MATHEMATICAL MODELING OF ORANGE SEED DRYING KINETICS

Drying of orange seeds representing waste products from juice processing was studied in the temperatures of 40, 50, 60 and 70 °C and drying velocities of 0.6, 1.0 and 1.4 m/s. Experimental drying kinetics of orange seeds were obtained using a convective air forced dryer. Three thin-layer models: Page model, Lewis model, and the Henderson-Pabis model and the diffusive model were used to predict the drying curves. The Henderson-Pabis and the diffusive models show the best fitting performance and statistical evaluations. Moreover, the temperature dependence on the effective diffusivity followed an Arrhenius relationship, and the activation energies ranging from 16.174 to 16.842 kJ/mo

Obtention of New Edible Biofilms from Water Kefir Grains in Comparison with Conventional Biofilms from Taro (Colocasia esculenta) and Cassava (Manihot esculenta) Starch

Microorganism biomass is a sustainable and innovative source of biopolymers, such as proteins and polysaccharides, that is suitable for the development of biodegradable films. The aim of this research was to evaluate the synthesis, morphology, rheology, and morphological and mechanical properties on the production of edible biofilms based on water kefir grains, and compare them with edible films based on thermoplastic compounds from starch (TPS) obtained from taro (Colocasia esculenta) and cassava (Manihot esculenta). Edible biofilms were prepared in solution with 30% wt/wt glycerol relative to starch mass and kefir grain biofilms using the casting method. A stationary rheological analysis was performed on the film-forming suspensions of kefir, taro starch, and cassava starch. Once the films were obtained, a physicochemical and morphological characterization was carried out. Results of the characterization showed the following main aspects: The results indicated an increase in biomass production using muscovado and pineapple peel. The film-forming suspensions had a dilating behavior; however, the results obtained not only show the viscoelastic behavior but also the elastic limit (σ0), which varied from 0.077 to 0.059 Pa for suspensions of water kefir grains and from 0.077 to 0.072 Pa for starch suspensions. These elastic limit variations can be defined as the minimum shear stress required to start the flow, and all these rheological data were adjusted to the Herschel–Bulkley model; the morphological and mechanical characterization of the films obtained showed homogeneous surfaces with transparency and without cracks; regarding the water activity, values lower than 6 were obtained, which indicates that there will be no growth of any microorganism, and the hardness data showed differences between those obtained from kefir and taro and cassava starch. The similar results of the rheological characterization in the formation of the kefir biofilm and the conventional edible starch films, in addition to the similar results in the water activity below 6 and the hardness, points to an attractive alternative capable of replacing the conventional materials with a mass production of biofilms of probiotic microorganisms. The results also revealed that water kefir grains biomass is a viable and innovative source of biodegradable materials, and these grains can be an alternative to conventional established starch materials

Effect of the Freeze-Drying Process on the Physicochemical and Microbiological Properties of Mexican Kefir Grains

The purpose of this study was to investigate how the properties of Mexican kefir grains (MKG) are affected by the operating parameters used in the freeze-drying process. The factors investigated were the freezing time (3–9 h), freezing temperature (−20 to −80 °C), pressure (0.2–0.8 mbar), and lyophilization time (5–20 h). The maximum range of change and one-way analysis of variance showed that lyophilization time and freezing time significant affects (p < 0.05) the response variables, residual moisture content and water activity, and pressure had a significant effect on the color difference and survival rate of probiotic microorganisms. The best drying conditions were a freezing time of 3 h, a freezing temperature of −20 °C, a pressure of 0.6 mbar, and a lyophilization time of 15 h. Under these conditions, we obtained a product with residual moisture content below 6%, water activity below 0.2, and survival rates above 8.5 log cfu per gram of lactic acid bacteria and above 8.6 log for yeast

Synthesis, Modification, and Characterization of Fe₃O₄@SiO₂-PEI-Dextranase Nanoparticles for Enzymatic Degradation of Dextran in Fermented Mash

During the sugar production process, undesirable compounds such as dextrans are produced and contaminate the flow of the sugar mill, reaching levels in the fluid of more than 10,000 ppm. Dextranase is an enzyme that has different industrial applications, since it catalyzes the hydrolysis of the bonds in random sites of the dextran. Therefore, the enzyme was immobilized using synthesized ferrite magnetic nanoparticles to degrade dextran in the fermented mash, because it is suitable to reuse and has a large surface area to bind dextranase on a solid carrier for easy magnetic separation. The synthesized bare and modified nanoparticles were characterized using SEM, EDS, FTIR, and XRD and confirmed the core–shell silica by increasing the silica composition from 0.2% of bare Fe3O4 NPs to 31.3% of modified Fe3O4 NPs. Ultrasonic treatment reduced the calculated crystal size with Scherer’s equation from 91.3 to 13.5 nm, providing more particles for immobilization. The solvothermal process synthesized ferrite nanoparticles (Fe3O4) and modified them with TEOS and PEI. The obtained immobilization efficiency was 28%. Perhaps it was lower; Fe3O4 degraded almost the same as the free enzyme. The percentage of dextran degradation with free enzymes and immobilized enzymes with Fe3O4 magnetic nanoparticles was 61 and 52%, respectively

Removal of an Ethoxylated Alkylphenol by Adsorption on Zeolites and Photocatalysis with TiO2/Ag

Two advanced removal methods (adsorption and photocatalysis) were compared for the elimination of an ethoxylated alkylphenol (nonylphenol polyethylene glycol, NPEG). For the adsorption process, zeolites were used in their natural state, and the process was characterized by DRX (X-ray diffraction) and SEM–EDS (Scanning electron microscopy). The analysis of the results of the adsorption kinetics was carried out using different isotherms to interpret the removal capacity of zeolites. The Temkin kinetic model better predicted the experimental data and was satisfactorily adjusted to models of pseudo-second order (PSO). On the other hand, for photocatalysis, nano-particles of Ag (silver) were deposited on titanium oxide (TiO2) Degussa-P25 by photo-deposition, and the catalyst was characterized by diffuse reflectance and SEM–EDS. The data obtained using the two removal techniques were analyzed by UV–Vis (ultraviolet-visible spectrophotometry) and total organic carbon (TOC). The kinetic data were compared. The photocatalytic process showed the highest efficiency in the removal of NPEG, corresponding to >80%, while the efficiency of the adsorption process was <60%. This was attributed to the recalcitrant and surfactant nature of NPEG