My first own recipe all grain!

[Ross]

So boil volume does not directly affect utilisation (at least not significantly), although the boil volume is indirectly picked up in the boil SG. (as in boil SG is roughly equal to (boil mass)/(boil volume))

Not quite correct - your current boil volumes produce IBU of approx 24IBU, If you used 15L start boil volume to end up with 19L, the IBU's would be nearer 38. Quite significant in my book.


Cheers Ross

[blandy]

Ross, that would be with a siferent boil SG though, wouldn't it.

I probably shoud rephrase my statemant:

"Holding boil SG and boil time constant, the effect of boil volume is negligable"
(otherwise it would be included in the table)

This means that one would expect a 60min boil of 10L at a SG of 1.045 would have the same utilisation as a 60min boil of 20L at a SG of 1.045.

----

This is the issue I have with these brewing software packages:
They do all the calcualtios for you, but unless you understand how the calculations are done, you'll never really know what answer to expect, and will therefore not know when the computer readout has an error.

I've recently made a spreadsheet that does many of the calculations I need to formulate a recipe, including estimates of OG, FG, boil SG, IBU (using Parpazian's table), etc. But I'll still check a few of these once I've got the main idea about what I'm using and how I'm using it.

[Ross]

Blandy,

I fed your recipe into beersmith for the results. i have brewed 100's of recipies, full boils & partials & I believe their figures are spot on. I don't have the knowledge to correct you on where you are going wrong, but I admire you wanting to work it out for yourself.
All I can safely say, from my extensive experience, is that the Beersmith figures are correct.

Good luck in working it out.

Cheers Ross

[Trough Lolly]

Blandy,
Not sure if this helps or not, but here's an extract from Promash FAQ's on hop utilisation:

Question: Why does ProMash produce different IBU estimates for my recipes than in printed books, magazines or other software programs?
Answer: The difference may be due to several factors:
The author of the recipe (or brewing software) may have used a different formulation type in the calculation. In ProMash, if you goto the System Settings, Hop Section, you will see there are four types of Hop Formulas to choose from (Rager, Tinseth, Garetz, Generic). You will notice that changing formulas from one to the other will change the IBU values is ProMash itself. So, in order to match IBU values in published articles or in other brewing software, you must be sure you are using the same equation type. Unfortunately most authors do not publish this, and many may in fact use their own proprietary formula. Many software programs (including ProMash) allow you to set the equation type to your preference.

ProMash ships with the default Hop Equation set to 'Rager'. Rager is the oldest formula to be published and as such, is published more frequently in printed recipes. This is not to say Rager is the most accurate, only that it is the default in ProMash. You can change the equation type in the System Settings, Hop Section to Rager, Tinseth, Garetzor Generic.

Are the alpha acid levels the same in the book or magazine article as the hops you are using in the ProMash recipe?
Cascade from one grower will have different alpha levels than Cascade from another. Within a recipe you can change the AA levels by simply double clicking on a hop within the recipe's hop list, and changing the AA level (you can change the setting permanently in the Hop Database). If you have not set the AA level to match that of the hop in the article, you will never match IBU values regardless of the formula used.

Are the hop forms the same? IE does the published recipe use whole hops while you are using pellets? Different forms of hops have different utilization values. ProMash ships with default values of 10% greater utilization for pellet hops and 2% greater utilization for plug hops. You can modify these defaults in the System Settings, Hop Section should you feel utilization values for pellet and plug hops differ. Whole hops are the baseline for every published IBU equation.

Concentrated Boils: Concentrated boils affect IBU values because the utilization is less in a concentrated boil due to higher wort density. ProMash will automatically account for lower utilization values in a concentrated boil in all equations (Rager, Garetz, Generic), with the exception of the Tinseth equation. Tinseth's equation is based on the 'average' gravity of the wort, not the final gravity as the other formulas are. As such, it is not an appropriate formula for concentrated boils (as you have 2 average gravities, the boil gravity and the gravity after dilution) and was intended for use with full wort boils only.

Recommendations: As many brewers ask us for our recommendation as to which Hop Formula is best for them, here is our opinion (please note this is an opinion only):
Brewers performing Full Wort Boils: Tinseth
Brewers performing Concentrated Boils: Rager

This means that one would expect a 60min boil of 10L at a SG of 1.045 would have the same utilisation as a 60min boil of 20L at a SG of 1.045.

