scholarly journals Drying rates of Rubi grapes submitted to chemical pretreatments for raisin production

2006 ◽  
Vol 41 (3) ◽  
pp. 503-509 ◽  
Author(s):  
Vânia Regina Nicoletti Telis ◽  
Vânia Araújo Lourençon ◽  
Ana Lúcia Gabas ◽  
Javier Telis-Romero
Keyword(s):  
Olive Oil ◽  
Soybean Lecithin ◽  
Aqueous Suspension ◽  
Convective Drying ◽  
Factorial Designs ◽  
Soy Lecithin ◽  
Drying Time ◽  
Drying Rates ◽  
Chemical Pretreatments ◽  
Drying Curves

The objective of this work was to determine the most appropriated chemical treatment to be used to dry grapes cv. Rubi for raisin production. Drying curves for convective drying with air at 50ºC, in a tray drier, were obtained for grapes submitted to chemical pretreatments with different concentrations of potassium carbonate and olive oil, and different dipping times, according to factorial designs. Convective drying curves were also obtained for grapes pretreated in aqueous suspensions of soybean lecithin, at varied lecithin concentrations and dipping times. Page model was adjusted to the experimental drying curves, and the calculated drying times showed that the best pretreatment consisted in dipping grapes for 2 minutes in a 5% olive oil and 6% K2CO3 emulsion, at 50ºC, which resulted in a drying time close to that of the pretreatment with 2.5% of olive oil, but with a lower consumption of this substance. In addition, the immersion of grapes in an aqueous suspension of 2% soy lecithin, at 50ºC, for 5 minutes, resulted in a total drying time slightly higher than the most effective pretreatment.

scholarly journals Effect of pre treatment methods on fruits drying of grapes under warm air condition

2018 ◽  
Vol 33 (01) ◽  
Author(s):  
Priti Jain ◽  
S. P. Shrivastava ◽  
Sheela Pandey
Keyword(s):  
Olive Oil ◽  
Soy Lecithin ◽  
Drying Time ◽  
Treatment Methods ◽  
Pre Treatment ◽  
Drying Rates

In the present study, grapes pretreated with different concentrations of potassium carbonates plus olive oil and soy lecithin with different dipping times. A dryer was built to perform the experiment under controlled condition of drying air at temperature 50°C and velocity 1.0 m/s. Grapes dipped into 1percentage olive oil plus 6percentage K2CO3 emulsion, at 50°C for 2 min. prior to drying showed shorter drying times and comparatively good quality raisin, whereas grapes dipped into 1.5percentage soy lecithin, at same conditions resulted in a total drying time slightly higher than the most effective pre treatment. The drying rates of grapes were modeled by the page equations. Grapes that are naturally dried usually darken in colour, whereas dipped grapes stay yellow-green.

scholarly journals Convective Drying of Sewage Sludge Layer in Through-flow

2020 ◽  
Vol 66 (9) ◽  
pp. 481-493
Author(s):  
Andraž Lipolt ◽  
Brane Širok ◽  
Marko Hočevar ◽  
Lovrenc Novak
Keyword(s):  
Sewage Sludge ◽  
Drag Force ◽  
Layer Structure ◽  
Measured Data ◽  
Matter Content ◽  
Convective Drying ◽  
Coefficient Of Determination ◽  
Dry Matter Content ◽  
Drying Time ◽  
Drying Rates

Drying of the sewage sludge layer was investigated in a convective laboratory dryer at air temperatures of 65 °C and 80 °C and air speeds of 0.53 m/s and 0.83 m/s. The sludge layer was formed by loading cylindrical extrudates on a grate of 0.5 m × 0.5 m size. The drying air was directed through the layer, as typically encountered in industrial belt dryers. Under such setup, the sludge layer structure and porosity significantly affect the air flow conditions and thus the drying rates. Shrinkage and cracking of the material during drying caused changes in the layer’s porous structure, that affected the pressure drop and the drag force due to passing of air through the layer. The decreasing of drag force over time was modeled by a simple function that showed excellent agreement to the selected measured data. The sludge layer drying kinetics was determined by fitting the measured data to the most common drying models. Two models, the modified Nadhari and the Wang Singh model, were determined as most suitable for modeling of drying curves. The total drying time per kilogram of sludge was modeled as a function of drying air temperature, drying air velocity and initial sludge dry matter content. The coefficient of determination (R2) of the model is 0.944. Total drying times between 43 minutes per kilogram and 76 minutes per kilogram of sludge were obtained for the investigated range of drying air conditions.

