Boil volume vs hop utilisation. Am I the only one confused?

[Lionman]

I just put down my first extract brew after a few kits under my belt.
23L batch size
4KG LDME
.5KG Medium caramalt
20g Magnum @ 45mins
15g Galaxy @ 25min
15g Chinook @ 25mins
15g Galaxy @ 10min
15g Chinook @ 10mins

Planning to dry hop this with

15g Galaxy @ ~ 7 days
15g Chinook @ ~ 7 Days

but I might up the dry hops a bit, probably double it.


Now, I used the spreadsheet to calculate this and it has come out at around

OG 1069
ABV 6.8 (Keg)
IBU 72.3

I measured the OG and it's at 1080 which may be a bit higher due to settling in the FV as I measured when I pitched which was around 8 hours after the fermenter was filled. I doubt there would be this much variation in OG though?

Out of curiosity I downloaded the Biermacht app and put the same recipe in and the results are somewhat different, with boil volume have a big impact on final IBU.

OG 1065
ABV 6.6
IBU 17

The difference between the OG and ABV levels are small and probably just to do with slight differences in the assumptions of the amount of fermentable's in the ingredients. But 17 IBU? I tasted the wort and I can tell you it's not 17 IBU.

I have read a bunch of threads on this forum and others about boil volume and impact on IBU but I am still pretty much none the wiser. I use a boil volume of 7l and there was plenty of bitterness coming out of the hops. I tasted the concentrated boil and could still taste it a day later (note to self, try to resist doing this in the future). It was very bitter, to say the least. I can't understand why Biermacht calculates such a drastic reduction in IBU based on boil volume?

If I followed this app I would have added about 1kg of hops to get up to a decent IBU level. Even with a full boil volume it still comes up short at around 57.9IBU. If I turn the HCF function on in the spreadsheet it reduces to 44.3IBU

Can anyone explain whats going on here? Is Biemacht just crap? Is the spreadsheet over estimating IBU? I'm not worried about my brew. I thnk it will be tasty regardless but for future brews it would be nice to have some confidence about what I'm going to get at the end.

 

[Rocker1986]

I've never even used Biermacht so I dunno anything about it.

You won't get any settling of (malt) sugars in the fermenter unless the malt itself wasn't dissolved properly to begin with. Once it's in solution that's where it stays unless you go over saturation point, which would take a lot more than 4kg of LDM to achieve in 23 litres. I always found the spreadsheet pretty accurate at predicting OG readings, so I'd probably go with that instead of the 1.080 you measured.

I think the boil volume does have an impact on utilisation but 17 IBUs sounds a bit ridiculous to me. I used to use the spreadsheet when I brewed extracts with the HCF on, and to my taste the beers always turned out as expected.

Out of curiosity, how much of the LDM did you use in the hop boil?

 

[ianh]

I would not use the HCF function, it was put there because some extract brewers were only boiling 2-3 litres. Having said that I would try and increase your boil volume to 10 litres.

I got most of the info for the spreadsheet for hops from here http://realbeer.com/hops/FAQ.html

Sorry not used the Biemacht app.

 

[Lionman]

Thanks for the replys.

I think it may be because Biermacht is assuming I boiled all my fermentable in 7l, when in reality I boiled the steeped grain liquid + 500g of the DME. I add the rest of the fermentable at flameout, dissolved them all, then added it to the fermenter, topped up to 23l and put it in the brew fridge. The spreadsheet tells you how much ingredients you need to add to 7l to get it to SG 1040 for the boil, so it woudl be calculating hop utilisation based on that.

If I use the IBU calculator on brewers friend it says my boil gravity is 1.223 lol. It calculates IBU of around 15, which look similar to what is happening in Biermacht.

I might message the dev and see if they can add a similar feature. I really like the spreadsheet but it's also handy to have something on the phone and unfortunately the spreadsheet used elements which android doesn't like.

