When you pour a wine into your wine glass and hold it up to a light we are fascinated by the clear and beautiful red color of the red wines or vibrancy of a white wine. This clarity is the results of having all suspended particles removed from the wine. Vintners use filtration processes to remove most of the suspended matter from wines but some suspended particles are too small and get through the filter. These materials that cannot be removed by filtration are removed using a fining agent. Finings are added to wines during various stages of the wine making process. Let’s start at the beginning and define what a fining is.
A fining is a substance that is added to the wine or beer to remove organic compounds. The items that are removed that affect the clarity of wines are generally proteins, polyphenols, sulfides or benzenoids. When I homebrew beer I add Irish moss, a fining agent, during the last 10-15 minutes of the boil process. This removes the proteins that cause a beer to be cloudy.
Benefits of adding finings to wine:
– Reduces harsh or bitter flavors.
– Reduces unwanted aromas.
– Removes browning pigmentation caused by oxidation.
– Promotes the fall-out of yeast cells after fermentation.
– Removes permanently suspended particles.
– Adds luster or polish to a wine’s appearance.
So how do these finings clarify our wines or beers? Filtering removes most of the suspended solids but not all. There are suspended solids that are very fine and are not captured by the filtration process. If a fining were not used, a bottle of wine stored for a period of time would form a fine layer of solids on the bottom of the bottle. Adding finings attract these materials to form larger solids with higher densities than the liquid allowing them to fall and collect on the bottom of the cask or fermenter prior to bottling. The mechanism that attracts these fine suspended materials in the wine or beer to the fining is an electrochemical where oppositely charged particles are attracted to one another forming a stable complex which has a neutral charge. This stable complex of material forms either a floating or settling mass depending on its density compared to the wine or beer. Most have higher densities and sink to the bottom.
There are also absorbent types of finings such as activated carbon. Carbon filters are used in the flow during transfer and removes benzenoid compounds which would otherwise create an unwanted sweet scent due to aromatic hydrocarbons. The carbon filters also remove polyphenols which are hydrolyzable (water soluble) tannins.
Below is a list of common finings used commonly today:
– Bentonite – Used in wine as a clarifier. Causes yeast cells and excessive tannins to fall out of suspension. Also reduces harshness in the wine’s aroma and lightens its color.
– Sparkolloid – Used as a topping agent following Bentonite or on its own in white and blush wines. Reduces proteins that can causes haze in lighter wines. Adds brilliance to a wine’s appearance.
– Gelatin – Primarily used in red wines where the presence of tannins are required for it to settle out completely. Reduces harsh flavors and aromas from the wine.
– Kieselsol/Chitosan (Kitosol 40) – Used together they clarify and polish a wine’s appearance.
– Isinglass – Not effective in clearing out heavy cloudiness in a wine. Used primarily as a final polish.
As we can see, chemistry is a very important part of wine production. Various fining agents or substances provide the ambiance when looking through a glass of red wine toward a light and seeing the brilliance of the red color along with the clarity of the wine. Giving the wine a swirl and placing it to your nose you get the beauty of what the vintner intended from the terroir and fine fruits that the wine is composed of, a beautiful aroma with clarity and brilliance of color.