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Showing posts from December, 2017

New thiol-enhancing yeast strains with low VA production

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By Karien O'Kennedy
The study had two aims: 1 - To evaluate hybrid yeast strains from the Nietvoorbij culture collection for their ability to enhance volatile thiols and produce low volatile acidity, and 2 - To investigate the expression of wine yeast proteins and to determine if regulated proteins correlate with metabolites released. This article summary will focus on the first objective of the study.
Basic project layout:
Fifteen hybrid strains (Saccharomyces intra-genus) were compared with six commercial wine yeast strains: Anchor VIN 7, Anchor VIN 13, Anchor N96, Zymaflore X5, Zymaflore VL3 and Fermicru 4F9.Fermentations were conducted in 21.9°Balling S. blanc juice in stainless steel canisters.Samples were taken every 48 hours during fermentation for basic chemical analysis.Volatile aroma compounds were identified and measured by GC and GC-MS/MS.Wines were sensorially evaluated by a 14 member expert panel.
Results: The project delivered many results but only some are highlighte…

To ferment hot, or not...

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By Karien O'Kennedy
The main aim of this study was to determine if it is indeed necessary to ferment at low temperatures to achieve the optimal balance between fruity and green varietal characters in S. blanc and whether chemical and sensory data correlate for the attributes high fruitiness / low greenness.
Project layout: Two different S. blanc juices from the 2008 vintage (results only published in 2017) were fermented with four different yeast strains: EC1118, Zymaflore X5, Enoferm M2 and L-1528.Fermentations were conducted at 12.5°C and 25°C in 750 ml bottles.Basic chemical analysis was conducted using a Foss WineScan spectrometer.Volatile compounds were analysed using a GC-MS.A trained sensory panel consisting of 11 students were used for sensory analysis.
Results: Only EC1118 yeast fermented to dryness. This is in accordance with the manufacturer’s temperature range recommendations (10 – 30°C).All three the other yeasts got stuck at 12.5°C as the minimum temperature recommendati…

Effect of global warming on vines

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The aim of this project was to determine what the combined effect of elevated temperature and Carbon dioxide (CO2) levels are on vines, over multiple seasons.
Project layout:  -An open top chamber (OTC) facility was established in a mature Shiraz vineyard in Australia; -An elevated CO2 and elevated temperature treatment could be applied to the chamber; -The effect of elevated temperature and CO2 could be studied individually and the experimental design also studied their interaction; -The treatment simulated what climate is expected to be in 2075, namely a 2°C increase in temperature and an increase of 650ppm CO2 in the air; -Phenology and leaf physiology/photosynthesis were studied; -Data was collected over three seasons.
Results -Higher temperatures alone affected phenology from the first season of the trial. Phenology was significantly advanced; -Elevated CO2 levels alone, only started affecting phenology in the third season of the trial. -The combination of higher temperatures plus higher C…

Late pruning and its carry-over effects

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The aim of this project was to determine if delayed pruning can be used as a tool to delay maturity. The study also assessed the carry-over effects of repeated late pruning on phenology, yield, leaf area and berry composition.
Project layout: A commercial vineyard site in Barossa was used. The trial was conducted over four consecutive seasons where the effects of three different times of pruning were compared to each other. 1.Winter (Control) 2.Budburst 3.2-3 leaves emerged
Results -Where vines were pruned at 2-3 leaves emerged, total soluble solids in grapes reached 12 Baumé 7 days later than the control in the first three seasons. In the last season, with this treatment, 12 Baumé was reached 14 days later; -Vines pruned at budbreak reached maturity in-between the control and the 2-3 leaves emerged treatments; -Late pruning did not effect yield in three seasons, but increased yield in one season; -Leaf area index at harvest in the 2-3 leaves emerged treatment was greater than or similar to t…