Reversed-phase high-performance liquid chromatography–fluorescence detection for the analysis of glutathione and its precursor γ-glutamyl cysteine in wines and model wines supplemented with oenological inactive dry yeast preparations

El pdf del artículo es la versión pre-print.A reversed-phase high-performance liquid chromatography-fluorescence detection methodology involving a pre-column derivatization procedure using 2,3-naphtalenedialdehyde in the presence of 5 and 0. 5 mM of dithiothreitol to determine total and reduced glutathione (GSH) and γ-glutamyl-cysteine (γ-glu-cys) in musts and wines has been set up and validated. The proposed method showed good linearity (R 2 >99% for reduced and total GSH, and R 2 >98% for γ-glu-cys) in synthetic wines, over a wide range of concentration (0-10 mg L -1). The limits of detection for reduced GSH in synthetic and real wines were almost the same (0. 13 and 0. 15 mg L -1, respectively) and slightly higher for γ-glu-cys (0. 24 mg L -1). The application of the method allowed knowing, for the first time, the amount of total and reduced GSH and γ-glu-cys released into synthetic wines by oenological preparations of commercial inactive dry yeast (IDY). In addition, the evolution of these three compounds during the winemaking and shelf life (0-9 months) of an industrially manufactured rosé wine supplemented with a GSH-enriched IDY showed that although GSH is effectively released from IDY, it is rapidly oxidized during alcoholic fermentation, contributing to the higher total GSH content determined in wines supplemented with GSH-enriched IDYs compared to control wines. © 2011 Springer Science+Business Media, LLC.IAO and JJRB acknowledge CAM and CSIC for their respective research grants. This work has been founded by PET2007-0134 project.Peer Reviewe

Inactivation of palladium-based oxygen scavenger system by volatile sulphur compounds present in the headspace of packaged food

An oxygen scavenger based on a catalytic system with palladium (CSP) was recently developed to remove oxygen in food packagings. Although the CSP worked with various types of food, with some foods, an inhibition of the CSP was observed. Because such catalytic systems are susceptible to poisoning by sulfurcontaining compounds, the aim of this study was to understand the inactivation of palladium-based catalysts in presence of foods containing volatile sulfur compounds (VSCs). To achieve this, the oxygen scavenging activity (OSA) of the CSP was evaluated in presence of selected food products. Afterwards, VSCs mainly present in these foods were exposed to the CSP, and the influence on the OSA was evaluated. Finally, headspace analysis was performed with the diluted VSCs and with the packaged food products using proton transfer reaction time-of-flight mass spectrometry. It was found that the catalytic activity of the CSP was inhibited when VSCs were present in the headspace in concentrations ranging between 10.8–36.0 ppbv (dimethyl sulfide, DMS), 1.2–7.2 ppbv (dimethyl disulfide), 0.7–0.9 ppbv (dimethyl trisulfide), 2.1–5.8 ppbv methional) and 4.6–24.5 ppbv (furfuryl thiol). It was concluded that in packaged roast beef and cheese, DMS may be the compound mainly responsible for the inactivation of the CSP. In packagings containing ham, the key compounds were hydrogen sulfide and methanethiol; in peanuts, it was methanethiol; and in par-baked buns, an accumulation of methional, DMS, butanethiol and methionol. When potato chips were packaged, it was demonstrated that when VSCs are present in low concentrations, oxygen can still be scavenged at a reduced OSA

The role of phenolic compounds on olive oil aroma release

In this study, atmospheric pressure chemical ionisation-mass spectrometry (APCI-MS) was successfully applied to understand the effect of phenolic compounds on the release of olive oil aroma compounds. Eight aroma compounds were monitored under in-vivo and in-vitro dynamic conditions in olive oil with and without the addition of virgin olive oil (VOO) biophenols. Three model olive oils (MOOs) were set up with identical volatile compounds concentrations using a refined olive oil (ROO). Phenolics were extracted from VOOs and were added to two MOOs in order to obtain two different concentrations of phenolic compounds (P+ = 354 mg kg−1; P++ = 593 mg kg−1). Another MOO was without VOO biophenols (P−). Phenolic compounds impacted both the intensity and time of aroma release. In the in-vivo study, 1-penten-3-one, trans-2-hexenal and esters had lower release in the presence of higher levels of biophenols after swallowing. In contrast, linalool and 1-hexanol had a greater release. The more hydrophobic compounds had a longer persistence in the breath than the hydrophilic compounds. VOO phenolics-proline-rich proteins complexes could explain the binding of aroma compounds and consequently their decrease during analysis and during organoleptic assessment of olive oil

Metabolic characterization of Palatinate German white wines according to sensory attributes, varieties, and vintages using NMR spectroscopy and multivariate data analyses

