Identifying and preventing protein haze
NOTE: White wines should almost always be fined for proteins.
Protein haze in white wines
Proteins are an issue in white wines. (In reds, there are more tannins and other phenols, and proteins precipitate in conjunction with these molecules.) If you don’t fine a white wine for proteins, you run the risk that these molecules (which are completely dissolved in the early stages of the wine) will gradually make longer and longer chains in the bottle. They can form a light, fluffy, stringy sediment that instantly breaks up and swirls into motion when you move the bottle. This does nothing to enhance the appearance of the wine. Consumers will usually return a commercial wine with this problem.
If you are unsure whether your wine is going to be susceptible to protein haze, heat a sample to 80°C for 30 minutes. After cooling, look for signs of haziness. Fining for proteins is sometimes called “hot stabilization.”
Fining for proteins
Kit wines often fine for proteins by adding bentonite to the juice at the start of the fermentation. This works, but you can also fine for protein later, usually when the wine is already fairly clear from racking. Bentonite is the traditional fining agent, because it has a negative charge to off-set the usual positive charge of proteins. Bentonite breaks the association of the protein molecules with water, attracts them, and helps them to precipitate.
Many home winemakers today use the Gelatin/Kieselsol fining combination that was developed in Germany for white wines. (Spagnol’s supplies a convenient package of the ingredients that is sufficient for one 23L carboy), but you can buy ingredients in bulk and the instructions are on the bottles. This combination is usually much easier to use than Bentonite. You always add the Gelatin first and a minute or two later the Kieselsol. The Kieselsol attracts the proteins and the gelatin helps both to precipitate out.
Prepared by Rod Church, September 3, 2005.