IBUs as a function of Boil Volume

[aurelius121ad]

I recently got a pirated copy of Beersmith to help me formulate recipes but now have ran into a problem. Past posts dont seem to answer this for some reason.

I dont really have the means to cool or boil a 17L wort (full batch for my fermenter) so a full boil is kinda out of the question for me. By playing with the boil volume I get drastically different IBUs so I gather that hope utilization is a function of wort density. I dont want to "waste" hops so I am thinking of trying for around a 8-10L boil with half the malt and then adding the rest of the malt at flameout. Will that give me the proper IBU in Beersmith if I set it to calculate boil volume at 16-20L?

Logically it makes sense: half the volume of water + half the malt would be the same gravity as all the wort + all the water. Or is the ratio of hops to the actual volume of liquid they are being boiled in too important to ignore?

[rwh]

By playing with the boil volume I get drastically different IBUs so I gather that hope utilization is a function of wort density.

Yep. The Tinseth method seems to be the de facto standard for estimating utilisation these days.

http://www.realbeer.com/hops/FAQ.html#units

I dont want to "waste" hops so I am thinking of trying for around a 8-10L boil with half the malt and then adding the rest of the malt at flameout.

That's what I do for kit/all extract beers.

Will that give me the proper IBU in Beersmith if I set it to calculate boil volume at 16-20L?

No idea as I've never used beersmith.

Or is the ratio of hops to the actual volume of liquid they are being boiled in too important to ignore?

No, the total volume is mostly irrelevant.

[aurelius121ad]

aurelius121ad wrote:I dont want to "waste" hops so I am thinking of trying for around a 8-10L boil with half the malt and then adding the rest of the malt at flameout.


That's what I do for kit/all extract beers.

Thanks, it seemed rational, just wanted to make sure I wasn't overlooking something.

[Trough Lolly]

Not at all....in fact you had intuitively discovered an important brewday process that many early brewers overlook.

Here's something to ponder when you're next wandering around Tiān'ānmén Guǎngchǎng - would you add more / less / same quantity of bittering hops if you had a 20L boil of 1.045 wort instead of a 10L boil of 1.045 wort (with thanks to an old BJCP study guide!!)

Rob, Kev, Doc, Boonie, Ryan et al - don't answer!!

Cheers,
TL

[matr]

Hey mate. Check this out - http://homebrewandbeer.com/forum/viewto ... =20#p83165

Hopefully this is what you are looking for. Hopefully I am right in what I have posted.

[aurelius121ad]

Here's something to ponder when you're next wandering around Tiān'ānmén Guǎngchǎng - would you add more / less / same quantity of bittering hops if you had a 20L boil of 1.045 wort instead of a 10L boil of 1.045 wort (with thanks to an old BJCP study guide!!)

我特少去天安门, 我去过好几次. 我想好了你的问题昨天晚上走回家的时候.

Your question is a bit unclear so I will answer both scenarios:

1. 20L boil for a 20 L batch vs 10L boil for a 10L batch.
- the 20L of wort would require more hops because there is 2x the water and 2x the fermentables hops would have to balance out.

2. 20L boil for a 20L batch vs 10L boil intended to be topped up to 20L and have more fermentables added after flame out
- I could be wrong but I would expect the 20L boil would require less hops because there is more liquid in the boil and more "room" for the hops to dissipate/dissolve/发 their flavor. My rational here is the following analogy: it would be easier to dissolve 1 tablespoon of sugar in 1 cup of water than it would be to dissolve 1 tablespoon of sugar into 1 tablespoon of water then add that tablespoon to 1 cup of water.

[rwh]

1. Correct.
2. Correct.

Though I think your analogy is flawed... A better analogy might be it's easier to dissolve 1 tablespoon of salt (or anything really, in this case we're talking about isomerised alpha acids) into a cup of plain water than it is to dissolve that tablespoon of salt into a cup of water that's already got a bunch of sugar dissolved in it.

[Trough Lolly]

Sorry, I've been offline crook for a few days - well done! It's often a hotly debated topic until it all "clicks"!!

Cheers,
TL

[aurelius121ad]

It shouldnt be all that hard for people to grasp. The reasoning behind both RWH and my analogies are the same... a high ratio of water molecule surface area to what is being disolved would have a quicker rate of solution (dissolution, dissolvolution, dissolvation, I dont know what the word is, I think I just made all those up!) than that of a lower ratio of water.

