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This work focus on the effect of Microwave power, Ozonation and Fenton reagent in microwave coupling Ozonation and Fenton oxidation process for the disintegration of COD of leachate. The experiment...

In this study, the drying kinetics and quality characteristics of microwave-assisted hot air dried beef chips were investigated. For this purpose, beef slices were treated with spice mixture (4 g/1...

In the present work, microwave energy was used for casting Al 7039 alloy at 2.45 GHz in the ambient cavity environment. Effects of input power and insulation of the mould assembly during irradiatio...

In this study, microwave drying characteristics of black mulberry were studied at microwave power levels of 90, 180 and 360 W. Obtained experimental drying results were applied to seven mathematica...

The investigation of injection locking of cooker magnetron by a solid-state microwave power source is reported. Experimental results show that a 2.45 GHz cooker magnetron can be locked in continuou...

Pulse-spouted microwave freeze drying (PSMFD) used for Chinese yam cubes was evaluated at three microwave power levels (400, 600, and 800 W). The drying characteristics, energy consumption, and qua...

Phenolic compounds were extracted from pistachio hull using microwave-assisted solvent extraction (MASE). The effects of four parameters, microwave power, extraction time, solvent to sample...

Many people are part of the history of the International Microwave Power Institute (IMPI): Founders, board, and general members, as well as speakers, and paper authors, among others. They have ofte...

The present work deals with investigating the influence of microwave power on mechanical properties of 20 wt.% coir reinforced high-density polyethylene (HDPE) composites. Chopped coir/HDPE composi...

Ferroelectric, barium strontium titanate thin film varactors have been used to rectify and detect microwave signals with frequencies ranging from 2 GHz to 3 GHz. Anharmonic dipolar resonant...

Due to the limitations of single index analysis, the merits and demerits of microwave-assisted permeation process cannot be comprehensively evaluated. However, the analytical hierarchy process (AHP) was applied to optimize the conditions of microwave-assisted diffusion of sugar in blackberry. In this paper, the results of a single-factor experiment were compared with blackberry preserved after the treatment of microwave. An orthogonal rotation test procedure was designed to calculate the composite score of preserved blackberry fruit using AHP, and to determine the optimum processing conditions based on sugar osmosis characteristics. The results showed that the sugar content, vitamin C (VC) content, and color difference of treated blackberry increased with the increase of microwave power, the residence time, and the resulting sugar concentration. The composite grade points are listed to show that the optimum results were as follows: power level, the residence time, and the sugar concentration were,...

Drying characteristic of titanium slag using microwave heating is attempted in the present work, so as to assess the effect of microwave power and sample mass, and to understand the mechani...

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 aw 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 q...

Using the water of lignite as gasification agent, this paper mainly studies the influence of microwave and isothermal gasification on the syngas production and H2/CO ratio to obtain the maximum pos...

Microwave drying of coal has the advantage of volumetric and selective heating, which saves energy and time. However, comprehensive assessment of the moisture migration during microwave drying is lacking. In this study, the low-field nuclear magnetic resonance (LF-NMR) was used for moisture characterization during microwave drying. Moisture migration occurs first in larger pores, whereas the smaller pores appear to remain water-saturated. As the microwave power increases, the drying capacity and drying rate both increase because high-power microwave can open the blind pores to promote moisture seepage. Furthermore, moisture migration during microwave drying is usually directional (i.e., along the bedding plane). The LF-NMR method provides a framework for the determination of moisture migration of coals.

In order to meet the requirements of large-power capacity in microwave-energy industry, the microwave coherent power combining by multiple magnetrons is a valid method to gain a large-power and high efficiency microwave source. In microwave energy applications, microwave absorption of industrial materials is varying in the heating duration and dependent on the dynamic change of materials. It is the first time that a 20-kW continuously power-adjustable injection-locked magnetron source has been achieved, and according to the experiment results, the maximum microwave coherent power combining output reaches 33.1 kW, and the coherent power combining efficiency is higher than 93%. The experiments show that the unbalanced output power between the two magnetrons does not affect greatly on the microwave coherent power combining efficiency. It is a great progress to develop the microwave power source which satisfies the power capacity requirement of microwave energy industry with the real-time power adjust...

