Results of many wine samples analysed by the Australian Wine Research Institute over the past 20 years have shown a steady increase in the mean alcohol level from 12.4% in 1984 to 14.2% in 2002. This trend stems from winemakers’ attempts to avoid unpleasant green fruit characters by leaving their grapes to hang longer as they strive for more mature flavours and tannins and softer acidity. The resultant higher sugar and hence high alcohol levels have been an unwelcome but necessary consequence of this pursuit of greater ripeness.

Alcohol Adjustment (AA)

Winemaking Tasmania has a range of equipment and expertise designed to maximise wine quality. The most recent addition to the winery is the Memstar alcohol adjustment machine. It’s a new technique based on a combination of two physical processes – reverse osmosis and evaporative perstraction.
It applies the principle of evaporative perstraction (sometimes referred to as ‘osmotic distillation’) to the permeate stream of reverse osmosis processed wine. It was invented in Australia by Wine Network Technology and is the subject of Australian and international patent applications. Winemaking Tasmania is the only licensee of this equipment and technology in Tasmania.

Why adjust wine alcohol?

High alcohol wines:

• Increase the intoxicating effect of the wine
• Lead to a reduced perception of wine aroma
• Are unpleasantly hot on the palate
• Are penalised in some export markets with extra taxes
• And in others with outright prohibition from sale

Click on the image to enlarge the diagram showing the Alcohol Adjustment process.

Getting the alcohol level right – the ‘sweet spot’ phenomenon

The ability to precisely reduce alcohol in wines has exposed the unexpected phenomenon of the alcohol ‘sweet spot’. It is a common experience for tasters to notice that when the alcohol level in a given wine is varied by as little as +or – 0.1%, significant changes in the flavour intensity and balance occur. ‘Sweet spots’ are those alcohol levels where the wine best expresses its fruit and balance. The process of finding them is sometimes compared to tuning a radio.

It is also common to find that there may be more than one sweet spot for a given wine and each of these could exhibit quite different style characteristics. For example, a Chardonnay at 14.2% may display rich, ‘New World’ qualities, but at 13.6% the flavours may be more subtle and ‘Burgundian’ and at 12.8%, possibly ‘Chablis-like’. Between these levels the wine will seem dull, harsh or otherwise unbalanced.

The Memstar AA process permits relatively small portions of wine to be treated, allowing the winemaker to determine at the outset the precise alcohol level that best suits the wine. The process can then be set to deliver this level and the winemaker can monitor the process and stop it anytime.

Memstar Alcohol Adjustment is different to all other approaches to wine alcohol reduction:

• No water is added to the wine;
• Patented reverse osmosis membrane-based process preserves flavours, tannin and colour;
• No dilution or degradation of wine quality
• No high temperature distillation
• Minimal volume losses – virtually only alcohol is removed

How the Service is offered by Winemaking Tasmania.

Our Alcohol adjustment service is fully mobile and available at short notice. The service requires no additional labour or materials other than those listed below.

Wines to be adjusted should be cellar bright (< 30 NTU) and between 14°C and 16°C

• Minimum batch size 1500 litres
• 2 X 5 pin 3 phase power outlets
• Supply of bottled food grade nitrogen
• Supply of clean fresh water
• Fork truck for unloading equipment
• All other equipment required is provided by WMT