1H NMR (nuclear magnetic resonance spectroscopy) has been used for metabolomic analysis of ‘Riesling’ and ‘Mueller-Thurgau’ white wines from the German Palatinate region. Diverse two-dimensional NMR techniques have been applied for the identification of metabolites, including phenolics. It is shown that sensory analysis correlates with NMR-based metabolic profiles of wine. 1H NMR data in combination with multivariate data analysis methods, like principal component analysis (PCA), partial least squares projections to latent structures (PLS), and bidirectional orthogonal projections to latent structures (O2PLS) analysis, were employed in an attempt to identify the metabolites responsible for the taste of wine, using a non-targeted approach. The high quality wines were characterized by elevated levels of compounds like proline, 2,3-butanediol, malate, quercetin, and catechin. Characterization of wine based on type and vintage was also done using orthogonal projections to latent structures (OPLS) analysis. ‘Riesling’ wines were characterized by higher levels of catechin, caftarate, valine, proline, malate, and citrate whereas compounds like quercetin, resveratrol, gallate, leucine, threonine, succinate, and lactate, were found discriminating for ‘Mueller-Thurgau’. The wines from 2006 vintage were dominated by leucine, phenylalanine, citrate, malate, and phenolics, while valine, proline, alanine, and succinate were predominantly present in the 2007 vintage. Based on these results, it can be postulated the NMR-based metabolomics offers an easy and comprehensive analysis of wine and in combination with multivariate data analyses can be used to investigate the source of the wines and to predict certain sensory aspects of wine

Brettanomyces bruxellensis yeasts: impact on wine and winemaking

Yeasts belonging to the Brettanomyces/Dekkera genus are non-conventional yeasts, which affect winemaking by causing wine spoilage all over the world. This mini-review focuses on recent results concerning the presence of Brettanomyces bruxellensis throughout the wine processing chain. Here, culture-dependent and independent methods to detect this yeast on grapes and at the very early stage of wine production are encompassed. Chemical, physical and biological tools, devised for the prevention and control of such a detrimental species during winemaking are also presented. Finally, the mini-review identifies future research areas relevant to the improvement of wine safety and sensory profiles

Metabolic constituents of grapevine and grape-derived products

The numerous uses of the grapevine fruit, especially for wine and beverages, have made it one of the most important plants worldwide. The phytochemistry of grapevine is rich in a wide range of compounds. Many of them are renowned for their numerous medicinal uses. The production of grapevine metabolites is highly conditioned by many factors like environment or pathogen attack. Some grapevine phytoalexins have gained a great deal of attention due to their antimicrobial activities, being also involved in the induction of resistance in grapevine against those pathogens. Meanwhile grapevine biotechnology is still evolving, thanks to the technological advance of modern science, and biotechnologists are making huge efforts to produce grapevine cultivars of desired characteristics. In this paper, important metabolites from grapevine and grape derived products like wine will be reviewed with their health promoting effects and their role against certain stress factors in grapevine physiology

Flavor Control in Baked Cereal Products

International audienceBaked cereal products represent one of the most consumed foodstuffs in the world. Extensive scientific research has been focused on the volatile composition of these types of products. It has been shown that in spite of the great number of compounds identified, only a small number of them are responsible for the aroma. Many factors can affect the aroma composition of baked cereal products and different strategies have been proposed to improve the endogenous aroma. Furthermore, the addition of exogenous aroma compounds is extensively employed when baked cereal products with special traits are required. This article reviews the different ways in which the aroma is generated in baked cereal products and the methods that can be used to control or modify their flavor, as well as the problems related to the flavoring and the different approaches that flavor technologists have proposed to solve these problems. Some important issues and directions for future research in the flavor of baked cereal products are listed

Feasibility and application of solvent assisted flavour evaporation and standard addition method to quantify the aroma compounds in flavoured baked matrices

International audienceIn order to determine the feasibility of the solvent assisted flavour evaporation extraction (SAFE) technique and the standard addition method to quantify the aroma compounds retained in baked matrices after processing, three doughs that mainly vary in one ingredient, M1 (with eggs and palm oil), M2 (without eggs but with palm oil) and M3 (without eggs and without palm oil) were flavoured with an aromatic formulation of 19 different aroma compounds in propylene glycol that is responsible for a viennoiserie aromatic note. From the 19 aroma compounds added, 12 of them were quantified, so was also the propylene glycol. After the application of standard addition method 36 linear regression models were obtained and 28 of them showed good r2 values and allowed quantification. The results from the comparison of the slopes (95%) showed significant differences of the aroma compounds depending on matrix composition, which influences the degree of interaction of the aroma compounds in the matrix and the losses of the aroma during processing. The percentage of retention of the aroma compounds after processing was lower in M3 than in matrices M1 and M2

Influence of eggs on the aroma composition of a sponge cake and on the aroma release in model studies on flavored sponge cakes

International audienceThe use of solvent-assisted flavor evaporation extraction (SAFE) and purge and trap in Tenax allowed the identification of more than 100 volatile compounds in a sponge cake (SC-e). Gas chromatography-olfactometry (GC-O) of the SAFE extracts of crumb and crust were achieved in order to determine the most potent odorants of SC-e. The change in the traditional dough formulation of SC-e in which eggs were substituted by baking powder (SC-b) as the leavening agent produced important changes in some key aroma compounds. The release curves of some aroma compounds-some of them generated during baking and others added in the dough-were followed by cumulative headspace analysis. In the flavored SC-b, the aroma release curves showed a plateau after 15 min of purge, while the release increased proportionally with the purge time in the flavored SC-e. In general, except for some of the aroma compounds with the highest log P values, the rate of release of most of the added and generated aroma compounds was significantly influenced by the changes in the cake formulation. The higher rates of release found for the aroma compounds in SC-b could contribute to explain its rapid exhaustion of aroma compounds in the purge and trap experiments and might lead to poorer sensorial characteristics of this cake during storag