Author Topic: Theory behind hop utilization  (Read 3752 times)

Offline steffenb

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Theory behind hop utilization
« on: June 16, 2016, 03:26:00 AM »
Hi All.

we've been wondering what is actually the theory behind higher hop utilization through larger scales. I hear the phrases 'kettle volume' and 'kettle geometry' quite often but is there a scientific explanation available that anyone might be able to share?

Very highly appreciated!
Steffen
« Last Edit: June 16, 2016, 07:11:01 AM by steffenb »

Offline brewfun

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Re: Theory behind hop utilization
« Reply #1 on: June 16, 2016, 07:12:55 AM »
It isn't just about the boil kettle, but about how many IBUs survive the total brewing process. Hop isomers are hydrophobic, which means they look for any reason to leave the wort and beer.

Much of the geometry is the volume to surface area ratio that is increased at larger scale. Homebrew sized kettles have more surface area to volume for isomers to cling to. Along with that is the way that heat is distributed across most of that surface area. A steam system has heat applied along the sides as well as the bottom, which increases turbulance and decreases hot spots. Direct fire systems typically also have a jacket that makes the heat follow the contours of the kettles.

With heat being more evenly distributed, isomerization happens a bit faster but fewer are destroyed in the boil by breakdown.

The story doesn't end there, though. Your entire process chain is involved. In a pro system, yeast is usually more precisely measured and oxygen pickup is dramatically reduced among other improvements, both mechanical and biological.

Is it predictable? Not precisely. The best way to get a handle on it, if you don't have a lab, is to make a basic beer and compare it to beers with known IBU levels like Sierra Nevada. After a couple of times making the same beer, you'll develop a feel for the IBU target you need to get the balance you're aiming for.
Beer Appreciation is the space between pints.

Offline brewfun

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Re: Theory behind hop utilization
« Reply #2 on: June 16, 2016, 07:53:37 AM »
As an illustration of scale, a 10 gallon batch boiled in a sankey keg (assume a 12 bbl preboil volume) has a volume of about 1.5 gallons per square foot. My kettle is boiling about 1300 gallons at about 7.5 gallons per square foot of surface.

Beer Appreciation is the space between pints.

Offline steffenb

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Re: Theory behind hop utilization
« Reply #3 on: June 17, 2016, 07:10:15 AM »
Dear Brewfun.

I really appreciate your answers. It feels much better now that I have an understanding ;-)

Enjoy your day.
Steffen