scholarly journals Mathematical modeling of pequi pulp drying and effective diffusivity determination

2017 ◽  
Vol 21 (7) ◽  
pp. 493-498 ◽  
Author(s):  
Elisabete P. de Sousa ◽  
Rossana M. F. de Figueirêdo ◽  
Josivanda P. Gomes ◽  
Alexandre J. de M. Queiroz ◽  
Deise S. de Castro ◽  
...  
Keyword(s):  
Experimental Data ◽  
Effective Diffusivity ◽  
Drying Kinetics ◽  
Convective Drying ◽  
Drying Time ◽  
Air Speed ◽  
Drying Curves ◽  
Increasing Temperature ◽  
Kinetics Of ◽  
Best Fit

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.

scholarly journals Drying Kinetics and Modelling of Convective Drying of Kedondong Fruit

2021 ◽  
Vol 21 (1) ◽  
pp. 93
Author(s):  
Cheak Theng Ee ◽  
Yee Jian Khaw ◽  
Ching Lik Hii ◽  
Choon Lai Chiang ◽  
Mohamad Djaeni
Keyword(s):  
Thin Layer ◽  
Moisture Diffusion ◽  
Drying Kinetics ◽  
Convective Drying ◽  
Small Scale ◽  
Hot Air ◽  
Kinetic Information ◽  
Drying Rates ◽  
Drying Curves ◽  
Effective Diffusivities

Kedondong is an underutilized fruit cultivated in a small scale in Malaysia and it contains nutrients that can be preserved through drying. The dried product can be sold as a premium fruit snack that could generate revenue for the producer. We studied the drying of peeled and unpeeled kedondong fruits using hot air (60-80°C). This study aims to investigate the drying kinetics (drying rates and effective diffusivities) of kedondong fruits and model the drying curves using thin layer models. Ten thin layer models were employed and solved using non-linear regression. Drying kinetics showed that only falling rate periods were observed, which implied that internal diffusion was the dominant mechanism for moisture release. Mathematical models showed that Modified Hii et al. (I) and (II) models were able to predict the drying curve well with the highest R2 (0.9992-0.9999), the lowest RMSE (8.0 x 10-4 - 2.5 x 10-3) and the lowest χ2 (4.0 ×10-5 - 2.0 x 10-4). Peeled  samples showed higher effective diffusivities (average 3.2 x 10-11 m2/s)  than unpeeled samples (average 2.7 x 10-11 m2/s). The activation energy was lower in peeled samples (25.8 kJ/mol) as moisture diffusion could occur more easily than unpeeled samples (32.1 kJ/mol). Results from this study provide kinetic information that can be used in scaling up of dryer and optimizing dryer performances.

scholarly journals Kinetic parameters identification of conductive enhanced hot air drying process of food waste

2020 ◽  
pp. 223-223
Author(s):  
Mihailo Milanovic ◽  
Mirko Komatina ◽  
Ivan Zlatanovic ◽  
Nebojsa Manic ◽  
Dragi Antonijevic
Keyword(s):  
Food Industry ◽  
Convective Drying ◽  
Diffusivity Coefficient ◽  
Drying Method ◽  
Drying Process ◽  
Air Velocity ◽  
Drying Time ◽  
Hot Air ◽  
Air Temperatures ◽  
Drying Curves

The efficient utilization of waste from food industry is possible after thermal treatment of the material. This treatment should be economically feasible and compromise the energy efficient drying process. The main goal of this investigation is to determine drying characteristics of nectarine pomace as a waste from food industry. The measurements were performed in an experimental dryer by combined conductive-convective drying method with disk-shaped samples of 5, 7 and 10mm thickness and 100 mm in diameter at the air temperatures of 30, 40, 50, 60 and 70oC, hot plate temperatures of 50, 60 an 70oC and air velocity of 1.5 m/s. The drying curves were compared to a few semi-theoretical mathematical models. The Logarithmic model showed the best correspondence. On the basis of experiments, it is determined that the drying process takes place in a falling rate period and it is accepted that the main mechanism of moisture removal is diffusion. The effective coefficient of diffusion was determined using experimental results by calculating the slope of the drying curves. Drying time and equilibrium moisture are determined for each experiment. Analysis of drying curves showed that the conductive-enhanced drying method reduces drying times and increases the diffusivity coefficient. The character of drying rate curves for conductive-enhanced drying was analyzed and compared with pure convective drying of nectarine pomace.