...and the same quantity of hops would yield approximately (not exactly) half as many IBU's in the larger batch. I agree with your statement regarding utilisation if you keep the boil gravity constant - but that's a theory...I don't believe there's a perfectly linear relationship by doubling the boil volume and simply doubling the quantity of hops. A number of actions and reactions occur when the hops are boiled and the oils are keyed through isomerisation, into the wort.

Cheers,
TL

[chris.]

blandy,

Going by this chart http://www.bmbrews.com.au/index.php/info/hopcalc.html

Assuming your boil gravity would be in the 1050-1065 range the utilization % would be 22%.
Using this I get a total of 27ibu for your 1st addition. This is a little closer.

One thing worth noting is the footnote on the above page -

"There are 3 sets of hop utilisation rates in use, compiled respectively by Jackie Rager, Glenn Tinseth and Mark Garetz. The Tinseth rates are the most widely used, and the table above is fairly close to the Tinseth rates. The Rager rates are higher while the Garetz rates are lower."

If you run the exact same recipe through any brewing software & compare the total IBU's the difference between the Rager, Garetz, & Tinseth calculations can be quite significant. As pointed out in the promash excerpt above calculating the exact IBU's is pretty much impossible.

[Pale_Ale]

Blandy, I'm sure I've read somewhere that even if the gravity is the same, the volume actually affects the hop utilisation. I understand your problem perfectly because I went through a similar thing trying to figure out IBUs for my small volume boils.

I remember reading somewhere that the difference between a 23L boil and a 6 litre boil is approx less 15% different in terms of hop utilisation with the decreased volume (assuming identical gravity!). For that reason I use the brewing programs then do this:

IBUs x 0.85

This seems to spit out a believable number and although I have no hard evidence to support this it works for me.

[blandy]

Thanks, Chris.

I think the main problem here is that I'm using the Rager tables (as the table in The Complete Joy has higher values than the Tinseth tables).

I aggree that using the Tinseth tables my IBU for the bitter comes out at about 25-ish. Also, using the Rager tables will result in my calculated IBU of 40-ish.

That said, would you guys expect my recipe to taste particularly bitter? In the end this is the whole point of IBUs. They are merely an estimate of how bitter the beer is.

Has anyone else made a relatively low-gravity beer with an IBU of about 25 (using the Tinseth tables)? how bitter does it taste? Is it on the bitter side of the bitterness spectrum? If the answer is Yes, then mission accomplished.

On the Rager scale I know that I'd call 30 IBU about average, but maybe this equates to about 17-20 IBU on the Tinseth scale.

On that note, I'll post my IPA recipe below.

[chris.]

This (from http://brewingtechniques.com/library/ba ... iller.html) seems to back up your thoughts Pale_Ale.

IBU Calculations for Small Batches

Q: I have a question regarding calculating approximate IBUs for home brewers. Because of equipment and space constraints, I brew from extracts. I am unable to do full 5-gallon boils. I normally do a 3.5-gallon boil and then add enough purified water after the boil to make up a 6-gallon batch. After fermentation losses, I am left with a good 5.5 gallons of beer.

I have seen no IBU calculation formula that a home brewer can use to approximate IBUs in boils of less than 5 gallons. Is there an easy way to determine IBUs in boils of this volume (plus taking into consideration the additional water added to make up the final volume) that doesn't require pages of arcane math?

A: The formulas I have seen are not based on a specific gallon figure; wort volume is something you have to plug in. But that may not be what you are referring to. It sounds like you are talking about the effect of high wort gravity on hop utilization (isomerization of humulone).

To this question I can give an approximate answer. If your original gravity (after dilution) is about 1.050, you are boiling your wort at about 1.085. That gravity is high enough to make a significant difference in hop utilization, but not a huge difference. Based on my brews with some barleywines of about 1.085 original gravity, I would estimate utilization at this gravity to be about 10-15% lower. For example, instead of 30% utilization for the boiling hops, I got about 25-27%.

The easiest way to adapt a formula designed for full wort boils would be to just go through all the calculations using 6 gallons as the wort volume and then multiplying the estimated IBU result by 0.85 or 0.9.

Note, however, that some IBU formulas have a calculation to compensate for wort gravity. If you use one of those formulas, use the true batch volume, but calculate IBUs based on the gravity of the wort at boil rather than the original gravity.

