Hop Stand IBU Estimate

This is an interesting question that has been discussed in this forum previously. I am currently studying the relevant technical brewing literature on the subject, but have yet to come up with a model (I am working on it). The isomerization of alpha-acids to iso-alpha-acids is definitely temperature dependent, so the amount of IBU's extracted depends upon the temperature (as well as time) of the hop stand. Vikeman does model hop-stand IBU's in his brewing spreadsheet, so that is a place to start.

 

76...80 most people can't discern a 4 IBU difference anyway...and there are a ton of additional variables to boot...freshness of hops, bag/no bag, strength of boil, real gravity of beer, yeast used, etc.

No software or estimate is going to be exact...do your hop stand as is and let your palate decide how close you were, IMHO.

 

I add an extra 2 mins to each addition when calculating, so 60 is 62, 15 is 17, 0 is 2, etc. Seems to get close when I adjust, my utilization is lower than Tinseth says it should be.

 

the easy answer is - if you get the temp low enough - say 140 degrees - youll extract maximum flavor, wont volatilize many oils, and only increase bitterness minimally. the complicated answers are found in this paper:

http://ir.library.oregonstate.edu/x.../1957/22805/MalowickiMarkG2005.pdf?sequence=1

 

I do my hop stands when the wort is in the 110-125F range so I don't expect any substantial isomerization to come out of them. That aside, if you are just adding the hop stand after flameout, the new beersmith 2.2 update actually has a calculator built in that is supposed to calculate this for you OP. Just select "steep/whirlpool" as the hop addition time and enter 30 minutes for the duration of the hop stand. In looking at the "options" in beersmith, they allow you to adjust the utilization factor for this addition, but recommend 50% utilization if you do the hopstand at 194F. Not sure what there basis is for the 50% and/or 194F though. Just woke up and haven't really given it much thought to be honest.

 

Great paper! I found this part rather interesting:

The author is referring to someone else's research on commercial brewing procedures, so it probably has little impact on us small-timers, but it's still very interesting. Great thesis.

 

I believe that current thinking on a commercial scale is that hop stands/whirlpool in the flameout-170F range will realize about 10% utilization. Compared to the roughly 30-35% max utilization they would get from a 60 minute addition. So I think we can estimate our hop stands to be about 20-25% of the value that our calculators predict for 60 minute additions. For my system, using ProMash and Tinseth scale, that ends up being roughly the equivalent to a 5 minute addition.

 

If those numbers are accurate, then I'd assume the new beersmith 2.2 calculators "50% at 194F" scale = 50% of the standard 30-35% utilization. When I get a chance I'll look for more info and post an update.

UPDATE:

The 2.2 update summary says this...

"After quite a bit of research, I’ve finally added IBU contributions for steeped/whirlpool hops. If you mark a hop addition as steep/whirlpool it will now estimate the hop IBU contribution from that addition. The default is to add approximately half the IBU contribution of a similar boil time hops based on a steep/whirlpool temperature of 90 C, though you can alter that percentage in the Options->Bitterness tab."

 

Using the Malowicki equations:

a 15 minute hopstand at 194 deg F will net 44.6% of IBUs vs boiling
a 30 minute hopstand at 194 deg F will net 47.7% of IBUs vs boiling
a 60 minute hopstand at 194 deg F will net 54.3% of IBUs vs boiling

So I consider the 50% to be a pretty good estimate; although I would never hopstand at that high a temperature. Here are estimates for other temps:

170 deg F ~ 15%
160 deg F ~ 9%
150 deg F ~ 5%
140 deg F ~ 3%

 

Great info thanks!

Does anybody ever worry about potential dms issues from extended hopstanding in the 140-170F range?

 

N

No, don't usually use Pilsner Malt in things I would hopstand a lot, but I might worry a little about bacteria in the lower part of the range for extended periods. (probably not warranted either)

 

Commercial brewers load the hops and run the beer into the whirlpool at near boiling, and it does not lose that much temp over 45 min to an hour. Then they dry hop to add aroma.

We can do what we want as homebrewers.

Ihave been whirlpooling for over 3 years no DMS after a good long boil.

 

I like this advice as far as how to use whirlpool hops as far as commercial brewers go: "If you throw hops into the whirlpool and then take two hours to cool, you will not get the effect you are looking for. We throw our late hops into the whirlpool at the last possible moment and then cool and transfer to the fermenter as quickly as possible." - Matt Brynildson

http://www.mrmalty.com/late_hopping.php

This makes sense to me. EDIT: Perhaps since we're talking about a Wookey clone, this makes the most sense for this recipe!

FYI - I make two beers regularly with loads of whirlpool hops (~ 4 oz added to 5 gallons at a temp of 140 deg F, stirred for 15-30 mins) - never had any DMS issues either.

