resumo
This paper describes the use of nuclear magnetic resonance (NMR) spectroscopy, in tandem with multivariate analysis (MVA), for monitoring the chemical changes occurring in a lager beer exposed to forced aging (at 45 degrees C for up to 18 days). To evaluate the resulting compositional variations, both principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were applied to the NMR spectra of beer recorded as a function of aging and a clear aging trend was observed. Inspection of PLS-DA loadings and peak integration enabled the changing compounds to be identified, revealing the importance of well known markers such as 5-hydroxymethylfurfural (5-HMF) as well as a range of other relevant compounds: amino acids, higher alcohols, organic acids, dextrins and some still unassigned spin systems. In addition, the multivariate analysis method of 2D correlation analysis was applied to the NMR data enabling the relevant compound variations to be confirmed and inter-compound correlations to be assessed, some reflecting common metabolic/chemical pathways and, therefore, offering improved insight into the chemical aspects of beer aging. (C) 2011 Elsevier B.V. All rights reserved.
palavras-chave
LIQUID-CHROMATOGRAPHY; H-1-NMR SPECTROSCOPY; DIMETHYL TRISULFIDE; BETA-DAMASCENONE; FLAVOR STABILITY; OLIVE OILS; NMR; CHEMOMETRICS; SPECTROMETRY; COMBINATION
categoria
Chemistry
autores
Rodrigues, JA; Barros, AS; Carvalho, B; Brandao, T; Gil, AM
nossos autores
Ana Maria Pissarra Coelho Gil
Professor Associado com Agregação
António de Sousa Barros
Bolseiro de pós-Doutoramentoagradecimentos
The authors acknowledge the Foundation for Science and Technology (FCT), Portugal, for funding through the grant FCT SFRH/BD/31056/2006. The Portuguese National NMR Network (RNRMN), supported with FCT funds is also acknowledged and the authors are grateful to M. Spraul, Bruker BioSpin, Germany, for providing access to spectral databases.