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Showing posts from January, 2018

Irrigation of grapevines trained onto high potential canopy systems in the Coastal region

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New Winetech funded project 2018 - The aim of this study is to compare the water use, yield and quality of drip irrigated vertical shoot positioned and bush grapevines to that of grapevines trained onto high potential yield trellis/canopy systems in the Coastal region.

In recent years, prices that producers earn per ton of grapes have not increased enough in relation to increasing production costs. Producers are subsequently increasing yields per hectare while trying to minimize costs in order to stay economically viable. Most often, this is achieved by increasing irrigation volumes or applications or by using high production canopy/trellis systems and/or mechanical pruning. Challenges with these approaches however is that injudicious application of irrigation can waste water and have negative effects on wine quality. There is also a general perception that high yielding grapevines produce lesser quality wines.
The effect of different canopy management practices in combination with diff…

Grapevine’s response to water stress

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New Winetech funded project 2018 - This study is based on unanswered or novel questions regarding water stress and the managing of irrigation to avoid unacceptable levels of stress that would have negative impacts on yield and quality.

Both grapevine scion cultivars and rootstock varieties differ in their tolerance and response to limited water supplies. The reaction of a grafted vine to water stress cannot necessarily be predicted from the scion and rootstock varieties’ individual reactions.
This focus of this research project is to compare the molecular/metabolic stress fingerprints of grapevine scion-rootstock combinations undergoing defined water stress. The main objective would be to characterise the differences in water management/acclimation potential of the different plant materials to water stress. This new project will tie into an existing Winetech funded project where researchers are evaluating a number of different scion-rootstock combinations and its effect on grapevine …

Cork as a closure for bottle-fermented sparkling wines during ageing on the lees

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New Winetech funded project 2018 - The aim of this study is to compare Method Cap Classique (MCC) wines fermenting and ageing under cork and crown caps. Anecdotal evidence shows that fermenting and ageing under cork instead of crown cap closures improve foam stability and bubble texture. However very little published literature is available on the topic. Objectives of the study will also include:
The impact of cork on yeast cell count and degree of autolysis;Measuring the presence of phenolics and tannins that potentially add texture/density to the base wine;Comparison of spectral data as an indication of the impact of complex molecules on foam stability and bubble function at the liquid/air interface;Comparison of foam and the rate at which the bubbles rise in ageing sparkling wines;Comparison of the role of cork phenolics on various macromolecules release during autolysis;The effect of cork migratory components on physical properties of the wine (texture/viscosity);The role of pheno…

Cost effective spectrophotometric method for the determination of YAN

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New Winetech funded project 2018 - The aim of the project is to develop an improved method to measure YAN, with ammonia and amino acids separately, using infrared spectroscopy. This improved measurement can be added to the range of measurements already conducted by instruments such as a FOSS WineScan. Scanning juice samples is more efficient than classical YAN measurements. This project follows onto a previous Winetech funded YAN project. As a result two datasets to set up the statistical model (calibration) already exist: YAN and amino acid measurements, as well as spectral data of juice for the 2016 and 2017 vintages. Studies conducted internationally testing the principle of using IR spectra for YAN, have very encouraging results. With the help of statistical software the two datasets (classical and spectral) will be used to build and validate the model that will make the correlation between IR spectra and YAN and amino acid concentrations. Three different IR instruments, with diff…