Sunday, September 27, 2015

Overview: Haze & Improving Beer Clarity

Describing what beer clarity is, how its defined and measured and the potential causes of haze or clarity problems in beer.

When Clarity Matters
Crystal clear beer is a goal for many beer styles. Commercial brewers go to great lengths to assure the clarity and stability of their finished beers. However, clarity does not always matter. For darker beers like Browns, Porters, Bocks, and Stouts, clarity is not as important, so we see many haze producing malts and adjucts added – since you won’t notice them in the finished product. Some beers are even intentionally hazy, such as hefe-weizen which is served with yeast intentionally mixed in – either by storing kegs inverted and turning them before serving, or bottle conditioning and serving them with the sediment.
Understanding and Measuring Haze in Beer
Haze in beer is nothing more than suspended particles that reflect light. The most frequent sources of haze are from yeast cells, proteins and polyphenols (tannins), but bacteria, foreign material, and even excessive finings can all contribute to haze in finished beer. Beer haze is measured using a Radiometer haze meter, a special device that shines light through a sample of beer and measures the intensity of the light reflected off particles in the sample at a 90 degree angle, typically on an EBC scale.

Even a high quality haze meter has its limitations due to a phenomena called “pseudo-haze”. Pseudo haze is when you have haze that is detectable by a haze meter, but may not be visible to an observer. Pseudo-haze is caused by small particles that reflect light but don’t affect the clarity of the finished beer.

The term “turbidity” is used to describe the particles that are visible, and pseudo-haze is the difference between the haze measured by the meter and the “turbidity” actually visible in the finished beer. Pseudo-haze can be a real problem for commercial brewers who want to consistently measure and control the haze stability of their beer.

Types of Haze in Beer
There are two major types of haze in beer. The first is a chill haze, which often occurs at near freezing temperatures but disappears as we warm the beer. The second is a permanent haze, which is simply present all the time. Chill haze, however, can be a major concern even for beers served at warmer temperatures since chill haze will often become a permanent haze over time as the beer matures.

Potential Causes of Haze in Beer
The vast bulk of effort in controlling clarity in a finished beer is focused around proteins and polyphenols (tannins) which primarily come from malt and hops. These will be covered in detail in part 2, but these two ingredients are the cause of most chill haze as well as permanent haze issues in a finished beer. A secondary concern is suspended yeast, which often contributes to clarity issues when a beer is young. While yeast does not often contribute to permanent clarity issues, some steps are needed to assure that yeast falls out of the beer quickly after fermentation.

The other causes of haze which are less common include:
  • Calcium deficient worts (causes Oxalates)
  • Wheat derived adjuncts (causes Pentosans)
  • Inadequately modified malt (Beta-glucans) – though very uncommon with modern malts
  • Dead bacteria from an infection
  • Damaged or overstressed yeast (Induces carbs and proteins)
  • Lubricants, excessive finings or other foreign material in the beer

That’s a quick overview of measuring haze and the major causes of clarity issues.

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