Browsing by Author "Bordeu, E."

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    A Review of Tannin Determination Methods Using Spectrophotometric Detection in Red Wines and Their Ability to Predict Astringency
    (SOUTH AFRICAN SOC ENOLOGY & VITICULTURE-SASEV, 2021) Wilhelmy, C.; Pavez, C.; Bordeu, E.; Brossard, N.
    Astringency is an important sensory attribute that influences red wine quality. The astringent sensation inside the mouth is caused by a group of molecules called tannins. These molecules in wine can be determined and analysed by spectrophotometric, analytical and recently electrochemical methodologies. This article focuses on the three methods most frequently used by the wine industry: Bate Smith or acid hydrolysis method, Adams Harbertson assay or BSA tannin assay, and methylcellulose precipitation (MCP) method. These methods differ on the principle upon which they are based, as well as on the kind of tannin that they can determine. The purpose of this article is to present the main advantages and disadvantages of the three spectrophotometric methods acid hydrolysis, BSA assay and MCP methods for tannin determination in red wine, in order to review their efficacy, group of tannins each method can determine, and their suitability for astringency prediction.
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    Isolation of WDR and bHLH genes related to flavonoid synthesis in grapevine (Vitis vinifera L.)
    (2010) Matus, J. T.; Poupin, M. J.; Canon, P.; Bordeu, E.; Alcalde, J. A.; Arce-Johnson, P.
    Anthocyanins and tannins are two of the most abundant flavonoids found in grapevine, and their synthesis is derived from the phenylpropanoid pathway. As described for model species such as Arabidopsis thaliana, maize and petunia, the end-point branches of this pathway are tightly regulated by the combinatorial interaction of three families of regulatory factors; MYB, bHLH (also known as MYC) and WDR proteins. Among these, only MYB genes have been previously identified in grapes. Here, we report the isolation of the first members from the WDR and bHLH families found in Vitis vinifera, named WDR1, WDR2 and MYCA1. WDR1 contributed positively to the accumulation of anthocyanins when it was overexpressed in A. thaliana, although it was not possible to determine the function of WDR2 by ectopic expression. The sub-cellular localizations of WDR1 and MYCA1 were observed by means of GFP-fusion proteins, indicating both cytoplasm and nuclear localization, in contrast to the localization of a MYB factor exclusively in the nucleus. The expression patterns of these genes were quantified in coloured reproductive organs throughout development, and correlated with anthocyanin accumulation and the expression profiles of the flavonoid-related MYBA1-2, UFGT, and ANR genes. In vitro grapevine plantlets grown under high salt concentrations showed a cultivar-dependent response for anthocyanin accumulation, which correlated with the expression of MYBA1-2, MYCA1 and WDR1 genes. These results suggest that MYCA1 may regulate ANR and UFGT and that this last control is easier to distinguish whenever MYBA genes are absent or in low abundance. Future studies should address the specific interactions of these proteins and their quantitative contribution to flavonoid synthesis in grape berries.
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    S-Abscisic acid, 2-chloroethylphosphonic acid and indole-3-acetic acid treatments modify grape (Vitis vinifera L. 'Cabernet Sauvignon') hormonal balance and wine quality
    (JKI-INSTITUT REBENZUCHTUNG, 2012) Gonzalez, A. S.; Olea, P.; Bordeu, E.; Alcalde, J. A.; Geny, L.
    The phenolic composition of red wine strongly determines its quality. Even when the applications of plant growth regulator (PGR) affect grape quality, there is almost no information on the effect of these treatments on the grape's internal hormonal balance and the wine composition and quality. In the present study, changes in the internal hormonal content following the application of (+)-S-abscisic acid (S-ABA), 2-chloroethylphosphonic acid (CEPA) and indole-3-acetic acid (IAA) at veraison were examined to determine their effects on 'Cabernet Sauvignon' grapes and wine composition in a plants in containers experiment and in a commercial vineyard experiment. Applied PGRs had a significant effect on the hormonal balance and phenolic composition of grape skins. The S-ABA-treated grapes showed a significantly higher skin internal free abscisic acid concentration in the plants in container experiment and the CEPA-treated grapes showed a reduction in skin internal IAA concentration in the commercial vineyard experiment. Winemaking was performed in the commercial vineyard experiment. Wine's chemical composition was affected by these treatments and an up-to 63 % increase in malvidin-3-glucoside concentration and an up-to 70 A increase in total tannin concentration were found in wines made from the CEPA-treated grapes. The alcohol content was 10.3 % higher (from 12.6 to 13.9 % v v(-1)) in wines made from the CEPA-treated grapes. No significant differences in the wine sensory attributes (aroma and mouth-feel) between the control and the PGR-treated wines were identified by a sensory panel.