scholarly journals Drying Kinetics Comparison of Methylcellulose Gel Versus Mango Fruit in Forced Convective Drying With and Without Electrohydrodynamic Enhancement

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Erik Bardy ◽  
Sabrine Manai ◽  
Michel Havet ◽  
Olivier Rouaud

Electrohydrodynamic convective drying (EHD drying) is a novel drying method used to enhance forced convection drying (FC drying) by using a wire-electrode to create an electrostatic field. In a previous study, the efficiency of EHD drying (using three different wire-electrode configurations) was compared to classical FC drying by measuring the drying rate of methylcellulose gel. Efficiency was quantified in terms of exergy (transient exergetic efficiency) through the use of a proposed model. In that previous study, it was stated that methylcellulose gel can be used to simulate a food product and can be controlled to a predetermined moisture content. The purpose of this current work was to compare how methylcellulose gel compares to a real food product (mango fruit) in terms of drying kinetics for both EHD and FC drying. Drying kinetics were quantified in terms of a per unit area measurement of the exergetic efficiency, exergy supplied and used, drying rate, and total drying time to reach a moisture content of 50%. Initial results show that for both EHD and FC drying, methylcellulose gel and mango fruit exhibit similar drying kinetics.

Author(s):  
Nurhasmanina Norhadi ◽  
Ammar Mohd Akhir ◽  
Nor Roslina Rosli ◽  
Farid Mulana

Drying is generally used to increase the shelf life of food products. In this context, mango fruit is used as a sample for the drying process because of its high commercial value and particularly high moisture content. The mango was sliced into few batches of sample with a size of 20 mm × 30 mm × 5 mm each. The experiments were conducted using tray and oven dryer at different temperatures of 40, 50 and 60 °C with a steady airflow rate of 1.3 m/s. The objectives are to study the effect of drying time, temperature and air velocity towards drying of mango fruit, to compare the physical characteristics of mango sample after drying and to determine the best drying kinetics model fitted to each tray and oven dryer. The results showed that the increase in drying time, temperature and air velocity would reduce the moisture content while at the same time, drying rate increased significantly. Tray dryer was found to be more effective than oven dryer because of higher drying rate with better product quality and appearance at the end. Furthermore, the gathered data were fitted into few widely used drying mathematical models and it was found that Henderson and Pabis model at 60°C is best suited for tray dryer whereas Page model at 40 °C is the best for oven dryer.


2016 ◽  
Vol 12 (6) ◽  
pp. 599-606 ◽  
Author(s):  
Flávia Daiana Montanuci ◽  
Raphaela Mulato Cavalcante ◽  
Camila Augusto Perussello ◽  
Luiz Mario de Matos Jorge

Abstract The study of process kinetics may aid the design and optimization of drying systems. This paper evaluated the influence of drying temperature (40, 60 and 80 °C) on the moisture content, drying rate, density, shrinkage and breakage of maize dried in two different dryers: oven and silo dryer. In both dryers, the temperature increase reduced drying time, final moisture content and shrinkage of the grains, however increased breakage. Drying rate was higher in the oven (6.4×10−4±2.3×10−4s−1 versus 5.4×10−4±1.2×10−4s−1), while shrinkage (15.2±4.7 % versus 24.4±5.6 %) and density increase (16.6±5.9 % versus 33.4±5.8 %) were more intense in the silo. There was a large release of husk in the silo dryer and the moisture content was slightly smaller in the lower layers respective to the upper ones.


Author(s):  
Erik Bardy ◽  
Merouane Hamdi ◽  
Michel Havet ◽  
Olivier Rouaud

Electrohydrodynamic (EHD) drying is a novel drying method used to enhance forced convective drying by using a wire-electrode to create an electrostatic field. In this study, it was hypothesized that an EHD enhanced forced convective drying process will not only increase the drying rate, but also the exergetic efficiency over time. A transient exergetic efficiency was defined as the ratio of the exergy use rate in the removing of moisture from the drying product, to the exergy rate of the drying air supplied. In the case of EHD enhanced forced convection, the exergy rate supplied by the wire electrode was also accounted for. Forced convection drying experiments were run on a test specimen simulating a food product (methylcellulose gel) using an air flow channel with and without EHD enhancement with varying air flow velocities. Initial results show that the moisutre loss rate of the methylcellulose gel increased with the application of the electrostatic field. In addition, for low velocities, the exergetic efficiency of EHD enhanced forced convection was higher for the first few hours of drying as compared to conventional forced convection. The exergetic efficiency of both conventional and EHD enhanced forced convection converged at greater air flow velocities.


