Drying kinetics and physical and chemical characterization of white-fleshed ‘pitaya’ peels

<div><p>ABSTRACT The objective of this work was to obtain the drying kinetic curves of white-fleshed ‘pitaya’ peels and characterize the obtained powder regarding physical and chemical parameters. Different mathematical models were fitted to the experimental data of drying kinetics, considering the coefficient of determination (R2), mean square deviation (MSD) and residual distribution as fit criteria. The peels had an initial moisture content of 93.38% (w.b.) and final moisture contents of 5.39% at temperature of 50 °C, 5.27% at 60 °C and 4.40% at 70 °C. After drying, the peels were disintegrated to obtain the powders and characterized for moisture content, reducing sugars, total titratable acidity, ascorbic acid, betacyanins, betaxanthins, water activity and color, in order to evaluate the influence of temperature on the quality of powders. The Page model was the one that best fitted to the experimental data, presenting coefficient of determination higher than 0.998, mean square deviation lower than 0.02 and random distribution of residuals. Increment in drying air temperature promoted increase of pH, ascorbic acid, luminosity and yellowness, and reduction of moisture content, reducing sugars, acidity, betacyanins, betaxanthins, water activity and redness. Considering the retention of betalains, the drying temperature of 50 °C is the most suitable for the production and use of ‘pitaya’ peel powder.</p></div

Drying and characterization of myrtle pulp

<div><p>ABSTRACT The objective of this study was to develop formulations of myrtle pulp with emulsifier/stabilizer (Emustab® and Super Liga Neutra®) in different proportions; characterize the best foam, based on density and over-run; and determine drying kinetics at temperatures of 50, 60, 70, 80 and 90 oC and thicknesses of 0.5, 1.0 and 1.5 cm. Incorporation of 1.5% Emustab® and 0.5% Super Liga Neutra® to the myrtle pulp (F1) proved to be effective for foam-mat drying. The addition of additives influenced the physicochemical parameters of the whole myrtle pulp. The Midilli et al. model showed the best fit to the experimental data.</p></div

Effective diffusivity in yacon potato cylinders during drying

<div><p>ABSTRACT The aim of this study was to obtain the effective diffusivity of yacon potato in fixed-bed dryer at different temperatures (50, 60 and 70 ºC) and drying air velocities (1.0, 1.5 and 2.0 m s-1). Non-linear regression analysis was performed by the Quasi-Newton method using the program Statistica 7.0, where the parameters of the models were estimated as a function of the drying air temperature. Approximation of Diffusion, Two Terms, Henderson & Pabis, and Page models fitted well the experimental data. Drying air temperature and speed influenced the drying time of the samples. The effective diffusivity increased with increasing temperature, ranging from 1.18 x 10-9 to 2.15 x 10-9 m2 s-1.</p></div