Trub or hot trub is the excess material left in the boil kettle after the wort has been transferred. Boil kettle trub typically consists of hop matter, grain fiber, tannins, and the dense proteins known as the hot break that combine during the first 15 minutes of the boil, and ultimately drop to the bottom of the kettle. It is recommended that the trub not be transferred to the fermenter, as it may impart off flavors on the finished beer.
The trub that was left over in the boil kettle after the boil took place and the wort was transferred into fermenters.
Boil Kettle Trub
Irish moss, a beer fining agent, is a blend of seaweeds used to clarify beer. It works by making the smaller molecules in the wort aggregate into larger particles and then fall out of suspension where they collect on the bottom of the brew kettle. Typically 1 tsp per 5 gallons of wort is added 15 minutes before the end of your boil.
Hot break is the clumping of proteins, solids, and tannins that fall out of the wort during the boil and eventually collect at the bottom of the kettle. A steady boil is the key to achieving a good hot break, which will typically occur 5-15 minutes after the boil begins. When the foam on top of your boil finally dissipates, you know that many of the proteins have coagulated and that your hot break has occurred. A hot break is important because it aids in removing undesirable and potentially off flavor causing tannins and compounds from the boil. It also helps improve clarity and reduces the risk of chill haze down the line.
Below is a photo of the hot break in a 20 gallon brew kettle, approximately 15 minutes after the boil first began.
Hot break, 15 minutes after the boil started.
The boil is the stage of the brewing process during which wort is boiled in the brew kettle and hops could be added. When hops are added to the boil, hop resin/alpha and beta acid isomerization occurs, which imparts bittering and hop aroma in the finished beer. A typically boil time lasts between 60 and 90 minutes. The longer the hops’ isomerization in the boiling wort, the greater the potential for bittering that exists. In addition to hop isomerization, the boil also sterilizes the wort, denaturing the enzymes that were active in the mash. The boil is also responsible for the hot break, which removes several unwanted compounds that can cause both unwanted flavors in chill haze.
Below is a photo of a boil kettle a few minutes after the boil was achieved.