Posts

Showing posts from November, 2017

Substituting must with green harvested wine or water to produce lower alcohol wines

Image
By Karien O'Kennedy
The aim of this study was to investigate two blending strategies to produce lower alcohol wines and comparing it to wines produced from earlier consecutive harvest time points. The study focussed mainly on the polysaccharide and tannin content of the resulting wines as these two parameters are associated with mouthfeel, astringency and perceived hotness. No sensory results were published in this study.
Project layout: Cabernet Sauvignon grapes were harvested in 2015 at four consecutive dates resulting in wines with alcohol levels ranging from 11.4% to 18.2% (control).Cabernet Sauvignon grapes were harvested at about 8°Brix and fermented with EC1118. The resulting green harvest wine (GHW) had an alcohol of 4.5% and pH of 2.76. Fermentation was sluggish but completed due to the very low pH being inhibitory to yeast.Juice from the control harvest was substituted from 10 - 14% of either GHW or water - yielding alcohol levels of approximately 17%, to up to 30 – 40% - …

Suphur free red wines through the use of grapevine-shoot extract

Image
This is a follow-up study to determine the effectives of grapevine-shoot extract as an alternative to sulphur dioxide (SO2) to preserve wines.
Project layout: Shiraz grapes were harvested and fermented to dryness in Ganimede fermenters. No SO2 was added at crushing. After completion of malolactic fermentation the wine was divided into three batches. 50 mg/l SO2 addition50 mg/l total stilbene content Vineatrol addition (VIN-50)100 mg/l total stilbene content Vineatrol addition (VIN-100)
Wines were stabilised for eight weeks at 0°C, racked, filtered and bottled under synthetic closure. Wines were stored at 16°C, relative humidity of 80% for 12 months. Wines were chemically and sensorially analysed after 12 months.
Results: The VIN wines had better colour and more stable colour pigments on analysis than the SO2 treated wine. The VIN-50 wine was similar in quality to the SO2 treated wine. The VIN-100 wine scored lower on sensory analysis than the SO2 and VIN-50 wines.
Significance of …

Sauvignon blanc: The effect of pre-budburst temperature on phenology, flowering, fruit-set and bunch composition

Image
In this study, researchers focused on the effect that temperature during winter dormancy and budburst has on the timing of key phenological stages as well as inflorescence primordia and grape composition.
Project layout Individual Sauvignon blanc grapevines in a commercial vineyard were heated for different periods of time from mid-winter (July) to budbreak (Oct). Treatment 1: Heating 1 July to budbreak (mean daily temp about 2°C higher than control) Treatment 2: Heating July only Treatment 3: Heating 1 August to budbreak Treatment 4: Control Buds and inflorescence structures on shoots, at every position along the cane were monitored during the whole growing season.
Results -Heating during dormancy had no effect on the number, or position of inflorescences on a shoot; -Heating during dormancy decreased the presence of side bunches. The presence of a tendril in lieu of a side bunch increased, especially higher up on the shoot. -Heating during July to budbreak and August to budbreak advanc…

Deficit irrigation of Cabernet Sauvignon to save water

Image
The objective of this study was to develop alternative deficit irrigation management strategies for wine grapes and to determine the impact of these strategies on water saving, crop yield, fruit composition and plant response.
Project layout: -The trial was conducted for four years in a 14-year old block of Cabernet Sauvignon in California, on well drained, sandy loam over clay soil; -The growing season was divided into three periods: 1.Budburst to fruit-set: No irrigation applied 2.Fruit-set to three weeks post fruit-set: 75% of calculated crop water use (ETc) was applied in all treatments 3.Three weeks post fruit-set until harvest: Irrigation resumed when leaf water potential reached -1.2MPa in one of three sustained deficit irrigation (SDI) treatments: a.LOW 25-35% of ETc b.MEDIUM 50% of ETc c.HIGH 65-75% of ETc -Grapes were harvested at 25°Brix and subsequent analysis done.
Results: Yields in the MED and HIGH treatments were more than in the LOW treatment.There was however no difference in yi…