Late extract addition and Hop Utilization.

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Schnitzengiggle

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I'm going to be brewing a Sweet Stout possibly this weekend, if not, next week for sure. I have researched threads on this and most say to reduce hops by about 20-25% or so due to higher hop utilization with lower gravities. I have begun doing late extract additons and using Beersmith for some calculations. Here is the recipe:

Type: Extract (Late Addition)
Batch Size: 5.00 gal
Boil Size: 3.00 gal
Boil Time: 60 min

Ingredients

Amount Item Type % or IBU
4.50 lb Amber Dry Extract (12.5 SRM) - Dry Extract 56.25 %
1.00 lb Wheat Dry Extract (8.0 SRM) - Dry Extract 12.50 %
1.00 lb Chocolate Malt (450.0 SRM) - Grain 12.50 %
0.75 lb Caramel/Crystal Malt - 60L (60.0 SRM) - Grain 9.38 %
0.75 lb Roasted Barley (300.0 SRM) - Grain 9.38 %
1.50 oz Fuggles [4.50 %] (60 min) - Hops 17.1 IBU
0.50 oz Goldings, East Kent [5.00 %] (15 min) - Hops 3.1 IBU
1.00 tsp Irish Moss (Boil 15.0 min) Misc
1 Pkgs Irish Ale (White Labs #WLP004) [Starter 1000 ml] Yeast-Ale

Beer Profile

Est Original Gravity: 1.050 SG
Est Final Gravity: 1.014 SG
Estimated Alcohol by Vol: 4.76 %
Bitterness: 36.3 IBU
Est Color: 46.0 SRM

According to Beersmith (Hops Bitterness Calcualtor), if I were to just steep my grains I would have a SG of 1.002 and if I were to add my bittering hops at the boil for 60 minutes that would give me 25.9 IBU's and with my last hop addition at 15 minutes that would give me another 6.5 IBU's. However, I will be adding all of my DME for the last 15 minutes of the boil, which will affect the gravity, reducing hop utilization. My Brew Sheet states that the Pre-Boil Estimated SG with all grains/extracts added is 1.084, though, all the DME will be added late (last 15 min).

Why would Beersmith calculate the Pre-Boil Estimated SG with all grains/extracts added when doing a "late addition"?

Why the difference between the Hop Bitternes Calculator on Beersmith (total=32.4 IBU's) and the actual recipe (total=36.3 IBU's)?

Will there be a significant difference in the total IBU's because of the higher gravity when adding all of the DME in the last 15 minutes?

I made sure to check the late extract additon in the recipe so I'm a little confused???
 

ssabin

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I have a spreadsheet that uses the hop utilization formula given in How to Brew. If you truly only used the steeping grains before you boiled, your starting gravity would be 1.0095 if you boiled with 3 gallons.

Note that in general, partial boils try to hit S.G during the boil that is similar to the final brew. I am comfortable shooting a little lower, but read that you should have SOME extract in the wort to help properly isomerize the alpha acids. I think I read that 1.020 is considered some sort of minimum.

Anyways, even with the S.G. at the start of the boil at 1.0095, I come up with 32.9 IBUs. If your boil S.G. were really 1.002, then you would end up with 35.4 IBUs.

One of the reasons I did my spreadsheet was that I had heard that Beersmith didn't handle late extract additions very well, and I see myself doing only extract brews for awhile, so I wanted the flexibility to account for different levels of lateness, etc.

So, I don't think it's good idea to boil your hops without some extract in the boil, but then you would likely need more hops to hit your target IBU level.
 
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Schnitzengiggle

Schnitzengiggle

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I'd like to hit middle of the road for hops and a Sweet Stout is 20-40 IBU's so I'd be happy w/30-34 IBU's or so. I'm just really confused about the conflicting info on these threads and what Beersmith came up with. Now that you mention it I did read somwhere about having some DME to isomerize the alpha acids more efficiently. I wonder if indeed the calculations from Beersmith would be accurate for the "recipe" given adding the DME at 15 minutes left in the boil. I suppose I could add the 1lb of Wheat DME after steeping grains and add hops. I would prefer not to be at the high end of the hop scale for this style as I personally don't think that hops should "shine" through in a traditional style stout other than an Imperial. I do appreciate your help, not too many have seemed to want to tackle these questions. Thanks fro the input, Brew on!
 

