http://www.beerborg.com/index/hop-stand-bittering-units-hsbus/“On an episode of Basic Brewing Radio (Dec. 13, 2018) , James Spencer introduced a way for individual brewers to calculate hop bitterness that he calls Hop Stand Bittering Units (HSBUs). As he explains in the podcast this is a way to consistently estimate the amount of bitterness you get from hops when they are added as a hop stand to your wort. This formula is dependent on your process and system and is a benchmark for you as an individual brewer to determine how much bitterness you are adding to your beer across batches. Your HSBUs will be unique to you and your process and is merely a gauge for your personal use to determine hop stand bitterness. Things you also need to keep in mind when using this formula are temperature of the wort and the duration or how long the hop stand is. So a higher temperature or a longer hop stand may yield more bitterness. So if you’re trying to determine a baseline make sure that your temp and duration are consistent across batches.
According to James, the basic formula is to multiply the number of ounces or grams of hops by the alpha acid percentage then divided by the volume of wort. Let’s say you always do your hop stand at 190F (87.7C) for 30 minutes. So if you had 1 oz (28 g) of Cascade hops with an Alpha Acid (AA) of 7% that you were going to add as a hop stand to 5 gallons (18.9 L) of wort the formula would be:
English: 1 oz X 7 AA = 7 | 7 divided by 5 gallons of wort = 1.4 HSBUs
Metric: 28 g X 7 AA =196 |196 divided by 18.9 liters of wort = 10.37 HSBUs
Likewise if you had 2 oz of Citra hops with an AA of 17.5% the formula would be:
English: 2 oz X 17.5 AA = 35 | 35 divided by 5 gallons of wort = 7 HSBUs
Metric: 56 g X 17,5 AA = 980 | 980 divided by 18.9 liters of wort = 51.85 HSBUs
With this formula you can now accurately calculate the amount of bitterness you add during a hop stand to any batch of beer.
If you find that the bitterness is too much or too little you can simply increase or decrease the amount of hops for the hop stand from batch to batch until you find the sweet spot for the desired bitterness. You could also tweak the bitterness by increasing or decreasing either the temperature or duration of the hop stand.”
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