scholarly journals Improved protocol for natural convection pumpkin drying

2021 ◽  
pp. 29-39
Author(s):  
Hakim Semai ◽  
Amor Bouhdjar ◽  
Aissa Amari
Keyword(s):  
High Temperature ◽  
Effective Diffusivity ◽  
Convective Drying ◽  
Agricultural Product ◽  
Diffusivity Coefficient ◽  
Drying Time ◽  
Thin Layer Drying ◽  
Different Temperatures ◽  
Energy Consuming ◽  
Drying Curves

The most effective way to preserve agricultural product is drying. However, vegetable drying is an energy-consuming procedure. Convective drying is the mode considered in this work. The study intends to explore a new way of pumpkin drying, which reduces drying time and minimizes heat consumption. The study considers pumpkin thin slices and pumpkin samples with cubic shape. The samples were subjected to free convection airflow at different temperatures (40 °C, 46 °C, 52 °C, and 60 °C) for each run. A varying airflow temperature was also considered. Airflow velocity was generated by buoyancy forces for each temperature. Drying curves were plotted and fitted to the widely used thin-layer drying models. The modified Page model came out as the best-fitted model. The effective diffusivity coefficient was determined for each case using the slope moisture curve.  It appeared that diffusivity was high and drying time was short, for high temperature. Drying processes for slice configuration and cube configuration showed that the latter was more efficient. When applying the regime of increasing temperatures to the cubic samples, data analysis showed that effective diffusivity was higher during the third step in comparison to all the other drying temperatures and the total drying time was similar to that obtained at drying regime on high temperature. With this procedure, the final consumed energy was much less and the time was shorter.

Impact of Fruit Ripeness on Physicochemical Properties and Convective Drying Characteristics of Kent Mango (Mangifera indica L. cv. 'Kent')

2011 ◽  
Vol 7 (3) ◽  
Author(s):  
Alfa Oumar Dissa ◽  
Hélène Desmorieux ◽  
Pascal Degraeve ◽  
Joseph Bathiebo ◽  
Jean Koulidiati
Keyword(s):  
Natural Convection ◽  
Thermal Diffusivity ◽  
Mangifera Indica ◽  
Soluble Solids ◽  
Convective Drying ◽  
Drying Characteristics ◽  
Mass Diffusivity ◽  
Drying Rates ◽  
Drying Curves ◽  
Time Required

Impact of ripeness on drying characteristics of mango was studied by considering different zones on the fruit. For each zone, ripeness was estimated by total soluble solids/acidity ratio, colour and texture of fruit flesh. For each state of ripeness, drying curves and time-temperature curves were established both in forced and natural convection. Mass diffusivity (estimated by considering two diffusion regions), thermal diffusivity and drying rates were deduced from these drying curves by considering product shrinkage. Results showed that the time required to reduce moisture content to any given level depended on the ripeness state, being highest for unripe samples and lowest for ripe samples. At each drying moment, temperature of ripe sample was higher than that of unripe sample. Mass diffusivity, thermal diffusivity and drying rates strongly increased with ripeness state. At 60°C, unripe and ripe fruit mass diffusivities ranged respectively from 1.69x10-10 to 9.87x10-10 m²/s and 3.38x10-10 to 1.77x10-9 m²/s. Thermal diffusivities ranged from 2.12 x10-11 to 6.44x10-10 m²/s and 2.74x10-10 to 8.05 x10-10 m²/s respectively for unripe and ripe samples. In natural convection, drying rates reached maximal values of 0.16 kg m-2 s for unripe sample and 0.47 kg m-2 s for ripe sample whereas in forced convection they reached respectively 0.43 and 0.67 kg m-2 s. Product shrinkage decreased with ripeness and was almost ideal for the major part of the drying process. Constants of suitable fitting models also varied considerably with fruit ripeness. This work showed that ripeness state influences strongly drying characteristics of mango fruit.

scholarly journals Effect of pre-treatments on solar drying kinetics of red seedless grapes (cv. Monukka)

