Using Hop Extracts for Beer Brewing

Hop extracts have the potential to revolutionize many aspects of both commercial and home brewing. While bittering extracts have been used for many years by large commercial brewers, we are now seeing a new generation of hop extracts entering the craft and home brewing markets.

Types of Hop Extracts

Hop extract typically consists of concentrated hop oils. The first hop extracts centered around concentrating and preserving alpha acids – as these provide the bulk of the bitterness in beer. By concentrating the oils it is possible to preserve them longer than a season which allowed hop growers and commercial brewers to preserve excess production from one season to the next. The highly concentrated oils also take up less space.

At the top level there are three basic types of hop extracts. The first called CO2 extract. CO2 extraction is a method for extracting and preserving the alpha acids along with many of the hop oils in a concentrated form that can be used much like the original hops. You can think of CO2 extract as simply concentrated hops. They are most often used in the boil, and behave much like hops would in the boil except they are concentrated to a level of 35-70% alpha acid.

A second type of hop extract is called Isomerized extract or ISO-extract. Isomerized extract (often called Isomerized Kettle Extract or IKE) also contains alpha acids but these have already gone through the transformation that takes place when we boil hops – called isomerization. You can think of these almost like pre-boiled hop extract. The isomerized alpha acids add bitterness directly to the beer, so you can add these at any stage in the brewing process. Isomerized alpha acids are most often used after fermentation to adjust the bitterness of a finished beer. You can even add them at bottling time “to taste” to get the flavor you want. These too are highly concentrated – often containing 50-70% alpha acid.

A third, and newer type of hop extract is hop oil extract. Hop oil extracts are typically distilled and concentrated to preserve the delicate hop oils we associate most often with whirlpool or dry hopping. Hop oils most often focus on the four major essential hop oils (Myrcene, Humulene, Caryophellene and Farnesene), but specific hop oils can now be bought that emphasize a particular single oil or flavor. Care needs to be taken when purchasing and using hop oils to make sure you get the oils you want and also the proper dosage, as it can be easy to “over-do” it.

Using CO2 Hop Extract

The most widely available hop extracts for home brewers are CO2 extracts. These include popular products sold under brand names such as “Hopshot”, “Hop Jizz”, and commercial CO2 hop resins sold in 100 ml cans. For home brewers, these are often packaged in 10 ml syringes, with dosages measured in milliliters. While alpha content can vary, the most popular brands have an alpha content of approximately 60-65%. CO2 extracts preserve much of the original hop aroma, and are a suitable replacement for traditional hops.

CO2 extracts are not isomerized, so you need to boil them just like regular hops to get bitterness. To estimate the bitterness added, you can treat them as a regular hop addition with an alpha content equal to their alpha concentration. For the popular brands this is 60-65% alpha, so I might add a new “Hopshot” hop entry with 65% alpha acid to develop a recipe.

For simplicity you can use the approximate density of 1 gram for 1 ml of hop extract. So adding 1 ml or 1 gram of 65% alpha extract boiled for 60 minutes to a 1.050 OG beer gives around 10 IBUs depending on your exact equipment losses and equation used.

Using Isomerized Hop Extract

Isomerized hop extract requires no boiling and adds bitterness no matter where it is added in the brewing process. Most often it is added after fermentation to adjust the bitterness of a finished beer, but it can be added post-boil or even earlier. When adjusting your beer you can even add it “to taste”. One disadvantage of isomerized hop extract is that it does not include much in the way of hop aroma, so you need to consider other aroma products or use iso-extract as a supplement to regular hops. Isomerized extract is also relatively expensive compared to hops or other extracts.

Again, for home brewing we are dealing most often with a few milliliters of hop extract, and isomerized alpha content of 50-70%. However the utilization of this alpha acid is 100% since the alpha acids are already isomerized.

Version 2.3 of BeerSmith will include calculations for this , but basically you can estimate the alpha content directly by calculating the IBUs added. Recall that 1 IBU is 1 mg/liter of alpha acid, and since we have 100% utilization of the alpha acid we can calculate alpha acid directly (approximating density 1 ml = 1000 mg):

IBU = (extract_vol_ml * alpha_content_pct * 1000) / (volume_beer_liters)

So for example 1 ml of 60% iso-alpha extract in a 20 liter (just over 5 gallon) batch would give IBU = (1 * .6 * 1000) / 20 = 30 IBUs

Hop Oil (Aroma) Extracts

While hop aroma oil extracts are not widely available to home brewers, they are being used at the commercial level often to enhance a particular aroma or flavor. For example you might want to enhance a citrus or piney flavor’/aroma by selecting an extract of certain hop oils (like myrcene). Since these products are distilled to preserve specific hop oils or sets of hop oils, their concentration and usage varies widely. As the hop oils are volatile and can be lost by boiling, these extracts are most often added post-boil or after fermentation.

Since they are not designed to preserve bitterness (alpha acids) there is no simple measure or formula for their use. Instead they are often used in very small quantities on test batches until the desired hop aroma/flavor is achieved. I would use these very sparingly “to taste” until you gain more experience with them.

The new version of BeerSmith has support for the first two types of extracts (CO2 and isomerized) so you can create hop entries for extracts and use them in recipes. To enter a new hop extract, enter the name and correct type and then set the alpha content equal to the percentage of alpha acid – typically 50-70% for CO2 extracts and a bit less for isomerized extract. In most cases you can get this number from the supplier.

So that is a quick summary of the basic types of hop extracts and how you can use them in your beer. Thanks for joining me on the BeerSmith Home Brewing Blog. Be sure to sign up for my newsletter or my podcast (also on itunes…and youtube…and streaming radio station) for more great tips on homebrewing. Also check out the How to Brew Video series I shot with John Palmer if you want to learn more about all grain brewing.