In Processing

It all started in the mid eighteen hundreds, when a gentleman with the name of Antonin Prandtl, invented the first dairy centrifuge in order to separate cream from milk. At that stage he was working (probably with some sort of butter addiction) for himself and not for Cadbury’s…

The principle was “refined” by Gustaf de Laval in 1879 who demonstrated the first continuous centrifugal separator, making its commercial application feasible. But what exactly is a centrifuge, and how can it add value to the wine industry?

A centrifuge is a piece of equipment which is driven by an electric motor that puts an object or liquid in rotation around a fixed axis, applying a force perpendicular to the axis. The centrifuge works using the sedimentation principle, where the centripetal acceleration causes denser substances (like yeast cells, grape particles, fining agents, etc.) to separate out along the radial direction. By the same token lighter objects (juice or wine in this case) will tend to move to the top. The net result thus, a very efficient separation of solids and wine.

Centrifugation technology has become so advanced over the years that it is considered a superior method for winery solids management and eliminates the need for unnecessary handling of wines and juices (with all its detrimental effects and risks like exposure to oxygen and consequent product losses & quality), e.g. several racking’s and pre-historic filtration actions.

I believe it is important to give compliments where it is due. A very fine piece of technology is the STS family of centrifuges. This is a superior method for optimal wine recovery from grape solids, fermentation lees and fining lees with negligible dissolved oxygen pick-up during the separation process, which was considered the major downside ages ago.

 So what exactly happens? Quite simple: Dirty liquid goes in, it is separated, and crystal clear liquid comes out…and of course solid matter or sludge that has the density of peanut butter at a moisture level of 95%.

In a few conversations with winemakers who use this technology, the following advantages came up: 1) Reduced juice and wine losses, associated with racking, filter aid adsorption, or even or de-sludge actions of older or under-performing centrifuges. 2) Reduced juice and wine quality “downgrades” .This classically happens where existing lees handling processes lead to the loss of quality as a result of oxygen pick up, or contamination, or human error. This of course may lead to a loss of freshness, loss of varietal integrity and character, or even reductive taints from prolonged exposure to lees. 3) Eliminating DE (diatomaceous earth) filtration, principally the lees Filter and Rotary Drum Vacuum filter not only reduce the amount of juice and wine handlings, but is also associated with direct hard savings in reduced DE consumption which also have health and auditing benefits. Occupational Health, Safety and Environment considerations of DE and the ability to proactively demonstrate a major reduction in DE usage in the cellar is an intangible benefit. 4) A key advantage over the older centrifuges is the very low oxygen pick-up, which is as low as 0.02 mg of oxygen per litre of wine. This means the same wine can be centrifuged multiple times during its maturation cycle, without the detrimental effect oxygen may have on particularly white wines. 5) If all the technical benefits are weighed, then it is also a no-brainer to see that the application of this technology also builds a very strong business case, and the immediate effect on the bottom line.

Key applications include clarification of: White juice from recently pressed grapes – cold-settled juice lees – white wines after primary fermentations (including yeast lees) – white wines after bentonite finings (including bentonite lees) – bentonite lees – stuck or sluggish ferments – late harvest and botrytis wines where primary fermentation must be stopped – Red wine after primary ferment (including gross lees) – gross red lees – red wine after malolactic fermentation – wines after cold stabilization – cleaning of wine with in-line cross-flow).

Forgive me if I start to sound like a STS representative… but I am just wondering if all directors or all big cellars know how much money can be saved on the bottom-line if the “optimal” technology or equipment is being used “optimally”…

Bertus Fourie is a winemaker, turned Enology lecturer and creator of the Barista coffee Pinotage.


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