But back to senario 2 (20L boil for a 20L batch vs 10L boil intended to be topped up to 20L and have more fermentables added after flame out) - In theory you could use the same amount of hops for both boils but increase the time for the 10 L boil though correct? Although I would expect the resultant flavor to be slightly different for all three conditions.

Any guesses (without the help of a cut and past online translator) as to what that sentance I wrote in Chinese means? Your Chinese pinyin (complete with the nice touch of tone marks) inspired me to up the anty a bit and answer partially in Chinese.

[warra48]

I think you are correct aurelius, as to the absorption rate being dependent on boil volume and gravity.

The amount of boil off and boil length is, I think, more complicated. Boil off, or evaporation, is partly dependent on the surface area of the liquid being boiled, if they are boiled in the same boiler. I find in my 40 litre kettle that my boil off is pretty much the same, whether I start with say 31 litres or 26 litres. Other factors which influence boil off is ambient temperature and humidity levels.

Having said all that, I don't think there is a pressing need, IMVHO, to lengthen the boil for a smaller volume. After all, if you are adding water at the end of the boil, you simply make it up to the volume you require by your additions. If you boil longer, you just need to add some more water. I agree that lengthening the boil for a samller volume might alter the flavour components from melanoidin reaction or caramelisation of the wort.

Now, here is my attempt at a translation, shoot me down if any of it is wrong:

Although I don't go to Tiananmen Square very often, I have been there several times. As I was walking home last night, I was thinking about your stimulating question.

[aurelius121ad]

I wasnt planning on lengthening the time of the boil for any of my brews, I just thought that in theory it would work. It seemed relevant to the discussion at hand.

As to your translation, it is pretty much spot on, not the way I would have worded it in English but it's right. How'd you come up with it? I dont know where the "stimulating" came from though!

This would be my translation:
I don't go Tiananmen Square much, I have been there quite a few times. I thought of an answer to your question while walking home yesterday though.

[rwh]

But back to senario 2 (20L boil for a 20L batch vs 10L boil intended to be topped up to 20L and have more fermentables added after flame out) - In theory you could use the same amount of hops for both boils but increase the time for the 10 L boil though correct? Although I would expect the resultant flavor to be slightly different for all three conditions.

Hang on. If you had all fermentables in the 10L boil then the boil gravity would be double. In that case your utilisation would drop. But if you have half the fermentables in a half-sized boil, the boil gravity would be the same as the OG. In either case you can use the same amount of hops boiled for the same amount of time and get the same result (at least in terms of IBU, which is what we're talking about here, right?). This of course ignores the effects of not boiling half the extract. Melanoidins are a good example of something that will end up different, as is break material, caramelisation, etc.

The only situation in which you'd have to boil for longer would be if you added all the fermenables to a reduced boil.

[warra48]

As to your translation, it is pretty much spot on, not the way I would have worded it in English but it's right. How'd you come up with it? I dont know where the "stimulating" came from though!

This would be my translation:
I don't go Tiananmen Square much, I have been there quite a few times. I thought of an answer to your question while walking home yesterday though.

I googled chinese/english translation, and came up with this site:

http://www2.worldlingo.com/en/products_ ... lator.html

I manipulated it into what to me looks like reasonable English, but the "stimulating" part was my own addition, call it dry hopped translation liberty.

It helps if you are bilingual in any event. You get to appreciate the nuances in different languages, and how a literal translation just doesn't work most of the time. I've particularly found that with sub-titles in foreign movies.

[aurelius121ad]

But back to senario 2 (20L boil for a 20L batch vs 10L boil intended to be topped up to 20L and have more fermentables added after flame out) - In theory you could use the same amount of hops for both boils but increase the time for the 10 L boil though correct? Although I would expect the resultant flavor to be slightly different for all three conditions.

Hang on. If you had all fermentables in the 10L boil then the boil gravity would be double. In that case your utilisation would drop. But if you have half the fermentables in a half-sized boil, the boil gravity would be the same as the OG. In either case you can use the same amount of hops boiled for the same amount of time and get the same result (at least in terms of IBU, which is what we're talking about here, right?). This of course ignores the effects of not boiling half the extract. Melanoidins are a good example of something that will end up different, as is break material, caramelisation, etc.

The only situation in which you'd have to boil for longer would be if you added all the fermenables to a reduced boil.

I know the process is more complex and maybe the chemistry works different for the oils and alpha acids of hops as compared to dissolving something soluble in water. I am thinking of it this way. Let's say I wanted to dissolve 1kg of sugar into 5 liters of water and then dissolve another 1kg of sugar into 10 liters of water. It would require less time stirring for the solution with a higher ratio of water to sugar than the solution with the lower ratio.