The microwave energy absorption behavior of the linear alkylbenzene sulfonate (LAS) surfactant detergent agglomerates was studied while considering changes in the physical properties of the samples. Microwave heating was used to change the internal structure of the agglomerates to make a reduced density (fluffy) product. The absorption of energy within LAS samples indicated fluctuating trends as microwave heating progressed. This was associated with the dielectric properties of the material which are strongly dependent upon the nature (“free” or “bound”) and quantity of water present in them at any instant which changes during heating. Therefore, complete profiles of the energy absorbed by the samples have been recorded to determine their actual power absorption behavior/total energy consumption over time. The bulk density of the agglomerates decreased significantly when exposed to microwave fields. Hot air drying can be combined with microwave heating to reduce the total heating time. It has been...

The ITER Electron Cyclotron Heating (ECH) system provides 20 MW of microwave power from 24 gyrotron sources. The power is transmitted through evacuated, corrugated waveguide transmission lines. The...

The drying of carrot slices in a microwave-assisted fluidized-bed drying (MWFBD) system was investigated. The drying conditions such as the initial microwave power density and the inlet air temperature were optimized. The effects of different pretreatment processes such as water blanching, osmotic drying with 20% sugar solution, and 1% citric acid solution on the drying of carrot slices were investigated under the optimized drying conditions. The drying kinetics and the physical properties of the dried carrot slices were analyzed. Different mathematical models of the drying process were explored and fitted to the drying of carrot slices in MWFBD. The pretreatment of the carrot slices reduced the drying time required and improved the qualities such as color and textural strength of the dried carrot slices.

The key objective of the present research is to optimize and investigate the biodiesel production from ricinuscommunis (castor) oil using microwave-assisted hybrid transesterfication process under various conditions such as microwave power, treatment time, ethanol:oil ratio and catalyst concentration (KOH). Response surface methodology (RSM) coupled with four factors with a three-level Box–Behnken response surface design (BBD) was employed to model the transesterfication technique. The obtained results were analyzed by analysis of variance (ANOVA) and a second-order polynomial model was developed to study the interactive effect of process factors on biodiesel production. Derringer’s desired function methodology was used for the optimization and optimum conditions for maximizing the biodiesel production. Under optimum conditions, the predicted biodiesel production was found to be 95% with a desirability value of 0.998. The fuel properties of the produced biodiesel were compared with the ASTM D6751 ...

This study aims to investigate the effect of ultrasonic pretreatment on drying time and quality properties of tomato slices dried by microwave combined with hot air at 60°C. The influence of ultrasound pretreatment (0, 20, and 40 min) and microwave power (120, 150, and 180 W) on drying time, color, total phenolic content, lycopene, vitamin C, and rehydration capacity of dried slices of tomato was studied. Results showed that as the microwave power level increased, drying time decreased significantly (about 46.4%). Ultrasound pretreatment decreased the drying time by 7.38% only at 120 W microwave power and 40 min of pretreatment compared to those without ultrasound pretreatment at the same microwave power. Depending on drying conditions, vitamin C and lycopene contents reduced from 433.94 to 81.89 mg AA/100 g dry solids and 3920.57 to 415.40 mg/100 g dry solids, respectively. The change in total phenolic content was not severe as much as vitamin C contents. Rehydration capacity of pretreated sample...

The aim of this study was to investigate the influence of microwave vacuum drying on carotenoids in pumpkin (Cucurbita maxima L.) slices. Carotenoids were measured using the reverse-phase high-performance liquid chromatography technique. It was shown that compared with hot air drying, microwave vacuum drying inhibited color changes and significantly (p < 0.05) improved total carotenoid retention (89.1%) in pumpkin slices. During the microwave vacuum drying process, microwave power had an important effect on total carotenoid and all-trans carotenoids. As microwave power increased, the total carotenoid content significantly decreased (p < 0.05), and the levels of individual carotenoids, including all-trans-α-carotene, all-trans-β-carotene, and all-trans-lutein, generally decreased. However, there was an overall upward trend for the levels of 13-cis-β-carotene, 15-cis-β-carotene, 9-cis-β-carotene, and 9-cis-α-carotene. The trans carotenoid quality of the finished products was improved within a certai...

