Química Nova

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

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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.
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.
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.
Metodologia para análise simultânea de ácido nicotínico, trigonelina, ácido clorogênico e cafeína em café torrado por cromatografia líquida de alta eficiência
(Sociedade Brasileira de Química, 2006) Alves, Sandriel Trindade; Dias, Rafael Carlos Eloy; Benassi, Marta de Toledo; Scholz, Maria Brígida dos Santos
A reverse phase liquid chromatography method was developed for simultaneous determination of trigonelline, caffeine, nicotinic and chlorogenic (5-CQA) acids in roasted coffee. A gradient of acetic acid/acetonitrile was used as mobile phase and detection was carried out in the UV. The samples were extracted with acetonitrile/water (5:95 v/v) at 80 ºC/10 min. Good recovery (89 to 104%), repeatability and linearity were obtained. Detection limits of 0.01, 0.15, 0.04 and 0.04 mg mL-1 were observed for nicotinic acid, trigonelline, 5-CQA and caffeine. The method, applied to arabica and robusta coffees with different degrees of roasting, was efficient and fast (~35 min) and also allowed identification of cinnamic acids.
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.
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.
Utilização do índice de retenção linear para caracterização de compostos voláteis em café solúvel utilizando GC-MS e coluna HP-Innowax
(Sociedade Brasileira de Química, 2007) Viegas, Marcelo Caldeira; Bassoli, Denisley Gentil
Gas chromatography coupled with mass spectrometry (GC-MS) is widely used for the characterization of volatile compounds. However, due to the complexity of the soluble coffee matrix, a complete identification of the components should not be based on mass spectra interpretation only. The linear index of retention (LRI) is frequently used to give support to mass spectra. The aim of this work is to investigate the characterization of the volatile compounds in soluble coffee samples by GC-MS using LRI values found with a HP-INNOWAX column. The method used allows a significant increase of the reliability of identifying compounds.
Influência do processamento e da torrefação sobre a atividade antioxidante do café (Coffea arabica)
(Sociedade Brasileira de Química, 2007) Santos, Marcelo Henrique dos; Batista, Bruno Lemos; Duarte, Stella Maris da Silveira; Abreu, Celeste Maria Patto de; Gouvêa, Cibele Marli Cação Paiva
The aim of this work is to evaluate the influence of processing (semi-dry and dry) and roasting (light, medium and dark) on the antioxidant activity of coffee brews, using tests to determine the reducing power and the DPPH scavenging, Fe+2 chelating and lipid peroxidation inhibition activities. All of the coffee brews presented concentration-dependent antioxidant activity. The light coffee samples presented the higher reducing power and DPPH scavenging activity. Its ion chelating capacity was similar to the medium samples, but was less than the green coffee chelating capacity. The semi-dry processing was more efficient than the dry processing only for the reducing power. All of the samples presented high lipid peroxidation inhibition activity. Based on the results the degree of coffee roasting seems to be more important than the processing to determine the antioxidant activity of brews.
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.
Materiais à base de óxido de ferro para oxidação de compostos presentes no efluente da despolpa do café
(Sociedade Brasileira de Química, 2008) Gonçalves, Maraísa; Guerreiro, Mário César; Oliveira, Luiz Carlos Alves; Rocha, Cristian Luciana da
Materials based on pure iron oxide and impregnated with niobia (Nb2O5) were prepared. Their catalytic activities were tested on the oxidation of compounds present in the wastewater from the processing of coffee berries. Particularly caffeine and catechol were tested. The oxidation reactions were carried out with the following systems (i) UV/H2O2, (ii) photo-Fenton and (iii) heterogeneous Fenton. All materials were characterized with X-ray diffraction, Mössbauer and infrared spectroscopy. Iron was mainly in the forms of goethite and maghemite. The oxidation kinetics were monitored by UV-vis and the oxidation products were monitored by mass spectrometry. The photo-Fenton reaction presented highest oxidation efficiency, removing 98% of all caffeine and catechol contents.
