.0350–0.1062). The ANNs performed the rehydration indices in an acceptable way (RMSE = 0.0528–0.2285). Both the rehydration indices and model constants depended (but to a different degree) on the investigated drying and rehydration conditions.

Experimental evaluation of performance, drying and thermal parameters of guava slabs dried in a forced convection indirect solar dryer without and with thermal energy storage

The forced convection indirect solar dryer (FISD) provides better quality food products for lower duration than open sun drying (OSD). The drying experiments on guava slices were executed on an FISD without a thermal energy storage (TES) (model-1) and with TES (model-2) to determine the impact of TES on drying. The guava slices attained a final moisture content in 14 and 9 sunshine hours in model-1 and model-2, respectively. The drying models appropriate to describe guava slices in model-1, model-2 and OSD were Page and modified Page models. The drying rate in model-1 and model-2 was found to be 0.3936 and 0.5728 kg/h, while the effective diffusivity was 7.98 × 10−9 and 8.63 × 10−9 m2/s (average), respectively. The average heat and mass transfer coefficients were 4.842 W/m2K and 4.20 × 10−3 m/s in model-1 & 5.394 W/m2K and 4.68 × 10−3 m/s in model-2. The average drying efficiency and specific moisture extraction rate were 6.84 % and 0.597 kg/kWh in model-1 & 9.77 % and 0.972 kg/kWh in model-2. The specific energy consumption and activation energy were decreased by 38.57 % and 5.25 % in model-2 compared to model-1. The performance, drying and thermal parameters were found to be better in model-2.

Convective drying of black rice grains (Oryza sativa L.): new mathematical modeling insights and thermodynamic properties

The aim of this study was to investigate the thin layer drying of brown rice grains at different temperatures (35-75 °C), exploring its kinetics and thermodynamic properties. Black rice grains (30% b.u.) were subjected to convective drying, and the experimental data were subjected to analysis of theoretical, semi-theoretical and empirical drying models, and thermodynamic parameters were calculated. Increasing temperature accelerated drying, shortening the time required to reach moisture balance. The modified Page model modified by Cavalcanti-Mata showed excellent fit to the experimental data, standing out for its simplicity and effectiveness in describing the relationship between water content and drying time. The analysis of thermodynamic properties revealed that the activation energy increased with temperature, evidencing its influence on moisture removal. The observed variations in thermodynamic properties reinforce the importance of considering energy factors in drying. The results offer insights to optimize the black rice grain drying process, contributing to advances in the food industry and providing a basis for future research in the processing of agricultural products.

Application of response surface methodology for optimisation of Cornelian cherry - Capia pepper leather dried in a heat pump drying system

The heat pump drying system was optimised for cornelian cherry-capia pepper leather production development using response surface methodology. The central composite design was used to optimise the process parameters in terms of drying time, coefficient of the performance of heat pump, coefficient of the performance of the whole system, specific moisture extracted ratio, energy consumption, drying rate and colour values. The optimal condition of independent variables was obtained as a cornelian cherry pulp concentration of 47.419% and drying temperature of 33.574°C with composite desirability of 0.846. Moreover, hydroxymethylfurfural (HMF) and effective moisture diffusivity (Deff) values of all runs were analysed. HMF was not determined in cornelian cherry-capia pepper leather. Deff values of cornelian cherry-capia pepper leather were between 1.026×10-9 - 1.532×10-9 m2s-1. The drying behaviour of cornelian cherry-capia pepper leather with optimal conditions acquired with the central composite design was evaluated with seven thin-layer drying models. The statistical parameters based on R2, root mean square of error and χ2 values were determined between 0.8267 to 0.9845, 0.004087 to 0.035626 and 0.000853 to 0.066247, respectively. Page and Modified Page models were assumed to represent the heat pump drying behaviour of the cornelian cherry-capia pepper leather in thin layers compared to the other models.