BarleyWater

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ssabin

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I think you'd be fine adding the wheat DME after you steep the grains.

I've noticed my spreadsheet is wrong, so I don't know exactly what your IBU level would be, but it should be somewhere around 30. It would be about 32 if you added the extract at flameout (something some folks do).

Looks like a pretty good plan, although I have your OG at 1.058. Beersmith seems to estimate less yield when steeping grains than the Palmer book. I really don't know which might be more accurate.
 
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Schnitzengiggle

Schnitzengiggle

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What about dilution when adding top off water as BarleyWater suggested in the thread links he listed, does top pff water dilute that much? So, if 2-2.5 gallons of topp off are being added after boil that will reduce the IBU's further? It makes sense, if you were to make tea and then add a bunch of water to that tea it would indeed be weaker than before the extra additon. I'm still new to this, but the only way I see reaching my target IBU's w.this recipe is to increas my bittering hops by 1oz making a total of 2oz's right?
 

ssabin

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No, I think what you posted will be fine, and I assumed you would top off to a finished total of 5 gallons. If you want to make the final batch size 5.5 gallons, you'd probably be OK, and you could counter that a bit by adding your final extract even later (it doesn't need 15 minutes in the boil - 10 shoul dbe fine, or even 5). Going from 5 to 5.5 gallons is a 10% change, so your IBUs would be about 10% less if you simply diluted more at the end. Thta would put you somewhere around 29 IBUs, so you wouldn't need to adjust much.

I really think 2 oz will be too much, although still within the style range. If you like hoppiness, then go for it. If you want to be at 30 IBU, you're good at 1.5 oz.
 
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Schnitzengiggle

Schnitzengiggle

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That is really what is confusing to me. Top-off water will dilute/reduce IBU's right? It seems as though Beersmith's calculations may be off, I did the math according to Palmer's equations in his book and just from the 1st hop additon I calculated only 20 IBU's @ SG 1.014 (assuming I did my math right I am notoriously bad at making mistakes). With Beersmith, the brew sheet (instructions) basically calculate the total wort gravity at 1.085 with all DME added, and I can't wrap my head around why it would calculate that SG when I entered the DME as late additions. I'm going to just go with my original recipe to see what happens. My concern isn't that the IBU's will be too high, it's that they may be too low contributing to an overly sweet beer. If anything, with late additions/partial boils from what I've read, it is hard to get very high IBU's such as in an IPA. Again it is just confusing to me that Beersmith gives me a mid 30's IBU but realistically if it is calculating SG @ 1.084 with all extract added then how could I possibly attain the IBU's it claims. I guess the better question is, does Beersmith calculate for top-off water in it estimations? If I say my total volume is ~5.00 gallons, and my boil voulume is 3.00 gallons, is it taking top-off into consideration? I would assume so, but I have read conflicting info on this topic adding to my misunderstanding.
 

ssabin

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That's why I have opted for the "homebrewed" home brew spreadsheet! At least that way I know the limitations and assumptions behind the calculations, and I can provide degrees of freedom or simplify as I wish.

Someone likely knows how beersmith accounts for late extract addition, but most of us would have to use it, see how it calculates thingsa, then provide a good guess at what it seems to be doing.

I'm guessing that if you do your own calculations using Palmer's utilization equation (it's not HIS equation, but we understand each other on that point), you will have a very good estimate of the IBUs.

Note that in general, late extract addition might let you get say up to 20% more IBUs for the same amount of hops, but 10% is probably more typical. This difference isn't going to make or break your beer. But I'm like you in that I like to understand EXACTLY what I'm attempting, so from that standpoint, I wouldn't trust Beersmith with properly handling late extract addition until you understand how that feature works. It sounds like that check box makes some general assumptions about what late extract addition means. Or, it may simply not calculate something correct in that mode.

Good luck!
 
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Schnitzengiggle

Schnitzengiggle

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I agree with you completely. I might be a little O.C. on this, but just like everyone here on this forum I want to make the best beer possible within my means. I didn't have a chance to taste the sample I took, because I accidentally got some star-san overspray into it with my squirt bottle. I know they say you can drink that stuff, but I would'nt. In a few weeks when I take my sample for gravity reading I'll post how it is. Thanks again for your input and advice!
 

