Fining Wine: An Introduction to Wine Clarification
“Cloudy with some heavy precipitation, turning fine in the late afternoon.” This sounds like a weather report doesn’t it? Yet these are often terms you would come across during the wine clarification and stabilization process.
During these processes, matter that is insoluble and suspended in the wine (such as yeast cells, bacteria, proteins, and a number of others) are removed before bottling. This process is often referred to as "fining wine" since certain fining agents are used to achieve this removal of matter.
Clarification procedures in winemaking fall into two distinct groups.
- Artificial Clarification
- Natural Sedimentation
This process is called ‘fining’ in the wine world.
Fining is further defined as:
‘When a substance is added to juice or wine to interact with certain constituents and precipitate them out. They can then be separated from the juice or wine at a later stage’’
What is fining? And why do it?
Fining agents are added to juice or wine to lower the concentration of the compounds that may otherwise adversely affect the sensory properties of the wine.
They can be added to:
- Clarify the wine to remove hazes or cloudiness, make them visually appealing.
- Remove hydrogen sulphide or other taints.
- Remove bitter flavors
Unfortunately most, if not all, the fining agents remove some of the desirable aroma and flavor compounds in the wine. For this reason, it is essential that the process of fining wines is carried out at the lowest rate possible to achieve the desired result.
The desired result will be from the perceptions of winemaker and they will determine what is best for the wine using ‘fining trials’.
How does fining work?
The process of fining is often quite complicated.
- Bond formation
- They may be electrical (charge) interaction
- Absorption and adsorption
Absorption - Is where something takes in another substance.
Adsorption - Is the accumulation of molecules on the surface of a material.
For example, a positively charged fining agent like gelatin will attract negatively charged tannins in the wine. This new compound becomes neutralized by these two opposing charges and will precipitate or (float down) to the bottom of the wine vessel.
What are the main fining agents?
The main fining agents used in winemaking can be classified as:
- Organic protein based e.g. gelatin, albumen, casein and isinglass
- Inorganic fining agents e.g. carbon and ferrocyanide
- Clarifying Agents e.g. bentonite clay
Organic Protein Based
All these fining proteins come from natural sources. The process of making additions to wine in this way, is similar to how we add milk/cream to our coffee and tea. It removes some of the bitterness and makes them more creamy and round to taste.
Albumin is a major constituent of egg whites. A single egg white has about 3-4 grams of active proteins and is the most preferred source of albumin used in fining wine. Where does other albumin come from? Animal blood.
Albumin is a gentle fining agent and is usually used on dry red wines, but it can be quite destructive on red wine coloring, so it must be used very carefully. During the albumin preparation, the whites must be kept completely fresh and not be allowed to foam up. Albumin is not only used for clarifying wines but for also improving the effect of the wine, this can make the wine appear rounder and softer in the mouth.
Gelatin and Isinglass
Unlike albumin, gelatin and isinglass are products derived from collagen and collagen is the protein that makes up the fibers of connective tissue such as tendons and skin.
- Gelatin is collagen from animals like pigs, cows and chickens and sourced from their bones, skin and connective tissues.
- Isinglass is the collagen of sturgeon fish, the collagen is usually sourced from the swim bladder, but can also come from its skin and structural tissues too.
Gelatin and isinglass are both totally water soluble, so they can be used to clarify white wines and be used to reduce astringency. However, gelatin can strip wines of their fruity character, so the smallest amounts are used. Isinglass is used mainly in fining white wines to expose fruit characters. Isinglass does not affect tannin levels as much and helps with clarification, but there is the risk of the wine smelling ‘fishy’ when used in excess!
Milk and Casein
Casein is the protein in milk and there are several types of milk fining materials that can be used:
- Potassium caseinate is water-soluble. In general it is used to remove undesirable aromas, to ‘bleach out’ the colors and to clarify white wines in particular.
- Skim milk - Skim milk is the most gentle of all the casein products and it provides a more delicate fining than casein alone
- Whole milk - Whole milk will leave cream on the top so usually a skim (trim) milk is preferred. Whole milk is then mixed up with water and slowly added to the wine.
Casein performs much less aggressive fining than gelatin and has minimal effects on the aromas and flavors in the wine. It can be used in white wines to reduce oxidized colors (browning) and oxidized flavors. Milk, trim or skimmed, is closely related to casein but is far more delicate.
