Química Nova

URI permanente para esta coleçãohttps://thoth.dti.ufv.br/handle/123456789/13323

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Análises quali- e quantitativa de cafés comerciais via ressonância magnética nuclear
(Sociedade Brasileira de Química, 2006) Tavares, Leila Aley; Ferreira, Antonio Gilberto
Coffee is one of the beverages most widely consumed in the world and the "cafezinho" is normally prepared from a blend of roasted powder of two species, Coffea arabica and Coffea canephora. Each one exhibits differences in their taste and in the chemical composition, especially in the caffeine percentage. There are several procedures proposed in the literature for caffeine determination in different samples like soft drinks, coffee, medicines, etc but most of them need a sample workup which involves at least one step of purification. This work describes the quantitative analysis of caffeine using ¹H NMR and the identification of the major components in commercial coffee samples using 1D and 2D NMR techniques without any sample pre-treatment.
Aplicação da cromatografia por exclusão e da cromatografia gasosa de alta resolução na análise do café
(Sociedade Brasileira de Química, 1997) Moreira, R. F. A.; Trugo, L. C.; Maria, C. A. B. de
The combination of high performance exclusion chromatography (HPEC) and gas chromatography (GC) was applied to the analysis of six coffee samples that were previously characterized by sensory tests as of good or poor quality. The data obtained by the two techniques were statistically evaluated by "Principal Components Analysis" (PCA) using selected peak areas. The results showed the potential of the described techniques for coffee analysis. The HPEC technique monitored with the U.V. detector at 272 nm and followed by PCA may be correlated with sensorial data, particularly if a wider group of samples is used.
Benefícios do café na saúde: mito ou realidade?
(Sociedade Brasileira de Química, 2009) Alves, Rita C.; Casal, Susana; Oliveira, Beatriz
Coffee is widely consumed and appreciated all over the world, both for their stimulating effect and organoleptic characteristics. Due to its complex chemical composition and the factors involving brews preparation, the consumer is exposed to a wide range of chemical compounds. Several investigations aimed to clarify and understand coffee health effects. There is no evidence that moderate consumption could be harmful. On the contrary, some benefits and possible protective effects against several pathologies have been suggested. This review compiles the main conclusions related with the "coffee and health" topic, reporting, when possible, the chemicals involved.
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 Oliveira
Chemometrics 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.
Componentes voláteis do café torrado. Parte II. Compostos alifáticos, alicíclicos e aromáticos
(Sociedade Brasileira de Química, 2000) Moreira, Ricardo Felipe Alves; Trugo, Luiz Carlos; Maria, Carlos Alberto Bastos De
This review is about the aliphatic, alicyclic and aromatic compounds (non-heterocyclic compounds) that are present in the volatile fractions of roasted coffees. Herein, the contents, aroma precursors and the sensorial properties of volatile phenols, aldehydes, ketones, alcohols, ethers, hydrocarbons, carboxylic acids, anhydrides, esters, lactones, amines and sulphur compounds are discussed. Special attention is given to the compounds of these groups that are actually important to the final aroma of roasted coffees.
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, Adriana
About 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.
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 Araújo
This 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.
Compostos bioativos e atividade antioxidante do café conilon submetido a diferentes graus de torra
(Sociedade Brasileira de Química, 2009) Morais, Sérgio Antônio Lemos de; Aquino, Francisco José Tôrres de; Nascimento, Priscilla Mendes do; Nascimento, Evandro Afonso do; Chang, Roberto
The bioactive compounds and antioxidant activity presented by Conilon coffee (C. Canephora) variety, produced in the Espírito Santo State, Brazil, were quantified. The light roast coffee showed the highest level of total phenols, trigonelline, caffeic and chlorogenic acids. The proanthocyanidin level was the highest for dark roast coffee, while caffeine level didn't show significative changes for the light and middle roast coffees. All the Conilon coffee extracts showed antioxidant activity depending on bioactive compounds concentration and roasting degree. The coffee samples submitted to a light roasting degree showed the highest antioxidant activity.
Correlação entre precursores e voláteis em café arábica brasileiro processado pelas vias seca, semiúmida e úmida e discriminação através da análise por componentes principais
(Sociedade Brasileira de Química, 2012) Arruda, Neusa P.; Hovell, Ana M. C.; Rezende, Claudia M.; Freitas, Suely P.; Couri, Sonia; Bizzo, Humberto R.
The influence of pre processing of arabica coffee beans on the composition of volatile precursors including sugars, chlorogenic acids, phenolics, proteins, aminoacids, trigonelline and fatty acids was assessed and correlated with volatiles formed during roasting. Reducing sugars and free aminoacids were highest for natural coffees whereas total sugars, chlorogenic acids and trigonelline were highest for washed coffees. The highest correlation was observed for total phenolics and volatile phenolics (R= 0.999). Experimental data were evaluated by Principal Components Analysis and results showed that washed coffees formed a distinct group in relation to semi-washed and natural coffees.
Determinação de açúcar total em café cru por espectroscopia no infravermelho próximo e regressão por mínimos quadrados parciais
(Sociedade Brasileira de Química, 2007) Morgano, Marcelo A.; Faria, Cristiano Gomes de; Ferrão, Marco F.; Ferreira, Márcia M.C.
