Brewing Glossary

For those reading MyBrewHome who are new to brewing, not yet brewing, or just not familiar with some of our arcane jargon, here are definitions of a few terms that appear in this blog.

Alpha Acid (AA): A class of chemical compounds found in hops, responsible for bitterness in beers. The amount of alpha acids in a particular hop is usually expressed as a percentage (e.g., 4% AA) or in “alpha acid units” (AAU). AAU’s are simply the percentage of AA multiplied by the ounces. So to add 8 AAU of hops to a beer recipe, one could add 2 oz of 4% AA hops, 1 oz of 8% AA hops, etc.

Beer Judge Certification Program (BJCP): A non-profit organization formed in 1985 that provides standards, qualifications and examinations for beer judges for amateur and commercial brewing competitions. BJCP also publishes style guidelines for beer, mead, cider and perry that are used as the standards for various styles. Website here. Current style guidelines are here.

Brettanomyces (Brett): A genus of yeast, different from ordinary brewer’s yeast (Saccharomyces). Brett imparts flavors described as “smoky”, “spicy”, “horsey/horse blanket” and “barnyard”. Originally common primarily in lambic style beers, Brett is becoming a staple in the American craft brew scene, but it is considered very aggressive and should be used with caution.

Flocculation: The tendency of yeast to drop out of suspension in a wort once fermentation is done. A highly flocculant yeast will drop out very quickly and form a thick, compact yeast cake from which the beer can easily be separated. A low flocculating yeast may stay suspended in the beer for weeks, or indefinitely in some cases unless the beer is refrigerated. No matter how flocculant a yeast strain is used, some yeast will always remain in a homebrewed beer unless it is pasteurized or filtered using specialized equipment.

International Bitterness Units (IBU): A measure of the bitterness imparted to the beer by hops. Homebrewers can estimate the amount of IBUs in a recipe based on the amount and variety of hops added and when they are added, but to measure the actual IBUs achieved in the beer requires doing some serious science.

Kraeusen (pronounced KROY-zen and also spelled krausen, or kraüsen by Spinal Tap fans): A thick, foamy head that forms on top of a wort while it is fermenting. Not the same as the head on the finished beer when it is poured, but similar in concept. Once fermentation is complete, the kraeusen will “fall” back into the beer and eventually flocculate out. A photo of an especially healthy kraeusen elicits the same feelings in the typical homebrewer as a photo from the Victoria’s Secret catalog does in the typical teenage boy.

Lauter: The process of separating the grains from the liquid wort after the mash is completed. Although commercial brewers often have a dedicated “lauter tun” separate from the mash tun to facilitate lautering with moving parts such as rakes, most homebrewers use a combined “mash/lauter tun” (or MLT for short) for both processes, with a false bottom that allows the liquid to be drained into the kettle for boiling while keeping the grain in place. See mash below.

Liquor: Any water that will become part of beer, in the mash, sparge, kettle or top-off (not water used for cleaning or cooling). Sounds much more badass than just saying “water”. Usually heated in a hot liquor tank (or HLT for short) before being added to the mash or sparge.

Lovibond (L): A measure of the color/darkness of grains, and less commonly the beer itself (the Standard Reference Method or SRM is more often used to indicate the color of the beer). Malted grains for beer vary in degrees Lovibond from around 1-2L for very pale base malts to 500L for black patent malt. Crystal malts are usually referred to by their Lovibond rating (e.g., Crystal 60L, Crystal 90L, etc.).

Mash: The process of steeping malted grain in hot water for a period of time (usually an hour) at a controlled temperature (usually between 145-155°F) to convert starches in the grain into sugar, which will be fermented later by the yeast into alcohol. This is done in a temperature-controlled vessel – either directly heated or insulated to maintain the appropriate temperature for the full hour – called a mash tun or mash/lauter tun (or MLT for short).

Must: Unfermented wine or mead. The equivalent for meadmakers and winemakers of what beer brewers call wort (see below).

Pitch: To add yeast to a prepared wort. Quite possibly the least athletic activity one can do that can be called “pitching”.

Rauch: The German word for “smoke”, usually used in the beer world to refer to malt that’s been smoked over beech or a similar wood (rauch malt or rauchmalz). Also used in the names of beers made with smoked malt, such as the traditional German Rauchbiers of Bamberg or pretty much any other style of beer the Teutonophile brewer chooses to apply it to (e.g., rauch porter, rauch IPA, rauch kriek – why not?).

Specific Gravity (a.k.a. gravity, SG): A measure of the density of a liquid relative to water (i.e., water has an SG of 1.000). Used in brewing to measure the amount of sugar in solution. SG starts high at the beginning of fermentation and drops as the sugar is fermented into alcohol. The difference between the original gravity (OG) and final gravity (FG) can be taken to calculate the alcohol by volume. Finished beer is higher, but a dry wine or mead can be lower, such as 0.996.

Swamp cooler: A budget-friendly method for controlling fermentation temperature. The fermenting vessel is placed in a larger container filled with cold water, and the water is kept cold by periodically swapping out frozen ice packs or frozen water bottles. The fermenter may be covered with a T-shirt to wick cold water up the sides and facilitate cooling through evaporation. A fan may also be added to the system to blow cold air across the fermenter.

Vorlauf: (from the German word for “recirculate” and also often called simply “recirculating” except by pretentious logophiles like myself) The first step in lautering. Some of the wort is run off into a small container, usually with lots of grain particles in it. This is poured back into the mash tun. The process is repeated, allowing the grain bed to compact more and more until the wort runs out free of particles … mostly.

Wort: Unfermented beer. A wise man once quipped, “Brewers make wort. Yeast make beer.”