So time is a variable in the function of dissolving something into solution. Increase the time the solid is exposed to the liquid and you get more of the solid dissolved into solution.

I didn't mean to open a can of worms with this. It seemed relevant as a theory and topic to discuss, it isn't something I wanted to do. I was just thinking it is theoretically possible although the flavor profiles would be different due to different percentages of the fermentables being subjected to heat longer (as was said) as well as the hops.

Or for another example, not that you would want to but lets say you had two boils of plain water. One at 20L and one at 10L. Then you add the same amount of hops to each and boils for an hour. Then you top up the 10L boil to 20L. I would expect the flavor and IBU to be different (however probably negligible).

[Trough Lolly]

我特少去天安门, 我去过好几次. 我想好了你的问题昨天晚上走回家的时候.

Hmmm, now don't laugh but my translation skills were poor when I was doing this for a living and that was 20+ years ago! Is it something along the lines of "I like to visit Tiananmen Square often. I thought about your question last night"??? That's probably rubbish, but as I said, it's been a hell of a long time!

Cheers,
TL

[Trough Lolly]

Lurching back on topic for a few moments, hop utilisation is non-linear:


You can see (in the above case with a 1.050 wort) that the extraction efficiency flattens out as you hit the 1hr mark which helps explain why most recipes suggest a 1hr boil. You can, of course, boil for longer durations to generate extra melanoidins in the final product and darken the colour of the resultant wort. Another interesting data point is the slightly greater efficiency with the relatively more concentrated pellets compared to flowers. That doesn't necessarily translate into better flavour and aroma properties - especially when you've picked the flowers earlier in the week and dried them out before using them on brewday.

Footnote: Stuffed up my hacked translation - I think you were writing that you dont get to Tiananmen Square often! As I said, my translation skills suck!

Cheers,
TL

[aurelius121ad]

我特少去天安门, 我去过好几次. 我想好了你的问题昨天晚上走回家的时候.

Hmmm, now don't laugh but my translation skills were poor when I was doing this for a living and that was 20+ years ago! Is it something along the lines of "I like to visit Tiananmen Square often. I thought about your question last night"??? That's probably rubbish, but as I said, it's been a hell of a long time!

Cheers,
TL

Not bad, especially if you didnt use any kind of electronic translator. Here's how I would say it in English:

"I rarely don't go to Tiananmen these days, I have been there quite a few times. I thought up an answer to your question last night while waling home though."



and for direct word for word:

I specially few go Tiananmen, I went good many time. I think good your question yesterday evening walk return home time."



And once again back on topic-

You learn something new every day. I didn't know the longer you boil the darker the wort becomes. I assume the intensity of the boil the boil plays a factor in that as well.

Either way I think I need to try a longer and hotter boil next time. I used an electric hot plate to boil my last batch which took forever to reach boiling temp and wasn't a very intense boil once it got there. However I thought this option was better than running out of propane mid boil and not being able to get a refill til the next day, which would have happened had I used the stove.

This liquid malt I have found (says it is a combination of rice and barley malt but not how much of each) gave me an almost clear wort. And a ridiculously high OG 1.142 (the hydrometer is not askew, I checked that). The batch was topped up to 17-18L, thoroughly mixed and had 3kg of extract and 400g of dark brown sugar (had to add more brown sugar than I initially intended to do something about the color!). Beersmith estimated 1.060, which I thought was pretty reasonable.

Oh well, I will know a bit more in a week or so when I start taking some FG hydro readings. This was my first brew using fresh hop pellets... I couldnt stop smelling the hops. They smelled so good. I havnt had a really hoppy beer in nearly a year, with my favorites being American IPAs the hop fragrance really sent me back home! I cant wait to try this brew in a month or 2!

[PaulSteele]

this is a very interesting thread and i think it deserves some kind of sticky action.

i found the answer to this after much pondering and research while trying to work out hop utilisation for a partial boil.

this thread would be very handy for somebody doing partial boils.

[Trough Lolly]

You learn something new every day. I didn't know the longer you boil the darker the wort becomes. I assume the intensity of the boil the boil plays a factor in that as well.

Indeed it does - and there are a host of reactions and things happening during a rolling boil. There's an excellent article in the Nov 2002 edition of "The Brewer International" that gives you a good insight into the workings going on in a boil.

If you're interested, the article is - here...

Zàijiàn!!
TL

[James L]

That article was rubbery (lovely)... (thought i'd join in on the chinese linguistics).

not trying to offend... just having a bit of fun...