Supercritical CO2 recovery of caffeine from green coffee oil: new experimental solubility data and modeling
(Sociedade Brasileira de Química, 2008) Azevedo, Álvaro Bandeira Antunes de; Kieckbusch, Theo Guenter; Tashima, Alexandre Keiji; Mohamed, Rahoma Sadeg; Mazzafera, Paulo; Melo, Silvio Alexandre Beisl Vieira de
The caffeine solubility in supercritical CO2 was studied by assessing the effects of pressure and temperature on the extraction of green coffee oil (GCO). The Peng-Robinson¹ equation of state was used to correlate the solubility of caffeine with a thermodynamic model and two mixing rules were evaluated: the classical mixing rule of van der Waals with two adjustable parameters (PR-VDW) and a density dependent one, proposed by Mohamed and Holder² with two (PR-MH, two parameters adjusted to the attractive term) and three (PR-MH3 two parameters adjusted to the attractive and one to the repulsive term) adjustable parameters. The best results were obtained with the mixing rule of Mohamed and Holder² with three parameters.
Preparação de carvão ativado em baixas temperaturas de carbonização a partir de rejeitos de café: utilização de FeCl3 como agente ativante
(Sociedade Brasileira de Química, 2008) Pereira, Elaine; Oliveira, Luiz C. A.; Vallone, Andréa; Sapag, Karim; Pereira, Márcio
Ferric chloride as a new activating agent was used to obtain activated carbons from agroindustrial waste. This material was prepared at three temperatures of pyrolysis, 200, 280 and 400 ºC. The carbonaceous materials obtained after the activation processes showed high specific surface areas (BET), with values higher than 900 m² g-1. The materials showed different behaviors in the adsorption of methylene blue dye and reactive red textile dye in water solutions. An important fact in the use of FeCl3 as an activating agent is that the activation temperature is at 280 ºC, well below of those commonly employed in chemical or physical activations described in the literature.
Preparação e caracterização de carvão ativado produzido a partir de resíduos do beneficiamento do café
(Sociedade Brasileira de Química, 2008) Brum, Sarah Silva; Bianchi, Maria Lucia; Silva, Vanésia Liane da; Gonçalves, Maraísa; Guerreiro, Mário César; Oliveira, Luiz Carlos Alves de
Coffee fruit processing is one of the most polluting activities in agriculture due to the large amount of waste generated in the process. In this work, coffee parchment was employed as precursor for the production of carbons activated with ZnCl2 (CAP). The material was characterized using N2 adsorption/desorption at 77 K, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The material showed a surface area of 521.6 m²g-1 and microporous structure. CAP was applied as adsorbent for the removal of methylene blue dye in aqueous medium. The adsorption capacity was found to be about 188.7 mg g-1.
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.
Variações de curto prazo nas emissões de CO2 do solo em diferentes sistemas de manejo do cafeeiro
(Sociedade Brasileira de Química, 2009) D’Andréa, Alexandre Fonseca; Silva, Marx Leandro Naves; Curi, Nilton; Freitas, Diego Antonio França de; Roscoe, Renato; Guimarães, Paulo Tácito Gontijo
Soil CO2 emissions represent an important component of carbon global cycle. However, information about short-term alterations of CO2 fluxes in soils of tropical regions are scarce. So, the objective of this study was to evaluate such variations in coffee plantations in Latosol (Oxisol). The CO2 emissions were not affected by environmental abiotic factors, such as temperature and soil water evaporation, but they were significantly correlated with the carbon content of microbial biomass (R=0.90, P<0.05). It happens a close relationship between root activity and soil CO2 emission in coffee plantations.
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.
Produção e caracterização de carvão ativado produzido a partir do defeito preto, verde, ardido (PVA) do café
(Sociedade Brasileira de Química, 2009) Ramos, Paulize H.; Guerreiro, Mário C.; Resende, Eliane C. de; Gonçalves, Maraísa
The black, green and sour coffee defect (PVA) contributes with 20% of the total coffee production. It should be separate from the normal coffee grains in order to improve the final quality of the beverage. In this way, the present work has the objective to use the PVA reject for the production of activated carbon. The activated carbon (CA) was prepared from PVA defect using zinc chloride as activating agent. The prepared material (CA PVA) was characterized and the adsorption tests were carried out using as organic models methylene blue (AM) and reactive red (VR). The CA PVA revealed to be more efficient in the removal of the organic contaminants compared to a commercial activated carbon.
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.
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.
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.