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

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.

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

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.

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

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

scholarly journals Research of physicochemical properties and antioxidant activity of beetroots as affected by vacuum microwave drying conditions

2021 ◽  
Vol 5 (3(61)) ◽  
pp. 40-45
Author(s):  
Yan Liu ◽  
Sergei Sabadash ◽  
Zhenhua Duan
Keyword(s):  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
Physicochemical Properties ◽  
Microwave Power ◽  
Sample Thickness ◽  
Microwave Drying ◽  
Antioxidant Power ◽  
Vacuum Degree ◽  
Vacuum Microwave ◽  
Ferric Reducing Antioxidant Power

The object of research is the beetroots, dried by vacuum microwave drying at different conditions. Physicochemical properties and antioxidant activity of beetroots were studied using vacuum microwave drying at different microwave power (500, 1000, and 1500 W), vacuum degree (–0.05, –0.07, and –0.09 MPa) and sample thickness (2, 4, and 6 mm). A colorimeter was used to evaluate the color quality of beetroots. Colorimetric methods were used to determinate contents of betalain, ascorbic acid and total flavonoid, and antioxidant activity (ferric reducing antioxidant power assay) of beetroots. Results showed that the drying time decreased with increasing microwave power and vacuum degree, while increased significantly with the increase of sample thickness. The lightness (L*) of dried beetroots was higher than that of fresh beetroots. The values of redness (a*) increased with the increase of vacuum degree. The values of yellowness (b*) increased with the growth of vacuum degree and microwave power, while reduced as the sample thickness added. The total color difference (∆E) of dried beetroots reduced with increasing vacuum degree, and displayed the lowest value (5.95) at a vacuum degree of –0.09 MPa as compared to fresh beetroots. The content of betacyanin, betaxanthin and ascorbic acid displayed a declining tendency with the growth of microwave power, while increased with the increase of vacuum degree. And the total flavonoid content of beetroots illustrated a decreasing tendency with the increase of vacuum degree, microwave power and sample thickness. The ferric reducing antioxidant power (FRAP) of dried beetroots decreased significantly with the increase of microwave power, and showed the highest value (14.70 mg trolox equivalents/g) at a microwave power of 500 W. The most favorable conditions for vacuum microwave drying of beetroots were microwave power of 500 W, vacuum degree of –0.09 MPa and sample thickness of 2 mm. It leads to better physicochemical properties of bioactive compounds and higher antioxidant activity of dried beetroots. The dried beetroots can be used as functional foods and value-added food products.

scholarly journals Drying characteristics of eggplant (Solanum melongena L.) slices under microwave-convective drying

2016 ◽  
Vol 62 (No. 4) ◽  
pp. 170-178 ◽  
Author(s):  
R.A. Chayjan ◽  
M. Kaveh
Keyword(s):  
Air Temperature ◽  
Microwave Power ◽  
Specific Energy Consumption ◽  
Solanum Melongena ◽  
Moisture Diffusivity ◽  
Moisture Ratio ◽  
Convective Drying ◽  
Air Velocity ◽  
Drying Time ◽  
Thin Layer Drying

A laboratory scale microwave-convection dryer was used to dry the eggplant fruit, applying microwave power in the range of 270–630 W, air temperature in the range of 40–70°C and air velocity in the range of 0.5–1.7 m/s. Six mathematical models were used to predict the moisture ratio of eggplant fruit slices in thin layer drying. The results showed that the Midilli et al. model had supremacy in prediction of turnip slice drying behavior. Minimum and maximum values of effective moisture diffusivity (D<sub>eff</sub>) were 1.52 × 10<sup>–9</sup> and 3.39 × 10<sup>–9</sup> m<sup>2</sup>/s, respectively. Activation energy values of eggplant slices were found between 13.33 and 17.81 kJ/mol for 40°C to 70°C, respectively. The specific energy consumption for drying eggplant slices was calculated at the boundary of 86.47 and 194.37 MJ/kg. Furthermore, in the present study, the application of Artificial Neural Network (ANN) for predicting the drying rate and moisture ratio was investigated. Microwave power, drying air temperature, air velocity and drying time were considered as input parameters for the model.

