BeerSmith Bitterness Calculations

[user 141939]

So I am not exactly sure how Beersmith calculates bitterness but I am assuming that it uses pre-boil volume and expected pre-boil gravity.

IF I don't hit the expected gravity and I end up under. I would want to adjust down my hop additions so I don't increase my bitterness. But if I type in a lower gravity for measured pre-boil gravity, the bitterness for the recipe does not change. Shouldn't it increase due to higher utilization?

I would like to use the software to figure out hop additions based on my actual pre-boil gravity and not on my expected. Is this possible?

 

[user 141939]

One more thing I've noticed... If i increase boil time, say from 60 to 120 minutes , it increases my bitterness. Even though my hop addition time remains the same (60 minutes).

This doesn't make sense to me. When I get to 60 minutes, I'm having the same volume and hops regardless of whether I've been boiling for an hour or just starting.

Is there an explanation for this?

Thanks!


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[BreezyBrew]

I have notice that as well. I wonder if it has to do with the smaller boil volume.

 

[PLOVE]

I think the designation of "hop" additions is really more for your notes, than how BS calculates bitterness. In other words, it helps you to keep track of hops you're using to bitter vs flavor vs aroma. As for calculations go, the longer you boil, the better the extraction. Thus, you should see an increase in bitterness if increase the boil from 60 to 120 min, just as you would see bitterness imparted if your flameout hops were actually boiled for 60 min.

Confusing to be sure, but it does help with recipe assembly, etc.
P

 

[RmikeVT]

Bitterness isn't a BeerSmith prorietary formula. Look in beersmith to see how you are measuring IBUs (Ranger, Tinseth or Garetz) and then look up the formula if you want to know how the variables work with each other.

But overall Bitterness is a function of Alpha Acid Units, Boil Volume, Gravity and length of boil.

To answer your second question --
You are boiling off more wort at 120 minutes, so when you get to 60 minutes you have less volume than you would have if you started boiling at 60 minutes, increasing your bitterness.

Overall --
I think you are over thinking this. Try to hit your volumes and don't worry about plus or minus 5 IBU's. Most folks can't taste the difference between 30 and 35 IBUs, some will even say its not perceivable and once you get close to the 70 IBU mark it really doesn't matter.

 

[user 141939]

Thanks for replies. I just added the calculations to my spreadsheet that I made so I can make hop additions based on actual pre-boil gravity. I can just plug in the pre-boil gravity and final volume and then just play with my hop additions until I get the number.

s for calculations go, the longer you boil, the better the extraction. Thus, you should see an increase in bitterness if increase the boil from 60 to 120 min, just as you would see bitterness imparted if your flameout hops were actually boiled for 60 min.

I didn't change my boil times for the hops. The additions were still 60 minutes and 30 minutes. So I changed the boil time to 120, but I did not change the hop additions to 120. This is why it doesn't make sense to me that the software would be increasing the bitterness.

To answer your second question --
You are boiling off more wort at 120 minutes, so when you get to 60 minutes you have less volume than you would have if you started boiling at 60 minutes, increasing your bitterness.

When I change from 60 to 120, The software adds an hours worth of boil off to my sparge water. So in my case it adds 1.25 gallons to the sparge do make up for the longer boil. So when I am doing my 60 minute hop addition, I have the same volume regardless of whether I chose a 60 or a 120 minute addition.

So basically, same hop additions, same wort volume, different bitterness. I guess I am still missing something, and it isn't a huge change but I just don't get why its changing at all. It doesn't matter anyways, I have the formulas in my spreadsheet now. If I had kept the hop additions based on what beersmith said, I would have overshot bitterness by about 12 units. I suppose it wouldn't have made a difference but I just like to keep it as close as I can. And I do tend to overthink things

I'm also new to all-grain and this was a RIS so I had no idea how far off I would be with the gravity (which ended up being quite a bit).

The recipe was written for 1.105 and based on 80% efficiency and a 60 minute boil. I guess some people are just mashing wizards! I had 60% efficiency.

 

[Yooper]

Gravity actually has nothing to do with hops utilization. I know that it used to be thought so, but in about 2008 even John Palmer said he "got it wrong" in how to brew.

IBUs are actually independent of wort gravity. In a 1.000 wort vs a 1.100 wort, there should be little difference in actual isomerization of hops oils (IBUs).

What DOES impact IBUs is adding water (ie dilution). If a wort has, say, 80 IBUs and is 2.5 gallons, and 2.5 gallons of water (as in partial boils) is added, then you'd get 40 IBUs as a result, no matter what the wort gravity was initially. For an OG batch, with no added water, that of course doesn't apply but many brewers do try to make an IPA with a partial boil and wonder why the bittering is insufficient.

Anyway, it's true that even the most gifted taster would not be able to discern a difference of 5 IBUs, and possibly even more IBUs.

 

[user 141939]

Ok, you could probably guess what my next question was going to be but looks like you already answered it in this thread...

https://www.homebrewtalk.com/f14/calculating-ibus-355730/

Thanks for the input.