Because of lignite’s high moisture content, it must be dried before most applications. Microwave radiation may be suitable for efficient drying because of its special heating properties. This study investigated the drying behavior of lignite samples from eastern Inner Mongolia by microwave thermogravimetric analysis. Three stages of microwave drying were observed: preheating, fast weight loss, and falling rate drying periods. Samples’ surface temperatures increased dramatically during preheating, dropped slightly in the second period, and rose again in the final period. The measured surface temperature was

Phosphate processing plants produce an excessive amount of phosphatic clay. This clay represents a serious environmental problem due to their disposal in huge ponds. Finding a feasible method to reduce the clay disposal area is needed. Although the flocculation process, in the presence of fibrous material, seems to be a good dewatering process for phosphatic clay wastes, the maximum solid percentage of flocculated clay does not exceed 18% (starting from 3 to 4%). Recently, the microwave proved a better performance in several research areas as compared to the conventional drying. In this study, clay dewatering by microwave was investigated. Several factors affecting the dewatering process were studied such as heating time, microwave power efficiency, and fiber percentage. Using the microwave, the solid content significantly increases in a reasonably short time. The time and power are the most significant among the studied factors. In addition, sand–clay mix was tested to improve the solid percentag...

A pilot-scale process for continuous in-flow microwave processing of foods, designed and implemented at SP Food and Bioscience, was evaluated for heat treatment of a homogeneous model food for high-temperature short-time (HTST) conditions, at constant total input microwave power, at 2450 MHz. The microwave system has three consecutive cavities, one excited by the TM020 microwave mode that heats primarily in the tube centre, and two TM120 mode cavities that heat primarily in the tube periphery. The temperature uniformity of the homogeneous model food after microwave heating is here evaluated in terms of spatial distribution, for different set-ups of input microwave power in each cavity and for different order of the placement of the cavities, while maintaining the total input microwave power. The microwave heating uniformity is evaluated, based on measured and calculated radial temperature profiles. Combined TM020 and TM120 heating was found to result in more uniform heating by means of spatial temperature uniformity over the tube cross section. Furthermore, appropriately selected microwave power distribution between the centre and periphery heating cavities results in a stable heating profile in the studied food, that differs only about 10 °C or less between highest and lowest average values directly after microwave heating.

The present research work is a novel cost-effective method for synthesis of magnetite. Magnetite is a carrier which is used in the targeted drug delivery system. The conventional methods of preparation of magnetite take around 6–7 h for the completion of reaction; moreover, the particle size of magnetite which we get by the conventional methods is above 5 µm, so the present work aims at preparing magnetite with microwave assistance which has found to reduce reaction time with particle size obtained below 5 µm. The aim of this study was to optimize magnetite synthesis using 23 factorial design by Design-Expert software. Magnetites were synthesized using oxidation of ferrous sulfate. In the next step, the effects of different variables on particle size are studied, including the stirring speed, microwave power (W), and stirring time. Based on the type and the variables studied, eight formulations were designed using factorial design method, and were then prepared, and their particle size was determi...

Petroleum coke is the main raw material to produce carbon anode. The content of vanadium in petroleum coke seriously affects the quality of carbon anode. Physical chemical properties of leachate in the process of improving vanadium leaching from petroleum coke were investigated. The effects of different parameters on vanadium removal were chiefly introduced. Systematic studies indicate that the high removal can be achieved under the following conditions: 10 g of petroleum coke, 20 mL of oxidation, 3 h of leaching time, 500 W of microwave power, and 400 mg/L of surfactant amount. Physical chemical properties of leachate changed along with the parameters. This is one reason for the leaching amount of change.