Effect of ultrasound‐assisted thin bed drying for retaining the quality of red bell pepper and compare the predictive ability of the mathematical model with artificial neural network

AbstractRed bell peppers (Capsicum annuum L.) are low in calories and high in nutrients, including vitamins A and C. Various factors such as weight loss, senescence, and microbial influence affect their quality during storage. To address this, the present study aims to preserve and retain the quality of red bell peppers using ultrasound‐assisted thin‐bed drying. The results were analyzed using an Artificial Neural Network (ANN) for more accurate prediction of variables involved in the process. Variations in moisture ratio and moisture content during drying were calculated and predicted. The Midilli model provided satisfactory curve fitting at an air velocity of 1.5 m/s, with R2 = 0.9993, χ2 = 0.0002, and RMSE = 0.0134. The two‐term and modified page models fit better with drying curves at air velocities of 2 and 2.5 m/s, with R2 = 0.9995, χ2 = 0.002, RMSE = 0.0016 and R2 = 0.9996, χ2 = 0.00003, RMSE = 0.00003, respectively. However, the trained standard backpropagation ANN algorithm demonstrated excellent predictive ability, outperforming the mathematical models with R2 = 0.9989 (training), MSE = 0.0001 (training), and R2 = 0.9996 (testing), MSE = 0.0002 (testing). Most importantly, the ultrasound‐assisted drying process retains the essential nutrients in red bell peppers, including vitamin C, carotenoids, polyphenols, and flavonoids, across various conditions. The antioxidant potential, as measured by DPPH and FRAP assays, remains largely unchanged compared to untreated samples. However, ABTS activity shows a significant difference at an air velocity of 1.5 m/s and temperatures of 60 and 70°C compared to the control sample.Practical applicationsIn terms of vitamins and antioxidants, red bell peppers are a great provider. Interestingly, capsaicin, the substance responsible for spiciness, is found in very little to no quantity in red bell peppers making it appealable to consumers. To achieve a certain level of processing, the quality of the dried product needs to be monitored while fulfilling the needs of consumers. Particularly, the quality‐determining parameters were vitamin C, total carotenoids, total polyphenols, total flavonoid content, DPPH, ABTS, and FRAP activity. These qualities were retained after drying with the potential novel combination of ultrasound with thin bed drying at low temperatures and air velocity. This means that the bioactive compounds responsible for improving the health of humans are readily available in dried form all year round. The drying kinetics were modeled, predicted, and compared with mathematical and ANN models.

Evaluation of drying kinetics and quality parameters of rosehip pestils dried by three different methods

BACKGROUND: Rosehip fruits cannot be eaten as entire fruits in their fresh feature so they processed into various products including pestils. OBJECTIVE: In the current work, rosehip pestil as a new healthy snack food was developed by using hot air (HA) drying at 55, 65 and 75°C, vacuum (VC) drying at 55, 65 and 75°C with 25 kPa and microwave (MCW) drying at 90 and 180 W. METHODS: The effect of three different drying methods on drying kinetics and quality parameters i.e., total phenolic content (TPC), antioxidant capacity (AC), Hydroxymethylfurfural (HMF) formation, lycopene, β-carotene content, element composition, color, texture and sensorial properties of rosehip pestils was studied. RESULTS: Wang and Singh model was best fitted for MCW drying at 90 W, however Page and Modified Page models were best fitted for other drying conditions. The rosehip pestils dried by MCW drying method had highest drying rate, TPC, AC, lycopene and β-carotene content, element concentration, color values, whereas their HMF content and sensorial properties were not acceptable. Sensory evaluation results indicated that rosehip pestils dried with HA was rated the most acceptable. CONCLUSIONS: It was concluded that rosehip pestil with its sensorial and nutritive properties could be an alternative product for the functional food market. However, it has been seen that the drying methods used alone have some disadvantages. For this reason, it may be possible to eliminate these disadvantages if hybrid drying methods (for example MCW drying followed by HA or VC drying) are preferred in future studies.

