Whirlpooling technique

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zimmerj81

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I just got a new 10 gallon system 2 months ago & I've been getting this bitterness that I just don't like. I changed too many techniques at once when I transitioned to the new system so it's been hard to figure out what is wrong.

I think it's because of my whirlpooling technique. After flameout, I would start whirlpooling for 10-15 mins and then letting it settle for another 15. However, during all that time, the hot wort is still in contact with the hops. I know that the isomerization slows down as the temp drops below boiling but I imagine that it would still be extracting bitterness. Has anyone had an experience like this? Do most people chill before or while whirlpooling?

I think I will start running it through my plate chiller back into the brew kettle to create the whirlpool while chilling. I was just running it through the plate chiller directly into carboys.

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I'm no expert on whirlpooling (only used the technique about twice) but I chill a little, to 170 or so, and then let it sit for 20-30 minutes and start chilling again. I'm sure there's a thread around here somewhere that states the temperature where alpha acids stop isomerizing (or a least significantly reduced isomerization), I think it's in the 170-180 range.
 
The process of whirlpooling is often blended with the idea of post-boil hopping or 'hop stands'. Whirlpooling is a process used by the pros, and by homebrewers emulating the pros, to primarily build a cone of hop trub in the center of the kettle. This is to limit the trub from going downstream. Whirlpooling also helps with wort cooling.

Post-boil hopping is a separate process that happens to be done at the same time for those who whirpool. The concept is, without an active, churning boil going, you're not volatizing off the flavor and aroma bearing hop oils. i.e., the water vapor isn't escaping the wort and carrying away hop compounds.

The next part of the story is post-boil temperature and how it still affects the hop oils. From 212*F to 175*F, you are still going to generate bitterness through isomerization of the alpha acids in the oils. But this will happen at a reduced rate. Rates are commonly cited as 10%-15% of typical IBU calculations for the same amount of boil time as you plan to sub-boil your hops.

Below 175*F you shouldn't see much bitterness but still have the benefit of flavor generation, which still requires heat to convert oils to different flavor compounds. You also retain some aromatic affects, which can be assumed to be relatively inversely proportional to temperature (sub-boil being poor retention with dry-hopping being the best retention).

For 99% of home brewers, who brew smallish batches (let's say 10 gallons or less, for the sake of argument), there isn't a lot of benefit to whirlpooling, but we can still take advantage of post-boil hopping.

Note that 175*F is the commonly cited bottom threshold for isomerization of alpha acids. I can't cite a paper or other proper reference verifying this value. As in many things brewing related, a lot of this is empirical based on experience and not testing.

edit: here's a reference:
http://byo.com/component/k2/item/2808-hop-stands
 
From pro brewers I have heard they don't see much drop at all in hop utilization during the whirlpool. They get almost full bitterness from there whirlpool additions. But the pros don't cool down to 175 before the whirlpool. There hops are added at almost boiling and whirlpool there for a while. I would cool to ~180 and whirlpool for 15 minutes then cool to pitching temp and let it settle out. This is what I do. If I'm doing an all late addition pale ale all add all hops at flame out and let them sit longer to still achieve the proper bitterness. If you dont your basically boiling all your other hop additions 30 more minutes. Hope that helps a little.
 
Weezy, thanks for the reference. I have that issue of BYO but apparently I missed that article. Since I don't have a thermometer on my brew kettle, I'm not sure how long it remains above 175. So it seems feasible that it could be the cause of the undesired bitterness.

I have some ideas now. My pump has an in-line RTD for my Blichmann Tower of Power so I can start the whirlpool using the pump while running it through my plate chiller to sanitize it, while being able to monitor temp with my TOP. Do that for 10-15 mins, then turn on the water for the plate chiller to begin cooling. That way, I'll also hopefully keep as much cold break in my kettle as possible.

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Another option would be to adjust your boil hop additions to compensate. Either reduce bittering charge or move them closer to flameout.
 
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