Dehydration study of apple slices by a non-thermal process.

This study investigated the impacts of a drying process under low temperature and reduced pressure (non-thermal drying) on the final dehydrated products characteristics. This process is based on the retention of water on molecular sieves with a good selectivity against these molecules. In this study, drying experiments of 7mm thick apple slices (AS) were performed and compared to apple slices pretreated by freezing. It was concluded that the dehydrated apple slices were depleted of the maximum amount of water after 12 hours of drying, with a final water content equal to 12 ± 1.75%, whereas after freezing pretreatment, a decrease in drying time to 7 hours was observed, as well as a decrease in water content to 10 ± 0.5%. This explains the effect of freezing pretreatment on accelerating water transfer. In addition, a convective drying was performed on the apple slices at 60°C, which allows comparison with the slices dried by our non-thermal drying process. In order to characterize the obtained fruits, characteristic analyses such as water activity (Aw), color, texture (hardness), and dimensions (diameter and thickness) were performed before and after each drying experiment. Thus, continuous measurements of temperature, humidity, and pressure, within the enclosure, were determined during the experiments using a wireless sensor system controlled by a programming Arduino. Finally, mathematical modeling by various models (Newton, Page, Midilli, etc.) was performed to determine the most suitable model describing the non-thermal and convective drying of apple slices.

Green solid-liquid extraction of cactus (Opuntia ficus-indica) cladode dietary fibers. I- optimization, pilot-scale production, and characterization.

In this research work, an optimization of an environment friendly extraction method of cactus (Opuntia ficus indica) cladode dietary fibers was conducted. For this purpose, a central composite experimental design with two factors (temperature and time) and five levels was established. The basic objective of this optimization was to maximize fiber yield using hot water as an extraction eco-solvent. The optimum extraction time (330 min) and temperature (100 °C) were determined with a constant medium agitation rate. Additionally, this study also aimed at establishing the validation of the statistical model to carry out the extrapolation of the extraction process at the pilot scale. The fibers extracted at the pilot scale showed yields (45.2 ± 0.01%) in agreement with those obtained through the optimization and validation lab-scale steps (44.97 ± 0.02). Fourier Transform Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD) and Scanning electron microscopy (SEM) analysis were conducted to investigate the structure and microstructure of pilot scale-produced fibers. FTIR spectrum and XRD pattern were typical to lignocellulosic fibers results. Sharp and thin peaks characteristic of cellulose were detected. Pure and crystallized phases were recorded with a 45% crystallinity index. SEM analysis presented elongated and organized cells with a uniform structure comparable to cellulosic fibers microstructure.

Dynamics and Kinetics of Cupric Ion Removal from Wastewaters by Tunisian Solid Crude Olive-Oil Waste.

The present paper aims to develop a low cost, efficient, and environmentally-friendly process to purify (industrial) waters contaminated by copper by the use of oil mill wastes, through kinetic, thermodynamic, and equilibrium investigations. To do so, the raw adsorbent was characterized using different analytical techniques including X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Then, the interaction between copper and olive residues were examined during batch adsorption tests at various operating parameters, such as pH, initial concentration, contact time, and particle size. Kinetic data were best fitted with Broeurs-Sotolongo kinetic model. Additionally, it was found that film and intraparticle diffusion steps controlled simultaneously the mass transfer of copper onto olive mill solid waste. Among the eight tested models, Broeurs-Sotolongo isotherm suited the most the sorption, with regards to the function errors analysis. It was deduced that the adsorption of copper does not involve chemical bonds with high energy which allows easier regeneration steps and higher number of biosorbent regeneration cycles without any need for applying high temperature in the desorption reaction systems. The adsorption capacity (18.93 mg/g) calculated on the basis of this model was close to the experimental value (18.4 mg/g) but more interestingly it brought up that 50% of the generated amounts of olive wastes in Tunisia could eliminate 1.84 kTons of copper from industrial waters.

Use of green chemistry methods in the extraction of dietary fibers from cactus rackets (Opuntia ficus indica): Structural and microstructural studies.

This work aims to compare the development of three green chemistry methods in the extraction of cactus (Opuntia ficus indica) dietary fibers. The influence of extraction conditions (solvent nature: water, lemon juice and ethanol; extraction process: maceration and steam explosion; extraction time: 30 min, 1 h, 3 h, 5 h) on the chemical and structural composition was studied. Fourier Transform Infrared (FTIR) spectroscopy proved that all treatments do not affect the cellulose structure and could induce the reduction of hemicelluloses and lignin content. The steam treatment with lemon juice was the best treatment in term of quality of the fibers extracted. Through X-ray Diffraction (XRD) analysis, it was demonstrated that this treatment contributed to the destruction of the amorphous phase with preservation of the crystalline phase. Scanning electron microscopy (SEM) showed that the microstructure of the sample surface was uniform and contains arranged fibers. Atomic Force Microscopy (AFM) revealed fibers with 80 nm of diameter.