An increasing number of microwave radiation applications have led to a large body of research on the effects of microwave radiation on heating. The effect of different design parameters was analyzed on the microwave-induced heating of saline water. In a completely randomized factorial experiment with three replications, effects of four salinity levels (0, 1,000, 10,000, and 30,000 ppm), three volume levels (100, 300, and 500 ml), and three power levels (200, 600, and 1,000 W) on heating time were studied. ANOVA results showed that the effects of power, volume, and salinity as well as all interactions were significant at the 1% level. The heating rate was calculated for heating water from 20 to 90°C. Heating rate varied from 0.0183 to 1.531°C/s, depending on the microwave power, volume and salinity. Results demonstrated that heating rate decreased with increasing salinity and increased with increasing microwave power and volume.

Intermittent microwave convective drying (IMCD) is an advanced technology that improves both energy efficiency and food quality in drying. Modelling of IMCD is essential to understand the physics of this advanced drying process and to optimize the microwave power level and intermittency during drying. However, there is still a lack of modelling studies dedicated to IMCD. In this study, a mathematical model for IMCD was developed and validated with experimental data. The model showed that the interior temperature of the material was higher than the surface in IMCD, and that the temperatures fluctuated and redistributed due to the intermittency of the microwave power. This redistribution of temperature could significantly contribute to the improvement of product quality during IMCD. Limitations when using Lambert's Law for microwave heat generation were identified and discussed.

Beetroot slices 18 mm in diameter and with a thickness of 9.6, 6.3, 3.35, or 2.6 mm were pretreated in 40°Bx chokeberry juice at a temperature of 50°C for 2 h and then dried by a vacuum-microwave (VM) method at different microwave power levels, such as 120, 240, 360, 480, and 480/120 W. The drying kinetics were described by a fitted model that incorporated contributions from the surface area of the samples, microwave power, and VM processing time. As the microwave power during VM drying increased, the bioactive potential decreased for untreated samples and increased for pretreated samples. Increasing the samples' specific surface area resulted in shorter drying time, lower temperature of the material during drying, and enhanced quality of the dried product. For osmotically pretreated beetroot slices with a specific surface area of 827 ± 18 m2m−3, a final VM drying step at 240 W is recommended to produce high quality vegetable snacks.

This study investigates experimentally and using mathematical modeling the microwave drying of wastewater sludge with determination of moisture diffusivity at different drying conditions. The drying behavior was observed at different power levels (480, 840, and 1,080 W) and different initial masses (90, 120, and 150 g). The observed drying kinetics were divided into three parts: a short adaptation period, a long constant drying rate period, and a falling drying rate period. The maximum drying rate was observed during the constant rate period. Mainly, the results show that the drying rate decreases with the initial mass increase (from 0.45 kg·kg−1·min−1 for 90 g to 0.25 kg·kg−1·min−1 for 150 g) and increases with an increase in power level (from 0.15 kg·kg−1·min−1 at 480 W to 0.45 kg·kg−1·min−1 at 1,080 W). The measurement of the sample dimensions shows that shrinkage can occur and, depending on the drying conditions, it ranged between 0.42 and 0.37 of the sample initial volume. Presenting a more a...

A puffed food using salted duck egg white and starch as ingredients was produced by using a novel pulsed-spouted microwave vacuum drying (PSMVD) technique. In this study, three types of samples (ratios of salted duck egg white to starch 1:10, 3:10, and 5:10) were prepared and the moisture content of these samples was dehydrated to about 12% in a PSMVD dryer, then the samples were under different microwave powers (1.34 kW, 2.01 kW, and 2.68 kW) for puffing. The product volume expansion ratio, textural crispness (breaking forces), color parameters (L*, a* and b*), and sensory scores were determined. It was observed that microwave power and different ratios of salted duck egg white to starch had a significant effect on the expansion effect of the samples. The results indicated that the best product quality was obtained under the ratio of salted duck egg white to starch at 3:10 and microwave power at 2.01 kW.

Burdock cube samples were dried using hot air and microwave pulsed spouted bed drying (MPSBD). Hot air drying was carried out at three temperatures (70, 80, and 90°C). MPSBD was carried out at three microwave power levels (1.0, 2.0, and 3.0 W/g). The results showed that MPSBD samples dried at 2.0 W/g for 30 min and at 1.0 W/g for 40 min had desirable color, flavor, and textural attributes. Gas chromatography–mass spectrometry results showed that the samples dried using MPSBD were richer in flavor compounds, especially in esters, compared to the hot air–dried samples.