2014 ◽  
Vol 3 (2) ◽  
Author(s):  
Inês Nunes Ramos ◽  
Teresa R.S. Brandão ◽  
Cristina L.M. Silva
Keyword(s):  
Edible Oil ◽  
Hot Water ◽  
Drying Time ◽  
Water Emulsion ◽  
Oil Emulsion ◽  
Oil Water ◽  
Drying Rates ◽  
Drying Curves ◽  
Kinetics Of ◽  
Best Fit

Two different pre-treatments were applied to grapes prior to drying in a mixed mode solar dryer. Grapes were blanched in water and in a 0.1% sunflower oil water emulsion, both at 99oC and for approximately 15 seconds. Several models were tested to fit the experimental data of drying curves but the normalized Newton model gave the best fit results. Samples blanched in hot water or in the 0.1% edible oil emulsion had faster drying rates than untreated samples. Contrary to what was expected, pre-treating with the 0.1% edible oil emulsion did not increase the drying rate to a higher extent than blanching. Pre-treatments did not give a noteworthy difference in the total drying time. However, they had an important role in accelerating initial drying rates, thus preventing moulds and bacterial growth and consequently increasing farmers’ income.

scholarly journals Modelling the kinetics of microwave drying of shallot (Allium cepa) slices

2021 ◽  
Vol 1195 (1) ◽  
pp. 012033
Author(s):  
C L Hii ◽  
C Govind ◽  
C L Chiang ◽  
D Mohammad
Keyword(s):  
Thin Layer ◽  
Allium Cepa ◽  
Microwave Power ◽  
Drying Kinetics ◽  
Microwave Drying ◽  
Convective Drying ◽  
Drying Methods ◽  
Drying Time ◽  
Thin Layer Drying ◽  
Drying Rates

Abstract Convective drying is typically used to dry shallot (Allium cepa) commercially. However, a long drying time with a relatively low efficiency has led to the pursuit of new and improved drying methods. Microwave drying was chosen to be used due to its numerous advantages such as improved drying time, high drying efficiency and better product quality. In this research, three microwave power (180 W, 300 W, 450 W) and convective drying at 100°C were used. Results showed that drying kinetics (moisture content and drying rates) decreased the fastest at higher microwave power and the slowest using convective drying. In order to determine the best model to describe the thin-layer drying kinetics, four semi-empirical models were used namely Newton, Page, Logarithmic and Two-term models. Page model was found to be the best in describing the thin-layer microwave drying kinetics. Effective diffusivity values increased with higher microwave power and were found to be in the range of 6.62 × 10−6 m2/s to 3.69 × 10−5 m2/s with convective drying being the lowest (6.62 × 10−6 m2/s) and 450W being the highest (3.69 × 10−5 m2/s). Microwave drying is therefore able to improve drying kinetics compared to convective drying.

scholarly journals An improved protocol for natural convective drying of pumpkin

2021 ◽  
Vol 48 (1) ◽  
pp. 29-39
Author(s):  
Hakim Semai ◽  
Amor Bouhdjar ◽  
Aissa Amari
Keyword(s):  
High Temperature ◽  
Effective Diffusivity ◽  
Convective Drying ◽  
Agricultural Product ◽  
Diffusivity Coefficient ◽  
Drying Time ◽  
Thin Layer Drying ◽  
Different Temperatures ◽  
Energy Consuming ◽  
Drying Curves

The most effective way to preserve agricultural product is drying. However, vegetable drying is an energy-consuming procedure. Convective drying is the mode considered in this work. The study intends to explore a new way of pumpkin drying, which reduces drying time and minimizes heat consumption. The study considers pumpkin thin slices and pumpkin samples with cubic shape. The samples were subjected to free convection airflow at different temperatures (40 °C, 46 °C, 52 °C, and 60 °C) for each run. A varying airflow temperature was also considered. Airflow velocity was generated by buoyancy forces for each temperature. Drying curves were plotted and fitted to the widely used thin-layer drying models. The modified Page model came out as the best-fitted model. The effective diffusivity coefficient was determined for each case using the slope moisture curve. It appeared that diffusivity was high and drying time was short, for high temperature. Drying processes for slice configuration and cube configuration showed that the latter was more efficient. When applying the regime of increasing temperatures to the cubic samples, data analysis showed that effective diffusivity was higher during the third step in comparison to all the other drying temperatures and the total drying time was similar to that obtained at drying regime on high temperature. With this procedure, the final consumed energy was much less and the time was shorter.

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