Astringency is a sensory attribute, related to the quality and mouthfeel of red wines. However, the origin of astringency sub-qualities, such as the typical drying astringency found in immature grapes, is still unknown. Astringency of red wines with similar tannin content but different astringency sub-qualities, from different harvest dates, is studied. Astringency was characterised in terms of friction coefficient, polyphenol content, sensory analysis and tannin/salivary–proteins aggregates characterisation. A different evolution during ripening was found for both Cabernet Sauvignon and Carménère, and tannin–protein aggregates showed differences in size, shape and surface. The velvety sub-quality appears to be related to aggregates with low precipitation, and with specific surface characteristics as roundness and Feret diameter. Results from this work propose an effect of aggregates on sensory perception and opens the possibility to explore their effect on oral lubrication.
How much do we currently know about the relationship between grape and wine phenolics and cell wall material?
The present post summarizes a review that relates the last decade’s findings on the relationship between phenolics and polysaccharides from grapes, throughout the entire winemaking process up to evaluating the impact of their relationship on the red wine sensory perception. The combination and interconnection of the most recent research studies, from single interactions in model wines to the investigation of the formation of complex macromolecules, brings the perfect story line to relate the relationship between phenolics and polysaccharides from the vineyard to the glass. Grape pectin is highly reactive toward grape and grape derived phenolics. Differences between grape cultivars or changes during grape ripeness will affect the extractability of these compounds into the wines. Therefore, the nature of the grape components will be crucial to understand the subsequent reactions occurring between phenolics and polysaccharide of the corresponding wines. It has been demonstrated that they can form very complex macromolecules which affect wine color, stability and sensory properties.
Characterization of wines by vineyard, region, and vintage by combining untargeted 1H NMR and targeted differential sensing
NMR spectroscopy was used to evaluate the chemical fingerprint of the wines, whereas the peptide-based sensing array is known to mimic the senses of taste, smell, and palate texture by characterizing the phenolic profile. Multivariate and univariate statistical analyses of the combined NMR and differential sensing array dataset classified the genetically identical Pinot noir wines on the basis of distinctive metabolic signatures associated with the region of growth, vineyard, and vintage year.
Phenolic matrix effect on aroma formation of terpenes during simulated wine fermentation – Part I: Phenolic acids
This post reports the results of study where fermentations were performed using simulated grape juice supplemented with terpene glycosides (TGs), extracted from Vitis vinifera L. Meili, and phenolic acids (gallic acid or p-coumaric acid). Free terpenes were detected using solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC–MS) every day during the fermentation, and the aromas of final wines were evaluated by panelists. Results showed that phenolic acids remarkably inhibited TG hydrolysis and free terpene volatilization, and affected wine aroma perception. These findings indicate that the matrix effect of phenolic acids can effectively control the release and modulate the global feature of wine aromas. See all at: http://science-and-wine.com/
Polyphenols in Wine Authenticity
Polyphenols are a diverse group of compounds of utter importance to wine quality. Current understanding of the polyphenolic composition in wine is well elaborated, however, recent studies continuously report novel findings involving them. It is evident that synergistic approaches between emerging analytical platforms in combination with advanced multivariate data analysis will be considered the spearheads toward fraud detection and the provision of authentic wines.
Coupling DAD and FLD for multiclass profiling of phenolic compounds in wine industry products
This post describes a tandem absorbance and fluorescence detection following liquid chromatography (LC-DAD-FLD) method for the determination of 32 phenolic compounds (PCs) in winemaking industry derived products. The applicability of the method was verified by the suitable quantification of analytes in complex samples of wine, bunch stem and grape cane extracts. The developed LC-DAD-FLD approach is highly recommended for processing large sets of samples in routine quality control of extracts or during characterization studies.
Extended harvest date alter flavonoid composition and chromatic characteristics of Plavac Mali (Vitis vinifera L.) grape berries
This post is about a study that delivers a comprehensive flavonoid fingerprint profile, physiochemical and external color characterization of Plavac Mali grapes through four harvest dates at two distinct vineyards (Split and Zadar) in the Eastern Adriatic region. Results show that berries of extended harvest dates underwent colorimetric improvements, trough decrease in CIELab color space parameters a* (reed/green), b* (yellow/blue), L* (lightness (0, black; 100 white)) and C (chroma, relative saturation) characteristics and increase in skin color index for red grapes. In conclusion, the extended harvest date promotes flavonoid composition, and improves the quality of Plavac Mali grape berries.
Effects of polyphenols on secondary structure of VVTL1 wine protein
Polyphenols are an important constituent of wines and they are largely studied due to their antioxidant properties and for their effects on wine quality and stability, which is also related to their capacity to bind to proteins. The effects of some selected polyphenols, including procyanidins B1 and B2, tannic acid, quercetin, and rutin, as well as those of a total white wine procyanidin extract on the conformational properties of the major wine protein VVTL1 (Vitis vinifera Thaumatin-Like-1) were investigated by Synchrotron Radiation Circular Dichroism (SRCD). The data demonstrate the existence of an interaction between polyphenols and VVTL1, which results in modification of its thermal and UV denaturation pattern. This information can be useful in understanding the behavior of wine proteins in presence of polyphenols, thus giving new insights on the phenomena that are involved in wine stability.
2019 In Review
This is the last post of 2019. The second year of Science & Wine existence, time for a brief reflection. This was a great year!