Potential of infrared drying and cell-protective agent efficiency on survival of Lactobacillus plantarum probiotic in fermented soybean meal

The drying effectiveness of fermented soybean meal (FSBM) was studied using infrared radiation, with cell-protective agents and drying temperature explored to maintain Lactobacillus plantarum 7–40 probiotic survival during decreasing FSBM moisture content (MC). Results showed that maltodextrin (MTD) was suitable for protecting probiotic cells, similar to fructo-oligosaccharides (FOS). The MC of MTD-containing FSBM decreased faster than other cell protectants, while high temperature infrared drying (IRD) reduced the MC more quickly than low IRD temperatures, thereby impacting probiotic L. plantarum 7–40 survival. IRD decreased the MC of the FSBM to close 10% faster than hot air drying (HAD) at 40 °C by 10 h. Mathematical models were used to simulate the IRD profiles of FSBM. The Page and modified Page models simulated the schematic moisture ratio better than the other drying models. The thermal death kinetics of probiotic under IRD were not significantly different comparing HAD. In comparison, the effective diffusivity of IRD was greater than HAD by 2.6 times compared to 40 °C. The IRD at 40 °C was suitable for drying FSBM and provided higher energy consumption efficiency than conventional HAD. Findings suggested that applying MTD as cell-protective agent gave high probiotic survival and did not impact FSBM moisture removal of IRD. IRD delivered improved energy consumption efficiency compared to HAD as an attractive process for dehumidifying probiotic-based products.

Research on the drying kinetics for the microwave drying of Y2O3–ZrO2 ceramic powder

Y2O3–ZrO2 ceramic powder has emerged as a vital structural and functional material in ceramic applications owing to its remarkable performance including wear resistance, temperature resistance, and corrosion resistance. Agglomeration during the drying process is the other key issue that needs to be resolved, which improving the quality of zirconia powder becomes crucial in reducing industrial expenses. This study focuses on investigating the influence of modern microwave heating technology on the drying kinetics of Y2O3–ZrO2 ceramic powder. The experimental results revealed that the average drying rate of Y2O3–ZrO2 ceramic powder increased with sample water content, microwave heating power, and sample mass. Four kinetic fitting models, namely Page, Wang and Singh, Quadratic Model, and Modified Page, were employed to analyze the experimental data for Y2O3–ZrO2 ceramic powder with a mass of 20 g, initial water content of 7.5%, and the microwave heating power is 480 W. Among these models, the Modified Page model demonstrated the best fit and effectively described the drying kinetics of Y2O3–ZrO2 ceramic powder. The Modified Page model successfully captured the kinetics across varying masses, microwave heating powers, and initial water content. FT-IR spectroscopy was employed to describe the material before and after microwave drying. The results exhibited a significant reduction in water molecule content in the Y2O3–ZrO2 ceramic powder after microwave drying, thus confirming the high efficiency and rapidity of the microwave drying procedure. This research provides comprehensive experimental data and offers a theoretical foundation for the industrial application of microwave-enhanced drying of Y2O3–ZrO2 ceramic powder.

Evaluating Kinetics of Convection Drying and Microstructure Characteristics of Asian Seabass Fish Skin without and with Ultrasound Pretreatment.

Convection drying in combination with ultrasound pretreatment has emerged as a promising technology for seafood manufacturing. The primary objective of this research was to model the mass transfer process of Asian seabass (Lates calcarifer) fish skin without and with ultrasound pretreatment during convection drying at different temperatures (45, 55, and 65 °C). Additionally, the study aimed to examine the impact of ultrasound pretreatment and temperatures on the drying characteristics and specific energy consumption for drying of Asian seabass fish skin. Seven semi-theoretical models, namely Lewis, Page, modified Page, Vega-Lemus, Verma, Henderson and Pabis, and two-term models, were employed to characterize the moisture transfer process. The results of the study indicated a decrease in the moisture content as the drying time increased at different drying temperatures. Higher drying temperatures were associated with an increased drying rate. Among the mathematical models tested, the modified Page model provided a satisfactory description of the thin-layer drying characteristics of fish skin. Fick's law of diffusion was utilized to determine the effective moisture diffusivities. Comparing the drying of fish skin without (SS) and with ultrasound pretreatment (US-SS), the drying of the latter generally showed higher Deff values. The temperature dependence of the effective diffusivity coefficient was well described by the Arrhenius-type model. An increase in the drying temperature resulted in an increment of the effective moisture diffusivity. In general, the skin pretreated using ultrasound had a reduced drying time, by up to 28%. Additionally, this approach contributed to an approximate 22% reduction in the specific energy consumption, concurrently enhancing the energy efficiency. The microstructure analysis showed that fresh and dried US-SS samples had a more open structure and higher porosity, in comparison to the corresponding SS samples. These findings contribute to the knowledge on the application of ultrasound as the pretreatment of fish skin before drying and provide valuable insights for the development of potential drying techniques in the seafood industry.

