https://repositorio.ufu.br/handle/123456789/5136 2026-08-02T07:08:20Z https://repositorio.ufu.br/handle/123456789/49124 Title: Estudo químico de lúpulos cultivados em diferentes localidades por RMN e CLAE - EM/EM e desenvolvimento de um método eletroanalítico para quantificação de iso-α-ácidos em cervejas Abstract: Hops (Humulus lupulus) are a key raw material in beer production, responsible for important sensory characteristics such as aroma and, notably, bitterness. During wort boiling, the α-acids present in hops undergo thermal isomerization to form iso-α-acids compounds directly linked to the beverage's bitterness intensity. In this study, commercial hop varieties were characterized using Nuclear Magnetic Resonance (NMR) and High-Performance Liquid Chromatography coupled with Mass Spectrometry. NMR analysis provided structural information via fingerprints, enabling the identification of major metabolites in the hop extracts, while HPLC-ESI-MS/MS analysis allowed for the annotation of the primary metabolites present in the samples. Specifically, for the Sabro hop variety, the α-acid mixture was separated yielding 31% of the hop extract and subsequently isomerized, resulting in a 42.5% yield of the iso-α-acid mixture. Structural confirmation was achieved through ¹³C NMR spectroscopy; α-acids exhibited a characteristic signal at δ 79.2 ppm, whereas the cis and trans isomers of the iso-α-acids showed signals in the δ 205.1–207.3 ppm range. Subsequently, an electrochemical study using a graphite sheet as the working electrode was conducted to investigate the behavior of iso-α-acids and their relationship to beer bitterness. The voltammetrics profiles obtained for α-acids and iso-α-acids displayed distinct potential regions; consequently, the analysis focused on iso-α-acids, as they are the primary contributors to the beverage's bitterness. Direct analysis of commercial beers revealed the presence of interfering compounds, such as sodium metabisulfite, necessitating sample pre-treatment via isooctane extraction. The efficiency of this procedure was monitored using HPLC-ESI-MS/MS, confirming the presence of iso-α-acids following the extraction step. Finally, bitterness values expressed in IBU were determined using Square Wave Voltammetry; the measured values (BS1 = 48.1; BS2 = 41.6; BS3 = 17.6) were close to those declared by the manufacturers (BS1 = 46; BS2 = 40; BS3 = 18). The results demonstrated that the developed electroanalytical method offers a higher-performance alternative for determining iso-α-acids and for future applications in beer quality control. 2026-07-17T00:00:00Z https://repositorio.ufu.br/handle/123456789/48995 Title: Influência das variáveis climáticas sobre a composição química e a atividade antimicrobiana dos óleos essenciais das folhas de Piper macedoi e Piper fuligineum Abstract: The genus Piper is distinguished by its wide diversity of secondary metabolites and the biological potential of its essential oils, whose chemical composition can be influenced by environmental factors, making seasonal studies important for understanding the dynamics of plant secondary metabolism. In this context, the present study aimed to evaluate the influence of seasonality on the chemical composition of the essential oils from the leaves of Piper macedoi and Piper fuligineum, as well as to investigate their antimicrobial activity against yeasts of the genus Candida and the bacterium Helicobacter pylori. Leaves were collected during six distinct periods between September 2024 and July 2025, encompassing different climatic conditions. Essential oils were obtained by hydrodistillation and characterized by gas chromatography coupled to mass spectrometry (GC-MS), gas chromatography with flame ionization detection (GC-FID), and nuclear magnetic resonance (NMR). A total of 36 constituents were annotated in P. macedoi and 40 in P. fuligineum, with a predominance of hydrocarbon and oxygenated sesquiterpenes. Germacreno D was the major constituent in both species, while the chromene 2,2-dimetil-2H-cromeno-6-carboxilato de metila stood out as one of the major metabolites in P. macedoi, with its structure being confirmed by NMR. The results demonstrated that P. macedoi exhibited a relatively stable chemical profile throughout the collection periods, whereas P. fuligineum showed greater chemical plasticity and stronger influence of climatic variables on its composition. Correlation analyses indicated associations between precipitation, atmospheric pressure, and temperature with the relative abundance of specific constituents and chemical classes. Regarding biological activity, the essential oils did not show activity against H. pylori at the concentrations evaluated. In contrast, selective antifungal activity was observed against Candida glabrata, particularly for certain collections of P. fuligineum, whose minimum inhibitory concentration values reached 23.48 μg mL⁻¹. Overall, the results expand the chemical and biological knowledge of both species and highlight the influence of seasonality on the modulation of secondary metabolism and the biological properties of their essential oils. 2026-07-17T00:00:00Z https://repositorio.ufu.br/handle/123456789/48986 Title: Avaliação do desempenho de um sistema automático de análise construído empregando as facilidades da impressão 3D Abstract: Developing regions often face challenges in accessing advanced analytical technologies due to financial and infrastructural limitations. However, recent advances in the accessibility and adaptability of 3D printing technologies have significantly contributed to overcoming these barriers. In this context, this work presents an evaluation of the performance of an automated liquid handling system named NuPE-Robot, characterized by its versatility, compactness, robustness, and ease of operation. The system was built using low-cost components, including standardized parts widely used in 3D printers and custom components produced by additive manufacturing. Its operation is controlled by open-source software developed in Python, enabling the automated execution of analytical protocols without the need for operator intervention. Once activated, the system is capable of automatically performing standard solution preparation, constructing calibration curves, and analyzing samples using 3D-printed detection platforms. Batch Injection Analysis (BIA) cells coupled with different detection strategies were employed, including multispectral sensor-based spectrophotometry, amperometry, and potentiometry. In addition, alternative colorimetric detection approaches using microvolumes of solution directly in hanging drops and micropipette tips were investigated, aiming to reduce reagent consumption and increase operational flexibility. To demonstrate the broad applicability of the developed platform, automatic calibration and determination procedures were implemented for six analytes: Fe(III), phosphate, nitrite, and glucose by colorimetric detection; paracetamol by amperometric detection; and chloride by potentiometric detection. In all cases, calibration curves with adequate linearity, precision, and accuracy were obtained, demonstrating the system’s ability to perform different analytical methodologies using a single integrated platform. The necessary adaptations were limited to the detection modules and experimental configurations specific to each method, highlighting the high modularity of the proposed instrumentation. The results obtained demonstrate that the NuPE-Robot is a viable alternative for automating chemical analyses in resource-limited laboratories, combining low cost, ease of reproducibility, and broad analytical versatility. Thus, the platform shows strong potential to democratize access to laboratory automation, contributing to the dissemination of modern analytical technologies in teaching, research, and quality control institutions, especially in developing regions. 2026-07-21T00:00:00Z https://repositorio.ufu.br/handle/123456789/48886 Title: Análise de metabólitos em kombuchas caseiras e comerciais por meio de RMN de 1H Abstract: Kombucha is an ancient, fermented beverage obtained through the action of a symbiotic culture of bacteria and yeast (SCOBY) on sweetened tea. In recent decades, kombucha consumption has grown worldwide, especially in Brazil, due to its potential functional properties associated with bioactive compounds such as polyphenols, organic acids, vitamins, and enzymes. This growing popularity has stimulated artisanal production, resulting in a wide diversity of flavors and preparation methods. This study aimed to investigate how changes in the plant matrix and the type of sugar used in homemade preparations influence the beverage's characteristics, searching for a combination that optimizes its chemical profile. Furthermore, the study measured the total phenolic content in the selected sample and compared the characteristics of homemade kombucha with those of commercial samples. Nuclear Magnetic Resonance (NMR) analyses allowed for the identification of fermentation compounds, such as organic acids, residual sugars, ethanol, and other metabolites, revealing variations in the chemical profile among different samples. Regarding the choice of tea, it was found that the plant matrix alone is not the sole determinant of compound formation. Instead, the metabolite profile showed a strong dependence on the type of sugar used and, notably, on the residual sugar remaining after the process. However, regardless of the combination of these factors, an increase in total phenolic content was evidenced, suggesting an enhancement of the final beverage's antioxidant capacity. In summary, this study demonstrates that kombucha is a complex beverage, sensitive to multiple production factors, such as the SCOBY, tea type, sugar, and seasonality, indicating an increase in antioxidant capacity and potential improvement in probiotic properties. 2025-09-26T00:00:00Z