05 Nov 2010 @ 12:57 PM 

Siebel Concise Course: Day 4 – Hop Utilization and Adjunct Brewing


I’m glad I’m already familiar with craft breweries, because if I wasn’t I wouldn’t be getting nearly as much out of this course.

This was, by far, my favorite day of the course so far. A lot of that has to do with the fact that we talked about math and brewing calculations and, like a true nerd, I really like math. It was fun. But on top of that, being familiar with the industry and with local startups has given me a perspective that I wouldn’t have had just coming into this course as a homebrewer.

For example, one of the calculations that we went over is hop utilization. For one thing, it was nice to have hop utilization calculations defined for me. Basically, as a rule of thumb (though it changes in a small way per brew system) you can expect roughly 32% hop utilization from any given hop addition per batch of beer. It’s good to know because when you’re formulating recipes, you want to know, say, how many hops to use to achieve a certain level of bitterness.

For example, let’s assume you’re making a 10hL batch of 45 IBU pale ale. (And for the purpose of this example, not only will we work in metric, but we’ll also assume one hop addition of 5.5% alpha acid Cascade hops.)

1 IBU = 1 ppm isomerized alpha acids = 1 mg/L isomerized alpha acids

So that means that in 10hL, we want 45g of alpha acids.

10hL = 1000L
1 IBU in 10hL = 1000mg (= 1g)
45 IBU in 10hL = 45000mg (= 45g)

Of course, that 45g represents what’s left in the beer. Assuming a 32% utilization rate, you need to actually put in 140.625g of isomerized alpha acids.

(45g / 0.32 = 140.625g)

Of course, the actual amount of alpha acids in the hops are just a small percentage of the dry weight of the hops, in the case of the Cascades that we’re talking about in this example: 5.5%. So if we’re looking for 140.625g of alpha acids we need 2556.82g of hops which is probably easier to think about as 2.6kg or roughly 5.6lbs.

(140.625 /.055 = 2556.82)

(Boy, I hope all that math is right. I’m working on the fly, here)

So, here’s the thing that I really took away: That hop utilization rate is assumed for every hop addition.

10 years of homebrewing experience tells me that – what the hell? If I put hops in right at the end of the boil I don’t get any bitterness from them – 32% utilization rate? Hah!

But – says the instructor – in a homebrew environment, I can cool things really quickly. A few minutes after I make my last hop addition, I’ve got my wort chiller going and I’m making a significant change to the temperature of my beer. In a commercial environment, I’m probably whirlpooling and, in fact, those hops that I put in will probably be in the wort for another half hour to an hour… isomerizing. Sure, the boil is over and I’m probably not driving off any more aromatics or flavor compounds, but alpha acids isomerize at a temperature well below boiling point. They are still contributing bitterness.

And all of a sudden it became clear to me why people have a hard time ramping hoppy recipes up from homebrew to a commercial environment. You’ll get better utilization rates on a bigger system, certainly, but that’s easy math. But how often will people take into account the fact that the alpha acids in their aroma hops will continue to isomerize post-boil? I would never have thought about it.

The other thing that came up that gave me a lot to think about was our discussion of brewing adjuncts. It was specifically built as a discussion about cereal cookers, but what I took away was a discussion about gelatinizing starches in adjuncts. It really made me think about my good friends at Fullsteam and their sweet potato beer.

I think it’s common knowledge that Fullsteam is using bags of sweet potato slurry in their mash (I say I think because I’ve seen 32 tweet about it, and I’m pretty sure that Brooks would be happy to launch into a diatribe about how much it gums up the mash at any given opportunity). What made me think about it was the discussion of retrogradation of starch.

To sum up: After starch is gelatinized, it is free for enzymes to be able to work through and break those starches down into sugars. But if the adjunct is allowed to cool (or, said our instructor, if it is over-boiled), the starches can re-form their original complex matrix, and in some cases even crystallize to a MORE complex matrix, and be much more difficult or even impossible for enzymes to break down.

So, this makes me wonder: How much retrogradation has taken place in that sweet potato slurry? I mean – they’re still getting fermentables out of it, clearly, so it’s definitely working. But could they save themselves a gummy mash by using a different, less processed, form of sweet potato? Who knows? These are the things I think about during the class.

I should also talk about why this post is so late. Well.. actually, instead of talking about it, I’m just going to post this:

That really should say it all.

Tags Tags: ,
Categories: industry
Posted By: erik
Last Edit: 05 Nov 2010 @ 03 26 PM


Responses to this post » (4 Total)

  1. ingrate says:

    Very interesting. And can i saw…your tweet the other night that was basically “I am drinking THIS and you are not.” was spot on awesome/mean/hilarious/true. Sigh…look at that List. /jealous.

    • Alice says:

      was up a bunch last night with little one and God laid you on my heart coinltualny! Casey, i’ve never prayed for you so much in one night 🙂 prayed for your peace as you slept the night before the amnio and for all you had in front of you in the day to come. thank you for letting us walk this road with you.

  2. Steve Sparks says:

    “But how often will people take into account the fact that the alpha acids in their aroma hops will continue to isomerize post-boil? I would never have thought about it.”

    When I did that monster IPA a few batches ago, with my 10gal rig, I threw in 5.5 oz of Nuggets (13%) at whirlpool, and got the whole batch cooled down about 10 minutes later…. and my bitterness was way too high. On the next batch I switched it to a hopback and then got a much nicer result out of it.

    So I guess the answer is when homebrewers are adding totally ridiculous levels of hops at whirlpool, they notice that sort of thing.

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