Ch. 15: Finishing

Question 1

Finishing

Answer 1

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.

Question 2

Clarification

Answer 2

All processes that are used to make a wine clear. These can include sedimentation, centrifugation, fining, and filtration.

Question 3

Sedimentation

Answer 3

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.

Question 4

Centrifugation

Answer 4

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.

Question 5

Fining

Answer 5

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.

Question 6

Colloids

Answer 6

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.

Question 7

Fining agents

Answer 7

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

Question 8

Bentonite

Answer 8

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.

Question 9

Egg white

Answer 9

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.

Question 10

Gelatine

Answer 10

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.

Question 11

Casein

Answer 11

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.

Question 12

Isinglass

Answer 12

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.

Question 13

Vegetable protein fining products

Answer 13

Fining agents derived from potatoes or legumes, and suitable for vegetarian and vegan wines.

Question 14

PVPP

Answer 14

An insoluble plastic powder fining agent that removes browning and astringency from oxidised white wine. It is genlter than charcoal.

Question 15

Filtration

Answer 15

The most common way of clarifying wine, it involves passing the wine through a filter that traps solid particles, leaving behind a clarified wine.

Question 16

Depth filtration

Answer 16

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.

Question 17

Diatomaceous earth

Answer 17

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.

Question 18

Sheet filters

Answer 18

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.

Question 19

Surface filtration

Answer 19

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.

Question 20

Membrane filters

Answer 20

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.

Question 21

Cross-flow filters

Answer 21

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.

Question 22

Stabilisation

Answer 22

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.

Question 23

Protein stability

Answer 23

Proteins in white and rose wines can form hazes in the bottle. Fining with bentonite stabilizes protein.

Question 24

Tartrate stability

Answer 24

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

Question 25

Cold stabilisation

Answer 25

A method used for tartrate stability. The wine is kept at 25F for around 8 days so that crystals form before bottling and can be filtered out.

Costs include equipment and energy to refrigerate the wine. Colloids need to be removed by fining before this process, otherwise, they could prevent the crystals from forming.

This method only removes the more common potassium bitartrate, not calcium tartrate.

Question 26

Contact Process

Answer 26

A method used for tartrate stability. Potassium bitartrate is added to the wine to speed up the crystallization process. Wine is usually cooled to around 32F for one or two hours, and that tartrates are filtered out.

This is a quicker, more reliable, and cheaper form of cold stabilization.

Question 27

Electrodialysis

Answer 27

A method used for tartrate stability. This process uses a charged membrane to remove potassium, calcium ions, and tartrate ions.

The initial costs are high, but the overall costs are lower than cold stabilization. It is faster and uses less energy.

Question 28

Ion exchange

Answer 28

A method used for tartrate stability. This process does not remove tartrates, but instead, replaces potassium and calcium ions with hydrogen or sodium ions. It is not allowed in some regions because of health effects of sodium.

Question 29

CMC (Carboxymethylcellulose) acid

Answer 29

A method used for tartrate stability. This cellulose is extracted from wood and prevents tartrates from developing into a visible size.

Because it is cheaper than chilling it is widely used on inexpensive white wines. It is not suitable for red wines as it reacts with the tannins, making it ineffective, and causes haze.

Question 30

Microbiological stability

Answer 30

Wines with Residual Sugar can potentially begin re-fermenting in the bottle. To prevent this, yeasts can be removed through sterile filtration.

Very few microbes can live in wine due to its low pH and high alcohol levels. Exceptions are lactic acid bacteria, acetic acid bacteria, and Brettanomyces (a spoilage yeast).

Lactic acid bacteria can be a problem if the wine has not gone through malolactic conversion, causing the process to happen in the bottle and producing cloudiness. The solution is to make sure that MLF is complete, or filtering out the bacteria.

For Brettanomyces, wine can be filtered or treated with DMDC (Velcorin) before bottling, which inactivates Brettanomyces.

Question 31

Tartrates

Answer 31

Colorless crystals that form in the bottom of the bottle. They naturally occur when triggered by low temperatures and are harmless. However, some consumers see them as a fault, so most inexpensive and mid-priced wines are stabilized before bottling .

Question 32

Cork taint

Answer 32

A moldy, wet cardboard smell, loss of fruitiness, shorter finish. Cork taint is caused by natural corks creating compounds such as TCA.

It can be prevented by cleaning the corks with steam, using technical or synthetic closures, rigorous quality control to discover and remove TCA, and including an inexpensive polymer barrier between the cork and the wine.

Question 33

Oxidation

Answer 33

The result of excessive exposure to oxygen, either in the winemaking process or because of faulty bottling, poor quality corks, or keeping a wine that is not meant to age for too long.

This causes premature browning, loss of primary fruit aromas and flavors, and vinegary aromas.

Question 34

Volatile acidity

Answer 34

Excessive amounts of VA give a pungent smell of nail polish and/or vinegar.

This is caused by acetic acid bacteria, inadequate levels of SO2, and excess oxygen exposure.

This can be reduced by sorting out damaged grapes, good hygiene, topping up wine vessels, careful racking (to avoid too much oxygen exposure), and maintaining adequate SO2 levels.

Question 35

Reduction

Answer 35

Sulfur-like odors, from struck match or smoke to onions to rotten eggs. Some of these odors are desired and can add to complexity. Rotten egg smell is always considered a fault. These are caused by high levels of volatile, reductive sulfur compounds.

Sulfur compounds can be caused by yeast under stress (lack of nutrients, oxygen, wrong temperature), exclusion of oxygen during aging in closed vessels, especially aging on lees.

Reduction can be avoided by making sure yeast has sufficient nutrients and oxygen, and that the must is at an adequate temperature. SO2 may need to be lowered.

Question 36

Light srike

Answer 36

Caused by light reacting with some wine compounds, forming volatile sulfur compounds. This leads to dirty drain odors.

Prevention includes keeping wine away from sunlight or other light sources, and using dark bottles.

Question 37

Brettanomyces

Answer 37

Off-aromas, including animal, spicy, and barnyard. It small levels, this can add complexity, but is considered a fault at higher levels. Brett also decreases fruit flavors and makes acidity and tannins more prominent.

Once a winery is infected by Brett, it is hard to get rid of. It can be present in old or new barrels.

Key ways to avoid Brettanomyces are:
Excellent hygiene
Effective SO2 levels
Low pH levels
Keeping the period between the end of fermentation and ML conversion quick so that SO2 can be added ASAP.

Question 38

List the 7 wine faults

Answer 38

Tartrates
Volatile acidity
Cork taint
Reduction
Light strike
Oxidation
Brettanomyces