Kinetics and Quality of Microwave-Assisted Drying of Mango (Mangifera indica)

The effect of microwave-assisted convective air-drying on the drying kinetics and quality of mango was evaluated. Both microwave power and pretreatment time were significant factors but the effect of power was more profound. Increase in microwave power and pretreatment time had a positive effect on drying time. The nonenzymatic browning index of the fresh samples increased from 0.29 to 0.60 while the ascorbic acid content decreased with increase in microwave power and time from 3.84 mg/100g to 1.67 mg/100g. The effective moisture diffusivity varied from 1.45 × 10−9to 2.13 × 10−9 m2/s for microwave power range of 300-600 W for 2 to 4 minutes of pretreatment. The Arrhenius type power-dependent activation energy was found to be in the range of 8.58–17.48 W/mm. The fitting of commonly used drying models to the drying data showed the Midilli et al. model as the best. Microwave power of 300 W and pretreatment time of 4 minutes emerged as the optimum conditions prior to air-drying at 7°C. At this ideal condition, the energy savings as a result of microwave application was approximately 30%. Therefore, microwave-assisted drying should be considered for improved heat and mass transfer processes during drying to produce dried mangoes with better quality.

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Temperature, microwave power and pomace thickness impact on the drying kinetics and quality of carrot pomace

Journal of Agricultural Engineering ◽

10.4081/jae.2019.872 ◽

2019 ◽

Vol 50 (1) ◽

pp. 28-37

Author(s):

Ernest Ekow Abano ◽

Robert Sarpong Amoah ◽

Eugene Kwabena Opoku

Keyword(s):

Activation Energy ◽

Ascorbic Acid ◽

Air Temperature ◽

Microwave Power ◽

Moisture Diffusivity ◽

Sample Thickness ◽

Microwave Drying ◽

Drying Time ◽

Air Drying

This study investigated the effect of air temperature, microwave power, and pomace thickness on the drying kinetics and quality of dried carrot pomace. The study established that the drying of carrot pomace occurs in the falling rate period, suggesting that drying was driven by molecular diffusion. The microwave-drying moisture diffusivity increased with microwave power and ranged between 1.57×10–8 and 2.61×10–8 m2/s. As regards convective air-drying, the moisture diffusivity values were between 3.38×10–10 and 8.27×10–10 m2/s. The microwave powerto-mass activation energy was 15.079 W/g for 5 mm, 7.599 W/g for 10 mm and 9.542 W/g for 15 mm dried samples. Meanwhile, the temperature-dependent activation energy for carrot pomace was found to be 27.637 kJ/mol for 5 mm, 17.92 kJ/mol for 10 mm and 38.76 kJ/mol for 15 mm thickness pomace. Generally, drying time decreased with increasing microwave power or air temperature. The ascorbic acid content of the fresh carrot pomace reduced after both microwave and convective air-drying. However, microwave power, and sample thickness had significant effect on the β-carotene content of dried products but air temperature did not have a significant effect. The effect of temperature and sample thickness on brown pigment formation was substantial with air temperature compared to microwave. The study has demonstrated that microwave drying, compared to conventional drying, enhances moisture removal, drying time, and preservation of carotenoids and ascorbic acid. Therefore, microwave drying can be considered as an alternative method for obtaining quality dried carrot pomace.

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Microwave Assisted Convective Air Drying of Sugarloaf Pineapples (Ananas Comosus)

Applied Engineering in Agriculture ◽

10.13031/aea.14380 ◽

2021 ◽

Vol 37 (5) ◽

pp. 763-774

Author(s):

Ernest Ekow Abano

Keyword(s):

