Tips & Tidbits - Chill Haze
A beer which becomes cloudy when put in the refrigerator and will only return to clear after returning to room temperature for several hours has a chill haze. This type of haze is not a result of infection or any other problem. It is a natural result of the brewing process.
Chill haze is a result of polyphenols (i.e. tannins extracted from malt and hops) combining with proteins to form particle which are insoluble when the beer is chilled and scatter light making the beer appear cloudy. When the beer is at room temperature these particles are soluble so the beer appears clear.
If we could remove all polyphenols and proteins from beer, there would be no possibility of haze. However, the beer would suffer from lack of body, no head and lack the characteristic grain and hop characteristics expected.
Reducing chill haze is a matter of reducing proteins, polyphenols or both. Proteins in the wort come in many sized. Small and medium sized proteins give the beer body and head retention. Only large proteins combine with polyphenols to cause chill haze. Proteins can be reduced by boiling vigorously to get a good hot break, making sure the pH of the boil is above 5.0, chilling well to get a good cold break, using kettle finings and using finings in the finished beer,
The most common kettle fining, Irish Moss also called “copper finings”, is added to the kettle 20 minutes before the end of the boil at the rate of 1 teaspoon per 5 gallons of wort. Irish Moss assists the coagulation and precipitation of proteins during the boil helping to create a good hot break.
Kieselsol, a proprietary name for silicon dioxide, is one of the most powerful clarifying agents available to homebrewers. Kieselsol electrostatically binds with positively charged proteins to initiate flocculation. It is packaged as Super-Kleer KC and comes with a package of Chitosan (basically a very large carbohydrate). Use after fermentation is complete as per the instructions on the package.
One of the most reliable post-fermentation fining agents for reducing polyphenols is PVPP known as Polyclar. A micronized white powder with a high surface area to volume ration, Polyclar readily absorbs polyphenols including tannins. It will also slightly reduce bitterness while lightening the color a shade. Used at the rate of at the rate of 6-10 grams (about ¼ ounce) for a 5 gallon batch. It has a tendency to foam, so allow plenty of head space. The necessary contact time is only a few hours. The beer should be racked off the sediment prior to bottling or kegging.
Gelatin Finings works on the principle of absorption where the large gelatin molecules adhere to yeast cells and other large pieces of protein material, such as those which cause chill haze, increasing their weight so they will fall out of suspension. For a 5 gallon batch of beer add ½ teaspoon of gelatin to ½ cup cool water and allow it to soak and swell for an hour. Then bring the mixture to a boil and add to the beer immediately to disburse.
Using sound brewing practices and fining agents to reduce the proteins and polyphenols in the finished beer, should allow you to produce clear beers without a chill haze.