IBU Confused

[scuppeteer]

I have just put my hop schedule through the Hop & grain database and it said I had 72IBU's. Can this be right or have I just made a really bitter bitter?

I boiled 2oz's Target (AA 13%) for 60min & 1/2oz Bramling X (AA 5.5%) for 15mins. Flame out I added nearly 4oz aroma for 60min, and the beer taste's pretty damn good, Bitter but loads of flavour.

What I'm wondering is, if I add the same amount of a different variety (similar AA's) to the next boil, am I gonna bugger it up or will it work out OK, so long as I add similar aroma quantities?

If it makes any difference ABV was 3.8%. Brew was 23litres.

Ta. :-}

[Kev888]

Its partly dependent on the gravity during the boil which you don't mention, but I'd say the database results seem likely to be correct for those figures. Thats quite a bitter one for the gravity then, I'm guessing a likely OG but I make the BU:OG ratio something like 1.8 - IIRC the safe limit for a ballanced beer is said to be roughly about 1, but it depends a lot on style and personal taste so in my view is a rule to break sometimes.

What matters for bitterness is the hop quantity, hop %AA, boil time, boil volume and wort gravity, so if you kept everything the same with a different hop variety then bitterness would be similar, though flavour and aroma probably wouldn't be. The same bitterness may also seem more or less appropriate depending on how dry or malty the finished beer is; again its down to personal taste though

Cheers
kev

[stringy]

Flame out I added nearly 4oz aroma for 60min

Do you mean you added the hops at flame out & then didnt chill for 60mins? I'm not sure how many IBUs you'll get from this, presumably the utilisation will decrease with temp.
Usually when I add hops at flame out I start chilling pretty much straight away, so don't really anticipate many IBUs from those hops

[scuppeteer]

Thanks for the response's guys.

The OG it was 1038 so would that work out Kev? I'm still learning lots so how do you work out the BU/OG ratio? The beer is quite bitter but has a very full bodied flavour (would that be the munich malt that does this). Great bitterness to start but then hints of grapefruit but with a very pleasant and lingering aftertaste.

To take a boil gravity, would I just do this as I would during fermentation? And how would I use this info for later?

I haven't yet invested in a wort cooler so I generally let the wort stand for a few minutes after boiling and then add the aroma's. I shouldn't get any more bitterness then should I?

Lots of questions I know, but much to learn I have!

[Kev888]

Probably the BU:OG ratio would be just under 2 in that case, then. Its simply the Bitterness Units divided by the gravity (ignoring the leading 1 and decimal point in the gravity, so 1.038 would be 38) - at least thats always been my understanding, but its so long ago that I can't say where it came from, and as I say its probably a rule to break for some styles and tastes.

Technically theres pre-boil and post-boil gravity of the wort in the boiler; obviously, as you boil the evaporation causes the gravity to rise. As post-boil gravity is essentially OG then I normally take boil gravity to mean pre-boil. You should measure it before it actually reaches boiling though, or extract some and cool it, partly to protect your hydrometer from the heat and partly because you'll need to compensate for any temperature above what the hydrometer is calibrated at (usually 16c or 20c) - hotter liquids are thinner so give a misleadingly low gravity reading unless compensated for.

You can use boil gravity to calculate your mash efficiency, but in this case we're interested in its effect on hop utilisation - somewhat counter-intuitively higher gravity worts extract more bitterness. Graham wheelers beer engine software (calculators button top right of this page) and that online calculator you mentioned will presumably do all this for you - even estimating the boil gravity so you don't need to measure it. Or there are tables that help you use the gravity manually, or you can calculate it (I set up a spreadsheet years ago to do this), e.g. here and a bit more simply explained here (the preceeding page of that link discusses ballancing the bitterness too). Its all a bit rough though - obviously the gravity changes throughout the boil and opinions vary on the extraction rates, and the %AA on hops is only a guide to begin with, so you often see disagreement between calculators.

You don't get much bitterness after the boil, but you can get a little - some calculators seem to include something for this eventuality whilst others don't. Its mainly flavour and aroma at flame out, but bitterness can supposedly be extracted above 80C so especially if you added fresh hops towards the end its likely there'll be more bitterness from those.

The slow cooling is unlikely to be a 'major' issue in my mind; boilers cool quite rapidly to begin with so it wouldn't have taken 'that' long to reach about 80c. If you want to avoid that though another technique is to add hops and steep (specifically avoid cooling) once the boiler has cooled to 80C - then theres very little bitterness extracted, just flavor and aroma (and if its really aroma you're after theres also dry hopping after fermentation).

Cheers
kev

[scuppeteer]

Thanks Kev, really helpful once you get your head round it. For the brew I did last night I reduced my copper hop quantity by 10% should be 52IBU's so hopefully the bitterness won't overtake the aroma's as much as previously. It smells absolutely great, will try my very best to leave it long enough to condition properly.