 

“Commercial brewers load the hops and run the beer into the whirlpool at near boiling, and it does not lose that much temp over 45 min to an hour. Then they dry hop to add aroma.

We can do what we want as homebrewers.”

Jeff, commercial brewers are sometimes ‘confined’ by the scale of their brew house. I believe that as homebrewers we have a bit of flexibility which may not be as easily achievable for commercial breweries. For example, a number of homebrewers discuss that they wait for their wort to cool a bit (e.g., 170 degrees F) before they add their end of boil hops. In other words, maybe we homebrewers have more flexibility in our brewing process? Do you have an opinion on homebrewing ‘best practice’ as regards end of boil/hop stand hop additions?

Cheers!

 

Lots of interesting references and conversational exchanges in this thread...

http://www.homebrewtalk.com/f128/dms-where-does-140f-come-132559/

I'll highlight the more interesting posts, but you should read the thread for full context.....


"Here is what I found in Homebrewing Volume I by Al Korzonas, page 90.

When wort is above 158*F S-methyl methionine (SMM) in the wort rapidly breaks down to dimethyl sulfide (DMS). As long as the wort is boiling the SMM is converted to DMS and is boiled off. When you turn off the heat and the boiling stops, DMS begins to increase in the wort. If you cool quickly, the DMS created will be below the flavor threshold and the finished beer will not have a detectable amount. However, if the wort spends a long time between boiling and room temperature (where DMS production is virtually nil), then the DMS level will become excessive. This is the primary reason that cooling the wort quickly is important.

Another reason for chilling quickly is that it produces a better cold break, which is made of clumped protein-polyphenol complexes that begin to form as the the wort drops below 140*F. If you dont get a good cold break the protein remaining in the wort can later cause problems for the yeast during fermentation and contribute to haze in the finished beer.

The 2 references given for the above paragraphs:

Fix, G J, Principles of Brewing Science (Brewers Publications, Boulder, 1989), 142.

DeClerck, J., A Textbook Of Brewing, Vol. 1 (Chapman and Hall, London, 1957), 300."

Followed by Jamil...

"Hmm did I say 60C was the conversion temp or that getting below 60C ensures no conversion is happening? Two different things. (Or was I just screwing up my C to F conversion like usual? )

Conversion happens around 70C. Rapid conversion happens around 80C. I've seen information that says the conversion of SMM to DMSO occurs "above 60C." (I'll put a link at the end of the post if I can find it.)

Keep in mind, 158F is not some magic number where conversion of SMM isn't happening anymore. Just like a lot of other brewing numbers, we're just picking the closest increment of 10C, in this case 70C.

I think you're fine if you can get the wort below 170F rapidly, then you keep cooling after that. Everything slows down and you'll be OK. However, to be certain that no DMSO is being formed, get below 60C (140F) and you're absolutely certain that no DMSO is being formed."

And finally...

"Briggs, et. al. above, suggests the importance of keeping the temperature between 160*F to 180*F to reduce bacterial growth (pp. 319, 344). If you follow the commonly quoted 140*F threshold, you are getting below the pasteurization temperature which is also 140*F (De Clerck, A Textbook of Brewing, Vol. 1, p. 514) and increasing the liklihood of putting more bacteria into your no-low-chill container.

The oft mentioned 140*F doesn't refer to the greatly feared breakdown of SMM to DMS, but the formation of DMSO, a much lower priority that has confused the issue. For the purposes of DMS reduction and reduced bacterial growth, the temperature of 80*C/176*F should be the focus, not 60*C/140*F."

 

Depending on how the whirlpool is built. When I was at Beer Camp the whirlpool hops were loaded in through a manway before runoff, and the whirpool was below the kettles in the pilot brewery. At FW THE whirlpool was more in the open, probably has a hatch on the top. Matt knows his stuff.

As for DMS, it takes some breweries an hour to run off though the heat exchanger to the fermenter. A long vigorous boil will leave little SMM to turn into DMS. Hey, I have done long whirlpools and not detected DMS, and won awards with those beers.

 

That is good stuff, thanks. The 140 degrees I'm referencing came from this article, showing myrcene won't boil off below 147 (even though it can be oxidized):

http://beersmith.com/blog/2013/01/21/late-hop-additions-and-hop-oils-in-beer-brewing/

That is funny about the DMSO reference though - DMSO is usually used to help penetrate cell walls, and is commonly used as a mild pain-relieving topical agent as well as a cryoprotectant. For a moment I was like "beer has DMSO? if I drink a beer with DMSO will that get me buzzed quicker?" anyway.

I'm certainly not worried about contamination in my 140 degree wort. The wort (and associated equipment) has just been boiled, is at 140 degrees, has just been loaded up with antibacterial hops, and is about to be assaulted by several hundred billion yeast cells. Let's see a few cfus of bacteria live through all of that...