1,721,030 research outputs found
The Effect of Copper Ions on Colour in Extracts of Cabernet Sauvignon and Sangiovese Skins Under Wine-like Conditions
Full text linkPigment-metal complexes are generally not considered to play significant roles in grape and wine colour. However, to the best of my knowledge, this hypothesis has never been investigated. In this work, grape skin extracts (cultivars Sangiovese and Cabernet Sauvignon) were allowed to react with copper sulphate aqueous solutions at different concentrations. High, and toxic, copper additions produced significant absorption increases in the green spectral region (corresponding to the typical absorption band of anthocyanins). Further studies will be necessary to characterise the nature of this interaction
Grape seed ripening evaluation by ortho-diphenol quantification
Full text linkTwo millennia of viticulture recognize the seed browning importance on tannin ripening and, thus, on grape and wine quality. This color change was recently attributed to phenolic oxidations. However an objective chemical index able to quantify the oxidation status of seed tannins was missing, probably due to the heterogeneous oxidation polymerizations. This work suggests the adoption of the ortho-diphenol quantification as indication of the tannin ripening process, because ortho-dihydroxylated substitutions are highly susceptible to oxidation. The method proposed is based on the ortho-diphenol characteristic complexation with molybdenum. Different cultivars (Merlot, Pinot noir, Croatina, Aladasturi, Alexandrouli, Odjaleshi and Tavkveri) were studied during three vintages in Oltrepò pavese, Italy. The color darkening correlated with the ortho-diphenol decrease. We believe this index could find useful applications in viticulture, supporting harvesting time decisions
Oxidized Polymeric Phenolics : Could They Be Considered Photoprotectors?
No full textPhotooxidative sunburn is the consequence of photosystem overexcitations. It results in tissue color changes as a result of chlorophyll degradation and accumulation of oxidized polymeric phenolics (OPPs), resulting from scavenging of reactive oxygen species (ROS). From a productive point of view, OPPs should be considered as damages, decreasing the economical and esthetical values of plants and crops. However, from a physiological perspective, OPPs could be also play a screening role against excessive photosynthetically active radiation (PAR), because they follow the criteria proposed for the identification of photoprotectors, as follows: (i) As a result of the complex conjugated double bond systems, OPPs absorb and, thus, screen the visible PAR. (ii) The accumulation of brown OPPs is well-known to be stimulated by light exposure, resulting in sunburn symptoms. (iii) OPPs induce PAR resistance; for example, the sunburned brown skin allows the fruit ripening to proceed without further interferences. (iv) The screen provided by the accumulated OPPs in death cells protect underlying tissues, demonstrating an increased resistance to radiation when other physiological processes are not functioning
Drought increases chlorophyll content in stems of Vitis interspecific hybrids
Full text linkPlants respond to drought stress through different physiological mechanisms. To highlight a specific adaptation strategy related to stem photosynthetic activity, woody tissue pigmentation was studied. In this work, 25 Vitis hybrids were studied in two experimental vineyards: one of them with sufficient water availability and the other showing drought stress. 1500 reflectance spectra of woody tissues were collected. Beside the spectral elaboration and interpretation, indexes for the pigment quantification were calculated. The content and the proportion in chlorophylls (a and b) in stems were significantly modified in response to water stress. Genotypes were classified based on their plasticity/elasticity and adaptive/susceptible behavior. The cluster analysis produced 4 main groups based on their average spectra and on the spectral variations between watered and stress conditions. The most interesting genotypes concerning this trait were pointed out. Nevertheless, this adaptation mechanism could also be due to an increased detoxification necessity related to other physiological disfunctions caused by water stress. A multi-parameter approach is encouraged for phenotyping of abiotic stress tolerant plant selection. In the next future, this work will support the release of new drought tolerant rootstocks for viticulture
Optical Properties of berry epicuticular waxes in four Georgian grape cultivars (Vitis vinifera L.)
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Chlorophyll and carotenoid quantifications in white grape (Vitis vinifera L.) skins by reflectance spectroscopy
No full textAccumulo e profilo antocianico in relazione al microclima termico e luminoso in Croatina, Sangiovese, Syrah e Nebbiolo
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