Terms & Concepts Defined (K-O)

Knockout - when the heat of the boil is turned off, also called flameout.

Kraeusen - (kroy-sen), the foamy head of deposits that builds up on top of the wort during fermentation, especially at the top of the fermenter or carboy.

Lactose - an unfermentable sugar that comes from milk and is sometimes added to stouts, hence, milk stout. See Dextrins and Saccharides.

Lager - one of the two basic types of beer (see Ale). Lager is fermented using Saccaromyces pastorianus, sometimes referred to as a bottom-fermenting yeast. This yeast can remain active at temperatures below 39°F. It also attenuates saccharides more slowly, causing the brewing process to move more slowly, and that allows for a clearer, cleaner brew, often associated with a crisper taste. It has a lower tolerance to alcohol, so the finished beers tend to have lower ABV values. Lagers also go through an additional step, that ales do not, called cold-conditioning (storage at cold temperature), and that develops more clarity by allowing more of the yeast, proteins, and hops to settle out of the lager. In general, lagers tend toward clear appearance with light and crisp flavor. See Top Fermentation.

Lauter - to strain or separate. Lautering acts to separate the wort from the grain after the mash via the vorlauf step, filtering and sparging.

Lauter Tun - a vessel specially designed for lautering. See MLT.

LME - liquid malt extract.

Lovibond - original scale to measure beer color is called degrees lovibond and was created by Joseph Williams Lovibond (1885).While beer color is now measured by the Standard Reference Method (SRM), Degrees Lovibond are still used to measure malt color. See Calculating SRM.

Lupulin Gland - small, bright yellow nodes at the base of each of the hop flower petals, which contain the alpha-acid resins used in brewing.

Magnesium [Mg] - the magnesium ion is a necessary yeast nutrient at low levels, but barley wort contains sufficient magnesium for the yeast. It also can help lower mash pH, but not as efficiently as calcium, and it is not flavor neutral in larger amounts. More than 40 ppm contributes astringent bitterness, and yet higher levels tend to have a laxative effect. A magnesium range of 10 ppm to 30 ppm for the wort is preferred.

Magnesium Sulfate - commonly referred to as Epsom Salt, lowers mash pH, but not as effectively as calcium sulfate or calcium chloride. If the source water is low in magnesium (less than 10ppm), magnesium sulfate can be used to bring it up within the range of 10 ppm to 30 ppm. Addition of this salt also raises the level of sulfate, so watch the chloride-to-sulfate ratio.

Maillard Reaction - a browning reaction caused by external heat wherein a sugar (glucose) and an amino acid form a complex, yielding certain flavors, darkened pigments and melanoidins. Takes place when toasting/kilning grain and during the boil, especially high gravity boils. (Not to be confused with caramelization of the sugars).

Malt - Malted grain. See Malting Process.

Maltase - an enzyme utilized by the yeast that catalyzes the hydrolysis of the disaccharide maltose and trisaccharide maltotriose into simple glucose components.

Malt Extract - concentrated and/or dried sugars (saccharides) extracted from malted grains, basically a concentrated wort. Brewing malt is the highest grade. Malt extract comes in two forms, liquid/syrup (approx. 20% water) and dry powder (approx. 4% moisture). Four pounds of dry malt extract (DME) equals roughly five pounds of liquid malt extract (LME). See Malting Process.

Malting Process - the malting process soaks the grain in warm water up to the point that the grain starts to germinate, releasing the enzymes that breakdown the starches of the endosperm into sugars (saccharides). That process is then halted by drying the grain, preserving the starches and enzymes for the brewer to use for making wort that's rich in fermentable sugars. Three stages: steeping, germination, kilning. 1) Steeping initiates malting by providing water and oxygen to the seed embryo. Steeping also hydrates the starches surrounding the embryo, facilitating its partial breakdown by hydrolytic enzymes during germination. 2) During germination stage, maltsters are concerned with barley respiration activity, vegetative growth, production of hydrolytic enzymes and their effect on the starches of the endosperm. 3) The green malt, after achieving target germination level, is transferred to a kiln to dry the germinated grain, halt the enzymatic actions, and develop desired colors, flavors and aromas. After the target kilning is achieved, the malted grain is cooled to room temperature to fix the color, flavors and aromas, and to prevent further enzyme deterioration.

Maltose - the most abundant sugar molecule (saccharide) in malt. A disaccharide, maltose consists of two bonded glucose molecules, the preferred food of brewing yeast.

Maltotriose - a sugar molecule (saccharide), a trisaccharide that consists of three bonded glucose molecules.

Mash - the hot water (hot liquor) steeping process that promotes enzymatic breakdown of the grist into soluble, fermentable sugars (saccharides). See Hydrolytic Enzymes.

Mash-out - Some brewers perform a mash-out at the end of mashing, consisting of raising the mash temperature to 170F before lautering. This step stops all of the enzyme action to preserve the fermentable sugar (saccharide) profile. For most mashes, the mash-out is not needed.

Mash Tun - a vessel specially designed for mashing. See MLT.

Mash pH - The pH level in your mash, wort, and beer affects processes from enzyme function to hop extraction to yeast vitality. Different enzymes required in the mash function at different optimum pH levels, but a happy medium is achieved between pH 5.2 and 5.6. This means healthy yeast, which also perform well at a pH of about 5.5. Proper mash pH also affects hop extraction rate in the boil, facilitate proper protein precipitation, clarification of the wort, and color pick-up, and ultimately affect the flavor of the beer. See Post-fermentation pH.

MCU - Malt Color Units used for calculating SRM, the color of the finished beer. See Lovibond and Calculating SRM.

Melanoidins - strong color and flavor compounds produced by browning Maillard reactions.

MLT - a mash/lauter tun, a vessel specially designed for the dual purpose of both mashing and lautering.

Monosaccharide - a simple sugar, a one molecule saccharide, that cannot be hydrolized to give a simpler sugar.

OG - original gravity describes the concentration of malt sugar (saccharides) in the wort prior to fermentation. The specific gravity of water at 59F is 1.000. Typical worts range from 1.040 to 1.080 after the malt has been extracted and dissolved prior to fermentation.