Inorganic Fining Agents
Carbon and potassium ferrocyanide are two inorganic fining agents that are typically used in commercial winemaking.
Carbon is most often used to clarify grape juice that is affected by high concentrations of botrytis or ‘bunch rot’.
And…carbon can be used to change red wines into white wines!
This results in almost the complete loss of character in the finished wine. This happens because carbon will remove phenolic compounds, especially the smallest phenolic compounds. Because it can remove the smallest of compounds ‘wine stripping’ is a huge problem.
It removes both the color and aromas from wines and because carbon also contains a large quantity of oxygen, oxidation usually follows carbon additions.
The agent used in sometimes called “blue fining”. Potassium ferrocyanide fining are used on wines, due to certain metals being used in wine production.
This ‘metal contamination’ with wines will happen either:
- Directly from winery equipment
- Accidentally by the addition of excess copper or iron particles, when winemakers are attempting to remove faults like hydrogen sulphide.
The wide use of stainless steel in modern wineries makes contamination from metal much less of a problem, but although it’s an uncommon occurrence, it is still possible. If there is copper contamination occurring, it will appear as a white/blue sediment in the wine.
The reason great care is required is that the ferrocyanide ion can break down, this can then free up the cyanide.
Yes. Extremely toxic, nasty business.
Blue fining is illegal in most countries, including the USA, but it is still legal in Australia and New Zealand.
Diatomaceous earth (DE) is used to clarify wines and make them appear clear. They are then ready for even finer filtration, like the pre-bottling filtration process. Although DE is not specifically regarded as a fining agent, it does have a specific use in clarification and filtration.
Bentonite clay for example is inexpensive and the most common fining agent. But as with the other fining agents, the down side to using this, is that it will remove or reduce the flavor and aroma compounds from wine.
Most wines will naturally clear on their own. However if the wine has fermented at a high temperature or has a bacterial population that is quite high, it is unlikely these wines will clear all by themselves.
- Red wines in particular have a better chance to clear with brilliant clarity.
- The lower the sugar content in the wine, the more effective the sedimentation process.
- This process of letting wines naturally clear over time, can take weeks, months or over a year.
Got some of your own juice or wine?
If you are experimenting with juice or wines of your own and you’re worried about whether it will clear naturally over time, you can try one of the fining agents above as they are quite easily accessible.
How do I do it?
The two golden rules for fining are:
- NEVER add a fining agent to your juice/wine without doing a trial on some small samples first.
- If there is not a positive difference to the wine, then don’t bother.
This basic procedure should be followed every time fining is carried out. It’s easy and lots of fun!
Separate off three samples of juice.
Label one as your control, leave this one alone. The other two samples will be a high addition and the other a low addition of the agent you’re going to add.
Prepare the fining agent as directed at a high and low concentration.
Add each concentration to each sample.
Allow time to settle (this may vary), then gently decant away the top layer of clear juice or wine off the top of the container, leaving the sediment at the bottom. This is process is called ‘racking’ or ‘racking off’.
After you have you have completed the trials, pull out the control sample and make an assessment of what you can see, smell and taste.
Fining is empirical, this means the amount of fining agent used is not directly related to the amount of wine constituent you want to remove from it. There is no exact quantity to add to it, therefore the trials are the only way find the optimum fining rate in a given wine or juice.
Factors that will affect a fining agents success
- The temperature of the wine or juice being fined is critical. Most fining agents used in wine will settle down more effectively with warmer temperatures of more than 15°C / 59°F and ideally closer to 20°C / 68°F
- The correct preparation of the fining agent prior to the adding it in. Many commercial preparations will come with specific directions for its use in juice/wine. Follow these for the best results.
- Thoroughly mix the fining agent in for it to be successful.
- The settling time will vary with the nature and temperature of the juice/wine. If the objective is to improve the clarity of the wine, time will be the most important factor in allowing this to happen. If you start racking the juice/wine off the fining too soon, you will leave much of the particles still in suspension. Your wine will look even worse!
Don’t be afraid to do some trials on your wine or juice, this is part of what winemakers do all the time.
The goal is ultimately to make a positive difference, so if you think someone you know could help you decide on what is best or at least give you some insight, invite them round to try your samples! Discuss the pros and cons of the addition.
Remember, someone is always responsible for the final decision, so make sure it’s the best one!