Pulsed air jet impingement drying characteristics of winter jujube slices

The drying curves, moisture effective diffusivity and drying activation energy of winter jujube slices were here investigated at different drying temperatures (55, 60, 65, 70, 75, and 80°C), wind speeds (6, 7, 8, 9, and 10 m/s) and pulsation rates (rotatational speed of material disk: 4, 5.5, and 7 rpm) in a single-factor experiment design. A mathematical model of pulsed air-jet impingement drying for winter jujube slices was fitted and verified. The results showed that the entire drying process could be described as falling rate drying; the moisture effective diffusivity was in the range 1.52–4.93 × 10^–9 m²/s and increased with increasing drying temperature, wind speed and pulsation rate. The drying activation energy was 43.9 kJ/mol as determined using the Arrhenius equation. According to the statistical parameters of the correlation coefficient (R²), root mean square error (RMSE) and the sum of squared errors (SSE), the modified Page model was selected as best for representing the correlation between moisture ratio and drying time.

Drying kinetics of fermented grape pomace: Determination of moisture effective diffusivity

ABSTRACT The aim of this study was to obtain the equilibrium moisture content of grape (variety ‘Tannat’) pomace through desorption isotherms, to evaluate the drying kinetics, determine the coefficient of effective diffusivity and physico-chemically characterize the grape pomace and the product obtained after drying. The desorption isotherms were determined at 50, 60 and 70 ºC and the experimental data were fitted using the GAB model (Gugghenheim, Anderson and de Boer). Drying was evaluated using a 22 factorial experimental design with three center points and effective diffusivity was obtained through the diffusion model of Fick’s second law. The grape pomace was characterized regarding the contents of moisture, protein, carbohydrates, lipids, ash and dietary crude fiber. The obtained isotherms showed sigmoid shape and the experimental data fitted well to the GAB model. The drying curves showed only a decreasing rate period. The effective diffusivity values were within the range for organic materials. Dry grape pomace showed high contents of protein and fiber and can be used in the development of new products, in order to increase the nutritional content and add value to this byproduct.

Drying Kinetics, Biochemical and Functional Properties of Products in Convective Drying ofAnchovy (Engraulis anchoita) Fillets

The aim of this work was to study the convective drying of anchovy (Engraulis anchoita) fillets and to evaluate the final product characteristics through its biochemical and functional properties. The drying temperatures were of 50, 60 and 70°C, and the fillet samples were dried with the skins down (with air flow one or the two sides) and skins up (with air flow one side). The drying experimental data were analyzed by Henderson–Pabis model, which showed a good fit (R2 > 0.99 and REQM < 0.05). The moisture effective diffusivity values ranged from 4.1 × 10–10 to 8.6 × 10–10 m2 s−1 with the skin down and 2.2 × 10–10 to 5.5 × 10–10 m2 s−1 with the skin up, and the activation energy values were 32.2 and 38.4 kJ mol−1, respectively. The product characteristics were significantly affected (p < 0.05) by drying operation conditions. The lower change was in drying at 60°C with air flow for two sides of the samples and skin up. In this condition, the product showed solubility 22.3%; in vitro digestibility 87.4%; contents of available lysine and methionine 7.21 and 2.64 g 100 g−1, respectively; TBA value 1.16 mgMDA kg−1; specific antioxidant activity was 1.91 mMDPPH g−1 min−1, and variation total color was 10.72.

Research of Drying Characteristics of Thompson Seedless Grape

Drying characteristics of Thomson seedless grape at different drying temperatures (45°C, 40 °C, 35 °C and 30 °C) were investigated in a Constant Temperature and Humidity Testing Machine. 8 different thin layer mathematical drying models are selected to fitting the date. The logarithmic drying model is satisfactorily to describe the drying process of grapes. In addition, this paper also calculated the moisture effective diffusivity (Deff) of Thompson seedless grape during drying process, and 45 °C has the maximum value 3.0702·10-11 m2/s. The energy of activation (Ea) is 59.03 kJ/mol. This means it will take 3279.44 kJ to remove 1kg water from the grape samples.

Moisture Effective Diffusivity in Porous Media with Different Physical Properties

In the drying of porous media, the mass transport occurs in the pores as well as on the surface of the solid. The mechanisms involved can take place simultaneously, influenced by the predominant one and can change depending on the moisture content. In this work, the moisture effective diffusivity was estimated in solids with distinct structural properties in order to verify the predominant mechanisms according to the moisture content, analyzing the influence of the physical properties. The materials studied were NaY Zeolite, Kaolin, Silica and Alumina. The results of diffusion coefficient present a minimum at low moisture content that can be related to pore size.