Filtering wine to make it clear is a crucial step in the winemaking process. It removes any particles or substances that may affect the appearance, taste, and stability of the wine. There are several methods and techniques used to achieve this, including fining, which I will delve into further in this answer.
Fining is a popular method for clarifying wine, and it involves the use of fining agents that bind to the unwanted particles in the wine and facilitate their removal. One commonly used fining agent is bentonite clay. Bentonite is a type of clay with excellent fining properties. It comes in the form of a fine powder that is mixed with water to form a slurry. This slurry is then added to the wine, where the clay particles attract and bind to the unwanted molecules, such as proteins, tannins, and phenols. These bound particles then settle to the bottom of the vessel, allowing for easier removal through racking or filtration.
I have personally used bentonite clay in my winemaking endeavors, and it has proven to be an effective fining agent. The process involves thoroughly mixing the clay with water until it forms a smooth, thick slurry. The slurry is then slowly added to the wine while stirring gently to ensure even distribution. After adding the bentonite, the wine is left undisturbed for a period of time, usually a few weeks, to allow the fining process to take place. During this time, the clay particles attract and bind to the unwanted particles, gradually clarifying the wine.
Another commonly used fining agent in winemaking is egg whites. you read that right! Egg whites are a traditional and effective fining agent that has been used for centuries. The proteins present in egg whites have the ability to bind to and remove unwanted particles in the wine. To use egg whites as a fining agent, they are first separated from the yolks and then lightly beaten. The beaten egg whites are then added to the wine and gently stirred in. Over time, the proteins in the egg whites coagulate and form larger particles that attract and bind to the unwanted molecules, ultimately clarifying the wine.
While I personally haven't used egg whites as a fining agent in my winemaking, I have witnessed its use in professional wineries and have seen the positive results it can achieve. It is worth noting that for those with egg allergies, alternative fining agents such as clay-based fining agents or vegan-friendly options like activated charcoal or pea protein can be used.
In addition to fining agents, there are other methods of filtering wine to achieve clarity. Filtration is a common technique used to physically remove particles from the wine. It involves passing the wine through a filter medium, such as diatomaceous earth, cellulose pads, or membrane filters. The filter medium acts as a barrier, trapping the unwanted particles while allowing the clarified wine to pass through. Filtration can be done using various equipment, such as plate and frame filters, cartridge filters, or crossflow filters. Each method has its advantages and considerations, depending on the desired level of filtration and the characteristics of the wine.
It is important to note that fining and filtration are not mutually exclusive, and winemakers often employ both techniques in combination to achieve the desired clarity. Fining agents can help remove larger particles and molecules, while filtration can further polish the wine by removing any remaining smaller particles.
Filtering wine to make it clear involves various techniques, with fining being a popular and effective method. Bentonite clay and egg whites are commonly used as fining agents, with each having its own unique properties and benefits. Filtration, whether through diatomaceous earth, cellulose pads, or membrane filters, can also play a vital role in achieving clarity. Ultimately, the choice of filtering method or combination of methods depends on the winemaker's preferences, the desired clarity level, and the characteristics of the wine being produced.