Isomerization temps

[JeavesBrew]

Is there a temperature at which isomerization stops? I'm going to guess that it depends on wort gravity, hop specs, etc... but there would have to be a point at which the chemical reaction can no longer occur. Am I right?

We whirlpool hot at the brewery for 15 minutes and then don't move it through the chiller for another 45. I'm having a hard time getting a nice hop flavor into the beer without extracting a generous amount of bitterness. It seems as though my flameout addition is really more of a 60 minute addition because of the lag between flameout and the chiller. I hear lots of talk of whirlpool hopping, but I'm guessing that these breweries are whirlpooling cold.

Any thoughts? Advice?

Thanks.

- Jess

[HinduKush]

Is there a temperature at which isomerization stops? I'm going to guess that it depends on wort gravity, hop specs, etc... but there would have to be a point at which the chemical reaction can no longer occur. Am I right?

We whirlpool hot at the brewery for 15 minutes and then don't move it through the chiller for another 45. I'm having a hard time getting a nice hop flavor into the beer without extracting a generous amount of bitterness. It seems as though my flameout addition is really more of a 60 minute addition because of the lag between flameout and the chiller. I hear lots of talk of whirlpool hopping, but I'm guessing that these breweries are whirlpooling cold.

Any thoughts? Advice?

Thanks.

- Jess

Why a 45 minute delay in knock out? WP 10 minutes, settle 10, KO. You still pick up some bitterness in any method of WP hopping.

[fa50driver]

Try a 'hop back' to get additional hop flavor without additional bitterness.

My experience is that you will extract hop bitterness while the beer is sitting in the whirlpool and during knockout if the temps are still hot (200+) but I was never able to get a number where alpha acid absorption actually stops.

[WaterEng]

Analytical work published by Malowicki & Shellhammer illustrates that isomerization is not dependent upon boiling but is proportional to temperature. Isomerization does drop off drastically as the wort temperature falls below 100C. The isomerization rate halves as the wort temperature falls from 100C to 90C. That 10C change is 18F, so for us metricly challenged Americans that is a big temperature drop and it will take time if the kettle is insulated. The implication is that significant isomerization can take place after flame out and whirlpooling. I've heard that some homebrewers are guessing about 15 to 20 IBU's contributed from a 45 minute stand.

[fa50driver]

I've heard that some homebrewers are guessing about 15 to 20 IBU's contributed from a 45 minute stand.

I wouldn't disagree, but I think that it depends on what hop addition is being considered. IE - I don't think that an additional 45 mins is going to contribute nearly as many additional IBU's from that first 90 minute hop addition as it would with the hops that were added at the end of the boil - those hops will see the greatest "additional" utilization due to the additional time spent at 200+

This is what makes using pro-mash so difficult to calculate IBU's with late hop additions. The software will say zero utilization when hops are added at the end of the boil. Perhaps that is correct if I use an immersion chiller in my homebrew kettle, but not when I am using a whirlpool,rest, and 45 min knockout on my production system.

[BigWilley]

You could chill a bit with your heatx during whirlpool to get it down to 180F and try that. Is the 45min wait neccessary?

[fa50driver]

To prevent any DMS formation and stop hop utilization on my light beers, I have circulated thru my HX to get temps down to 180 then whirlpool, rest, knockout, but this only works well when there aren't many hops in the kettle and you have a good filter pre-HX. If I were to try this on an IPA with 30 lbs of hop debris in the kettle, I would either be changing my pre-HX filter every 10 minutes or tearing down my HX very fast.

I have come to the conclusion that the best way to get hop flavor is with a hop back. I have tried floating hop bags during knockout, but I don't think that I get much out of it. Hops added at whirlpool seem to contribute more bitterness than flavor.

[BigWilley]

Time to build a GIANT Immersion chiller! Homebrew style.

[fa50driver]

Time to build a GIANT Immersion chiller! Homebrew style.

How would you do that - wrap 1/2 inch copper tubing around a grundy and then lift it into the kettle with a winch every time? :-)


I thought of having a jacketed whirlpool vessel fabricated and circulating chilled water through the jacket to reduce temp before knockout. That would work good for a four vessel brew-house... Probably take care of potential DMS issues and increase the efficiency of the HX as well.

[BigWilley]

Funny thing is, I actually have a 2" stainless steam "HALO" installed in the bottom part of my kettle to replace the failed bottom zone steam jacket. I could pipe in some valves and T's and run chilled water through it during the whirlpool and see what happens!

[fa50driver]

I would try it. The cold wort would surely stratify to the bottom, so it would only be effective while you whirlpool and circulate the wort, but I suspect that it would definitely pull some heat out of the system - perhaps enough to get the wort below 190 depending on how long you circulate...

[WaterEng]

Funny thing is, I actually have a 2" stainless steam "HALO" installed in the bottom part of my kettle to replace the failed bottom zone steam jacket. I could pipe in some valves and T's and run chilled water through it during the whirlpool and see what happens!

That cooling water would be perfect to direct to your HLT for your next brew if you're brewing at a somewhat frequent basis. Its already heated to probably 150F or thereabouts. You could claim some green energy credits that way and it would be a real way to recover energy for your system. The only bad thing is that you're limited in the volume of water (and energy) that you could capture in the HLT. It would also some optimization of the flow rate. Flowing fast through the loop increases the reduction in wort temp, but produces a lower temperture discharge to the HLT. Decreasing the flow rate through the loop increases the temperature of the discharge to the HLT, but may not meet your cooling requirements or time requirements.

Give and take.

[BigWilley]

Yeah, I already get more hot water than I need into the HLT (which is small) during knockout. I would love to build my own brewery from the ground up with all that I know now! I could make it about 10X more efficient.

[jwalts]

Here's a thread that covers some of the same ground:

http://www.probrewer.com/vbulletin/s...ad.php?t=19619

You'll never really know what you're getting from your whirlpool unless you test it, but the IBUs will be significant. I've changed my hop calculations since that thread was active; they're in a file called Recipe_Barrels.xls that you can download here:

http://sites.google.com/site/republicbrewpub/

Essentially, the calculations treat your total whirlpool/settling/knockout time as an inefficient boil (e.g. 90 minutes from the beginning of the whirlpool to end of knockout might be the equivalent of a 15-minute boil). If you reduce the total time from 90 minutes to 60 minutes, the spreadsheet will reduce your whirlpool utilization. The calculations are based on what you think you achieve in a typical batch, such as your flagship (enter your values in the "Brewery" section), so there are no magic numbers and the accuracy of the calculations will improve if your assumptions are based on lab test results.

Once you estimate your whirlpool IBUs, you can reduce your bittering hops at the beginning of the boil to hit your target.

Joe

[BigWilley]

Ive noticed a big jump in bitterness in my Pale since I have pushed more of the hop load into the whirlpool. I think I was originally using a 5% utilization factor which I bumped up to 10% but seems like it is probably more like 15% based on my perception of the bitterness. I also know that when I have had my beers tested they always show more IBU's than I have calculated. I pretty much use my calculations as a rough guide in recipe formulation and adjust from there based on how the beer actually tastes.