https://repositorio.ufu.br/handle/123456789/5147 2026-08-06T22:03:34Z 2026-08-06T22:03:34Z https://repositorio.ufu.br/handle/123456789/49257 2026-08-04T06:21:32Z 2026-06-30T00:00:00Z

Title: Obtenção e caracterização do pó do aquoso da folha de Ora-pro-nóbis (Pereskia aculeata) seco por spray drying Abstract: Ora-pro-nóbis (*Pereskia aculeata*) is an Unconventional Food Plant (UFP) belonging to the Cactaceae family, recognized for its high protein content as well as its fiber, vitamins, and bioactive compounds. Traditionally used in cooking, its leaves can be consumed raw or sautéed. The presence of mucilage, proteins, and bioactive compounds attracts interest from both the food and pharmaceutical industries: the former for the enrichment of functional products, and the latter due to studies on antioxidant activity and nutraceutical potential. Because it is highly perishable, its consumption is largely restricted to family farming, which hinders large-scale commercialization. Drying aids in the preservation of perishable foods and facilitates the storage, transport, and application of the resulting powders in food products. Therefore, this study aimed to obtain and characterize a powder derived from the aqueous extract of ora-pro-nóbis leaves produced via spray drying. To this end, the study evaluated the effect of heat treatment prior to drying, as well as drying with and without the use of maltodextrin as a carrier agent, and the effect of temperature (100°C and 140°C) on the physicochemical properties (moisture, water activity, hygroscopicity, antioxidant activity, total chlorophylls, protein content, morphology, and particle size) of the resulting powder. The results showed that the powder obtained with heat treatment and the use of maltodextrin generally exhibited lower moisture content compared to the powder obtained without heat treatment or the carrier agent. Powder hygroscopicity ranged from 13.81% to 26.60%, influenced primarily by the addition of maltodextrin. Regarding color, the powders with higher lightness (L*)—that is, the lighter-colored ones—were those obtained using maltodextrin, likely due to the white color of the carrier agent. The powders exhibited a tendency toward green (a* parameter) and yellow (b* parameter) coloration. Antioxidant capacity was also evaluated, with the highest values observed in experiment 4, which involved heat treatment at 140°C without the use of maltodextrin. Partial degradation of the chlorophyll present in the leaves occurred due to the heat treatment, influencing the chlorophyll content results for the resulting powders. The treatments performed had no impact on protein analysis results. SEM images show that the particles generally exhibit irregular morphology, rough surfaces, and a tendency to agglomerate. The largest particle sizes were found in experiments 3 (100°C, with heat treatment, without maltodextrin) and 4 (140°C, with heat treatment, without maltodextrin).

2026-06-30T00:00:00Z https://repositorio.ufu.br/handle/123456789/49204 2026-07-31T06:23:43Z 2026-03-12T00:00:00Z

Title: Sedimentação de suspensões aquosas de carbonato de cálcio em condições não isotérmicas: uma investigação experimental por atenuação de raios Gama Abstract: This study investigated the sedimentation behavior of solid particles under lateral heating conditions, with emphasis on the coupling between particulate mass transport and heat transfer mechanisms. The experimental system consisted of an aqueous calcium carbonate suspension, and dyed silica oxide was employed as a tracer previously validated in terms of density and particle size distribution compatibility. Physical characterization was performed through pycnometry and laser diffraction analysis. The final structure of the sedimented bed was determined using the gamma-ray attenuation technique, enabling the determination of vertical profiles of local solid volume fraction. Thermal measurements revealed the development of a significant lateral temperature gradient near the oil reservoirs, establishing a non-isothermal condition along the width of the experimental cell. The solid volume fraction profiles indicated a consolidated bed with values ranging from approximately 0.52 to 0.55 in the lower region, accompanied by a systematic lateral displacement of the solid–liquid interface near the walls. The hypothesis of differential compaction was ruled out, as no significant variations in packing degree were observed across the cell width. Visual analysis using the tracer revealed inclined sedimented structures near the walls, consistent with transverse particle redistribution induced by natural convection arising from the imposed thermal gradient. The results demonstrate that sedimentation under lateral heating exhibits multi-dimensional behavior governed by the coupling between mass transport and heat transfer, and therefore cannot be adequately described by a simplified one-dimensional isothermal model.

2026-03-12T00:00:00Z https://repositorio.ufu.br/handle/123456789/49147 2026-07-30T06:26:15Z 2025-07-29T00:00:00Z

Title: Investigação numérica e experimental de sistemas de concentração solar com lentes de Fresnel para desinfecção de água Abstract: Universal access to water is one of the United Nation’s 17 sustainable development goals and a fundamental human right. However, factors such as extreme poverty, geographical isolation, and climate change pose challenges to ensuring access to safe water for populations located mainly in rural communities in underdeveloped and developing countries. Among the existing technologies for water treatment in remote regions, solar water disinfection (SODIS) stands out, which can be intensified by solar concentrators that increase the intensity of sunlight, shortening the time required for exposure and increasing the rate of microorganism inactivation. This study evaluated the potential of alternative solar concentrators, such as point and linear Fresnel lenses, in photoactivated processes such as SODIS using computational fluid dynamics to solve the equations of momentum, radiation, and species transport. To this end, two experimental units and their respective computational models were developed and validated experimentally through actinometry with potassium ferrioxalate, and a simulation design was conducted to evaluate the effect of operational variables on the main responses that characterize the performance of these concentrators. A mechanistic model of E. coli disinfection based on the generation of reactive oxygen species (ROS) and inactivation of cell protection enzymes available in the literature was implemented in the computational models to enable the numerical evaluation of the performance of these Fresnel lens concentrator systems. The results obtained indicate that the computational models developed reproduced the radiation and velocity fields properly, and a high potential for radiation intensification in the reactors was observed using the lenses. In the linear Fresnel concentrator system, it was found that the recirculation flow rate has a small effect on the reaction rate within the range of 0.4 L·min-1 to 3.95 L·min-1, and the conversion depends mainly on the position of the reactor and solar irradiation. Disinfection kinetics results showed that for the point lens it is important to ensure adequate radiation distribution, while in the unit with a linear lens it is necessary to seek a balance between increasing the fluid’s residence time in the reactor and the fluid dynamics inside the tubular reactor. Both solar concentrator systems were able to substantially reduce the treatment time of conventional SODIS to just a few minutes of operation, based on the dimensions of the development of the experimental rigs.

2025-07-29T00:00:00Z https://repositorio.ufu.br/handle/123456789/49146 2026-07-30T06:26:11Z 2026-06-15T00:00:00Z

Title: Memorial descritivo

2026-06-15T00:00:00Z