Some of the latest experimental winemaking processes

This post relies heavily on my Cape Wine Academy Diploma in Wine lectures and papers. Here I briefly discussed four experimental winemaking processes: Reverse osmosis, Thermo-vinification, Micro-oxygenation and Reductive winemaking.

  • REVERSE OSMOSIS

Concentration of must or wine is achieved by several techniques, all of which remove water from the liquid, leaving a higher proportion of solid extracts to water in the solution. Reverse osmosis is a fine filtration process using very fine filter membranes and pressure differentials to allow water to pass out of solution. It is used on fermented wine, to raise the alcohol level by removing water. This usually takes the place of chaptalisation in climates where sugar levels are difficult to achieve, and the resulting acid levels can be unacceptably high. It is also increasingly used to lower alcohol levels in fermented wine by selectively removing the alcohol molecules.

  • THERMO-VINIFICATION

A technique of extracting colour from red grape skins, by heating the must or berries to about 70 degrees Celsius before fermentation, then pressing the grapes and fermenting off the skins. The heat releases anthocyanins, but, because the process does not allow proper maceration, it is used mostly for lower quality wine. Refinements of this technique, giving the grapes very brief exposure to temperatures of around 90 degrees Celsius, and then allowing normal maceration, are sometimes used for better quality wines.

  • MICRO-OXYGENATION

All wine needs some oxygen in the various processes, to start yeast growth in fermentation, to facilitate settling in barrel, and to develop aldehydes. Controlled oxygen exposure adds to a wine’s resistance to oxidation spoilage, and helps polymerise (bind) phenols, like tannins and anthocyanins, giving the wine a better texture and steeling the colour more permanently. Micro-oxygenation provides a means of administering precise dosage of oxygen, by dissolving microscopic bubbles in the wine through a ceramic stone element. The process has been in use since 1990.

  • REDUCTIVE WINEMAKING

Oxygen spoils wine by reacting with carbon-based substances and volatile acids, in a process that is similar to very rapid ageing. Although some oxygen is required to allow the fermentation to start, at other times it is pretty harmful, especially in delicate and aromatic white wine. Reductive processes introduce oxygen scavengers, like ascorbic acid, which consume the available oxygen in wine. Excessively reductive conditions can distort the flavour and balance of the wine, and give rise to off-odours, especially sulphur originated, like hydrogen sulphide. There is also a danger of “pinking” when bottling.