haze

Haze is visible turbidity in beer or wine, a suspension of fine particles that clouds what should be a clear or translucent liquid. These particles scatter light, creating the characteristic cloudiness that signals either a process fault or a stability problem. While some styles tolerate haze by design, most commercial beers and wines must meet strict clarity standards, and haze is often grounds for rejection at quality gates or in the finished product.

The particles causing haze come from several sources. Protein-polysaccharide complexes form during fermentation and cooling, especially when mash pH or boil temperatures are not controlled tightly. Starch particles may remain if the grain bill was too high or the mash was undersparked. Yeast cells themselves can cause transient haze if they do not flocculate fully. Oxidized tannins and oxidized hop compounds create chill haze, which appears when beer cools but may disappear on warming. Metal ions like iron or copper, even in parts-per-billion quantities, accelerate oxidation and haze formation.

Chill haze and permanent haze

Chill haze appears below 50 degrees Fahrenheit and vanishes when beer warms; it is caused by tannic polyphenol complexes that precipitate in cold. Brewers can test for chill haze by cooling a sample to near freezing and examining it. Permanent haze, by contrast, does not clear on warming and indicates either colloidal instability, microbial infection, or irreversible particle formation. Both damage shelf life and brand perception, but only permanent haze signals a fundamental quality failure.

Prevention depends on the source. Proper mash temperatures (145 to 158 degrees Fahrenheit for most single-infusion brews) and sparging with slightly acidified water reduce protein and starch carry-over. Lengthy boils and vigorous whirlpool action settle heavier particles before cooling. Chilling rapidly through the trub layer and holding at cold temperatures for 24 to 48 hours before packaging allows proteins and tannins to drop out. Additives like isinglass (collagen derived from fish bladder) or pea protein can bind fine particles and accelerate settling. For wines, bentonite clay or gelatin serve the same purpose.

Haze measurement is routine in quality labs. Nephelometry and turbidimetry quantify cloudiness in nephelometric turbidity units or formazin turbidity units (FTU). A value above 1 FTU is typically considered hazy by beer standards; wines may tolerate slightly higher levels depending on style. Spectrophotometry at 430 nm wavelength is also used. The choice of test method matters because suspended particle size distributions vary widely, and some methods catch finer particles than others.