RESUMO
In this study, the aroma profile of 10 single origin Arabica coffees originating from eight different growing locations, from Central America to Indonesia, was analyzed using Headspace SPME-GC-MS as the analytical method. Their roasting was performed under temperature-time conditions, customized for each sample to reach specific sensory brew characteristics in an attempt to underline the customization of roast profiles and implementation of separate roastings followed by subsequent blending as a means to tailor cup quality. A total of 138 volatile compounds were identified in all coffee samples, mainly furan (~24-41%) and pyrazine (~25-39%) derivatives, many of which are recognized as coffee key odorants, while the main formation mechanism was the Maillard reaction. Volatile compounds' composition data were also chemometrically processed using the HCA Heatmap, PCA and HCA aiming to explore if they meet the expected aroma quality attributes and if they can be an indicator of coffee origin. The desired brew characteristics of the samples were satisfactorily captured from the volatile compounds formed, contributing to the aroma potential of each sample. Furthermore, the volatile compounds presented a strong variation with the applied roasting conditions, meaning lighter roasted samples were efficiently differentiated from darker roasted samples, while roasting degree exceeded the geographical origin of the coffee. The coffee samples were distinguished into two groups, with the first two PCs accounting for 73.66% of the total variation, attributed mainly to the presence of higher quantities of furans and pyrazines, as well as to other chemical classes (e.g., dihydrofuranone and phenol derivatives), while HCA confirmed the above results rendering roasting conditions as the underlying criterion for differentiation.
Assuntos
Coffea/química , Café/química , Furanos/química , Odorantes/análise , Pirazinas/química , Compostos Orgânicos Voláteis/química , América Central , Coffea/metabolismo , Café/metabolismo , Etiópia , Furanos/classificação , Furanos/isolamento & purificação , Furanos/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Temperatura Alta , Humanos , Indonésia , Reação de Maillard , Análise de Componente Principal , Pirazinas/classificação , Pirazinas/isolamento & purificação , Pirazinas/metabolismo , Sementes/química , Paladar/fisiologia , Compostos Orgânicos Voláteis/classificação , Compostos Orgânicos Voláteis/isolamento & purificação , Compostos Orgânicos Voláteis/metabolismoRESUMO
Four new secondary metabolites, giovaninones A-D (1-4), were isolated from an ethyl acetate extract of a culture of a marine-derived Streptomyces strain designated SS99BA-2. Chemical analysis was completely conducted in a coupled automated LC-SPE system with the use of a cryogenic NMR probehead and HRMS. The application of this system to identify, purify and elucidate all the structures is described.
Assuntos
Pirazinas/química , Água do Mar/microbiologia , Streptomyces/metabolismo , Brasil , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Pirazinas/isolamento & purificação , Pirazinas/metabolismo , Metabolismo Secundário , Streptomyces/química , Streptomyces/genética , Streptomyces/isolamento & purificaçãoRESUMO
A synthesis of 2-methyl-6-vinylpyrazine was carried out by way of a 'one pot' reaction. In order to establish the efficiency of this synthesis the extraction of the volatiles released by male papaya fruit flies was performed by SPME (solid phase micro-extraction). The compound was separated and identified using GC/MSD (gas chromatography/mass spectrometry detector).
Assuntos
Benzenossulfonatos/química , Micro-Ondas , Pirazinas/química , Pirazinas/síntese química , Animais , Cromatografia Gasosa-Espectrometria de Massas , Espectroscopia de Ressonância Magnética , Masculino , Estrutura Molecular , Pirazinas/isolamento & purificação , Tephritidae/químicaRESUMO
New convulsive compounds, brasiliamides A (1) and B (2), were isolated by activity-guided fractionation from okara fermented with a soil isolate of Penicillium brasilianum Batista JV-379. Their structures were elucidated on the basis of spectral and chemical evidence and by X-ray crystallography of the hydrogenated product of 2. In the 1H- and 13C-NMR spectra of 2, the signals were complicated, all being doubled or broadened in several deuterated solvents at room temperature. The conformational change of 2 was clarified as the rotational isomerization of amide bonds in solution by NMR measurements at various temperatures. Four rotamers of 2 at two amide bonds were presented at -60 degrees C in CDCl3, whereas only two isomers were apparent at room temperature, owing to rapid rotation of one of the amide bonds. Brasiliamides A and B respectively showed convulsive activity against silkworms with ED50 values of 300 and 50 microg/g of diet.