Edmundo Bordeu

Post-veraison sunlight exposure induces MYB-mediated transcriptional regulation of anthocyanin and flavonol synthesis in berry skins of Vitis vinifera

Anthocyanins, flavan-3-ols, and flavonols are the three major classes of flavonoid compounds found in grape berry tissues. Several viticultural practices increase flavonoid content in the fruit, but the underlying genetic mechanisms responsible for these changes have not been completely deciphered. The impact of post-veraison sunlight exposure on anthocyanin and flavonol accumulation in grape berry skin and its relation to the expression of different transcriptional regulators known to be involved in flavonoid synthesis was studied. Treatments consisting of removing or moving aside the basal leaves which shade berry clusters were applied. Shading did not affect sugar accumulation or gene expression of HEXOSE TRANSPORTER 1, although in the leaf removal treatment, these events were retarded during the first weeks of ripening. Flavonols were the most drastically reduced flavonoids following shading and leaf removal treatments, related to the reduced expression of FLAVONOL SYNTHASE 4 and its putative transcriptional regulator MYB12. Anthocyanin accumulation and the expression of CHS2, LDOX, OMT, UFGT, MYBA1, and MYB5a genes were also affected. Other regulatory genes were less affected or not affected at all by these treatments. Non-transcriptional control mechanisms for flavonoid synthesis are also suggested, especially during the initial stages of ripening. Although berries from the leaf removal treatment received more light than shaded fruits, malvidin-3-glucoside and total flavonol content was reduced compared with the treatment without leaf removal. This work reveals that flavonol-related gene expression responds rapidly to field changes in light levels, as shown by the treatment in which shaded fruits were exposed to light in the late stages of ripening. Taken together, this study establishes MYB-specific responsiveness for the effect of sun exposure and sugar transport on flavonoid synthesis.

Isolation of WDR and bHLH genes related to flavonoid synthesis in grapevine (Vitis vinifera L.).

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.

Rapid Measurement of Phenolics Compounds in Red Wine Using Raman Spectroscopy

This paper presents the development of a new method to measure the main phenolic compounds found in Cabernet Sauvignon red wines. A portable Raman spectrometer was used for this purpose, providing scattering spectra to analyze quantitatively the samples and determining the concentration of the compounds of interest. The Raman spectra were obtained from the wine samples corresponding to different seasons, vineyards, and harvests. The subsequent model calibration was based on reference analytical values obtained using standard laboratory techniques. Several preprocessing and correlation methods were applied to the data in order to adjust models for polyphenols, anthocyanins, and tannins and also to reduce the effect of fluorescence. The optimization of the models was carried out using R2 and root-mean-square error of validation (RMSEV) indices. The correlations of R2 = 0.895 and RMSEV = 5.55 mg/L were obtained, showing the potential of this technique for field measurements.

Comparative study of wine tannin classification using fourier transform mid-infrared spectrometry and sensory analysis

Wine tannins are fundamental to the determination of wine quality. However, the chemical and sensorial analysis of these compounds is not straightforward and a simple and rapid technique is necessary. We analyzed the mid-infrared spectra of white, red, and model wines spiked with known amounts of skin or seed tannins, collected using Fourier transform mid-infrared (FT-MIR) transmission spectroscopy (400–4000 cm−1). The spectral data were classified according to their tannin source, skin or seed, and tannin concentration by means of discriminant analysis (DA) and soft independent modeling of class analogy (SIMCA) to obtain a probabilistic classification. Wines were also classified sensorially by a trained panel and compared with FT-MIR. SIMCA models gave the most accurate classification (over 97%) and prediction (over 60%) among the wine samples. The prediction was increased (over 73%) using the leave-one-out cross-validation technique. Sensory classification of the wines was less accurate than that obtained with FT-MIR and SIMCA. Overall, these results show the potential of FT-MIR spectroscopy, in combination with adequate statistical tools, to discriminate wines with different tannin levels.