Author(s):  
Justyna Szadzińska ◽  
Dominik Mierzwa

The studies present convective drying of parsley with an intermittent microwave application. Eight different drying programs including convective drying (CV) were carried out in a laboratory-scale hybrid dryer. The influence of intermittent conditions on drying time, drying rate, energy efficiency and product quality was analysed. The results demonstrated that intermittent–microwave convective drying improves the drying kinetics and reduces energy consumption. Moreover, a higher retention of vitamin C, smaller color change and a better ability to rehydration were observed for the parsley samples dried using intermittent drying than for CV.Keywords: intermittent drying, microwaves, energy, vitamin C, rehydration.  


2012 ◽  
Vol 2 (1) ◽  
pp. 14-20
Author(s):  
Yuwana Yuwana

Experiment on catfish drying employing ‘Teko Bersayap’ solar dryer was conducted. The result of the experiment indicated that the dryer was able to increase ambient temperature up to 44% and decrease ambient relative humidity up to 103%. Fish drying process followed equations : KAu = 74,94 e-0,03t for unsplitted fish and KAb = 79,25 e-0,09t for splitted fish, where KAu = moisture content of unsplitted fish (%), KAb = moisture content of splitted fish (%), t = drying time. Drying of unsplitted fish finished in 43.995 hours while drying of split fish completed in 15.29 hours. Splitting the fish increased 2,877 times drying rate.


Author(s):  
Elisabete P. de Sousa ◽  
Rossana M. F. de Figueirêdo ◽  
Josivanda P. Gomes ◽  
Alexandre J. de M. Queiroz ◽  
Deise S. de Castro ◽  
...  

ABSTRACT The aim of this work was to study the drying kinetics of pequi pulp by convective drying at different conditions of temperature (50, 60, 70 and 80 °C) and thickness (0.5, 1.0 and 1.5 cm) at the air speed of 1.0 m s-1, with no addition of adjuvant. The experimental data of pequi pulp drying kinetics were used to plot drying curves and fitted to the models: Midilli, Page, Henderson & Pabis and Newton. Effective diffusivity was calculated using the Fick’s diffusion model for a flat plate. It was found that, with increasing thickness, the drying time increased and, with increasing temperature, the drying time was reduced. The Midilli model showed the best fit to the experimental data of pequi pulp drying at all temperatures and thicknesses, presenting higher coefficients of determination (R2), indicating that this model satisfactorily represents the pequi pulp drying phenomenon. There was a trend of increase in the effective diffusivity with the increase in pulp layer thickness and temperature.


Author(s):  
Niladri Chakraborty ◽  
Rajat Chakraborty ◽  
Asit Kumar Saha

Abstract Kiwi fruit (Actinidia deliciosa) (KF) is one of the best fruits available due to its large amount of nutrients. Despite its many health benefits, there are no previous reports on its preparation in other readily ingestible forms. The objective of the present study was to make a new food product from KF. The KF pulp was fortified and blended with several raw materials (such as rice flour and oat flour) using a stepwise short time addition and mixing methodology since this avoids unwanted biochemical and chemical reactions. The blended and reduced moisture KF paste was freeze-dried on a round silver coated steel plate (RSCSP), supplying the heat of sublimation using a newly designed cubic heater. The freeze-drying (FD) time was 4.5 h and the drying kinetics were studied using four established models. The effective moisture diffusivity (Deff) during FD (at 50 °C) was 1.532 x 10-6 m2/s and the activation energy (E) estimated for the FD was 28.35 kJ/mol. The freeze-dried sample was ground and placed under vacuum to reduce the weathering effects. The quality of the stored product was evaluated using the proximate analysis, physicochemical analysis and a sensory evaluation using a hedonic scale. The raw, fresh KF had a moisture content of 85.07% and the final freeze-dried product one of 3%. The carbohydrate, total sugar, protein, fat, total ash, crude fibre and vitamin C contents of the final product increased by 563%, 400%, 355%, 386%, 672%, 106%, and 117% respectively. Of the 66 panelists, the % consumer acceptances for the different attributes were: sweetness (68.18%), sourness (90.91%), saltiness (100%), bitterness (100%), flavour (95.45%), texture (77.27%) and overall acceptability (81.82%). Using conventional freeze-drying (CFD) for blended KF pulp without fortification, with the same RSCSP and the same cubic heater for sublimation, the drying time was found to be 7 h to reach the same final moisture content of 3%.


