Leça do Bailio, Portugal
Leça do Bailio, Portugal
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Moreira N.,University of Porto | Moreira N.,Catholic University of Portugal | Meireles S.,UNICER | Brandao T.,UNICER | De Pinho P.G.,University of Porto
Talanta | Year: 2013

An automated headspace solid-phase microextraction (HS-SPME) combined with gas chromatography and ion trap mass spectrometry detection (GC-IT/MS) was developed in order to quantify a large number of carbonyl compounds in beers. Carbonyl compounds were previously derivatized with O-(2,3,4,5,6- pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA). Volatile carbonyl compounds associated with staling beer aroma includes alkanals, alkenals, alkadienals, dicarbonyl compounds, Strecker aldehydes, ketones and furans. The HS-SPME was performed using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber. The procedures were optimized for HS-SPME pre-incubation temperature and time, extraction temperature and time, and PFBHA addition. A central composite design was used in the optimization of extraction conditions and PFBHA addition. The volatile compounds showed optimal extraction incubating 5 ml of beer with 700 mg l-1 of PFBHA for 7 min and extracted for more 20 min at 45 C. The method was validated with regard to the linearity, repeatability, inter and intra-day precision and accuracy. The method achieved detection limits ranging from 0.003 to 0.510 μg l-1, except for furans (1.54-3.44 μg l-1). The quantification limits varied from 0.010 to 1.55 μg l-1, except for 2-furfural (4.68 μg l-1), 5-methyl-2-furfural (5.82 μg l-1) and 5-hyfroxymethylfurfural (10.4 μg l-1). Repeatability values of all compounds were lower than 17%. The method accuracy was satisfactory with recoveries ranging from 88% to 114%. The validated method showed to be suitable for a fast and reliable determination of main carbonyl compounds in beers. © 2013 Published by Elsevier B.V.

Rodrigues J.A.,University of Aveiro | Barros A.S.,University of Aveiro | Carvalho B.,UNICER | Brandao T.,UNICER | And 2 more authors.
Journal of Chromatography A | Year: 2011

Beer stability is a major concern for the brewing industry, as beer characteristics may be subject to significant changes during storage. This paper describes a novel non-targeted methodology for monitoring the chemical changes occurring in a lager beer exposed to accelerated aging (induced by thermal treatment: 18 days at 45. °C), using gas chromatography-mass spectrometry in tandem with multivariate analysis (GC-MS/MVA). Optimization of the chromatographic run was performed, achieving a threefold reduction of the chromatographic time. Although losing optimum resolution, rapid GC runs showed similar chromatographic profiles and semi-quantitative ability to characterize volatile compounds. To evaluate the variations on the global volatile signature (chromatographic profile and m/. z pattern of fragmentation in each scan) of beer during thermal deterioration, a non-supervised multivariate analysis method, Principal Component Analysis (PCA), was applied to the GC-MS data. This methodology allowed not only the rapid identification of the degree of deterioration affecting beer, but also the identification of specific compounds of relevance to the thermal deterioration process of beer, both well established markers such as 5-hydroxymethylfufural (5-HMF), furfural and diethyl succinate, as well as other compounds, to our knowledge, newly correlated to beer aging. © 2010 Elsevier B.V.

Rodrigues J.E.A.,University of Aveiro | Erny G.L.,University of Aveiro | Barros A.S.,University of Aveiro | Esteves V.I.,University of Aveiro | And 4 more authors.
Analytica Chimica Acta | Year: 2010

The organic acids present in beer provide important information on the product's quality and history, determining organoleptic properties and being useful indicators of fermentation performance. NMR spectroscopy may be used for rapid quantification of organic acids in beer and different NMR-based methodologies are hereby compared for the six main acids found in beer (acetic, citric, lactic, malic, pyruvic and succinic). The use of partial least squares (PLS) regression enables faster quantification, compared to traditional integration methods, and the performance of PLS models built using different reference methods (capillary electrophoresis (CE), both with direct and indirect UV detection, and enzymatic essays) was investigated. The best multivariate models were obtained using CE/indirect detection and enzymatic essays as reference and their response was compared with NMR integration, either using an internal reference or an electrical reference signal (Electronic REference To access In vivo Concentrations, ERETIC). NMR integration results generally agree with those obtained by PLS, with some overestimation for malic and pyruvic acids, probably due to peak overlap and subsequent integral errors, and an apparent relative underestimation for citric acid. Overall, these results make the PLS-NMR method an interesting choice for organic acid quantification in beer. © 2010 Elsevier B.V.

Rodrigues J.A.,University of Aveiro | Barros A.S.,University of Aveiro | Carvalho B.,UNICER | Brandao T.,UNICER | Gil A.M.,University of Aveiro
Analytica Chimica Acta | Year: 2011

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. °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. © 2011 Elsevier B.V.

Martinartin A.,digit Inc | Luque J.,digit Inc | Pla O.,digit Inc | Selvielvi S.,Unicer
Boletin de la Sociedad Espanola de Ceramica y Vidrio | Year: 2013

Digital Decoration Systems, SL (DIGIT-S) with Unicer, SL, has implemented a system to improve and optimize the process of decorating by inkjet printing for ceramic industry. It provides a comprehensive solution, KROME Ceramics, to improve the cost effectiveness of product and process through the implementation of a working system based on the control of digital decoration process and the synchronization of all elements that make up the decorative modules, including the creation of a workflow, management of files that are generated during the process, a correct color management system, and of course, optimizing and evaluating inkjet inks integrating all elements involved: Lighting, Computer, Software, Monitor, Plotter, Paper, Ink, Inkjet, Bodys, Enamels and Oven.

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