Evaluation of Mass Transfer Properties in Convective Drying of Kiwi and Eggplant

2017 ◽  
Vol 13 (7) ◽  
Author(s):  
Raquel P. F. Guine ◽  
Mariana F. S. Brito ◽  
Jéssica R. P. Ribeiro
Keyword(s):  
Activation Energy ◽  
Mass Transfer ◽  
Operating Temperature ◽  
Convective Drying ◽  
Convective Mass Transfer ◽  
Air Flow Rate ◽  
Plant Foods ◽  
Different Temperatures ◽  
Drying Conditions ◽  
Transfer Properties

AbstractThe present work aimed at studying the mass transfer properties of two plant foods, kiwi (a fruit) and eggplant (a vegetable). For this convective drying experiments were conducted at different temperatures (from 50 to 80 ºC) and an air flow rate of 0.5 m/s, using slices with 6 mm thickness for both products. For the mathematical modelling two different methods were used, one based on the thin layer model and the other based on the Fick’s second law of diffusion. The results obtained allowed concluding that different methodologies allowed to obtain different values of the mass transfer properties, so care must be taken when choosing an appropriate calculation method. Regarding the values of diffusivity and mass transfer coefficient, in all cases they were found to increase with increasing operating temperature. Both the activation energy and the activation energy for convective mass transfer were similar for kiwi and for eggplant, indicating that both foods behave in a very similar way when exposed to the drying conditions tested.

scholarly journals Drying kinetics and mass transfer properties in the drying of thistle flower

2019 ◽  
Vol 22 ◽  
Author(s):  
Raquel P. F. Guiné ◽  
Luísa Fontes ◽  
Maria João Reis Lima
Keyword(s):  
Mass Transfer ◽  
Effective Diffusivity ◽  
Moisture Diffusion ◽  
Convective Drying ◽  
Milk Clotting ◽  
Constant Rate ◽  
Different Temperatures ◽  
Drying Conditions ◽  
Transfer Properties ◽  
Natural Drying

Abstract Thistle flowers, and particularly their stigmas, are used to coagulate milk in the production of a number of traditional Portuguese cheeses due to their high milk-clotting activity provided by the high content of aspartic proteases. The aim of the present work was to determine the mass transfer properties of thistle flower under different drying conditions: natural drying and convective drying. Convective drying took place in a convection chamber set at different temperatures (35 to 65 °C) and the process was terminated when the sample presented a moisture content of about 5% or less. The traditional drying method was also used, placing the thistle flowers in a dry place sheltered from the sun, and leaving them to dehydrate at the variable room temperature. The present work allowed for the conclusion that convective drying was much faster than natural drying, and that the drying rate increased with temperature. The drying curve revealed an initial constant rate period followed by a falling rate. All the five thin layer models tested to fit the experimental data were shown to adequately describe the drying of the thistle flowers, but the best one was the Page model. The drying constant increased with temperature as did the effective diffusivity and the mass transfer coefficient. The results allowed one to estimate the activation energy for moisture diffusion (57 kJ/mol) and for convective mass transfer (78 kJ/mol). Thus this study showed the possibilities for designing efficient drying processes for the thistle flower used for milk-clotting in the manufacture of traditional cheeses.

scholarly journals Description of Cumbeba (Tacinga inamoena) Waste Drying at Different Temperatures Using Diffusion Models

Foods ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1818
Author(s):  
João P. L. Ferreira ◽  
Wilton P. Silva ◽  
Alexandre J. M. Queiroz ◽  
Rossana M. F. Figueirêdo ◽  
Josivanda P. Gomes ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Effective Mass ◽  
Sample Surface ◽  
Fruit Production ◽  
Diffusion Models ◽  
Convective Drying ◽  
Convective Mass Transfer ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Drying Conditions