As you may know if you've been reading BT for a while, I'm a skeptic when it comes to IBU formulas. None of the ones I have used has been that helpful. In any case, you end up having to fine-tune the hopping schedule to get the flavor balance you are looking for.

Just on calculating IBU's in general. I found this article, where they tested 33 different beers brewed using the same recipe & same ingredients, interesting:

Results: After we discarded two anomalous results,* the average adjusted IBU level of 33 beers was 62.1, with the distribution of results producing a bell curve with a peak at about this point (see Figure 1). Although more than 80% of the results were within 15% of the average value (and almost half were within 5% of this figure), there still was a swing of almost 25 IBUs between the lowest and highest reliable results. These results aptly illustrate the difficulty in calculating IBUs with a simple formula; such formulas can provide only a rough estimate of IBU levels (3). In this experiment, the hop amounts, alpha-acid content, and boil times were identical, and the wort gravities were comparable - yet the adjusted IBU levels still varied by as much as ±20% from the average value. Thus, factors not usually considered in any conventional IBU formula - water chemistry, boil strength, kettle shape, etc. - clearly play a significant role in hop utilization rates. These results also underscore why you simply must assay your beer if you really want to know your IBU levels. Although our results demonstrate the limitations of any IBU calculation, most amateur brewers (including me) will still use one in designing a recipe, and thus it is a fair question to ask what the various IBU formulas predicted.

An overview of the specific gravity and LMDA stations.

One of the first IBU formulas for amateur brewers that I know of was published by Byron Burch (4). This formula predicted an IBU level of 45.6 for the HBD Palexperiment beer. Jackie Rager's seminal work, which has formed the basis for many subsequent efforts, estimated an IBU level of 53.5 (5). Greg Noonan's well-regarded methodology predicts 56.9(6). Mark Garetz's popular formulation, which he based on Rager's work, gave 41 IBUs (7).* Glenn Tinseth's approach, which makes very different assumptions than the other commonly-used formulas, generated an IBU level of 48 (8 ). Ray Daniels' approach, which uses the basic Rager formula but with separate and more comprehensive utilization charts for whole and pellet hops, predicted that the IBU level would be 67.9 (3). But the top place in the HBD Palexperiment IBU sweepstakes goes to a fiendishly simple little device created by Randy Mosher known as "Dr. Bob Technical's Incredible Hop Go Round" (Alephenalia Publications, Seattle, Washington). This slide-rule device estimated the IBUs for the beer in question at 61.# (The Palexperiment hopping schedule is shown on page 21.)
http://brewingtechniques.com/library/ba ... onham.html

[chris.]

Oh yeah I forgot to mention Pliny the Elder. A double IPA brewed by Russian River (USA). Vinnie the brewer has shared the recipe with homebrewers & If you plug the recipe into beersmith etc. the predicted IBU is well over 200IBU. I recall hearing that recently it was subjected to a gas chromatigraph (sp?) test which revealed it had a measly 60 something IBU's.

IBU calculation's are a great idea in theory but still won't give you a 100% accurate result.

[blandy]

Blandy's IPA recipe

Brewed on Saturday 17/2/07

Malt
3kg Pale malt
450g crystal malt
220g amber malt

3kg liquid light malt extract (OK, it's not entirely AG but I can't fit another 4kg of grain in my tun)

Hop pellets

Horizon (AA = 9.3%)
40g boiled for 45mins

Cascade (AA = 5.9%)
20g boiled for 15mins
10g boiled for 5mins
10g to be dry-hopped at rack

Yeast
wYeast Flying Dog Ale Yeast (Fido the 2nd)

Other stuff
Infusion mashed grain at about 68*C until starch conversion complete
boil volume ~10L, boil SG 1.070 (estimate)
Malt extract added after boil
Final volume 19L
OG 1.080

IBU:
62 (Rager tables)
42 (Tinseth scale) ---- OK IS EVERYONE HAPPY WITH THIS NOW??

Even with all those sweet unfermented sugars still in the wort, this stuff tasted pretty bitter out of the hydrometer test flask.

[chris.]

Using Beersmith I get -

55.6 (Rager)
44.6 (Tinseth)

Close enough

[BierMeister]

IBU calculation's are a great idea in theory but still won't give you a 100% accurate result.

