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Showing posts from May, 2019

Reducing the use of Copper in organic viticulture

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By Lucinda Heyns
Copper based active ingredients are essential for disease control in organic farming. However, copper accumulates in the soil and can lead to toxicity that negatively affects microbial biomass and activity. The aim of this study was to test the efficacy of a phosphite based product against downy mildew.
Foliar fertilizers based on potassium phosphate and magnesium phosphate has been proven to provide some protection against downy mildew. Phosphites stimulate the production of phytoalexins – metabolites produced by plants that assist with systemic induced resistance and that break cell membranes of pathogens
PROJECT LAYOUT: The trial was done in a 15-year old dryland Barbera vineyard in Italy. Four treatments were applied: Control: Untreated vines – no disease control agent applied.Cu: Traditional copper based product (20% Cu) used against downy mildew. Total of 4.5kg/ha Cu.CuS: Traditional copper based product plus Scudo - a liquid fertilizer consisting of copper chel…

Downy mildew infection affects flavour profile of Merlot and Cabernet Sauvignon

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By Lucinda Heyns
The aim of this project was to determine the effect of downy mildew on the aroma profile and ageability of Merlot and Cabernet Sauvignon.The compounds responsible for the atypical aromas perceived, were also identified.
PROJECT LAYOUT: A Merlot and Cabernet Sauvignon vineyard in Bordeaux was selected for the trial.Vines were trained on a VSP system and cane pruned.The control section followed a normal spray program to protect vines against disease.In the other section, no fungicides were applied.Healthy and infected grapes were harvested separately.Using a standard winemaking protocol, the following wines were made:A control wine made from healthy grapes.Additional wines simulating 5% - 20% infection were also made.
RESULTS: The study showed that berries that are infected with downy mildew shrivel, and the constituents of the berry is modified, affecting the chemical and sensory profile of the wine.Maceration and alcoholic fermentation both delivered wines with cooked…

The effect of oxygen exposure during winemaking on metal ion concentrations in final wines

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The aim of this study was to investigate the effect of oxygen during pressing and handling in modulating the metal ion composition in a Chardonnay wine throughout vinification, and as such determine whether certain metal ions preferentially accumulate in specific wine fractions (i.e., grape solids post-pressing, wine lees, or in the finished wine supernatant). In this study, the different levels of oxygen exposure were achieved through inert and oxidative press conditions, as well as the protected or oxidative handling of juice and just-fermented wine. The metal ions investigated included macro metal ions, metal ions known to have catalytic abilities, as well as metal ions introduced into wine through metal winemaking equipment.
EXPERIMENTAL LAYOUT: Chardonnay grapes from the Barossa region (2014 vintage) were hand-picked and whole-bunch pressed (3 tonnes per load) using a Bucher-Vaslin XPF50 Inertys®.Two pressing protocols were followed, inert mode and aerobic (or normal) mode.The in…

Wine aroma persistence

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By Karien O'Kennedy

The aim of the study was to better understand the behaviour of wine aroma compounds in the mouth under real consumption conditions and using real wines.
EXPERIMENTAL LAYOUT: A rosé wine of low aromatic intensity was spiked with five aroma compounds typically found in wine: esters: isoamyl acetate (banana), ethyl hexanoate (apple), ethyl decanoate (grape); a terpene alcohol, linalool (floral); and one C13-norisoprenoid, β-ionone (violets). This rosé wine was divided into three experimental wines: a control and two wines spiked with two different commercial tannins. Nine individuals took part in the study. Individuals were instructed to take a sip of wine, rinse their mouths for 30 seconds without opening the soft palate, then spit out the wine and then swallow. They had to swallow every 60 seconds for four minutes. The nose space of the individuals were monitored with a Teflon nose piece that connected both nostrils of the subjects to a proton transfer reaction-…