One approach to improve sustainable agro-industrial fruit production is to add value to the waste generated in pulp extraction. The processing of cumbeba (Tacinga inamoena) fruits generates a significant amount of waste, which is discarded without further application but can be a source of bioactive compounds, among other nutrients. Among the simplest and most inexpensive forms of processing, convective drying appears as the first option for the commercial utilization of fruit derivatives, but it is essential to understand the properties of mass transfer for the appropriate choice of drying conditions. In this study, cumbeba waste was dried at four temperatures (50, 60, 70 and 80 °C). Three diffusion models were fitted to the experimental data of the different drying conditions. Two boundary conditions on the sample surface were considered: equilibrium condition and convective condition. The simulations were performed simultaneously with the estimation of effective mass diffusivity coefficients (Def) and convective mass transfer coefficients (h). The validation of the models was verified by the agreement between the theoretical prediction (simulation) and the experimental results. The results showed that, for the best model, the effective mass diffusivities were 2.9285 × 10−9, 4.1695 × 10−9, 8.1395 × 10−9 and 1.2754 × 10−8 m2/s, while the convective mass transfer coefficients were 6.4362 × 10−7, 8.7273 × 10−7, 8.9445 × 10−7 and 1.0912 × 10−6 m/s. The coefficients of determination were greater than 0.995 and the chi-squares were lower than 2.2826 × 10−2 for all simulations of the experiments.

scholarly journals Influence of the temperature and ultrasound application in drying kinetics of apple skin

2018 ◽  
Author(s):  
Juan A. Cárcel ◽  
Matheus P. Martins ◽  
Edgar J. Cortés ◽  
Carmen Rosselló ◽  
Ramón Peña
Keyword(s):  
Physical Structure ◽  
Drying Kinetics ◽  
Convective Drying ◽  
Drying Time ◽  
Different Temperatures ◽  
Ultrasound Application ◽  
Quality Of Products ◽  
Drying Conditions ◽  
Kinetics Of ◽  
By Products

The great amount of waste produced by food industry contains interesting bioactive compounds. The extraction of these compounds requires the by-products previous stabilization being the convective drying one of most used techniques to this end. Drying conditions can affect both drying kinetics and final quality of products. The apple skin, byproduct of apple juice or cider industries, is rich in functional compounds such as polyphenols or vitamin C. The main goal of this contribution was to quantify the influence of temperature and ultrasound application in drying kinetics of apple skin. For this purpose, drying experiments at different temperatures (-10, 30, 50 and 70 ºC) and with (20.5 kW/m3) and without application of ultrasound were carried out. Drying kinetics were modelled by using a diffusion based model. As can be expected, the higher the temperature the faster the drying. Ultrasound application accelerated the process at every temperature tested being the influence slightly lower than found from the literature for other products. This can be attributed at the physical structure of the apple skin, less porous than the pulp. In any case, the application of ultrasound significantly reduced the drying time. Keywords: by-products; dehydration;diffusivity; mass transfer

scholarly journals Influence of drying temperature and ultrasound application in some quality properties of apple skin.

2018 ◽  
Author(s):  
Juan A. Cárcel ◽  
Matheus P. Martins ◽  
Edgar J. Cortés ◽  
Susana Simal ◽  
Antonio Mulet ◽  
...  
Keyword(s):  
Vitamin C ◽  
Antioxidant Properties ◽  
Quality Parameters ◽  
Convective Drying ◽  
Total Phenolic ◽  
Drying Temperature ◽  
Quality Properties ◽  
Different Temperatures ◽  
Ultrasound Application ◽  
Drying Conditions

The great amount of waste produced by the food industry can be an interesting source of bioactive compounds. To this end, convective drying is one of the most extended method to stabilize the industrial by-products. However, drying conditions can affect not only drying kinetics but also the bioactivy of some compounds. Apple skin constitutes one of the main by-product generated in apple juice or cider production. It contains important amounts of functional compounds such as polyphenols or vitamin C whose extraction can be interesting. The main aim of this work was to determine the influence of drying conditions, temperature and application of ultrasound, in some quality parameters of dried apple skin. For this purpose, apple skin samples were dried at different temperatures (-10, 30, 50 and 70 ºC) and with (20.5 kW/m3) or without application of ultrasound. Color, total phenolic content, antioxidant activity and vitamin C was measured in fresh and dried samples. The increase of drying temperature and the ultrasound sligthly reduced the antioxidant properties of samples while no influence in sample color was observed. Keywords: by-product; antioxidant; polyphenol; vitamin C; color.

scholarly journals Study of the drying kinetics and calculation of mass transfer properties in hot air drying of Cynara cardunculus