SumnerH

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Just to throw some numbers out on this, if you do the math then you'll find that Rager and Tinseth aren't really affected by doing dilution or not. You wind up scaling by opposite and balancing factors when you scale down for the boil and back up for the dilution.

Garetz is affected by dilution, but not vastly.

Here's 3 sets of IBU calculations. The first is a full 19l (~5 gallon) boil at 1.050 with 30g (~1 oz) of 0.08 AA hops for 60 minutes:
Rager 38.76 IBU
Tinseth 29.14 IBU
Garetz 23.19 IBU

The second is done with a "halfway" adjustment for partial boil--it adjusts the OG upwards to account for the higher gravity during boil, but doesn't adjust the boil volume downward or dilute at the end:
Rager (partial 3 gallon, gravity only) 38.77 IBU
Tinseth (partial 3 gallon, gravity only) 21.66 IBU
Garetz (partial 3 gallon, gravity only) 20.12 IBU

The final one does a "complete" partial-boil adjustment. It scales down the boil volume to 3 gallons, and then dilutes back up at the end:
Rager (partial 3 gallon, gravity and dilution) 38.77 IBU
Tinseth (partial 3 gallon, gravity and dilution) 21.66 IBU
Garetz (partial 3 gallon, gravity and dilution) 19.29 IBU
 

SumnerH

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Now back on the original topic, what's the best way to account for hop utilization in a late addition? Anyone have the formulas for that or a good idea how to approach it?

My inclination is to go with the extracted portion of the hops to figure out how much is left in the hops, and use that as a starting place in the new gravity's utilization spectrum and run the clock from there.

An example might be illustrative.

Tinseth chart:
Code:
Time    1.030   1.060
---------------------
  0	0.000	0.000
  3	0.034	0.026
  6	0.065	0.049
  9	0.092	0.070
 12	0.116	0.088
 15	0.137	0.105
 18	0.156	0.119
 21	0.173	0.132
 24	0.187	0.143
 27	0.201	0.153
 30	0.212	0.162
 33	0.223	0.170
 36	0.232	0.177
 39	0.240	0.183
 42	0.247	0.189
 45	0.253	0.194
 48	0.259	0.198
 51	0.264	0.202
 54	0.269	0.205
 57	0.273	0.208
 60	0.276	0.211
 70	0.285	0.218
 80	0.291	0.222
 90	0.295	0.226
120	0.301	0.230
If I have a hops addition that's 30 minutes @1.030 and then 30 minutes @1.060, I'd look up the utilization @30 minutes (0.212).

I'd then assume that hops at that utilization will pick up at the 60-minute line @1.060 (that's where 0.212 falls, more or less--actually 0.211), and adding 30 minutes at the new gravity would give 0.226 total utilization.

(In reality I'm doing this by formula, but the tables are easier to visualize and explain things).

That seems like the most reasonable way of figuring utilization in boils of non-uniform gravity.

Of course, it probably needs to be re-thought in light of recent news about the impact of gravity on utilization...
 

ssabin

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I have this exact type of calculation in my spreadsheet. It does use the fitted equation for utilization as a function of time and gravity. I'll explain how I did my calculation using your example (and also using the chart for simplicity, although I use an equation instead).

If the boil went for 30 minutes before the extract addition, that provides the easy part - 0.212 utilization for the first 30 minutes.

I then note that if the hops had been boiled at the higher gravity for the first 30 minutes and continued on for another 30 minutes, the utilization would have been 0.162 at 30 minutes and 0.211 after 60 minutes, or a difference of (0.211-0.162)= .049. I add that to the value for the first 30 minutes (0.212) to get a total utilization of 0.261.

As a sanity check, boil the full 60 minutes at SG = 1.030 would get a utilization of 0.276, and if boiled for the full 60 minutes at SG=1.060 would get a utilization of 0.211, or to summarize:

Utilization versus method:

all extract added immediately (60 minutes at 1.060) = 0.211
add remainder at 30 minutes = 0.261
add remainder at end of boil = 0.276

To me, this logic makes sense as it preserves the affect of time independently from the effect of gravity. Of course, we really don't know if the fitted equation accounts for interactions of gravity and time properly or not, so my method is a guess as well. The nice thing is that the error can't be that large as the extract remainder is added later and later. I see no reason to add it prior to the last 10 minutes, and many like to add it at flameout. So this method should be pretty close for most of us.
 
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