Química Nova
URI permanente para esta coleçãohttps://thoth.dti.ufv.br/handle/123456789/13323
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19 resultados
Resultados da Pesquisa
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 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 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.Item Evaluación de DES, FSC y SPME/CG-MS para la extracción y determinación de compuestos responsables del aroma de café tostado de Vilcabamba - Ecuador(Sociedade Brasileira de Química, 2016) Figueroa, Jorge G.; Vargas, Luis F.The aim of this study was to compare the usefulness of three extraction methods: solid-phase microextraction (SPME) with four different coating (PDMS, PDMS/DVB, DVB/CAR/PDMS and PA), supercritical fluid extraction with carbon dioxide (SCF) and simultaneous distillation and extraction (SDE) for isolation of flavor compounds from roasted ground coffee (Coffea arabica L. var. Typica) of Vilcabamba (Ecuador). Identification and characterization of volatile compounds were achieved using gas chromatography / mass spectrometry (GC-MS). Analysis of variance and principal components analysis was done. For the SPME method the coating material affect the amount and concentration of compounds extracted, the DVB/CAR/PDMS coating provided the most representative aroma extract (44 compounds were identified). The SCF method allowed extracting a higher amount of compounds and also their identification by GC-MS (72) that SDE (64) and SPME (57), in addition provide higher extractions. The acetic acid, caffeine, furfuryl alcohol, furfural, 5-methylfurfural, butylated hydroxytoluene and maltol were the compounds with higher concentrations found with SPME and SDE, with SCF were found higher concentration to compounds with high molecular weights (> 194 g mol-1). Preferably SPME-DVB/CAR/PDMS method should be used for a characterization of coffee aroma compounds.Item Saponificação assistida por micro-ondas na extração de diterpenos em café arábica torrado(Sociedade Brasileira de Química, 2017) Bianchin, Mirelli; Yamashita, Fabio; Benassi, Marta de ToledoThe extraction of kahweol and cafestol involves saponification reaction. This step is important for the efficiency of the extraction as the diterpenes are susceptible to structural changes during hydrolysis. The microwave-assisted saponification has been successfully used in different matrices, but there is no previous report of the use of this technique in the saponification of diterpenes. Therefore, the effect of microwave-assisted saponification on the extraction of kahweol and cafestol in roasted coffee was evaluated. A 32 factorial experimental design was used in order to evaluate the effect of temperature (70, 80, and 90 ºC) and reaction time (4, 8, and 12 min). The quantification of diterpenes was performed by high-performance liquid chromatography and the results were compared to with those obtained by a method, which uses thermostatic bath for saponification. Temperature and time had a significant effect (p < 0.05) on diterpenes levels. For simultaneous saponification of kahweol and cafestol, the optimal reaction conditions were 80 ºC / 12 min. The use of microwave-assisted procedure lead to lower yields of kahweol (24%) and cafestol (35%) compared to reference method. However a significant reduction of reaction time (80%) was achieved, and the procedure also has the advantage of controlled process conditions and the possibility of extended scale.Item Espectroscopia no infravermelho médio e análise sensorial aplicada à detecção de adulteração de café torrado por adição de cascas de café(Sociedade Brasileira de Química, 2012) Tavares, Katiany Mansur; Pereira, Rosemary Gualberto Fonseca Alvarenga; Nunes, Cleiton Antônio; Pinheiro, Ana Carla Marques; Rodarte, Mírian Pereira; Guerreiro, Mário CésarMid-infrared spectroscopy and chemometrics were used to identify adulteration in roasted and ground coffee by addition of coffee husks. Consumers’ sensory perception of the adulteration was evaluated by a triangular test of the coffee beverages. Samples containing above 0.5% of coffee husks from pure coffees were discriminated by principal component analysis of the infrared spectra. A partial least-squares regression estimated the husk content in samples and presented a root-mean-square error for prediction of 2.0%. The triangular test indicated that were than 10% of coffee husks are required to cause alterations in consumer perception about adulterated beverages.Item Uso de perfis cromatográficos de voláteis de cafés arábicas torrados para a diferenciação das amostras segundo o sabor, o aroma e a qualidade global da bebida(Sociedade Brasileira de Química, 2010) Ribeiro, Juliano S.; Augusto, Fabio; Ferreira, Márcia M. C.; Salva, Terezinha J. G.In this work, the volatile chromatographic profiles of roasted Arabica coffees, previously analyzed for their sensorial attributes, were explored by principal component analysis. The volatile extraction technique used was the solid phase microextraction. The correlation optimized warping algorithm was used to align the gas chromatographic profiles. Fifty four compounds were found to be related to the sensorial attributes investigated. The volatiles pyrrole, 1-methyl-pyrrole, cyclopentanone, dihydro-2-methyl-3-furanone, furfural, 2-ethyl-5-methyl-pyrazine, 2-etenyl-n-methyl-pyrazine, 5-methyl-2-propionyl-furan compounds were important for the differentiation of coffee beverage according to the flavour, cleanliness and overall quality. Two figures of merit, sensitivity and specificity (or selectivity), were used to interpret the sensory attributes studied.Item Composição volátil dos defeitos intrínsecos do café por CG/EM-headspace(Sociedade Brasileira de Química, 2009) Bandeira, Raquel D. C. C.; Toci, Aline T.; Trugo, Luiz C.; Farah, AdrianaAbout 20% of Brazilian raw coffee production is considered inappropriate for exportation. Consequently, these beans are incorporated to good quality beans in the Brazilian market. This by-product of coffee industry is called PVA due to the presence of black (P), green (V) and sour (A) defective beans which are known to contribute considerably for cup quality decrease. Data on the volatile composition of Brazilian defective coffee beans are scarce. In this study, we evaluated the volatile composition of immature, black-immature, black defective beans and PVA compared to good quality beans. Potential defective beans markers were identified.