Air Temperature ◽

Microwave Power ◽

Moisture Diffusivity ◽

Hot Air Drying ◽

Drying Time ◽

Air Drying ◽

Microwave Assisted ◽

Hot Air ◽

Effective Moisture ◽

Drying Conditions

HighlightsMicrowave pretreatment before drying reduced drying time significantly.Microwave-assisted drying increased the effective moisture diffusivity coefficient.Microwave pretreatment before convective hot-air drying improved quality parameters.The Middili et al. (2002) model best fitted the microwave-assisted drying of sugarloaf pineapples.Abstract. This study’s objective was to provide the optimum drying conditions to produce quality dried sugarloaf pineapples using microwave pretreatments before the conventional hot air drying. For this, the effect of microwave power (385 to 697 W), microwave time (2 to 4 min), and air temperature (50°C to 70°C) on the drying kinetics and quality of sugarloaf pineapple were evaluated using the Box Behnken response surface methodology. To reach a 17.44±0.09% kg/kg dry matter moisture content, we found the optimum drying conditions for sugarloaf pineapples to be 697 W microwave power for 2.26 min before convective hot air drying at a temperature of 64.75°C. The predicted drying time, ascorbic acid content, and browning index were 13.68 h, 20.89 mg/100 g, and 0.099 Abs unit at this optimum condition, respectively. The pineapple slices’ effective moisture removal rate pretreated with microwave before drying was higher than the control and was between 6.42 × 10-10 m2/s and 11.82 × 10-10 m2/s while ones without a microwave were between 3.54 × 10-10 m2/s and 8.78 × 10-10 m2/s for drying at air temperature between 50°C and 70°C. It was discovered that the Midilli et al. (2002) model was the most appropriate thin layer model for microwave-assisted drying of sugarloaf pineapples. The pineapple slices’ drying rate potential generally increased with microwave power and pretreatments time but not the corresponding increase in the air temperature. Drying time for microwave-assisted drying was in the range of 11 to 20 h, while the ones without microwaves were between 18 and 24 h. Therefore, microwaves should be considered a pretreatment step to the industrial production of sugarloaf pineapple to reduce drying time and produce better quality products. Keywords: Drying, Hot air, Microwave, Moisture diffusivity, Sugarloaf pineapple.

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Effects of drying methods on color retention and chlorophyll of celery (ApiumgraveolensL.), spinach (Spinacia oleraceaL.), Malabar spinach (Basella albaL.)

The Journal of Agriculture and Development ◽

10.52997/jad.6.06.2020 ◽

2020 ◽

pp. 53-61

Author(s):

Dat Q Tran

Keyword(s):

Microwave Drying ◽

Drying Methods ◽

Hot Air Drying ◽

Drying Time ◽

Air Drying ◽

Color Retention ◽

Hot Air ◽

Drying Techniques ◽

Dried Vegetables

Dried vegetables are considered convenient for storage, transportation and preservation. The different drying techniques could influence the quality of resulting products. This study aimed to evaluate the effects of three distinguish drying methods as hot-air drying, foam-mat drying and microwave drying on the color retention and chlorophyll of green vegetables powder. Fresh spinach(Spinacia oleraceaL.), celery (Apium graveolensL.), Malabar spinach (Basella albaL.) were dried by different methods: hot air at 60oC, foam-mat at 60oC and microwave at 270 W until the samples reached approximately 9% of moisture content (wb). The drying time of the dried samples by microwave, foam-mat and hot-air method were 60, 210 and 240 min, respectively. Foam-mat dried vegetables were found to have the best quality in terms of color and the residual chlorophyll content. The findings suggest that foam-mat drying is promising in dried vegetable processing

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Microwave and steam blanching as pre-treatments before air drying of Moringa oleifera leaves

Journal of Agricultural Engineering ◽

10.4081/jae.2020.1044 ◽

2020 ◽

Vol 51 (4) ◽

pp. 200-208

Author(s):

Ernest Ekow Abano ◽

Robert Sarpong Amoah ◽

Catherine Mbabazi

Keyword(s):

Microwave Power ◽

Moringa Oleifera ◽

Drying Kinetics ◽

Drying Time ◽

Air Drying ◽

Moringa Oleifera Leaves ◽

Pre Treatment ◽

Microwave Time ◽

Drying Conditions ◽

Short Time

The objective of this work was to identify the optimal drying conditions to produce better quality dried Moringa oleifera leaves with the best drying kinetics using microwave and steam blanching pre-treatments prior to hot air drying. For this purpose, the effect of microwave power, microwave time, steaming time, and air temperature on drying kinetics and quality of Moringa leaves was evaluated using the response surface methodology. In order to achieve a moisture content of 8.0% kg H2O/kg dry matter, the optimal conditions identified were a steaming time of 2.58 min (2 min 35 sec) prior to air drying at 70°C and a microwave power of 270 W for 3 min, followed by air drying at 70°C. At this optimal condition, a confirmation test for steam-assisted air drying gave a drying time (DT) of 53 min, ascorbic acid (AA) of 2.49 mg/g, and the antioxidant activity (AOA) of 67.244% inhibition. For microwave-assisted air drying, the confirmation experiment gave a DT of 43 min, AA of 2.699 mg/g, and AOA of 74.46% inhibition. Both pre-treatments before air drying followed a falling rate drying period at the initial stages and later a constant rate drying period. Our results showed that microwave blanching should be considered as a pre-treatment in industrial production of Moringa leaves to produce better quality dried products in a relatively short time.

