Have you caught the haze craze? Up until the last decade, hazy beers were mostly seen as mistakes or unfiltered styles like Belgian and German wheats. However, since New England IPAs became popular and profitable, it seems that the less clarity your beer has, the better.
There are many ways to create haze in beer, as well as ways to prevent it. If you are aiming for a hazy beer, it is important to understand how to maximize haze formation. In this article, we will explore the role of pH in creating successful murky beers.
The Basics: What Is Beer Haze?
The type of turbidity most affected by acidity levels is called non-microbial colloidal haze. It is mainly formed by proteins and polyphenols from grain and hops and does not significantly impact the flavor and aroma of a hazy beer. On the other hand, microbial haze is caused by yeast deposits and bacteria, which can result in off-flavors.
Colloidal haze occurs when the proteins and polyphenols in the wort or beer combine and form particles that are not soluble in water. These particles scatter light, causing the haze effect. Controlling colloidal haze can be achieved by adjusting protein levels or polyphenol content. However, the pH also plays a role in maintaining a stable haze in the finished product.
Protein and Polyphenol Haze
Colloidal haze forms when proteins and polyphenols bind together to create molecules that are both insoluble in water and large enough to scatter light (known as the Tyndall effect). Although proteins make up 40-75% of the particles in haze, it is believed that reactive polyphenols trigger haze formation.
Scientists are still studying the relationship between proteins, polyphenols, and pH levels. However, experiments have shown that beer protein haze forms most efficiently at a pH between 4 and 5.5, with maximum haze formation occurring at lower pH levels and higher alcohol by volume (ABV) levels.
In a 2003 study published in the Journal of the American Society of Brewing Chemists, researchers found that maximum haze formation in wort occurred at a pH between 5 and 5.5. They also observed that a beer with 6% ABV had the most turbidity between pH 4.5-5, while a beer with 12% ABV had the most haze potential at pH 4.5.
During a presentation in 2013, Karl Siebert, a food science professor emeritus from Cornell University (one of the authors of the ASBC paper), clarified that haze formation reaches its peak just above a pH of 4 and weakens as the pH goes up or down.
How Does the Science of Haze Formation Work?
There is still much that is unclear about haze formation, but it is certain that haze indicates a lack of molecular stability. In order to precipitate out of a liquid, polyphenols need to form a stable network by cross-linking with proteins.
Polyphenols are not very soluble in water, especially at a pH above 5.5. This causes them to come together and combine with other large molecules, similar to the water-insoluble proteins called hordeins found in barley. Proteins show the least solubility in water near their isoelectric point, which is the pH at which their net charge becomes zero. The isoelectric point for hordein is above 4, which also happens to be the pH at which it precipitates most effectively with polyphenols. Therefore, it is not surprising that beer haze forms most robustly just above a pH of 4.
Mashing for Haze Formation
While you don’t usually need to manually adjust the pH of your mash to encourage haze, you can promote it by using protein-rich grains like malted oats, malted wheat, and chit malt. Unmalted barley can also help. Avoid oversparging or letting the pH of your mash become too high, as these may result in astringency. A mash pH below 5.4 is ideal.
Hot Breaks and Haze
During the boiling process, heat causes protein and polyphenolic complexes to coagulate and form a hot break. Higher temperatures and pH levels aid in coagulation and hinder haze formation. Larger coagulated particles are more likely to precipitate and form trub, which can be easily removed during whirlpool or hop-back. It is important to keep the molecules in fine flocs so that they remain dispersed throughout the liquid. After boiling, it can be beneficial to lower the wort temperature to 170-180 degrees F before adding hops during whirlpool.
Dry-Hopping for Haze Formation and Stability
Dry-hopping is an effective way to create haze and is crucial in making a hazy IPA. Hops, in their natural form (not oils), contribute significant amounts of polyphenols, similar to malts. By adding hops during fermentation, these materials can avoid getting trapped in the hot break during boiling and the cold break during wort cooling. Adding hops in the fermenter may raise the pH, but scientists are still uncertain about the exact cause. Small dry-hop doses as early as the first day of fermentation may assist in haze stability, as the protein-polyphenol interaction is optimal at the typical post-knockout pH of around 5.
Clear Data is Key for Keeping Things Unclear
While there are several factors that can affect colloidal haze stability, pH consistently influences the brewing process, from mashing to fermentation. Even if you measure the appropriate mash pH early on, it is essential to monitor pH throughout the entire process to ensure successful haze formation.