2020 ◽  
Vol 5 (1) ◽  
pp. 740-750
Author(s):  
Raquel P. F. Guiné ◽  
Maria João Lima
Keyword(s):  
Mass Transfer ◽  
Thin Layer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Moisture Diffusion ◽  
Equation Model ◽  
Convective Drying ◽  
Cynara Cardunculus ◽  
Thin Layer Drying ◽  
Transfer Properties

AbstractIn the present work, mass transfer properties of thistle flower (Cynara cardunculus L.) were evaluated for the convective drying carried out at temperatures between 35 and 65°C, with an air flow of 0.5 m/s. The calculations followed two different algorithms, based on mathematical models derived from the thin layer drying equation and Fick’s second law of diffusion. The results obtained indicated that different methodologies resulted in different values of mass transfer properties, which is an alert that care must be taken when choosing which calculation method might be more appropriate in a specific practical application. In all cases, the values of moisture diffusion and mass transfer coefficient were found to increase with increasing operating temperature. The values of diffusivity increased from 2.7866 × 10−9 to 1.4027 × 10−8 m2/s for the thin layer model-based algorithm and from 1.9256 × 10−10 to 1.2033 × 10−9 m2/s for Fick’s equation model. The values of the mass transfer coefficient increased from 8.4335 × 10−8 to 8.4400 × 10−7 m/s and from 5.8277 × 10−9 to 7.2398 × 10−8 m/s, respectively, for the thin layer and Fick’s law-based models.

Convective Drying of Apples: Kinetic Study, Evaluation of Mass Transfer Properties and Data Analysis using Artificial Neural Networks

2014 ◽  
Vol 10 (2) ◽  
pp. 281-299 ◽  
Author(s):  
Raquel P. F. Guiné ◽  
Ana C. Cruz ◽  
M. Mendes
Keyword(s):  
Neural Networks ◽  
Mass Transfer ◽  
Artificial Neural Networks ◽  
Convective Drying ◽  
Network Modelling ◽  
Feed Forward ◽  
Study Evaluation ◽  
Feed Forward Neural Networks ◽  
Artificial Neural ◽  
Transfer Properties

Abstract In the present work, the effect of drying was evaluated on some chemical and physical properties of apples, and the functions were modelled using feed-forward artificial neural networks. The drying kinetics and the mass transfer properties were also studied. The results indicated that acidity and sugars were significantly reduced by drying. Regarding colour lightness decreases, whereas redness and yellowness increased. As for texture, the dried samples were softer and less cohesive as compared to the fresh ones. Mass diffusivity increased with temperature, from 4.4×10−10 m2/s at 30°C to 1.4×10−9 m2/s at 60°C, and so did the mass transfer coefficient, increasing from 3.7×10−10 m/s at 30°C to 7.4×10−9 m/s at 60°C. As to the activation energy, it was found to be 34 kJ/mol. Neural network modelling showed that all properties can be correctly predicted by feed-forward neural networks. The analysis of the networks’ behaviours input layer weight values also shows which properties are more affected by dehydration or more dependent on variety.

scholarly journals Measuring REA-based drying kinetics through temperature-moisture content relationship

2018 ◽  
Author(s):  
Xiao Dong Chen ◽  
Aditya Putranto
Keyword(s):  
Heat Transfer ◽  
Activation Energy ◽  
Mass Transfer ◽  
Moisture Content ◽  
Mass Balance ◽  
Reaction Engineering ◽  
New Approach ◽  
Engineering Approach ◽  
Relative Activation ◽  
Drying Conditions

The reaction engineering approach (REA) has been proposed and implemented for modeling a number of challenging drying cases. While the modeling is simple and accurate, it is effective to generate the drying parameters. The relative activation energy is the fingerprint of the REA which describes the changes of internal behaviors inside the materials during drying. In this paper, a new method, based on combined heat and mass balance, is proposed and implemented to retrieve the relative activation energy of flat materials. The results indicate that the new approach can be used to retrieve well the activation energy of flat materials. The relative activation energy retrieved by the new approach is independent on the external drying conditions. This new approach can also potentially be used to evaluate the change of surface area of materials during drying Keywords: reaction engineering approach (REA);, modeling; relative activation energy; mass transfer;, heat transfer 

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