2020 ◽  
Vol 4 (4) ◽  
pp. 512-521
Author(s):  
Durry Munawar ◽  
Dewi Sri Jayanti ◽  
Raida Agustina

Abstrak. Pemanfaatan kulit melinjo sebagai produk makanan olahan belum banyak diketahui oleh masyarakat. Biasanya kulit melinjo tidak dimanfaatkan lagi dan dibuang begitu saja padahal kulit melinjo dapat diolah kembali menjadi beberapa produk makanan seperti keripik kulit melinjo, manisan, teh, pewarna makanan. Penelitian ini bertujuan untuk mengetahui karakteristik pengeringan dan mutu dalam pembuatan keripik kulit melinjo dengan alat pengering tipe tray dryer pada suhu 35oC dan 45oC. Masing-masing suhu tersebut diulang sebanyak dua kali. Hasil penelitian menunjukkan bahwa pada suhu 35oC kelembaban udara yang diperoleh adalah 70,50% dengan lama pengeringan 390 menit (6,5 jam) dan rata-rata laju pengeringan sebesar 1,08 bk/menit, sedangkan pada suhu 45oC kelembaban udara yang diperoleh adalah 60,72% dengan lama pengeringan 300 menit (5 jam) dan rata-rata laju pengeringan sebesar 1,32 bk/menit. Kecepatan aliran udara ruang pengering pada suhu 35oC dan 45oC adalah konstan (2,4 m/s). Rata-rata kadar air awal kulit melinjo adalah 82,26% sedangkan kadar air akhir adalah 21,36%. Susut bobot pada suhu 35oC adalah 77,56% dan pada suhu 45oC adalah 77,32%. Hasil uji organoleptik terbaik adalah pada suhu 35oC dengan skor 4,28 untuk warna, 4,50 untuk aroma, 4,53 untuk rasa dan 4,40 untuk tekstur.Characteristic Melinjo Peel (Gnetum gnemon L) Drying with Tray Dryer for Making Melinjo Peel ChipsAbstract. The use of melinjo peel as a processed food product is not widely known in the public. Melinjo peel is usually no longer used and thrown away even though the peel could be reprocessed into several food products such as melinjo peel chips, confectionery, tea, and food coloring. This research aimed to determine the characteristics of drying and quality in the making of melinjo peel chips with tray dryer at 35oC and 45oC. Each temperature is repeated twice. The results showed that at a temperature of 35oC, the humidity was 70.50% with a drying time was 390 minutes (6.5 hours) and the average of drying rate was 1.08 dw/minute, meanwhile at 45oC the humidity was 60.72% with a drying time was 300 minutes (5 hours) and an average of drying rate was 1.32 dw/minute. The airflow velocity of the drying chamber at 35oC and 45oC was constant (2.4m/s). The average of initial moisture of melinjo peel was 82.26% and final moisture was 21.36%. The weight loss at 35oC was 77.56% and at 45oC was 77.32%. The best results of organoleptic test was at temperature 35oC with score 4.28 for color, 4.50 for flavor, 4.53 for taste and 4.40 for texture.


Author(s):  
Andrea V Mahn ◽  
Paola Antoine ◽  
Alejandro Reyes

Drying kinetics of broccoli florets in a tunnel dryer was studied. Effective moisture diffusivity (Deff) and activation energy for moisture diffusion (E0) were estimated. The effect of air temperature, air flow rate and particle size on antioxidant capacity, greenness and texture were calculated through a 23 factorial design. Air flow rate and temperature significantly affected drying time. Deff fluctuated between 2.82 x 10-10 and 2.00 x 10-9 (m2/s), and E0 was around 42 KJ/mol, agreeing with values reported in literature. The maximum antioxidant activity was obtained at 60°C, air flow rate of 4 m/s and 1.5 cm particle diameter, resulting in a 70 percent reduction in free radical scavenging ability and a 29 percent increase in total reductive capability. Air temperature had significant effect on greenness, and air flow rate significantly affected texture. The optimization of convective drying of broccoli allows maximizing antioxidant activity and minimizing cost by saving energy and time.


2017 ◽  
Vol 39 (2) ◽  
pp. 225 ◽  
Author(s):  
Guilherme Euripedes Alves ◽  
Flávio Meira Borém ◽  
Eder Pedroza Isquierdo ◽  
Valdiney Cambuy Siqueira ◽  
Marcelo Ângelo Cirillo ◽  
...  

The objective of this study was to evaluate the correlation between a group of physiological variables (electrical conductivity, potassium leaching, and germination percentage) and a group of drying kinetics variables (drying time and drying rate) in addition to verifying the relation between drying kinetics variables and coffee quality as a function of processing type, temperature, and drying airflow. Coffee drying was conducted in a fixed-layer dryer at two temperatures and two airflows. After drying, an evaluation of the physiological and sensorial quality was conducted. Based on the results obtained, the following conclusions were drawn: coffee that is processed via a dry method is more sensitive to mechanical drying with heated air than coffee processed via a wet method, resulting in poor physiological performance; airflow does not interfere with the physiological quality of pulped and natural coffees; a temperature increase from 40 to 45°C resulted in a decrease in the physiological quality only for pulped coffee; and an increase in the drying rate as a result of an increase in the drying temperature to 40°C had a negative effect on the sensorial quality of pulped coffee. 


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