Fining Agents, Isinglass, Chitosan, Bentonite
Fining is the action of removing particles that make a haze in wine by combining them with materials that bind to them and force them out of suspension, leaving the wine clear and bright. It not only improves a wine’s appearance; it also makes sure that it is stable. Stable means that it won’t change if appearance, taste, aroma, or chemical composition while in storage. Winexpert uses three primary types of fining agent in its wine kits.
The isinglass we use is a by-product of a food fishery done in South America. The fish in question is a fresh water species of whitefish, technically known as a 'Cichlid'. The swim bladders are harvested and dried, and later shipped to North America. Here they are purified, dried again with liquid nitrogen, pulverised to a powder, and then mixed into a low-pH solution to be used as finings. The whitefish used to make isinglass is a scaled fish, rather than a shellfish. Winexpert white and blush kits are usually supplied with isinglass.
Even though the raw material in Chitosan is derived from shellfish, the way it is processed completely destroys all proteins. Proteins are the compounds that cause the allergic reaction in human beings, so if there are no proteins, people will experience no reaction.
The shells are ground to a fine powder and soaked in sodium hydroxide (essentially lye, the same ingredient in oven cleaner that breaks down proteins in the material on the wall of a dirty oven). This material is processed three times to achieve the grade that we use as a fining agent. This process degrades all of the protein in the shells.
What is left is actually a part of the Sucrose Polymer family, a long-chain polysaccharide that is a form of sugar so complex that it resembles polyester more than actual table sugar. Chitosan is derived from chitin extracted from ocean shellfish, the same organic material that makes up fingernails and human hair. As a fining agent, it works by a process of molecular adsorption. This is where the Chitosan has an electrical charge that attracts oppositely charged particles clouding the wine, binding them and pulling them out of suspension.
Chitosan is also used as a food additive and dietary supplement. It is so safe that it is currently used in water treatment facilities across Canada and the world.
Bentonite is a type of clay, known as aluminosilicate. Its technical name is Montmorillonite. It’s found with various minerals attached to it, such as sodium, calcium and magnesium. It was originally found in Fort Benton, Wyoming (where the name came from). It’s used in winemaking, beauty treatments, mineral extraction, water treatment, and kitty litter.
When used in winemaking, it is stirred into the wine to remove proteins and other haze causing particles. It works through adsorption. This means that it attaches itself to a particle, and together they are too heavy to stay in suspension, falling to the bottom of the carboy, leaving the wine clear and stable. Bentonite settles out so completely that it does not leave any residue of taste or colour behind.
Some wine kit companies (like Winexpert) add their bentonite on the first day, and some add it after fermentation. This is one of the fundamental differences between kits that you may have noticed. The reasons behind it go beyond technology, straight into winemaking philosophy.
When bentonite is added on the first day, it disperses through the wine and most settles to the bottom within a few hours. At the end of 48 hours, however, the bentonite is back in circulation. This is because of the process of gas nucleation that the CO2 in the wine is undergoing.
As the yeast ferments the sugar, it converts it into carbon dioxide (CO2) and alcohol. The bubbles of gas don't actually appear out of nowhere: they want to come out of suspension on some kind of point, where a nucleus of gas can form the beginning of a bubble. thus, we get the term 'nucleation'. This point could be a scratch in the carboy, a bit of grape material, or a particle of bentonite. The bentonite is surrounded by a bubble of gas and floats up to the surface of the wine. When the bubble bursts, the particle of bentonite drops back down to the bottom of the carboy, all the time working to adsorb the other particles clouding the wine. In this way, the bentonite is circulated around the wine continuously for days, doing its job.
When bentonite is added to a wine kit post-fermentation, it does not have the advantage of the CO2 lift that it would get during fermentation. Therefore the winemaker is obligated to stir it through the wine repeatedly, ensuring the thorough dispersal.
In addition, because the bentonite will quickly settle out before it can effectively clear the wine, significantly more is needed when used post-fermentation. Winexpert kits typically use 10 or 15 grams of bentonite, while some companies use up to 80 grams! Not only does this amount cause the formation of a deep, loose sediment bed; it also has the effect of stripping the wine.
Finings are considerably more powerful than most people suspect. With a sufficient dosage of finings, it is actually possible to strip a red wine to the point where it becomes 'white'. Too much fining can lead to a stripping of colour and flavour, making it necessary to formulate much darker and stronger wine kits to compensate. By adding the bentonite on the first day, we are allowed to make the formulation much closer to the desired finished wine, without extra additions or manipulation.
Written by Phyl on April 19, 2011.