In this work a fast method for the determination of the total sugar levels in samples of raw coffee was developed using the near infrared spectroscopy technique and multivariate regression. The sugar levels were initially obtained using gravimety as the reference method. Later on, the regression models were built from the near infrared spectra of the coffee samples. The original spectra were pre-treated according to the Kubelka-Munk transformation and multiplicative signal correction. The proposed analytical method made possible the direct determination of the total sugar levels in the samples with an error lower by 8% with respect to the conventional methodology.
Determinação de compostos bioativos em amostras comerciais de café torrado
(Sociedade Brasileira de Química, 2005) Monteiro, Mariana Costa; Trugo, Luiz Carlos
Coffee is a product consumed all around the world, Brazil being the biggest exporter. However, little is known about the difference in composition of the different brands in terms of bioactive substances. In the present study, ten of the most consumed brands of coffee in Rio de Janeiro were analyzed. Caffeine contents, trigonelline and total chlorogenic acid varied from 0.8 g/100g to 1.4 g/100g; 0.2 g/100g to 0.5 g/100g and from 3.5 g kg-1 to 15.9 g kg-1, respectively. The large heterogeneity observed in the amounts of the bioactive compounds can be attributed to different formulations of the various brands, as well as to different roasting conditions.
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.
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 la
A 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.
Discriminação entre estádios de maturação e tipos de processamento de pós-colheita de cafés arábica por microextração em fase sólida e análise de componentes principais
(Sociedade Brasileira de Química, 2011) Arruda, Neusa P.; Hovell, Ana M. C.; Rezende, Claudia M.; Freitas, Suely P.; Couri, Sonia; Bizzo, Humberto R.
A fruit chemical composition reflects its maturation stage. For coffee, it is also the reflex of the post harvesting processing type, dry, semi-wet and wet. The object of this work was to verify if headspace solid phase microextraction coupled to gas chromatography (HS-SPME-GC) could be used to discriminate between samples harvested in different maturation stages and treated by different processes. With application of principal component analysis to the area of 117 compounds extracted by SPME, using divinylbenzene/Carboxen/polydimethylsiloxane fiber, it was possible to discriminate, in the roasted and ground coffee, the maturity stage and processing type used.
Efeito do processo de descafeinação com diclorometano sobre a composição química dos cafés arábica e robusta antes e após a torração
(Sociedade Brasileira de Química, 2006) Toci, Aline; Farah, Adriana; Trugo, Luiz Carlos
The decaffeinated coffee market has been expanding increasingly in the last years. During decaffeination, aroma precursors and bioactive compounds may be extracted. In the present study we evaluate the changes in the chemical composition of C. arabica and C. canephora produced by decaffeination using dichloromethane. A significant change in the chemical composition of both C. arabica and C. canephora species was observed, with differences between species and degrees of roasting. Major changes were observed in sucrose, protein and trigonelline contents after decaffeination. Changes in the levels of total chlorogenic acids and in their isomers distribution were also observed. Lipids and total carbohydrates were not affected as much. The sensory and biological implications of these changes need to be investigated.
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 Spacino
In 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.
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 César
Mid-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.
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.
Experimento com abacate, borra de café, licuri e leite de coco para extração de óleo, produção de biodiesel e análise espectral
(Sociedade Brasileira de Química, 2018) Cunha, Silvio; Rodrigues, Marina Costa; Mattos, Rosiene Reis; Teixeira, Leonardo Sena Gomes; Santos, Airam Oliveira; Santos, Elaine V.; Souza, Rauan S.; Andrade, Givaldo dos Santos; Paula, Rodrigo De; Jesus, Djane S. de
An undergraduate organic chemistry experiment for oil extraction and biodiesel production using alternative biomass was developed, whereby oils of avocado, coconut and spent coffee grounds were obtained and submitted to transesterification reaction with CH3OH under NaOH catalysis. Avocado and coffee oils were obtained by typical extraction and coconut oil was obtained through water evaporation of coconut milk in a domestic microwave oven. The commercial oil of licuri (Syagrus coronate), a Brazilian native biomass, was also converted to biodiesel. All four oils and four biodiesels were characterized by 1H-NMR and FTIR, and a comparative study of these spectra reveled that FTIR analyses alone provides enough information to discriminate between oil and biodiesel and confirm transesterification reaction. Besides, the unsaturation degree of all oils was determined by 1H-NMR. A mechanistic proposal concerning the role of NaOH catalysis is presented, excluding the sodium methoxide formation.
Indicadores químicos de qualidade da matéria orgânica de solo da sub-bacia do Rio das Mortes sob manejos diferenciais de cafeeiro
(Sociedade Brasileira de Química, 2008) Oliveira Júnior, Antônio Claret; Silva, Carlos Alberto; Curi, Nilton; Guilherme, Luiz Roberto Guimarães; Rangel, Otacílio José Passos
This work evaluated the chemical quality of organic matter (OM) of a Brazilian Oxisol cultivated with coffee plants, under organic and conventional managements. Total organic C (TOC), light fraction C (LF-C) and C in humic (HA-C) and fulvic (FA-C) acids fractions was measured. Amongst the evaluated indexes, TOC and LF-C discriminated better OM attributes as a function of management. The stratification ratio (TOC5-10cm/TOC10-20cm) did not show differences between the systems studied. The organic system can contribute to the sustainability of coffee plantations in Brazil, because it maintains the chemical attributes of OM closer to the indexes verified under forest conditions.