Carrageenans are extracts of marine algae (seaweeds) used in the brewing of some beers to remove materials that could potentially cause hazes in the finished beers. The carrageenans consist of a family of polymers of polysaccharides found at levels of 2%–7% in red seaweeds. The three main carrageenan-producing seaweeds are Chondrus crispus (commonly known as Irish Moss), Euchema spp., and Gigartina spp. Furcellaran (or Danish agar) is a compound related to carrageenan extracted from the red seaweed, Furcellaria jastigiata. The carrageenans are used in brewing to remove hot- and cold-break proteins from wort and other proteins that would eventually cause hazes in chilled beer. The opposing electrical charges on carrageenans (negative) and wort proteins (positive) lead to interactions that form unstable gels, resulting in the formation of sediments that are separated from the main body of the wort. Carrageenans are natural products and subject, therefore, to biological variability. Consequently, carrageenans are often blended together to produce a consistent product. Carrageenans for use in brewing are described as copper or kettle finings and aid the brewer by reducing wort boiling times (energy saving), reducing “trub” collection time, reducing trub losses, and improving beer stability and filtration performance.
Irish moss and formulated carrageenans are sometimes used to enhance the effectiveness of fining (clarifying) beer with isinglass. In this situation the carrageenans are known as “auxiliary finings.” Because the carrageenans have a similar electrical charge to that of the yeast cells they assist in creating the yeast-isinglass matrix and facilitate a more effective sedimentation process.