In this study, Fuji apple slices were dehydrated using freeze drying (FD) combined with microwave assisted with vacuum drying (VMD). The optimal parameter for the diversion point of moisture content from FD to VMD process was at the moisture level of 21%, and for VMD the optimal parameter for vacuum pressure was at 9.15 kPa and microwave power density was at a level of 3.18 w/g. The results show that the two-step technique can significantly reduce total FD time required by up to 40%, while the nutritional value of the dried apple chips remained unchanged compared to FD used alone.

In this study, color and microstructure changes of tomato samples were investigated after microwave (90, 160, 350, and 500W), convective (50 and 75 degrees C), and microwave-convective (90W-50 degrees C, 90W-75 degrees C, 160W-50 degrees C, and 160W-75 degrees C) drying treatments using a laboratory microwave-convective oven. The combined microwave-convective drying decreased the drying time required when compared to drying with either convective or microwave drying alone. The color of the samples dried at 50 degrees C was closest to the fresh samples compared to other drying conditions. All color values of fresh tomato were affected by drying. Scanning electron microscopy images showed that disruption of the tomato samples significantly elevated with increasing drying temperature or microwave power level.

The aim of this work was to study the influence of microwave power variation during microwave–vacuum drying on both drying time and dried material quality. Red beetroot and carrot were chosen as the material. The quality of the dried material was described by its color change and β-carotene loss (for carrot) due to drying. The first series of experiments consisted of drying under constant microwave power. Only the lowest microwave power gave an undamaged product. During the second series of experiments, the microwave power was changed in time intervals. However, the use of interval conditions either had a small influence on the process time or did not provide satisfactory quality of the dried samples. During the third series of experiments, initial drying was performed with higher microwave power and then the process was continued with the lowest applied power. This method shortened the process time and gave the best quality of material.

Specific absorption rate (SAR) is used as the measure of rate at which radio frequency (RF) energy is absorbed by an object when exposed to an electromagnetic field. The word “SAR” is usually associated with the human exposure to RF/microwave energy from different electromagnetic sources and, therefore, SAR limits have been defined only for human by the government of India. ICNIRP (International Commission on Non-Ionizing Radiation Protection) RF exposure guideline was maintained in India up to 31 August 2012, and thereafter Indian government has reduced the maximum permissible RF exposure levels to one-tenth of ICNIRP guideline with effect from 1 September 2012. On the other side, the whole plant kingdom gets exposed to continuous RF electromagnetic field (24 hours a day, 365 days a year) from cell phone towers that transmit high RF/microwave power for radio coverage. High permittivity and loss parameters are observed in most plants, fruits and vegetables due to high water content and ionic conce...

Saskatoon berries were dried using a vacuum assisted microwave technique. Central composite rotate design and response surface methodology were used to develop the regression models and to study the influence of drying processing variables (microwave power, drying time, and fruit load) on color, mechanical properties, and microstructure of dried berries. All the three variables had significant effects on the above mentioned properties (p< 0.05). Drying affected the color at variable levels and increased the lightness of dried berries compared to frozen berries. Hardness, gumminess, and chewiness of dried berries increased and springiness and cohesiveness of dried berries decreased with microwave power and drying time. The porosity and the destruction level in the microstructure of dried berries increased with the microwave power. The findings of this study will be useful to identify desirable microwave-vacuum drying operating conditions for targeted dried Saskatoon berry products.

The drying homogeneity of the microwave–pulsed spouted bed drying (MPSBD) method was studied via preparing tubers granules by MPSBD under different predefined conditions. The effects of three parameters (microwave power, moisture content transition point, and loading) on the homogeneity of prepared tubers granules were studied. Based on response surface analysis results, it was concluded that the optimum conditions for tuber granules prepared by MPSBD method is 1.10 W/g microwave power, 80% moisture content transition point, and 90 g material loading. It was proven that the experimental result from the predicted optimal condition agreed with the model-predicted results, which evidenced the accuracy of the response surface analysis. Furthermore, the brighter color and higher rehydration capacity of samples prepared by MPSBD indicates that MPSBD is a promising method that can be applied in the food dehydration industry.

