Ch. 15: Finishing Flashcards
Finishing
Clarifying and stabilizing the wine for bottling. Finishing may also include other checks and actions; for example, to correct the level of dissolved oxygen and SO2 in a wine.
Clarification
All processes that are used to make a wine clear. These can include sedimentation, centrifugation, fining, and filtration.
Sedimentation
When wine is stored in a cool cellar, particles with higher density than the wine fall to the bottom of the container. The wine can then be racked off, leaving the sediment behind. Some winemakers believe that clarification by sedimentation avoids potential loss of texture and flavor that might occur if the wine is fined and filtered, and so for some premium wines, this is the only way that the wine is clarified.
Sedimentation takes time, which adds to its cost. Thus, sedimentation is usually only suitable for premium and super-premium wines. For wines that are barrel aged, sedimentation is part of the aging process.
Centrifugation
A rapid clarification process that spins the wine at high speed to clarify it. This can allow early bottling. Because of the high initial cost, it is usually used for high-volume wineries.
Fining
Fining is a procedure in which a fining agent is added to speed up the process of the separating solids from the wine. It removes microscopic particles too small to be removed from filtering, and helps clarify the wine and stabilize it agains hazy formations later in the bottle.
As fining can also remove desired components from the wine or make the wine unstable when too much is added, it is important to add only the minimum effective amount.
Colloids
Microscopic particles in wine that can be removed with fining, but are too small to be removed by filtration. They can potentially make the wine cloudy or hazy if not removed.
Fining agents
Clarify wine by attracting colloids with the opposite charge, binding with them, and forming a solid large enough to be removed by racking or filtration.
There are 3 categories of fining agents:
* those that remove unstable proteins
* those that remove phenolics that contribute to undesirable color or bitterness
* those that remove color and off-odors
Bentonite
A fining agent for unstable protein. It is a form of clay that binds to unstable proteins and color matter. It has minimal effect on flavor and texture. It produces large amounts of sediment, and so wine is lost when it is racked off. Bentonite can also be used to clarify must.
Egg white
A fining agent that removes harsh tannins. It tends to be used for high-quality red wines because it removes harsh tannins and clarifies the wine. It is an allergen so must be declared on the label in some regions if it is above a specified limit. It is not suitable for vegan wines.
Gelatine
A fining agent extracted from pork that removes bitterness and astringency in red wine, and browning in white wine. It must be added in the smallest effective amount because it it is easy to over-fine, stripping out flavor and character, and creating a risk of hazing later. Not suitable for vegan wine. Can also be used to clarify must.
Casein
A fining agent derived from milk that removes browning from white wines. Must be declared as an allergen in some countries. Not suitable for vegan wines. Can also clarify must.
Isinglass
A fining agent derived from fish bladders. It is a protein collagen that very effectively clarifies white wines, giving them a bright appearance. The minimal effective amount must be used to avoid a fishy odor and hazing later. Not suitable for vegan wines.
Vegetable protein fining products
Fining agents derived from potatoes or legumes, and suitable for vegetarian and vegan wines.
PVPP
An insoluble plastic powder fining agent that removes browning and astringency from oxidised white wine. It is genlter than charcoal.
Filtration
The most common way of clarifying wine, it involves passing the wine through a filter that traps solid particles, leaving behind a clarified wine.
Depth filtration
One of the two main types of filtering. This method traps particles in the depth of the material that forms the filter. It is effective for wine with a lot of particles, such as wine that has just been pressed, or lees. It is not an absolute filter as some particles can make it through the filter under certain circumstances.
Diatomaceous earth
The most common form of depth filtration, it is inert silica used as a filter medium for a rotary vacuum filter. Wine is sucked by vacuum from the outside of a rotary drum, through the DE, to the inside of the drum.
This method is used to filter very thick and cloudy wine, and is oxidative. It can remove large (lees), or very small particles (yeast).
Costs include the initial investment, and disposing of used DE.
Sheet filters
A depth filtration system where the wine is passed through a sheet of the filtering material. The more sheets there are in the filter, the quicker the wine can be filtered.
Costs include the initial investment, although the cost of filter sheets is low. Trained employees must operate the machines.
Surface filtration
One of the two main types of filtering. A surface filter stops particles that are bigger than the pore size of the filter. They are absolute filters. Membrane and Cross-flow filters are the two types of surface filters.
Membrane filters
A type of surface filter, they are slower than depth filters with small pores, so the wine must be pre-filtered first. They are usually used as a final precaution immediately before the wine is bottled to ensure that the wine is completely clear and mircobiologically stable. This is sometimes called Sterile filtering. Yeasts and bacteria are reliably removed using this method.
The initial investment is small, but the cartridges are expensive and need to be replaced. This is a very common form of filtration during the bottling/packaging process.
Cross-flow filters
A type of surface filter, they allow the wine to pass through the filter while uniquely cleaning the surface of the filter as it works. Solid particles cannot pass through the filter. They can filter with a high load of particles or lees very quickly. There are no replacement sheets, cartridges or earth to buy or dispose of.
The machines are expensive, making the more suitable for large wineries.
Stabilisation
Refers to several winemaking interventions which prevent unwanted effects in the finished wine, such as hazes, deposits, and browning.
Tartrate stability, fining, and filtering all contribute to clarification AND stabilisation.
Protein stability
Proteins in white and rose wines can form hazes in the bottle. Fining with bentonite stabilizes protein.
Tartrate stability
Tartrates are harmless deposits of crystals that can form in a finished wine. Although they are harmless, they can be considered a fault by some wine drinkers. All high-volume winemakers will stabilize tartrates to prevent the crystals from forming.
The options for tartrate stability include:
* Cold stabilization
* Contact process
* Electrodialysis
* Ion exchange
* CMC (Carboxymethylcellulose)
* Metatartaric Acid