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

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Ernest Ekow Abano
Keyword(s):  
Microwave Power ◽  
Energy Savings ◽  
Mangifera Indica ◽  
Ascorbic Acid Content ◽  
Ideal Condition ◽  
Drying Time ◽  
Air Drying ◽  
Microwave Assisted ◽  
Pretreatment Time

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.

scholarly journals Effect of hot air assisted infrared drying on drying characteristics and quality of rice bran pellets

2018 ◽  
Vol 192 ◽  
pp. 03040 ◽  
Author(s):  
Sahachart Sansak ◽  
Jiraporn Sripinyowanich Jongyingcharoen
Keyword(s):  
Air Temperature ◽  
Rice Bran ◽  
Oil Content ◽  
Reference Sample ◽  
Moisture Diffusivity ◽  
Drying Time ◽  
Drying Characteristics ◽  
Hot Air ◽  
Different Levels

The objective of this study was to determine drying characteristics and quality of rice bran pellet subjected to hot air assisted infrared (HA-IR) drying at different levels of infrared (IR) intensity (750 – 3750 W/m2) and air temperature (40 – 80°C). The rice bran pellets were dried from 0.18 to 0.08 g water/g dry matter. The maximum drying rate (DR) and drying time were in the ranges of 0.0030 – 0.0165 g water/g dry matter·min and 8 – 54 min, respectively. Higher IR intensity and air temperature resulted in greater maximum DR and shorter drying time. The same trend was also observed for the effective moisture diffusivity (Deff) values which were between 0.3103×10-7 and 2.7603×10-7 m2/s. As compared to the commercial reference sample of dried rice bran pellets, the products of this study had higher oil content and lower FFA content. The oil content was affected by IR intensity only while the FFA content was affected both by IR intensity and air temperature. HA-IR drying could improve drying characteristics of the rice bran pellets and produce better quality of the dried products.

scholarly journals Moisture and thermal diffusivity of lentil seed under convective infrared-microwave: Modelling with and without shrinkage

2016 ◽  
Vol 62 (No. 3) ◽  
pp. 129-140 ◽  
Author(s):  
R.A. Chayjan ◽  
S.A. Radmard
Keyword(s):  
Thermal Diffusivity ◽  
Moisture Content ◽  
Microwave Radiation ◽  
Air Temperature ◽  
Microwave Power ◽  
Infrared Radiation ◽  
Moisture Diffusivity ◽  
Microwave Drying ◽  
Drying Rate ◽  
Mathematical Equations

The effect of infrared radiation and microwave radiation on the moisture and thermal diffusivity characteristics of lentil seeds during infrared and microwave drying was investigated. Using mathematical equations, values and curves, moisture and thermal diffusivity were obtained. This study was to determine the moisture and thermal diffusivity of seed lentil with and without shrinkage at input temperatures 40°C and 60°C, infrared powers 1,000 W and 2,000 W and microwave power 270 W and 450 W, when the moisture content was reduced from 60 to 9% (d.b.). Drying rate was increased with increased air temperature, infrared radiation and microwave powers. Also drying rate decreased continuously with decreasing moisture content. The calculated values of moisture diffusivity by considering shrinkage were smaller than the values of moisture diffusivity without considering shrinkage. Moisture diffusivity with and without shrinkage decreased with decrease in moisture content of lentil seeds and thermal diffusivity with and without shrinkage decreased with increased moisture content. Both moisture and thermal diffusivity values decreased with increase in temperature.

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

2013 ◽  
Vol 65 (1) ◽  
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.

scholarly journals Effect of Temperature and Microwave Power Levels on Microwave Drying Kinetics of Zhaotong Lignite

Processes ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 74 ◽  
Author(s):  
Pengfei Zhao ◽  
Chenhui Liu ◽  
Wenwen Qu ◽  
Zhixiu He ◽  
Jiyun Gao ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thin Layer ◽  
Apparent Activation Energy ◽  
Microwave Power ◽  
Microwave Drying ◽  
Hot Air Drying ◽  
Air Drying ◽  
Hot Air ◽  
Thin Layer Drying ◽  
Rate Period

Microwave drying is a promising and effective way to drying and upgrading lignite. The influence of temperature (100–140 °C) and microwave power levels (500–800 W) on thin-layer drying characteristics of Zhaotong lignite under microwave irradiation were investigated. Fourteen thin-layer drying models were used to analyze the microwave drying process while six thin-layer drying models were used to analyze the hot-air drying process. The microwave drying processes at all temperature (100–140 °C) or low microwave power levels (500–700 W) exhibited four periods: a warm-up period, a short constant period, the first and second falling rate period, while one falling rate period was found during hot-air drying. The effective diffusion coefficient of lignite were calculated and it increases with increasing temperature and microwave power levels. During microwave drying, the two-term exponential model is the most suitable model for all applied conditions, while the Modified Page model is the most suitable model to describe the hot-air drying experiments. The apparent activation energy were determined from Arrhenius equation and the values for the first and second falling rate period are 3.349 and 20.808 kJ·mol−1 at different temperatures, while they are 13.455 and 19.580 W·g−1 at different microwave power levels. This implies the apparent activation energy is higher during the second falling rate period, which suggest that the dewatering of absorbed water is more difficult than capillary water. The value of apparent activation energy in hot-air drying is between the first and second falling rate period of microwave drying. Results indicate that microwave drying is more suitable to dewatering free water and capillary water of lignite.

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

2013 ◽  
Vol 791-793 ◽  
pp. 132-136 ◽  
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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