This is is part 2 of the recipe formulation basics. Here is part 1.
Bitterness is more difficult to measure then gravity. To do it correctly the beer needs to be analyzed by a laboratory. For most home brewers, that is not going to happen. However, there are a number of mathematical formulas that can give the home brewer a good prediction of what the bitterness actually is in the beer.
Terms to know:
- Alpha Acid percentage: percentage of alpha acid in the individual hop cone
- Alpha Acid Unit : percentage of alpha acid in a given sample of hops by the weight in ounces of that sample. One ounce of hops with an alpha content of 1% contains 1 AAU
Bitterness in a beer is measuered in International Bitterness Units: measure of the actual bitterness level of beer. 1 IBU=1 part per million of isomerized alpha acid.
Two of the most popular formulas for estimating IBU are from Jackie Rager and Glen Tinseth. Each uses the hop weights, volume of beer, hop utilization, and hop alpha acid percent. Both are more complicated then can be analyzed here, but the brewer can here or here or any number of other sites. There are also many websites available to do all the calculations for the brewer without worrying about all the annoying math.
The bitterness is important because the goal of the brewer is to make a beer that has a good balance between the hops and the malt depending on the style.
Color, like bitterness, is best measured with laboratory equipment. Again, there are formulas available that can give the home brewer an expected color range for the beer. However, these are even more of an approximation then the bitterness measurements and vary greatly from brewer to brewer. The simplest way to calculate color unit (CU) is to multiply the weight (in pounds) of each malt in the recipe by the malt’s color rating. Add all the figures and divide by the size of the recipe in gallons.
The color of beer is based on the color of the malt used and is measured in Lovibonds or with the equivalent Standard Reference Method (SRM). Both of these are usually provided by the maltster. One formula for estimating color gives the Malt Color Unit (MCU) is good for paler beers: MCU = (Weight of grain in lbs) * (Color of grain in degrees lovibond) / (volume in gallons). The other more complicated formula is good for darker beer: SRM color = 1.4922 * (MCU ^ 0.6859).
In this case a recipe calculator can estimate this automatically for the home brewer. In fact, a good recipe program like BrewMate (free) or BeerSmith ($21.95) can calculate all this information for the brewer’s recipe.
All the talk of recipe formulation is preparation for moving to the next level of brewing. However, while it may seem overkill for a simple 5-gallon patch of pale ale made with extract, it helps the brewer understand all that goes into beer and make better beer, even with just a simple extract recipe.
For questions, queries, cheers, or jeers contact Ryan at firstname.lastname@example.org.