 

[Lionman]

You won't get any settling of (malt) sugars in the fermenter unless the malt itself wasn't dissolved properly to begin with. Once it's in solution that's where it stays unless you go over saturation point, which would take a lot more than 4kg of LDM to achieve in 23 litres. I always found the spreadsheet pretty accurate at predicting OG readings, so I'd probably go with that instead of the 1.080 you measured.

Yeah I thought it was weird. I measured some tap water straight after to double check the hydrometer and it was bang on 1.000.

Maybe an extra 500g of DME slipped in there somehow? I wouldn't put it past me, haha.

 

[Rocker1986]

Another possibility is that perhaps the wort at the bottom was more concentrated if you simply topped it up with water and didn't give it a good stirring after that. If it was all stirred in properly then perhaps there was more DME added inadvertently. :lol:

 

[Lionman]

Another possibility is that perhaps the wort at the bottom was more concentrated if you simply topped it up with water and didn't give it a good stirring after that. If it was all stirred in properly then perhaps there was more DME added inadvertently. :lol:

Yep, that's a possibility. I didn't actually stir it this time (laziness). I added the cold water 1L at a time and poured it in from a height to assist in aerating the wort. I assumed it would be enough to mix it through but I was probably wrong.

Is it too late to give it a stir now with a sanitised plastic spoon? If I don't will it matter? I wouldn't mind a relatively accurate OG reading.

 

[Rocker1986]

Depends how long ago the yeast was pitched but if it was me I wouldn't bother stirring it now. The yeast will still find and ferment the sugars whether they're evenly distributed through the wort or not. The spreadsheet predictions are pretty accurate from my experience though, and the 1.069 sounds about right from the fermentables listed and batch size.

Hope you used enough yeast!

 

[Lionman]

Depends how long ago the yeast was pitched but if it was me I wouldn't bother stirring it now. The yeast will still find and ferment the sugars whether they're evenly distributed through the wort or not. The spreadsheet predictions are pretty accurate from my experience though, and the 1.069 sounds about right from the fermentables listed and batch size.

Hope you used enough yeast!

By the time I get home from work it would be about 36 hours or so since I pitched 1 packet of US-05 just sprinkled directly over the surface. This morning there were signs of yeast colonies developing on the surface in a few patches of what appeared to be early stages of krausen developing. Temp is controlled at 17c, and it usually ferments slow and steady at this temp from what I have seen.

No doubt it will be alcoholic either way.

 

[Rocker1986]

I'd probably be pitching two packets for that OG, although it'd likely still work with one. Could probably bump it up to 18 and then raise it up to around 21 after 5 days or so just to be sure. I normally ferment US-05 at 18C with good results although 17 is fine too, it's just one packet is probably a bit of an under pitch.

 

[Lionman]

I would not use the HCF function, it was put there because some extract brewers were only boiling 2-3 litres. Having said that I would try and increase your boil volume to 10 litres.

I got most of the info for the spreadsheet for hops from here http://realbeer.com/hops/FAQ.html

Sorry not used the Biemacht app.

Thanks for making the spreadsheet. It's a truly invaluable tool for the budding brewer. I have learnt so much through using it and it has given me the confidence to play with recipes and experiment with ingredients. It hasn't let me down yet.

 

[Lionman]

I'd probably be pitching two packets for that OG, although it'd likely still work with one. Could probably bump it up to 18 and then raise it up to around 21 after 5 days or so just to be sure. I normally ferment US-05 at 18C with good results although 17 is fine too, it's just one packet is probably a bit of an under pitch.

Yeah probably is but I'm tight and another packet adds $5 the cost of the batch!

I might raise the temps though, I had issues with high temps before I had temp control (nasty kit beer that was) so tend to keep it on the low side. How low should SG go before you start to raise the temps?

 

[manticle]

Gravity (which volume can affect obviously) will influence IBU contribution.
There are also 3 (as far as I know - might be more) different formulae commonly used for calculating IBU contribution - Rager, Tinseth and one other I can't remember. Make sure both software sheets are using the same formula if you're looking for a proper comparison between the two platforms.

