In celery, leaves, roots, and fruit contain a high value in medicinal properties and are used to prepare syrups, tinctures, infusions, or oils; however, its leaves are commonly discarded, wasting their nutritional and medicinal content. The dehydration of these leaves is a conservation option, increasing their shelf life. This study analyzes direct and mixed solar drying (SD and SM) kinetics and their effect on celery leaves. The moisture contents, drying rate, water activity, and colorimetry were obtained. Moreover, the fitting of experimental data to the mathematical models proposed in the literature. The moisture content stabilized at 150 min in the SM at the shortest time with a maximum drying rate of 0.1179 g∙water/g∙ dm∙min. The initial and final water activity was 0.98 and 0.412 in the SM and 0.403 in the SD. The SD better conserved the leaf color, with a total color change (ΔE) of 2.56, while the value obtained with the SM was 5.42. The experimental results of both technologies were better adjusted to the model Two exponential terms with an R² of 0.999. The results show that the solar drying of the celery leaves is feasible, and a quality product is obtained sustainably.
Today, the food industry processes are increasing both the costs and the consumption of energy through fossil fuels. The dehydration process to preserve food is increasingly used worldwide to safeguard both its organoleptic and nutritional properties, so it is essential to use renewable energies to replace conventional technologies. Mexico is a great producer and exporter of different mango varieties, with excellent culinary quality and nutritional properties. In the present work, direct cabinet-type solar dryers were used, and drying times between 420 and 540 min were obtained in fresh samples with 74.5% and 7.5% of initial and final humidity, respectively. Compared to its new mango content, glucose decreased in the dry samples.
Sugar is a natural high-calorie sweetener. Its excessive consumption is associated with health problems such as obesity, diabetes, heart disease, and degenerative issues. The stevia plant is a great natural substitute. It provides no calories and has medicinal properties such as oral antibacterial, hypoglycemic, and anti-hypertensive with a high nutritional value. In this work, the effects of temperature and air velocity in drying kinetics of stevia leaves were studied using a convective drier operating with air velocities (2, 3, and 4 m/s) and temperatures controlled (45 °C, 55 °C, and 65 °C). The highest drying rate was obtained at 65 °C and 4 m/s air velocity at 0.05 kg water/kg dry matter min. The experimental data were fitted to theoretical drying models to determine the best approach. It is found that the Page model gives a good fit for all experiments, with correlation coefficients ( R2) > 0.9994. The equations to correlate this model's variables with air and temperature were determined. The results show that Δ E and glucoside values increase when temperature and air velocity increase.
Oregano is a plant with many nutritional and medicinal properties; there are also other applications in the chemical industry. In this work, the drying kinetics of oregano leaves are studied using a cabinet-type dryer with and without a forced convention, open sun drying, and indirect solar drying. The samples had an initial moisture content of 80 % and the final content of 9 %. The results indicate that indirect solar drying provides better control of operating conditions and greater protection against temperature effects, producing better quality in the dry product. The time required to reach the equilibrium moisture content in all experiments ranged from 375 to 600 min. The data were also adjusted to various mathematical models, resulting In Weibull, Logarithmic, and Page, which best represent the drying behavior of oregano leaves. The statistics used for indirect solar dryer are R2 of 0.9969, 0.9968, and 0.9945, X2 of 0.0363, 0.0363 and 0.0599 respectively.
The consequences on health and low life quality caused by the problem of water scarcity, as well as the interrelation between energy and water supply, call attention to water desalination by Freezing Melting (F/M), which is a well-known technique but unfortunately, not used for this application, which is considered the most sustainable, in terms of its lower energy demand compared with commercial desalination techniques (about 70% less than thermal desalination). However, it presents some problems regarding the saline trapping in the ice, therefore, in this work, an experimental analysis is carried out to achieve a better understanding of the saline displacement, using an aqueous solution of sodium chloride, frozen at different temperatures, and configurations containers, with a F/M progressive desalination. It has been found that, at a freezing temperature of 8oC, it is possible to purify up to an average of 78.12% of the frozen salt solution, obtaining an easy-to-separate brine.
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