Red wine phenolic composition: the effects of summer pruning and cluster thinning

P.M. Canon, A.S. Gonzalez, J.A. Alcalde, and E. Bordeu. 2014. Red wine phenolic composition: the effects of summer pruning and cluster thinning. Cien. Inv. Agr. 41(2): 235-248. The quality of red wine is directly associated with its phenolic composition, which can be controlled using several viticultural techniques that affect the vegetative/productive balance of the plants, such as summer pruning and cluster thinning. However, these techniques may also involve high costs and production losses. This study aimed to evaluate the effects of summer pruning and cluster thinning on the phenolic compositions of grapes and wine over three consecutive seasons. The treatments included long (120 cm shoot length) and short (60 cm shoot length) summer pruning and 50% cluster thinning with control treatments conducted in vineyards with cvs. Cabernet-Sauvignon and Carmenere and located in a warm area (Cachapoal, Chile) and cvs. Cabernet-Sauvignon and Pinot Noir located in a cold area (Casablanca, Chile). These treatments generated differences in the microclimatic conditions (radiation and temperature) and the vegetative/productive balance of the plants. Depending on whether the grapevine vigor was high or low, short summer pruning increased or decreased the phenolic composition. The effects of cluster thinning varied according to the natural productivity of each season, increasing the phenolic composition when the natural yields were high and producing no significant effects when they were low. The decision to make these viticultural practices to improve the phenolic composition of the wine depends on the seasonal vineyard vigor and potential productivity. Thus, measures are only applied when a severe imbalance in the vegetative/productive equilibrium occurs or when the microclimatic conditions of the vineyard must be improved.

Pisco: production, flavor chemistry, sensory analysis and product development

Abstract: Pisco is a young brandy produced predominantly from Muscat wines in the north of Chile and also in Peru. The chapter describes the areas of production in Chile, wine production and distillation techniques and gives an overview of production figures and the main markets nowadays. The sensory properties and flavor chemistry of Pisco are described emphasizing the properties that make it different from other young or non-aged wine brandies. Sensory practice and consumer research in particular for product development in the Chilean Pisco industry are finally discussed.

Monitoring peroxides generation during model wine fermentation by FOX-1 assay.

The quality of wine is mainly determined during the alcoholic fermentation that gradually transforms the grape juice into wine. Along this process the yeast goes through several stressful stages which can affect its fermentative ability and industrial performance, affecting wine quality. Based on their actual application on industrial winemaking, commercial Saccharomyces cerevisiae strains (EC1118, QA23, VIN7 and VL3) were used. They were inoculated in batch laboratory fermentations in a model wine solution for evaluating the production of reactive oxygen species (ROS) during the yeasts alcoholic fermentation. For first time total hydroperoxides were determined by FOX-1 assay to follow ROS generation. The total hydroperoxides accumulated along the 10 days of fermentation peaked up to 10.0 μM in yeast EC1118, of which 1.3 μM was hydrogen peroxide (H2O2). The FOX-1 based analytical approach herein presented is a valuable tool for the quantification of ROS oxidative damage during winemaking.

White wines aroma recovery and enrichment: Sensory-led aroma selection and consumer perception

We developed a sensory-based methodology to aromatically enrich wines using different aromatic fractions recovered during fermentations of Sauvignon Blanc must. By means of threshold determination and generic descriptive analysis using a trained sensory panel, the aromatic fractions were characterized, selected, and clustered. The selected fractions were grouped, re-assessed, and validated by the trained panel. A consumer panel assessed overall liking and answered a CATA question on some enriched wines and their ideal sample. Differences in elicitation rates between non-enriched and enriched wines with respect to the ideal product highlighted product optimization and the role of aromatic enrichment. Enrichment with aromatic fractions increased the aromatic quality of wines and enhanced consumer appreciation.

Erratum to: Pre-alcoholic fermentation acidification of red grape must using Lactobacillus plantarum

Red grape musts from overripe grapes are characterised by high pH and sugar concentration. Corrections with organic acids are commonly used to secure the alcoholic fermentation and improve the organoleptic characteristics of the wine. In this study we test an alternative biological acidification method using the ability of Lactobacillus plantarum to produce high concentrations of lactic acid. The time course of sugars, organic acids and pH were measured. Available sugars were consumed by L. plantarum producing up to 8.3 g L of lactic acid. Lactic acid changed the pH from 3.9 to 3.4 after 14 days postinoculation without yielding a relevant concentration of acetic acid (0.34 g L).