Hop Utilization (A Geeky Take)

One of the lessons it really took me a while to learn is how different hop additions truly affect the finished beer. I started to really get into craft beer (which at the time was still colloquially referred to as "microbrew") shortly before I started brewing. So by the time that I was really starting to experiment with recipes and deviate from kits, I'd developed a palate for hops. Furthermore, I was in a purely experimental mode and brewing without doing a ton of research and definitely without the aid of brewing software to help me calculate the effects of recipe changes or additions.

As I've researched more, started to use software and take measurements religiously, I've dialed in my understanding on a few parts of recipe formulation. This post is about hops and bitterness. All of the calculations herein are performed using the Rager formula. (Apparently this is less accurate for full-volume boils than Tinseth, but it's what I've been using and it's what the guys at the brewing network use. Since most homebrewers probably aren't using lab equipment to accurately measure IBU's, we're just looking for a consistent way to measure.)

The IBU scale ranges from 0-100. According to most sources, you really can't discern bitterness past 100, but you will pick up additional hop aromas from late boil additions or dry hops once you've hit 100 IBU.

There are five variables in the Rager formula which affect bitternes: wort volume, wort gravity, alpha acid %, hop mass and addition time. I held the wort volume and wort gravity constant and ran some numbers for both this post and my own curiosity. The results were interesting and pointed out a few things I hadn't fully realized before.

(The table I used to create the graph is here.)

The conclusion I'd already come to by using brewing software and digging in to styles is that it doesn't take much of a bittering addition to max out one's taste buds. A 1 oz charge of bittering hops is really all you need for an IPA or any other highly bitter beer. Much beyond that and you're just wasting hops.

One thing I didn't realize is that the utilization (according to Rager) for a 90 minute boil is almost exactly the same as a 60 minute boil. So don't bother extending your boil time for higher bitterness. (Use it for wort concentration on high gravity beers or DMS reduction, but those are two separate posts.)

The other thing which I dug into is the affect of a flame-out addition. Based on some other sources, the extraction of bitterness from hop additions happens at temperatures above 158F. As such, your flame-out or late additions may end up contributing more bitterness than aroma if you're not cooling your beer quickly. (I noticed a substantial difference in the level of hop aroma I got this summer when I incorporated a proper wort chiller into my process.)