I think this is spot on chris. I am a fan of Graham WHEELERs receipes and he basically says that utilisation runs between 20% and 30% but due to all the variances(boil length, exact AA% of the hops, boil verasity(spelling), age of hops, etc...) he uses the flat 20% in all his receipes. I believe this a good guide and he uses the same calculation as Blandy uses.

IBU=weight of hops(gms) x utilisation(20) x alpha acid
..........................volume brewed x 10

As has been previously said the IBU's themselves are a guide only to taste and if you want an exact figure then you will have to purchase some really expensive equipment.

EDIT: This caculates to an approx. IBU of 39 for the above receipe so close enough eh?

[rwh]

The best reference I have found for all things hops is here:

Norm Pyle's Hops FAQ

It should be obvious that the alpha acid utilization is a widely debated topic, and that it is not an exact science. Homebrewing systems vary so widely that it is impossible to be very accurate with the IBU estimates. The homebrewer who strives to be accurate within 10% of actual can probably achieve it, and verify it with known commercial examples. The human tongue is accurate enough for this delightful experiment. Precision with IBUs is certainly achievable, with careful record-keeping, including personal sensory descriptions, and the use of a consistent set of formulae and utilization tables. These steps will go a long way toward consistent quality beer.

[rwh]

One more thing: sounds like you're trying to do a traditional IPA here, rather than a modern one (IBUs of 60 are pretty much unheard of in modern IPAs). Note that an IPA is a variation of a British ale, not an American one so I'd recommend switching your hops to something British. Say:

40g Challenger at 60 minutes
25g Goldings at 15 minutes
25g Goldings at 5 minutes
Target IBU: 60

I have an all-extract IPA recipe of my own devising on my blog if you'd like to compare.

[blandy]

Hi RWH,

It's a boit late to swap the recipe as I'm racking it tomorrow. So I guess I'll have traditional bitterness and traditional alcohol strength, but un-traditional hops.

I'm sure it will still be a great beer, so no worries.

[rwh]

Oh, no doubt. Let me know when I can have a taste!

[chris.]

The best reference I have found for all things hops is here:

Norm Pyle's Hops FAQ

It should be obvious that the alpha acid utilization is a widely debated topic, and that it is not an exact science. Homebrewing systems vary so widely that it is impossible to be very accurate with the IBU estimates. The homebrewer who strives to be accurate within 10% of actual can probably achieve it, and verify it with known commercial examples. The human tongue is accurate enough for this delightful experiment. Precision with IBUs is certainly achievable, with careful record-keeping, including personal sensory descriptions, and the use of a consistent set of formulae and utilization tables. These steps will go a long way toward consistent quality beer.

Good point rwh. The scale is more important than the actual numbers. Pick a formula & stick to it & adjust subsequent recipes to taste.

As for precision with IBU's I'm not sure. When you take into account differing water profiles affect on bitterness, Co-humolene % of different types of hops, & just general perceived bitterness (in terms of malt to bitterness balance) I doubt whether anybody could accurately pin point a beers IBU (even the brewer of the abovementioned Pliny had picked it as being around 30-4IBU higher than it actually is) [/i]

[blandy]

Ok guys, here's an update on these brews.

The Bitter went into bottles today. Bulk primed with 80g cane sugar. FG 1.008
As for taste, it is bitter and has some really interesting hop flavours and aromas. It's about the colour of VB origional ale, if a bit redder (due to the roasted barley)

The IPA was racked as well yesterday. No Idea of the SG at the moment, as there was too much sludge coming out of the tap to get a good reading, but it's still going strongly; so we decided to give it another 2 weeks in 2ndary befor bottling. The alcohol flavour is distinctive but not overpowering, and apart from the usual beery flavours, there is a gin aftertaste (probably doe to the extra alcohol). Bitterness kicks in late: on the first sip it took me about 5 seconds for it to take over my tastebuds, but it was well worth the wait.

I've made 3 starters from the yeast slurry form the IPA, and will cap them when they've stopped fermenting. We intend to make some bread, a pizza, and possibly some more beer with this leftover yeast.

I'll get back with more updates when it's cold and carbonated.

[rwh]

We intend to make some bread, a pizza, and possibly some more beer with this leftover yeast.

You can do that? What about the hop residue in the slurry?

[blandy]

You can do that? What about the hop residue in the slurry?

Um, then the pizza will have a beery taste too? I can immagine that could be a good thing...