Effect of Drying on Porous Characteristics of Orange Peel

The purpose of the study was to determine the effects of different temperatures (40, 50 and 60 °C) and air velocities (1 and 2 m/s) on shrinkage, porosity, pore size distribution, color and microstructure of orange peel. Empirical models were also proposed to predict shrinkage and porosity as a function of moisture. A strong negative correlation was determined between moisture and shrinkage. Air temperature had no significant impact on the final shrinkage and porosity values. During drying, porosity of the samples first increased until a critical value, at which point further decrease in moisture resulted in collapse of pores. The porosity of the orange peel was correlated with moisture by a third-order polynomial. Pore size distribution curve of raw sample showed two major peaks, a wider and a sharper peak at around 19.8 and 7.18 μm, respectively. After drying, the peaks became shorter and the curve shifted to the left, indicating that the amount of pores and their diameter decreased. The SEM analysis revealed that at extreme process conditions, the orange peel surface was cracked and the characteristic distribution of the waxy components was obstructed.

Osmotic Dehydration of Tomato Assisted by Ultrasound: Evaluation of the Liquid Media on Mass Transfer and Product Quality

The treatment of a food in liquid media involves mass transfer and could aid to preserve some food properties. The assistance of ultrasound (US) could even improve the process. Therefore, the aim of this study was to evaluate US (frequency 25 kHz, powder intensity 8 kW m–3) in tomato treatment in sucrose and NaCl solutions, common osmotic agents. Moreover, for testing the influence of the media, distilled water and maltodextrin solution completed the set of tested liquids. Water loss (WL), solid gain (SG), water activity (aw), color parameters, like the total color difference (ΔE) and microstructure were evaluated. The advantages of NaCl and sucrose solutions were the high WL and SG values besides low aw and ΔE. The alterations in the microstructure of US-treated samples in distilled water or maltodextrin suggested that a product with low solid incorporation and reduced drying time could be obtained in a further drying.

Modeling and Improving the Performance of Cabinet Solar Dryer Using Computational Fluid Dynamics

In this study, a new approach for numerically modeling of an entire cabinet solar dryer is proposed. Collector, drying chamber and chimney are the three principle sections considered in the present modeling. The collector section containing a cover and an absorber plate is modeled applying energy and fluid flow equations to obtain temperature distribution inside the collector. Due to the non-linear behavior of the governing equations as well as variety of effective variables, an iterative method is employed for solution. Regarding the geometry complexity of the drying chamber along with the air compressibility (that in turn causes coupling of momentum and energy equations) drying chamber is simulated by CFD method. Chimney’s effect and effective parameters in suction are comprehensively considered in the present model. The numerical results are in line with experimental results which show that the model can be applied with certainty to employ the dryer for drying highly demanded and time-consuming products in a scientific, sanitary, and timely manner. The model is then optimized by adding some baffles to achieve higher efficiencies and accelerate the drying process.