Effects of conductive drying on drying kinetics and retention of bioactive compounds in mistletoe leaves

The aim of this study was to investigate the effect of conductive drying on the quality characteristics of mistletoe leaves. Drying generally took place in both constant and falling rate periods. Page and Modified Page models with the highest R2 and lowest χ2 and RMSE values were found to satisfactorily describe the drying behavior of the mistletoe leaves. Changes in total phenolic content (TPC), total antioxidant activity (TAA), and ascorbic acid content (AAC) of mistletoe leave samples were measured during conductive drying at three different temperatures (50, 60, and 70 °C). Total phenolic content was determined as 686.61±2.96 mg GAE/100 g DM in fresh samples and ranged between 150.97–105.09 mg GAE/100 g DM after drying. The total antioxidant activity values of dried mistletoe leaves decreased significantly compared to fresh ones. The ascorbic acid content of mistletoe leaves was found to be 84.00±2.42 mg/100 g DM before drying. The total antioxidant activity and ascorbic acid content samples were degraded following the second order reaction kinetics. However, the change in the total phenolic content occurred in accordance with the first-order kinetic model. The higher antioxidant activity, phenolic compounds, and ascorbic acid content, and lower half-life values were observed in conditions where the temperature (50 °C) is low.

Development of infrared-assisted hybrid solar dryer for drying pineapple slices: Investigation of drying characteristics, mass transfer parameters, and quality attributes

The research aims to the development and performance evaluation of an infrared-assisted hybrid solar dryer (IR-HSD) for drying pineapple slices. The IR-HSD contains an evacuated tube solar collector, blower assembly, drying chamber, infrared heater, phase change material (PCM) chamber, etc. The study investigates and compares the thermal profiling, drying kinetics, mass transfer parameters and quality attributes of pineapple slices dried using different methods, such as direct drying, phase change material (PCM)-assisted drying, PCM + IR-assisted drying, and sun drying. The average temperatures achieved inside the drying chamber for direct drying and PCM-assisted drying were 60.16 °C and 57.29 °C, respectively, while the temperature reached 60 °C for PCM + IR assisted drying. The average drying rate in PCM + IR drying was higher than in direct and PCM-assisted drying methods. The best-fitting models were the Modified Page model for direct and PCM + IR-assisted drying and the Midilli-Kucuk model for PCM-assisted and sun drying. The higher effective moisture diffusivity for PCM + IR-assisted drying was 2.59 × 10−9 m2/s, followed by direct and PCM-assisted drying. Similarly, the convective mass transfer coefficient obtained was 1.085 × 10−7 m/s, 8.321 × 10−8 m/s, and 1.381 × 10−7 m/s for direct, PCM-assisted, and PCM + IR-assisted drying, respectively. The superior quality attributes such as total flavonoid content (TFC), total phenolic content (TPC), and antioxidant activity were observed in all drying approaches with retention of colour except open sun drying, which decreased significantly. FTIR spectroscopy analysis confirmed the presence of different bioactive, including aromatic compounds, phenols and hydrocarbon functional groups. The infrared-assisted hybrid solar drying of pineapple slices showed a better drying process and quality attributes.

