THE CLARIFICATION PROCESS
Unstable proteins or solids such as yeast particles could create a haze in the wine, white wine could be brown due to oxygenation and red wine could be way too bitter and astringent. Clarification is here to help winemakers create a stable appealing product through different procedures.
SEDIMENTATION
Sedimentation is the easiest clarification process of them all. Suspended particles precipitate on their own by keeping wine still. This normally happens when wine is matured in wood and progressively racked into other vessels in order to remove lees and solids.
Although not costly in terms of equipment needed it is expensive in terms of time, labor and space: barrels are expensive to buy, maintain and keep, they take a lot of space and require proper storage conditions and labor to move around.
Solids also take a long time to naturally precipitate. Some winemakers decide to use only sedimentation in order to clarify a wine but this decision usually fits ultra-premium, higher level wines due to the costs and reasons outlined above.
Centrifugation could be used in order to clarify large volumes of wine quickly.
Although not widely used due to equipment and maintenance costs it is a great choice for big, established vineyards who need to make the best out of time and return on investment.
FINING AND FILTERING
What even are fining and filtering? They are both part of the post-fermentation clarification process.
Fining works by adding a substance that binds to specific proteins, color compounds or flavors to speed up the precipitation of suspended material and filtering unwanted elements while providing stability against the formation of hazes in the bottle.
Filtering works by passing wine through a filter medium that captures molecules larger than the size of the filter pores.
They both clarify a wine although fining focuses on protein stability and removing tannin, off- color or off-flavors while filtering focuses on microbial stability and aesthetic reasons such as a more polished, refined wine.
FINING
Fining components must be used in minimum quantities otherwise they could strip wine of wanted characteristics.
Egg whites are gentle, can remove harsh tannins and clarify a wine. It is a really popular method among high quality pinot noir producers.
Gelatin can be used to remove bitterness, astringency and browning in a white wine although bentonite is the most widely used option for the latter.
Vegetable proteins from potatoes or legumes are available to produce vegetarian or vegan wines with no allergens.
DEPTH FILTRATION
Filtration is further divided into depth filtration and surface filtration.
Depth filtration works with a porous filtration medium that can be made up of a single or multiple layers with depth and traps particles within its structure by mechanical retention, by adsorption or electric charge. It can cope with fluids with many particles in them and does not block easily although it is not an absolute filter: if filter is old or pressure is too high some particles will go through it. Diatomaceous Earth (DE) and sheet filters are the most common options.
DE works by using processed diatomaceous earth as a medium to clarify. Wine is sucked by a vacuum from the outside of a rotatory drum, trough DE, to the inside of the drum. It works really well for very thick and cloudy wines, comes in different particles size therefore can remove a wide range of solids from smaller particles to bigger yeast matter and it is an oxidative method due to oxygen presence involved in the process although the machine could be flushed with inert gas to avoid oxidation. The machine needed is really expensive while DE is not but must be properly disposed adding to costs.
Sheet filters are pads or sheets of filters used to clarify wine. The more sheets used the faster a wine can be clarified. The system involved requires an initial investment and trained workers to operate the machine but pads are not expensive.
SURFACE FILTRATION
Membrane filters are generally absolute filters with precisely defined maximum pores sizes able to provide ‘sterile’ filtration. Sterile filtration refers to completely clearing a wine before bottling by removing microbes and yeast particles for stability. The initial investment is small but filters are really expensive and an on-going investment.
Due to the small size of pores, wine must be pre-filtered before otherwise the filters will clog. Cross-flow filters or tangential filters allow a wine to pass through while cleaning the surface of the filter as it works. They can clarify a wine really quick taking on heavy loads of solids or lees, don’t need any replacement but the initial investment is high therefore this method works well for large, well- established wineries.
Any of these techniques are highly personal as a winemaker might decide to use all or none. Some believe that filtration can negatively impact a wine stripping its flavors, aromas and texture while others argue how a wine will recover soon after filtration and even improve in the bottle due to an increased stability.
As a wine lover I truly appreciate to see the difference in style and winemaking techniques all over the world. That sense of terroir and personality is what I seek the most and is what gives wine a truly authentic character.