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

Biotechnological Strategies for Controlling Wine Oxidation

Apart from the controversial positive effects of moderate wine consumption on human health, wine antioxidant capacity plays a key role in winemaking technology. From juice extraction to bottle storage, oxygen management is one of the most critical points for making quality wines. In the past, the protection of juice and wine from oxidations was based on the sole use of sulfur dioxide; more recently, the toxicity and the allergenic potential of this additive, together with the increased knowledge on wine oxidation mechanisms, have given rise to new biotechnological approaches and producing trends, leading to a significant reduction of sulfites in winemaking. The aim of this paper is to review the oxidation mechanisms of grape juice and wine and to discuss the opportunities to reduce as much as possible sulfur dioxide addition by a proper management of alcoholic and malolactic fermentation and by the supplementation of some important yeast nutritional factors (e.g., thiamine). The use of natural antioxidants complementing the activity of sulfites (i.e., ascorbic acid, glutathione, yeast lees, and yeast derivatives) is also discusse

Validation of the use of multiple internal control genes, and the application of real-time quantitative PCR, to study esterase gene expression in Oenococcus oeni

The study of gene expression and accurate quantitation of target genes in any organism depends on correct normalisation. Due to the increase in studies on Oenococcus oeni gene expression, there is a clear need for alternative reference genes in order to reliably measure expression levels. In this manuscript, we propose the approach of using multiple reference genes to provide a more robust basis for establishing a reference gene set. The identification and evaluation of a panel of nine reference genes, including the commonly used ldhD, for real-time PCR normalisation was performed in O. oeni. Expression levels of these reference genes were then measured by real-time qPCR in an independent set of O. oeni samples (n = 30). The nine genes were ranked according to their stability of gene expression measure (M) using geNorm to identify the most consistently expressed reference genes. This approach resulted in the identification of multiple reference genes that may be used for a screening and more robust normalisation of target gene expression measured by real-time RT-qPCR. Expression of esterase genes was then measured in these O. oeni samples in the presence of known esterase substrates. The results give an indication of how these genes may be involved in ester synthesis and hydrolysis in O. oeni.Krista M. Sumby, Paul R. Grbin, Vladimir Jirane