Money Saving Tips – Hops Utilization Factor

Sunday, November 2nd, 2008

Minimizing costs and maximizing beer is a wonderful thing to put into practice. This post discusses the idea of getting more bittering potential from hops. With hops going for $32/pound this is worth paying attention to.

Alpha acids in hops are isomerized into bitter flavors during the boil. The utilization factor is a number that expresses how easily and completely this process takes place. Higher utilization translates into a higher amount of international bittering units (IBUs). The utilization factor decreases as the boil gravity increases. This means the more sugary your wort is, the less bittering you will get per ounce of hops. Therefore by lowering the gravity of the boil it is possible to stretch hops bittering quality.

This tip really only applies to extract brewers who are able to add fermentable sugars in a more flexible manner than all-grain brewers who need a full wort boil. All grain brewers do not suffer from such setbacks in hops utilization because their wort boil gravity is essentially what the original gravity of the recipe is. Most extract books say to add all the dry/liquid malt extract at the start of the boil to 3 gallons of water, then dilute to five gallons afterwards. This hurts the hops bittering potential!

The basic procedure to get your wort gravity down is to use half of your extract for the entire boil at the time the bittering hops are added. With 15 minutes to go (usually after 45 minutes of boiling), add the rest of the extract to bring up the gravity to where the recipe calls for. This will sanitize the extract and sufficiently integrate it into the wort before cooling.

You can see this in action by playing with this website’s IBU calculator.

Let’s consider an example: a simple lager with 2 oz of Hallertauer hops, Alpha Acid rating of 3.9, boiled for 60 minutes, no other hops additions.

In the case of an extract batch with an original gravity of 1.055 for a 5 gallon batch, but only boiling 3 gallons, we get 18.53 IBU’s.

If we tell the calculator the boil gravity was only 1.028 (half the sugars), we get an IBU rating of 27! For calculation purposes we get close to what we would see with a full wort boil (enter 5 gallons for boil size and 1.055 for gravity) and it comes out to around 25.

A 38% increase in hops bittering potential is pretty good. That translates into a 38% savings in the cost of our bittering hops. It also means more bitter beer which a lot of home brewers really like – including the author!

Note: this practice may throw off the style of beer your batch fits into by boosting bitterness beyond where it needs to be. It will also allow you to make your next IPA much more bitter for the money. IPAs are particularly expensive to make these days because they call for 2x-3x hops, and about half of that is for bittering.