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Dried Figs Quality Improvement and Process Energy Savings by Combinatory Application of Osmotic Pretreatment and Conventional Air Drying

Foods ◽

10.3390/foods10081846 ◽

2021 ◽

Vol 10 (8) ◽

pp. 1846

Author(s):

Varvara Andreou ◽

Ioanna Thanou ◽

Marianna Giannoglou ◽

Maria C. Giannakourou ◽

George Katsaros

Keyword(s):

Quality Improvement ◽

Energy Savings ◽

Osmotic Dehydration ◽

Effective Diffusion ◽

Drying Time ◽

Air Drying ◽

Solid Gain ◽

Pre Treatment ◽

Process Energy ◽

Time And Energy

This study concerns the implementation of osmotic dehydration (OD) as a pre-treatment of air-drying in fig halves, aiming at drying acceleration, energy savings and product quality improvement. The effect of solid/liquid mass ratio, process temperature (25–45 °C) and duration (up to 300 min) on water activity (aw) and transport phenomena during OD, was modelled. The effective diffusion coefficients, drying time and energy consumption, were also calculated during air-drying at 50–70 °C. At optimum OD conditions (90 min, 45 °C), the highest water loss and solid gain ratio were achieved, while the aw (equal to an initial value 0.986) was decreased to 0.929. Air-drying time of OD- and control samples was estimated at 12 and 21 h, at 60 °C, respectively, decreasing the required energy by up to 31.1%. Quality of dried figs was systematically monitored during storage. OD-assisted air-drying led to a product of improved quality and extended shelf-life.

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Influence of Microwave Osmotic Dehydration Pre-Treatment on the Second Stage of Air-Drying Kinetics of Apples

International Journal of Food Engineering ◽

10.2202/1556-3758.1927 ◽

2011 ◽

Vol 7 (3) ◽

Cited By ~ 2

Author(s):

Elham Azarpahzooh ◽

Hosahalli S. Ramaswamy

Keyword(s):

Energy Savings ◽

Osmotic Dehydration ◽

Sucrose Concentration ◽

Drying Kinetics ◽

Drying Time ◽

Air Drying ◽

Second Stage ◽

Freeze Dried ◽

Pre Treatment ◽

Kinetics Of

The effect of microwave-osmotic dehydration pre-treatment under continuous flow medium spray (MWODS) conditions on the second stage air-drying kinetics of apple (Red Gala) cylinders was evaluated. MWODS pre-treatment was carried out using a response surface methodology involving 5-levels of sucrose concentration (33-66.8°B), temperature (33-66.8°C) and contact time (5-55 min). Drying time and coefficient of moisture diffusion (Dm) and coefficient of moisture infusion (Im) during rehydration were evaluated as responses and the results were compared with their air-dried (AD) (worst scenario) and freeze-dried (FD) (best scenario) counterparts without the osmotic treatments. The diffusion and infusion coefficients were based on the solution of Fick's diffusion model. Empirical models developed for all response variables were significant (P ? 0.001) and the lack of fit was not significant (P > 0.05). MWODS pre-treatments significantly influenced the Dm values and reduced the air-drying time of apples by 30-65 percent in comparison with untreated apple thereby providing opportunity for better energy savings. On the other hand, the values of Im during the rehydration process were highest for the freeze-dried samples followed by apples air-dried after MWODS treatment, and the least for the untreated air-dried samples.

