Alpha Acid

Alpha acids have a mild antibiotic/bacteriostatic effect against Gram-positive bacteria, and favor the exclusive activity of brewing yeast in the fermentation of beer. Alpha acids are responsible for the bitter flavor in the beer.

The degree of bitterness imparted by hops depends on the degree to which otherwise insoluble alpha acids (AAs) are isomerized during the boil, and the impact of a given amount of hops is specified in International Bitterness Units. Unboiled hops are only mildly bitter. On the other hand, the (non-bitter) flavor and aroma of hops come from the essential oils, which evaporate during the boil. Hop resins are composed of two main acids: alpha and beta acids.
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Alpha Acid Unit (AAU)

AAU = (hop alpha acid %) x (hop weight in ounces)

Smart Brewer Calculated Original Gravity (COG)

This is the Calculated Original Gravity measured by Smart Brewer. Unlike the the "Actual Original Gravity" entered by the user the Calculated OG is determined based on the fermentables of the recipe and the final size of the recipe. Each fermentable has a different potential gravity. The Calculated Original Gravity is determined purely by math. The size of the final batch, the efficiency of a given brew system and the potential gravity per gallon for each fermentable (referred to as "potential" or ppg) all contribute to the Calculated Specific gravity.

Note: Smart Brewer grabs the potential from each fermentable in a recipe, calculates the weight of the fermentable compared to the total weight of all the fermentables, compares the size of the batch and finally the efficiency to produce this number.


Traditionally, cohumulone (R=isobutyryl) has been considered to add a harsh, unpleasant bitterness to beer, and so low-cohumulone varieties were considered more desirable for brewing purposes; most noble hops have relatively low cohumulone. For this reason, cohumulone is often the only alpha acid identified specifically by hop producers. Cohumulone is indicated as a percentage (by weight) of the total alpha acid content of a hop.
However, recently the role of cohumulone has been called into question, as new high-alpha hop varieties that are also high in cohumulone have come onto the market which are considered to impart a good bitterness.
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Efficiency defines the "efficiency" of a given brew system. There are two components to brewing efficiency. The first component is the "process" of brewing. This would include the length of mash, the temperature(s) of the mash, the gap setting on the grain mill (if it's an all grain batch using only grain), and the sparge process. The second component is the "equipment" you are using while brewing. This includes your hoses, mash tun, sparge tank and brew pot. To determine the efficiency you first need to calculate the ideal Original Gravity based on the fermentables in your recipes. The difference beteen your "Actual Original Gravity" and your "Ideal Original Gravity" is your efficiency. This should not be confused with your "Calculated Original Gravity" that takes into account for your efficiency. No brewing system is 100% efficient. Smart Brewer defaults at 75% efficiency if no efficiency is entered when submitting a recipe.

Final Gravity (FG)

Final gravity (FG), sometimes called Terminal Gravity, which is a measure of the specific gravity of the fermented beverage. (FG is the "sugar after fermentation" measurement.) Typically, FG is measured only once fermentation is completely finished - that is, all of the fermentable sugars have been turned into ethanol.
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In colloid chemistry, flocculation refers to the process by which fine particulates are caused to clump together into floc. The floc may then float to the top of the liquid, settle to the bottom of the liquid, or can be readily filtered from the liquid.

I.E. the GREATER the cloudiness the LESS the flocculation rate. The greater the number of dense clumps the clearer the beer. -ajk Credit to: Wikipedia: Flocculation


Humulene is thought to lend the distinctive "noble" character to noble hops; most varieties traditionally considered noble are high in humulene, while many bittering hop varieties have very low levels. The noble character is strongest when the hops are used in dry hopping or late hop additions; if boiled for longer periods, humulene lends the finished beer an herbal or spicy character.
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Malt Color Units

The simplest equation for estimating the color of beer is to use Malt Color Units (MCU). A malt color unit is defined to be simply the color of each grain times the grain weight in pounds divided by the batch volume in gallons. If more than one grain is used, the MCU color is calculated for each addition and then added together. This malt color unit equation provides a good estimate of color in SRM for beers that are light in color (SRM color < 10.5).
MCU = (grain_color * grain_weight_lbs)/volume_gallons -- Good for beer colors < 10.5 SRM
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Original Gravity (OG)

Original Gravity is the density of beer prior to fermentation and after the boil. This is also the measurement made AFTER any addition of water to increase the final volume of the batch. A typical Original Gravity (OG) might be described as 1.050. High alcohol recipes will have a higher Original Gravity (OG).