IBUs, hops and beer bitterness

WARNING: This post is kind of nerdy.

I often find myself stalling, looking for an answer when someone walks into the brewery and asks “How many IBUs does that beer have?” It happened more than usual last weekend while we sat at our table at the South Sound IPA Festival in Tacoma. People grazing on 4 oz pours of hoppy beer have been trained to look to IBUs as a marker for the most heavily hopped IPAs, but there’s more to it than this. IBU stands for International Bitterness Unit, and it is a measurement of isomerized alpha acids. Bear with me, I’ll break it down.

Alpha and beta acids are the two easiest stats to find on a bag of hops, in spite of dozens of other important qualities in any given hop varietal. Though chewing on a hop cone will always give you the most unpleasantly bitter experience of your life, neither alpha, nor beta acids will add bitterness to beer without a fundamental change. For alpha acids, that fundamental change is isomerization (rearranged molecular structure using heat), and beta acids, it’s oxidation (chemically reacting with oxygen). European “noble” hops are prized for having relatively balanced alpha to beta ratios, and many brewers age their hops to target beta acid forms of bitterness, which wouldn’t count toward IBUs at all. Here in west coast styled IPA land, we aim for all things resinous, and the alpha acid is king. Isomerization requires boiling, and the longer you boil, the more of this type of bitterness is created in your beer. Alpha acids come from the resin glands in hops, which also produce flavor and aroma oils (hoo boy, does it get complicated from here). You can look for myrcene for resinous qualities, cis-rose for fruity, octanal for citrus, 4MMP for black currant, linalool and geraniol for floral, or my favorite, Caryophylla-3,8,dien-(13)-dien-5-beta-ol for cedar notes. These flavor and aroma oils are volatile, and boil off quickly, so while you might gain bitterness from isomerization, you lose what most IPA lovers call “hoppy”. This is why we throw tons of pretty hops that you can smell from across the room into the boil kettle during the last few minutes of the boil. We call this “hop bursting”.

A beer made with 16 metric tons of IBUs and no hop bursting would not satisfy the average IPA drinker. So when the question comes up “How many IBUs? Tell me how many!!! I WANT MORE IBUs!!!!!”, I hesitate a little, wondering how far to go with the conversation. Many of the most revered IPAs only have 70 IBUs and dump liquid CO2 extracted hop oils into the beer after it’s been made. This is a verse from a different song, however, and we’ll get into that another day.

The bottom line is that there is a difference between “hoppy” and “bitter”. If all you want is bitterness, your cheapest option would be 4 or 5 bags of black tea steeped in your cup for a half hour. You’ll find yourself face to face with a truckload of tannins. Ever come upon a stream in the Olympic Peninsula colored orange from all the decomposing cedar upstream? Mouth puckering tannins aren’t inherently bitter, but can be perceived that way. In beer, tannins counteract malt sweetness by drying it out, and malt balances IBUs. You can get tannins from the hops, or from the husks of the grains during the mashing process. The point is, bitterness is complex, and while many might not care to know, in a world with a bazillion IPAs, it helps to at least know the difference between hop flavor and hop bitterness. It’s for this reason that the question “What do you have that isn’t hoppy?” also gives me pause, because theoretically, you could have a beer with tons of “hoppiness” and extremely low bitterness. I may or may not be brewing that beer this week.

MOVING ON … here are your options this week, and their IBUs, which you’ll probably never see again:

  1. Rye IPA (67 IBUs)
  2. West Coast IPA (65 IBUs)
  3. Imperial IPA (111 IBUs)
  4. Pale Ale (43 IBUs) out until Friday
  5. Wheated Red Ale (44 IBUs)
  6. Cascadian Dark Ale (96 IBUs)
  7. Imperial Rye IPA (100 IBUs)
  8. Belgian Strong Ale (36 IBUs) next up, Belgian Dark Ale
  9. Single Hop w/Cluster Hops (54 IBUs) next up, Single Hop w/Citra hops
  10. Bière de Garde (25 IBUs)
  11. Auld Alliance (26 IBUs)
  12. Bee’s Wine Ginger Beer (no IBUs at all)