Toggle navigation. Starter Kits. Kegerator Conversion Kits Homebrew Commercial. Sake Making. Food Processing Equipment Ingredients. Bar Tools. New Products. Make sure your all of your beers will have the proper bitterness using our IBU calculator. If you are like us and most other brewers, you love Hops! Whenever a brewer is using AAUs in a recipe to describe the quantity of hops, it is important to specify how long each addition is boiled. The boiling time has the largest influence on how bitter a hop addition makes the beer.
If no times are specified, then the rule of thumb is that bittering hops are boiled for an hour and finishing hops are boiled for the last minutes. Many brewers add hops at 15 or 20 minute intervals and usually in multiples of a half ounce for ease of measurement. To calculate how much bitterness the final beer will have from these hop additions, we apply factors for the recipe volume V , gravity of the boil and the boil time.
The time and gravity of the boil are expressed as the utilization U. The equation for IBUs is:. The proper units for IBUs are milligrams per liter, so to convert from ounces per gallon a conversion factor of 75 For the metric world, using grams and liters, the factor is Gravity of the Boil The recipe volume is 5 gallons. The gravity is figured by examining the amount and concentration of malt being used. Since this recipe calls for 6 lbs. But, since we are only boiling 3 of the 5 gallons due to of the size of the pot, we need to take into account the higher gravity of the boil.
It is the gravity of the boil 1. As you will see in the next section, hop utilization decreases with increasing wort gravity. The higher concentration of sugars makes it more difficult for the isomerized alpha acids to dissolve.
I use the initial boil gravity in my utilization calculation; others have suggested that the average boil gravity should be used.
The average being a function of how much volume will be boiled away during the boiling time. This gets rather complicated with multiple additions, so I just use the initial boil gravity to be conservative.
The difference is small—overestimating the total bitterness by IBUs. Utilization The utilization is the most important factor. Beers can range from 1 to about IBUs, whereby the taste threshold for most humans is roughly between 4 and 9 IBUs—different studies suggest slightly different sensitivity intervals, but all within this range.
The theoretical saturation point of iso-alpha acids in beer is approximately IBUs, which corresponds to In practice, however, this value is rarely achieved because it assumes that there are no other hop-derived resins in the beer, which is rarely the case.
IBU values measured in the wort in the brewhouse drop dramatically, and largely unpredictably, during fermentation. Measuring the true IBU value of beer requires complicated laboratory techniques such as ultraviolet light UV spectrophotometric assay or high-pressure liquid chromatography HPLC. See chromatography. The UV method is more common and can usually be performed even by small brewery laboratories, but it tends to be less accurate than the more sophisticated HPLC method, for which only large laboratories tend to be equipped.
Trained flavor panelists, too, are often able to taste and approximate IBU values in beer with reasonable accuracy. However, any strong sweetness and too many malty notes, especially in higher-gravity, more assertive beers, can counterbalance and cover up much of the bitterness and thus make bitterness assessments based purely on tasting more difficult. Regardless of how IBU values are derived, however, they do not provide information about the quality of the bitterness.
In wine, for instance, tannin content can be measured, but this does not tell anything about the smoothness, roughness, or astringency of the wine.
Likewise, low-IBU brews, such as many malt liquors, for instance, can taste rough, whereas high-IBU beers, such as well-brewed rich Russian imperial stouts, can taste smooth and velvety. Also, measured IBUs in beer, like tannins in wine, decrease as the beverage ages.
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