A combined analysis of the drying and decomposition kinetics of wood pyrolysis using non-isothermal thermogravimetric methods

In this paper, we evaluate the pyrolysis of wood biomass as a combination of drying and thermal decomposition via the Page and modified Page models for drying kinetics as well as the Friedman and Vyazovkin methods for solid-state decomposition kinetics. This approach was applied to data obtained from thermogravimetric analysis of three wood species (spruce, pine, and birch) at 5, 20, and 30 K/min temperature programs.According to the Page model, the average activation energies for spruce, pine, and birch wood between 30 and 150 °C were 12.87 ± 1.08, 13.32 ± 0.48, and 11.61 ± 0.59 kJ/mol, respectively. While all activation energies fell between 11.0 and 14.5 kJ/mol, the modified Page model predicted slightly higher energies, with an average absolute difference of 6.4% from Page's predictions. The activation energies and pre-exponential factors predicted by both models were lower at low heating rates, with the pre-exponential factor yielding significantly large differences between 5 and 30 K/min. These results showed that drying kinetics were significantly affected by heating rates. In addition, the goodness-of-fit analysis revealed that both models were reasonably accurate when predicting wood drying kinetics.For the analysis of solid-state decomposition kinetics, a comparison of Friedman's linear differential method (FR) and Vyazovkin's nonlinear integral method (NLN-INT) was conducted at temperatures higher than 150 °C. In contrast to the NLN-INT method, the FR method predicted activation energies slightly higher, with an average absolute difference of about 8.4%. Evaluation of the relative errors revealed that both the FR and NLN-INT methods performed similarly. However, the Friedman (FR) method provided a reasonable fit to multistep decomposition kinetics through the simultaneous estimation of activation energies and pre-exponential factors. Nevertheless, the activation energies estimated by both the FR and NLN-INT methods were unreliable at conversions of α < 0.15 and α > 0.85. Validation of the kinetic results was conducted with differential thermogravimetric data at a heating rate of 5 K/min.

DRYING CHARACTERISTICS AND QUALITY OF RED PEPPER SLICES UNDER HOT AIR FOLLOWED BY MICROWAVE FINISH DRYING

Red pepper slices were subjected to hot air, microwave and hot air followed by microwave finish drying. Hot air followed by microwave finish drying decreased the drying time required when compared to drying with hot air drying. Among the five thin layer drying models that were used to fit the experimental data, Page and Modified Page models gave the highest correlation coefficient, lowest root mean square error, and reduced chi-square, thus indicating that Page and Modified Page models best described the hot air drying of red pepper slices. In this study, ascorbic acid degradation and color changes during drying were also investigated. In the drying process at 65ºC for 9 hours, ascorbic acid content decreased to 330.94±1.45 mg/100g dry matter after 8 hours. After 8 hours, no ascorbic acid was found. Moreover, the kinetics of ascorbic acid and color changes of red pepper slices, due to drying by hot air drying were studied. It was confirmed that ascorbic acid degradation followed first order kinetics. The results indicate that hot air followed by microwave finish drying may be an alternative method for the drying of red pepper slices since it provides good quality product in shorter time.

Preparation of onion powder by freeze-thaw pretreatments: Influence of different thawing methods on drying kinetics and quality properties

Onion is one of the foremost vital vegetables/spices delivered as a source of cash salary and for flavoring nourishments. In any case, postharvest misfortune amid capacity remains a major challenge. Therefore, in this study the effects of freeze-thaw pretreatments on drying kinetics and qualitative properties (color, total phenol content, antioxidant activity, total flavonoid content) of hot air dried onion was studied. Three pretreatment methods, including ultrasound (U), freezing-water thawing (F-T, 25°C), and Freezing- ultrasonic- assisted thawing (U-T) were individually used. FTIR spectra of the prepared powder samples showed the sample treated with F-T has a similar spectrum to the raw onion sample, demonstrating the least modification in sample structure relative to the alternative prepared samples. Results showed that the use of F-T pretreatment before grape drying reduced the color changes, total phenol content (from 16.92 ± 0.31 to 12.95 ± 0.13 mg GAE/g DW), total flavonoid content (3.8 ± 0.15 to 2.83 ± 0.09 mg QE/g sample), antioxidant activity effective moisture diffusion coefficient and activation energy (from 12.43 (control samples) to, 13.51 (U), 16.31 (F-T), and 20 ± 3 kJ/mol (T-U)). The optimum model for the drying kinetics of treated and controlled onions was the Modified Page model, with the greatest R2 and the lowest RMSE and χ2. Generally, the appropriateness of F-T pretreatment is employed in onion hot air drying to enhance the quality properties of dried onion.