This paper presents a comprehensive review of thin-layer drying-curve models available in the literature and their comparisons for single-layer drying applications from 2003 to 2013. In this regard, a total of 67 models are selected and classified under 28 performance assessment criteria for comparison purposes. These models are then evaluated by considering the following parameters: (1) product type; (2) pretreatment type; (3) drying parameters, such as temperature, air velocity, layer thickness, microwave power levels, amount of solar radiation, vacum pressure, frequency of sound wave, excitation amplitude, relative humidity, bed depth, product shape, pH, salt content, absolute pressure, etc.; and (4) drying method employed. Furthermore, the best models obtained are employed for product drying applications and compared for different drying methods, drying parameters, and dried products.

Response surface methodology was used to optimize the influence of microwave power (300–600 W), plant material-to-solvent ratio (0.05–0.2 g/cm3), and extraction time (10–30 min) on the efficiency of microwave-assisted extraction of the cherry laurel (Prunus laurocerasus L.) fruit. From experimental data, a quadratic polynomial mathematical model (R2 = 0.9949) was developed to predict the extract yield. All considered factors were statistically significant for extraction efficiency, while the most important factor was extraction time. Microwave power of 550 W, plant material-to-solvent ratio of 0.05 g/cm3, and time of 25 min were determined as optimal conditions with a maximum yield of 9.36 g/100 g fresh plant material, which was confirmed through laboratory experiments (9.12 ± 0.61 g/100 g fresh plant material). An economic condition for simultaneous maximum extract yield (7.58 g/100 g fresh plant material) with minimal energy and solvent consumption was determined by the desirability function method (18....

Microwave assisted chemical reaction is increasingly studied in recent years by using the modified domestic microwave oven to heating on chemical reaction in the laboratory scale study. But the problems of temperature distribution non-uniformity and low power efficiency in the heating process are becoming a new obstacle in the application of microwave chemistry. An optimized microwave oven with two sources is proposed in this paper from the view of feeding system to overcome these disadvantages. As water is usually concerned as important solvent and reactant, a beaker of water is used as heating load in this study. By modeling the process of heating water for 180 s, the standard deviation and the average temperature are compared between the domestic microwave oven and the optimized microwave oven with two sources. As a result, the power is utilized more efficiently as a 20.14% increase can be seen by using the optimized microwave oven under the same microwave power and more uniformity is obtained ...

Cucurbit[n]urils (CBs) were synthesised using microwave irradiation technique, and the factors to affect the yields of CBs such as total reaction time, interval time and microwave power were investigated. The structure and electrochemical property of CBs were characterised by 1H nuclear magnetic resonance, Fourier transform infrared and cyclic voltammetry. The results showed that CB powder with yield of 85·72% can be obtained under optimal conditions of total reaction time 300 s, heating 1 min with interval 90 s and microwave power 280 W, and electrochemical property of Fe3O4 is intensified significantly after CBs were loaded on the surface of Fe3O4. Surprisingly, compared with the conventional techniques, microwave preparation time of CBs is shortened 60 times.

The effects of magnetron arrangement and microwave power combination on the drying uniformity of carrot were investigated in this study. The drying uniformity was influenced by magnetron location and quantity. Using one magnetron resuted in poor drying uniformity. However, when two magnetrons were applied, the drying uniformity was 80% after drying for 16 min, which was 93.49% when power combination of three magnetrons at powers of 400, 500, and 600 W were used. The optimal magnetron locations and a suitable microwave power combinations were determined to improve the drying uniformity of carrot.