If you're going to be tight with anything, don't be tight with yeast.

 

[Rocker1986]

Yeah probably is but I'm tight and another packet adds $5 the cost of the batch!

I might raise the temps though, I had issues with high temps before I had temp control (nasty kit beer that was) so tend to keep it on the low side. How low should SG go before you start to raise the temps?

That's why I make yeast starters, but that might be something for down the track.

I don't really time the temp raise by the SG reading (except lagers but that's a different story) although in saying that after brewing numerous batches of similar OG's with the same yeast it's reasonably predictable where it will be by a certain timeframe. For my ales it's usually day 5 that I raise the temp on the controller, and just let it naturally rise by itself inside the fridge; it probably takes a day or so to come up depending on the time of year. By that point it should be getting to 3/4 done, maybe more, so it should be fine to raise it - but 21 isn't too high to produce shitty flavours at that stage anyway. The high temps are an issue at the beginning of the fermentation, but you've obviously solved that now.

 

[Lionman]

Gravity (which volume can affect obviously) will influence IBU contribution.
There are also 3 (as far as I know - might be more) different formulae commonly used for calculating IBU contribution - Rager, Tinseth and one other I can't remember. Make sure both software sheets are using the same formula if you're looking for a proper comparison between the two platforms.

If you're going to be tight with anything, don't be tight with yeast.

Yeah I have been reading about this but it doesn't make a lot of sense to me. Also people talking about perceived vs actual bitterness which makes it even less intuitive. I think the whole bitterness is a bit of a fuzzy science and the numbers don't quite mean what I thought they did. If there are multiple ways of calculating IBU and they can all lead to somewhat different numbers, whats a man to do? What do commercial brewers do?

I have pitched on a similar G before with a single packet and it turned out extremely delicious so I'm not too concerned about the pitching rate. I hear what you're saying though. I could have bout coppers yeast at $3.5 a packet instead. haha

That's why I make yeast starters, but that might be something for down the track.

I don't really time the temp raise by the SG reading (except lagers but that's a different story) although in saying that after brewing numerous batches of similar OG's with the same yeast it's reasonably predictable where it will be by a certain timeframe. For my ales it's usually day 5 that I raise the temp on the controller, and just let it naturally rise by itself inside the fridge; it probably takes a day or so to come up depending on the time of year. By that point it should be getting to 3/4 done, maybe more, so it should be fine to raise it - but 21 isn't too high to produce shitty flavours at that stage anyway. The high temps are an issue at the beginning of the fermentation, but you've obviously solved that now.

I have half-arsed attempted to proof yeast in the past and I didn't really see much benefit in it. I don't think this was really 'making a starter' though. I think I will try again at some point but regularly agitate it and use some DME instead of sugar. There are a lot of conflicting reports about the benefits of yeast starters so I guess I need of experiment to find out if it will work for me. If I was going to do a beer any bigger than this one I probably would, and I can see a 9-10% IIPA in my near future.

I think I'll take your advice and push the temps up to 18, wait another 4 days and then push them up to 21. At this time f year I think I will be relying on the heater to d the work as it has been generally below 18 recently.

Do you dry hop when you ramp up the temps or do you wait for FG?

 

[Rocker1986]

I've never bothered with this "proofing" technique. I do re-hydrate dry yeast, but it's just in plain tap water for about 15-20 mins. Starters are made in bigger volumes with DME or AG'ers sometimes use excess wort from their batches for them. Usually constantly agitated on a stir plate. I make them for every batch now because I also harvest yeast from them for re-use later. Keeps costs down too.

Normally I dry hop after it hits FG.

 

[manticle]

Most commercial brewers can analyse actual ibu or arrange for analysis. Most homebrewers are estimating with the help of software and their palate.

 

[Lionman]

... palate.

This is the most important part... :drinks: