Química Nova
URI permanente para esta coleçãohttps://thoth.dti.ufv.br/handle/123456789/13323
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Resultados da Pesquisa
Item Café com quimioterapia: uma aplicação do planejamento fatorial fracionário 2|5-1(Sociedade Brasileira de Química, 2023-03-03) Silva, Kaique Carvalho da; Caldeira, Gabriel Rocha Figueira; Nogueira, Kenya Gomes; Canela, Maria Cristina; Filgueiras, Paulo Roberto; Souza, Murilo de OliveiraChemometrics is a subfield of chemistry that emerged from advances in analytical instrumentation and computing. When seeking to solve chemical problems that depend on many concomitants experimental variables, chemometrics can be employed in order to extract as much information as possible in the least possible number of experiments. In addition, it is possible to evaluate the important effects and interactions among the variables to understand the processes being monitored in each system. In this sense, this article aimed to develop a didactic experiment of caffeine extraction using an espresso machine, applying the 25-1 fractional factorial design. The variables studied were temperature (75 and 78 °C), pressure (2 and 15 bar), granulation (bean and ground), type of coffee (special and traditional) and period of the day (morning and afternoon) to obtain maximum extraction of caffeine. The coffee extracts obtained were analyzed using UV-Vis molecular absorption spectrophotometry. The developed experiment showed the potential to spread the application of chemometrics in the academic environment and to facilitate the teaching of fractional factorial design.Item Infravermelho portátil na região do próximo (NIR) aplicado no controle de qualidade de cafés adulterado por borra(Sociedade Brasileira de Química, 2021-12-02) Correia, Radigya M.; Cunha, Pedro H.; Agnoletti, Bárbara Z.; Pereira, Lucas L.; Partelli, Fábio L.; Filgueiras, Paulo R.; Lacerda Jr, Valdemar; Romão, WandersonThe objective of this work was to control the purity level of canephora coffees (Conilon coffee) from the state of Espírito Santo (Brazil), as a function of the addition of grounds produced by the coffees themselves using a portable microspectrometer in the infrared region. (microNIR), associated with chemometric tools. The PCA model grouped the coffees according to the level of adulterant in the samples and showed that the presence of moisture and polysaccharides is important for the discrimination between pure and adulterated samples. PLS-DA and SIMCA classification models were built with commercial samples and resulted in the discrimination of authentic and non-authentic samples with accuracy values above 90% and 82% for PLS-DA and SIMCA, respectively. The quantification results presented by the PLS model were satisfactory for all models, reaching the best results at 75 °C with RMSEP values of 6.13 wt%, R2p = 0.9917; and LOD in the range of 5.6-8.9 wt%; LOQ = 17-26.8 wt%, according to IUPAC; relative standard deviation for repeatability of 1.0 and 1.7 wt%; and intermediate precision of 3.4 and 1.1 wt% for low (<10 wt%) and high (≈ 90 wt%) levels of adulterants, respectively. Therefore, this work represents the first exploratory study to analyze adulterations with coffee grounds by portable NIR, demonstrating the potential of the equipment against this type of adulteration.Item Sorção e lixiviação de tiametoxam em solos tratados com lodo de esgoto e cultivados com cafeeiro(Sociedade Brasileira de Química, 2012) Magalhães, Ciro Augusto de Souza; Lima, José Maria de; Costa, Alisson Lucrécio da; Silva, Evânia Geralda da; Silva, Carlos Alberto; Bettiol, Wagner; Nóbrega, Julio Cesar Azevedo; Guimarães, Paulo Tácito GontijoThe objective of this study was to evaluate the sorption and leaching of thiamethoxam in dystrophic Red Yellow Latosol (LVAd), dystroferric Red Latosol (LVdf) and Red-Yellow Argisol (PVAd) with coffee under the effect of sewage sludge doses. There was thiamethoxam sorption decreasing at higher doses of sewage sludge in LVAd and LVdf. In the PVAd, sorption was higher in samples that received the highest dose of sewage sludge. At 150 days after the application of thiamethoxam, the compound began to be detected in the effluent, in all soils. Dissolved organic carbon had no influence on the thiamethoxam leaching.Item Teores de trigonelina, ácido 5-cafeoilquínico, cafeína e melanoidinas em cafés solúveis comerciais brasileiros(Sociedade Brasileira de Química, 2013) Marcucci, Carolina Tolentino; Benassi, Marta de Toledo; Almeida, Mariana Bortholazzi; Nixdorf, Suzana LucyCommercial Brazilian regular and decaffeinated instant coffees (33 brands) were studied. The levels ranged from 0.47 to 2.15 g 100 g-1 for trigonelline, 0.38 to 2.66 g 100 g-1 for 5-caffeoylquinic acid (5-CQA), 0.24 to 4.08 g 100 g-1 for caffeine, and 0.253 to 0.476 (420 nm) for melanoidins. Variations in bioactive compound levels among batches were observed. There was no relationship between the drying process and the composition of the products. In general, Gourmet and decaffeinated coffees had higher trigonelline and 5-CQA but lower caffeine and melanoidin content than regular products.Item Efeito do solvente na extração de ácidos clorogênicos, cafeína e trigonelina em Coffea arabica(Sociedade Brasileira de Química, 2014) Moreira, Ivanira; Scheel, Guilherme Luiz; Hatumura, Pedro Henrique; Scarminio, Ieda SpacinoIn this research work the effects of four solvents and their mixtures on the extraction of chlorogenic acids, caffeine and trigonelline in crude extracts of four coffee cultivars, traditional red bourbon, IAPAR59, IPR101 and IPR108 cultivars, were investigated by UV spectrophotometry and UV spectra obtained from RP-HPLC-DAD. The experimental results and the principal component analysis of UV spectra showed that the effect of solvent extraction of the metabolites does not depend on cultivars, because the spectral characteristics are similar, but the concentrations are different. The UV and UV-DAD spectra for four simplex centroid design mixtures were also similar but the concentrations of caffeine, trigonelline and the chlorogenic acids are different and depend on the solvent used in the extraction.Item Compostos bioativos do café: atividade antioxidante in vitro do café verde e torrado antes e após a descafeinação(Sociedade Brasileira de Química, 2010) Lima, Adriene Ribeiro; Pereira, Rosemary Gualberto Fonseca Alvarenga; Abrahão, Sheila Andrade; Duarte, Stella Maris da Silveira; Paula, Fernanda Borges de AraújoThis study aimed to evaluate the effect of coffee decaffeination with dichloromethane on the in vitro antioxidant activity of this matrix. It were determined the content of total phenolics, chlorogenic acid and caffeine of the coffee samples. The assessment of the antioxidant potential was investigated by DPPH radical scavenging method, reducer power and Fe2+ chelation activity. The process of decaffeination and roasting caused changes in the levels of the compounds investigated. The results show that the decaffeination by the dichloromethane method reduces the in vitro antioxidant potential of coffee.Item Método para determinação de carboidratos empregado na triagem de adulterações em café(Sociedade Brasileira de Química, 2011) Pauli, Elis Daiane; Cristiano, Valderi; Nixdorf, Suzana LucyThe objective in this work was to validate a chromatography method for the determination of total carbohydrates in soluble coffee, using a HPLC-UV-VIS with postcolumn derivatization system, in order to verify adulterant additions. The validated method was accurate and robust. Adulteration could be observed by increasing xylose and glucose levels in samples with addition of coffee husks and starchy products while decreasing of galactose and mannose characteristic carbohydrates presenting in high concentration in soluble coffees produced by arabica and robusta coffee beans.Item Determinação simultânea de precursores de serotonina - triptofano e 5-hidroxitriptofano - em café(Sociedade Brasileira de Química, 2010) Martins, Ana Carolina C. L.; Silva, Tarliane M.; Gloria, M. Beatriz A.Epidemiological studies attributed positive effects in the central nervous system (CNS) to coffee. Among possible active constituents, serotonin, a neurotransmitter in the CNS, is present; but dietary sources do not cross the blood-brain barrier. Tryptophan and 5-hidroxytryptophan (5-HTP) are serotonin precursors and can affect brain concentrations. An ion-pair-HPLC, post-column derivatization with o-phthalaldehyde and fluorimetric detection before and after hydrolysis with NaOH and extraction with methanol: water was developed for the simultaneous determination of these compounds. It was selective, sensitive (LOD = 0.3 and 0.2 mg/mL), precise (91.3 and 94.2% recovery for tryptophan and 5-HTP, respectively), and linear from 0.3 to 40 mg/mL for both compounds. It was applied to green and roasted arabica and robusta coffees.Item Teores de compostos bioativos em cafés torrados e moídos comerciais(Sociedade Brasileira de Química, 2010) Souza, Romilaine Mansano Nicolau de; Canuto, Gisele André Baptista; Dias, Rafael Carlos Eloy; Benassi, Marta de ToledoThe amounts of nicotinic acid, trigonelline, 5-CQA, caffeine, kahweol and cafestol in 38 commercial roasted coffees ranged from 0.02 to 0.04; 0.22 to 0.96; 0.14 to 1.20; 1.00 to 2.02; 0.10 to 0.80 and 0.25 to 0.55 g/100 g, respectively. Evaluation of color and content of thermo-labile compounds indicated similarity in roasting degree. Differences in the levels of diterpenes and caffeine, components less influenced by the roasting degree, could be mainly explained by the species used (arabica and robusta). Gourmet coffees showed high concentrations of diterpenes, trigonelline and 5-CQA and low levels of caffeine, indicating high proportion of arabica coffee.Item Development and validation of a method for the analysis of ochratoxin a in roasted coffee by liquid chromatography/electrospray-mass spectrometry in tandem (LC/ESI-MS/MS)(Sociedade Brasileira de Química, 2012) Bandeira, Raquel D. C. C.; Uekane, Thais M.; Cunha, Carolina P. da; Geaquinto, Luths R. O.; Cunha, Valnei S.; Caixeiro, Janaina M. R.; Godoy, Ronoel Luiz O.; Cruz, Marcus Henrique C. de laA method using LC/ESI-MS/MS for the quantitative analysis of Ochratoxin A in roasted coffee was described. Linearity was demonstrated (r = 0.9175). The limits of detection and quantification were 1.0 and 3.0 ng g-1, respectively. Trueness, repeatability and intermediate precision values were 89.0-108.8%; 2.4-13.7%; 12.5-17.8%, respectively. To the best of our knowledge, this is the first report in which Ochratoxin A in roasted coffee is analysed by LC/ESI-MS/MS, contributing to the field of mycotoxin analysis, and it will be used for future production of Certified Reference Material.