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Drying Kinetics, Rehydration Characteristics and Sensory Evaluation of Microwave Vacuum and Convective Hot Air Dehydrated Jackfruit Bulbs

Jurnal Teknologi ◽

10.11113/jt.v65.1120 ◽

2013 ◽

Vol 65 (1) ◽

Cited By ~ 2

Author(s):

Mohd Rozainee Taib ◽

Ida Idayu Muhamad ◽

Chee Loong Ngo ◽

Pang Soon Ng

Keyword(s):

Air Temperature ◽

Power Output ◽

Microwave Power ◽

Model Fitting ◽

Equation Model ◽

Drying Time ◽

Hot Air ◽

Air Dehydration ◽

Vacuum Dehydration

Microwave vacuum and convective hot air dehydration of jackfruit (Artocarpus Heterophyllus) bulbs were carried out to study the effects of different dehydration treatments on drying characteristics, rehydration ability and quality attributes. Jackfruit bulbs were dehydrated by microwave power output of 58, 140, 220, and 321W respectively combined with vacuum level of -65 cmHg during microwave vacuum dehydration. Convective hot air dehydration was also conducted with the hot air temperature of 60, 70, and 80°C, respectively. Microwave vacuum dehydration with microwave power output of 321 W resulted in 133 times faster in drying time compared to convective hot air dehydration with hot air temperature of 60°C. All dehydration data were subjected to Newton and Page’s equation model fitting, where Page’s equation model was well fitted for all dehydration conditions with R2 > 0.994. Furthermore, microwave vacuum dehydration produced better quality of dehydrated jackfruit bulbs with higher rehydration ability and sensory attributes.

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Study on the Effect of Vacuum Microwave Drying on Quality of Okra

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.791-793.132 ◽

2013 ◽

Vol 791-793 ◽

pp. 132-136 ◽

Cited By ~ 1

Author(s):

Jing Yi Li ◽

Zhen Hua Duan

Keyword(s):

Microwave Power ◽

Fracture Resistance ◽

Colour Change ◽

Microwave Drying ◽

Rehydration Ratio ◽

Drying Time ◽

Vacuum Degree ◽

Vacuum Microwave ◽

The Impact

The purpose of this paper is to investigate the impact of vacuum microwave drying on the quality of okra. The curves of colour, fracture resistance, rehydration ratio and the content of vitaminC were obtained at various drying times, vacuum degrees and microwave powers. Results showed that an increase in drying time and microwave power resulted in serious colour change when compare the dry product to fresh okra. However, the higher the vacuum, the slighter the colour changed. The fracture resistance decreased and the brittleness was good when drying time was increased to high level of 14min and 16min. Increasing vacuum degree also made fracture resistance decreased; rehydration ratio increased with the time and microwave power increased, but decreased if the time exceeds 14min. The rehydration ratio of okra is also affected by the vacuum degree, increasing which led the rehydration ratio increased significantly at the beginning of drying and then slowly; the greater the drying time and microwave power, the more lost of vitaminC, however, higher vacuum degree was found to be beneficial to save the vitaminC.

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Research on Lemongrass Oil Extraction Technology (Hydrodistillation, Microwave-Assisted Hydrodistillation)

Indonesian Journal of Chemistry ◽

10.22146/ijc.40883 ◽

2019 ◽

Vol 19 (4) ◽

pp. 1000 ◽

Cited By ~ 3

Author(s):

Thien Hien Tran ◽

Duy Chinh Nguyen ◽

Thuong Nhan Nguyen Phu ◽

Van Thi Thanh Ho ◽

Dai Viet Nguyen Vo ◽

...

Keyword(s):

Essential Oils ◽

Microwave Power ◽

Raw Material ◽

Extraction Time ◽

Volatile Components ◽

Extraction Technology ◽

Microwave Assisted ◽

Lemongrass Oil ◽

Water Ratio

Microwave-assisted hydro-distillation (MAHD) is preferred to traditional extraction methods due to shorter extraction time, the inability of volatile components to be damaged or decomposed which in turn improve the efficiency and quality of essential oils. In this research, we investigated the parameters that affect the extraction of lemongrass oil process by MAHD method and compare with those of hydro-distillation (HD) method. Four parameters were identified which are: raw material size, raw material to water ratio, extraction time and microwave power. The results show that the optimum condition for determining the lemongrass essential oil content is 20 mm in the 90 min extraction time with a microwave power of 450 W at raw material to water ratio of 1:3 (g/mL). When compared to the HD method, we found that the yield lemongrass oil of MAHD method is 0.35% on 90 min and the yield of HD method is 0.2% on 360 min. The quality of oil samples at different extraction method was evaluated by determining their chemical constituents through GC-MS. The highest identified component is Citral with 93.28% for MAHD, while the HD was 83.85%. Therefore, MAHD method is highly efficient and shorten the time needed for the extraction of essential oils.

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