Reduced protein quality is one of the concerns currently confronting the supply and utilization of wheat distillers dried grain with solubles (DDGS) as an animal feed ingredient. This study assessed the protein quality of wheat DDGS, expressed as acid detergent insoluble crude protein (ADICP) and lysine content, by blending wet distillers grain (WDG) with varying condensed distillers solubles (CDS) levels and drying using forced air convection, microwave, and microwave–convection methods. As the CDS level was increased, the protein content of wheat DDGS generated from the three drying methods increased. Interactions of CDS level with drying air temperature, microwave power, and microwave–convection settings had a significant effect (p

This study was conducted to evaluate the quality of and structural changes in parsley (Petroselinum crispum Mill.) during vacuum, microwave, and convective (hot air) drying. The selected quality attributes of the dehydrated parsley samples were investigated on the basis of ascorbic acid and chlorophyll retention, as well as color change and overall appearance. Ascorbic acid is an important indicator of quality, and its selection was due to its heat-labile nature. Ascorbic acid deterioration depends on air temperature, microwave power, and drying time. The lowest ascorbic acid value was found after convective drying, followed by vacuum drying and microwave drying. With convective drying, the appearance values of the dried parsley decreased when the drying period was extended. However, with microwave drying, appearance values were not drastically changed. The color values obtained from leaves supported the chlorophyll findings. At the end of the study, microwave drying at 750-850 W ensured the shortest drying time and the best overall quality of parsley; thus, it was chosen as the most appropriate technique for parsley drying.

Optimization of the process parameters for osmotic dehydration of 12.2-mm potato cubes was carried out using response surface methodology. The experiments were conducted using a central composite rotatable design (CCRD) with four factors, viz. sucrose concentration (27.5–42.5% w/w), salt concentration (7.5–12.5% w/w), total osmosis time (26.25–68.75 min), and microwave power density for the initial 4 min (0.375–1.125 W/g of total weight of solution and potato cubes) at two levels each to take into account the individual and interaction effects of the factors. A sample-to-solution ratio of 1:10 and pressure of 0.16 kPa for the initial 4 min were kept constant throughout all of the experiments. It was found that the linear effects of all factors on the water loss (WL) and solids gain (SG) were highly significant. The optimum condition was found at a sucrose concentration of 36.35%, salt concentration of 12.50%, osmosis time of 68.72 min, and microwave power density of 0.38 W/g for the initial 4 min, with a ...

Microwave-assisted spouted bed (MSBD) drying of lettuce cubes was investigated experimentally. Response surface methodology was used to optimize the process with spouting air temperature, microwave power level, and superficial air velocity. The dried product obtained was compared with that obtained using other drying technologies such as hot air drying, air spouted bed drying, vacuum microwave drying, and vacuum freeze drying. The comparison is based on the rehydration ratio, chlorophyll content of the product, color, and the drying time required.

Microwave phosphorylation was applied to modify soy protein isolates (SPI) to improve their emulsifying properties. A Box–Behnken model was obtained to optimize preparation conditions by response surface methodology. The four factors investigated were SPI content, sodium tripolyphosphate (STP) addition, microwave power, and reaction time with the emulsifying activity index (EAI) of the modified product as evaluation index. The optimized conditions were found to be SPI content of 71 g/L, STP addition of 115 g/kg, microwave power of 480 W, and reaction time of 3 min. Under these conditions, the EAI and emulsifying stability index (ESI) of the modified SPI were 0.878 and 33.9 min, respectively. Compared to the original SPI, the EAI and ESI of the modified SPI increased about 113.1% and 26.6%, respectively. Modification of SPI with STP under microwave irradiation might be a potential way to increase the emulsifying properties of SPI.

Freeze drying (FD) yields the best quality of dried apple slices but requires a long drying time and is not cost-effective. To mitigate these problems, a microwave freeze drying (MFD) technique was developed to dry apple slices. The relationship between corona discharge and microwave power at various pressures and initial moisture content conditions was studied to avoid the possibility of corona discharge during MFD. It was found that with change of moisture content and temperature of samples during MFD, the dielectric property also changed, which resulted in dynamic microwave dissipation. Based on the dielectric property of samples, a changed microwave loading scheme can lead to perfect product quality and greatly reduce the drying time; thus, MFD can be used to replace the traditional FD technique.