IBU and SRM values with fermentor target

Discussion in 'Recipe Editor' started by zsoker, Sep 6, 2019.

  1. zsoker

    zsoker New Member

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    Using the fermentor target and the auto calculated post boil values and a manually set Fermentor batch size.

    When the post boil value is altered the IBU/SRM values remain the same.

    When the Batch size is modified the IBU/SRM values change.

    Can you explain please why it should not be the other way around?

    Why would the IBU/SRM change just because only volume X goes into the kettle from the total post boil volume? Arent these final values derived from boil times and boil volume?

    Am I wrong somewhere?
     
  2. Nosybear

    Nosybear Well-Known Member

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    I think you are talking about changes in utilization with volume. In other words, the behavior is exactly as it should be. Hop utilization depends on sugar concentration as well as boil time so changing volume without changing sugar content changes IBUs. A more dilute wort with the same amount of hops will extract more iso alpha acid than a more concentrated wort. And IBUs are mg/liter of iso alpha acid.
     
  3. zsoker

    zsoker New Member

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    Yes, I'm aware of that. BUT, why do they change AFTER when I turn the gas off?
     
  4. Nosybear

    Nosybear Well-Known Member

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    Confused, how can turning the gas off affect the software?
     
  5. zsoker

    zsoker New Member

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    Let me try to detail it. My question is about the IBU/SRM values at post boil vs what gets into the fermenter.

    As an example, we start with 25L to boil and at the end of the boil (when we turn the gas off) there is 21L. We cool it, and move 19L into the fermentor and leave 2L behind.

    Are you saying that the IBU/SRM of the 19L will be different from the 21L that we ended up at the end of the boil? (Assume we just poured the whole thing into the fermentor) Why would it be?
     
  6. Nosybear

    Nosybear Well-Known Member

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    No. Look at the units: mg alpha acid per liter wort. Each liter has the same number of IBUs. So the measure is the same for what goes into the fermentor and what stays in the kettle.
     
  7. zsoker

    zsoker New Member

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    Yes, I agree. But the software says that if I pour more or less into the fermentor then I get a different IBU/SRM.

    "When the Batch size is modified the IBU/SRM values change."

    Open any of your receipes
    Set to TARGET:FERMENTOR
    Set or calculate a value for POST BOIL
    Set the value of the BATCH SIZE to the same as the POST BOIL value (lets assume we just dump it all in without even cooling)
    Now change the BATCH SIZE to lesser value while leaving all else the same. Notice the IBU/SRM changes. (In my view they should not change here)
    Now change the POST BOIL size to a different value. IBU/SRM does not change. (In my view they should change here)
     
  8. Nosybear

    Nosybear Well-Known Member

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    I think they took the Post Boil out (I hope they did, that's confusion). Nope, they didn't.... Post boil should be the basis of the IBU calculation. Let's imagine an extreme case: I make 10 liters of wort at 25 IBUs. That's my "post boil". I've extracted 250 mg of iso-alpha acid. So let's say my batch size is 1 liter, what I do with the other nine, immaterial. That 1 liter has 25 mg of iso alpha acid for a bitterness of 25 IBU. The mg of iso-alpha acid is an amount and if you change the batch size, it changes. What does not change is the IBUs, the rate of bittering in mg/l. If that's not the behavior - IBUs calculated on the post-boil volume with no regard for the batch size, the behavior is incorrect.

    I believe the pre "post boil" calculator calculated based on batch size, whether you were targeting the fermentor or the kettle. Adding the "post boil" made it explicit: Post boil is simply the amount in the kettle after the boil and the only volume that matters for IBUs (come on, admins, do you mean post boil hot or post boil cold, that 4% difference could be important to someone out there....). The problem with the software changes for us old guys is that we've adapted our processes to the software. I can hit my numbers because I know where to "fudge" a bit. I imagine it is possible to model the entire brewing process with software down to the three drops of wort it takes to use my refractometer. It's not necessary nor is it desirable. You can't model knowledge with software and some aspects of brewing require knowledge.
     
  9. zsoker

    zsoker New Member

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    RE: "Post boil should be the basis of the IBU calculation" Ok, so you are saying the same I'm
    RE: "The problem with the software changes for us old guys is that we've adapted our processes to the software"
    I'm not sure if I follow but since a new feature is implemented - post boil value is brand new, why not make it right. I imagine if the "old guys" are confused what does it do to a new user.
     
  10. J A

    J A Well-Known Member

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    We won't be able to make sense of it because the editor has been sort of ruined by the attempted "improvements. All I can figure is that the programmers don't understand the brewing process. I thought they'd reversed some changes and reverted to a point that it had been working in such a way that estimates matched real-world results pretty closely but it appears not.
    When I open a snapshot recipe from a brewday and it opens with different values from the "view" page and I can't find a combination of settings that matches what I know is accurate from actual measurements, I don't trust the software.
    Until they get the relationship between batch size, preboil and post boil figured out, none of it will make sense.
     
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  11. Nosybear

    Nosybear Well-Known Member

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    Problem is all of those are easy: Pre-boil is what you put in the kettle. Post boil is what is in there after you've boiled the wort (hot or cold?). Batch size should say Fermentor Volume, it's what you start fermentation with. Batch size should be the amount you package. Maybe if there were clear definitions, it would help.
     
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  12. J A

    J A Well-Known Member

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    Couldn't agree more. Batch size and final volume of finished product is never the same. We all know from experience that to get a 5 gallon keg filled, we need to have at least 5.5 gallons going into the fermenter which means 6 or so remaining after the boil which means 7.5 or thereabouts going into the kettle which means starting with 8.5 or 9 gallons of total mash liquor. From there conversion efficiency determines the amount of sugars in the wort and therefore the IBU contribution of the hops. The math involved is relatively straightforward but all those volumes are completely dependent on a brewers specific system and associated losses and the efficiency is dependent on equipment and process.
    Trying to simplify things to a point that a new brewer can come up with an accurate recipe without knowing any of those things is a losing proposition.
    As far as I'm concerned "brewhouse efficiency" has no place outside of commercial brewing. We only really care about conversion efficiency as it relates to the attributes of the finished beer, not the final volume. And that should relate only to pre-boil volume and gravity. Boil off tells us very accurately the gravity and IBUs we can expect once the boil is done. Those numbers don't change whether we put all of it or half of it in the fermenter and attenuation is computed from gravity measurements and has nothing to do with volume we started with or how much we get to pour in the glass.
     
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  13. Mark Farrall

    Mark Farrall Well-Known Member

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    It's always had kinks when fermenter was the target. It would adjust everything based on the losses in the equipment profile rather than just the things that are changed by that efficiency loss. If you didn't have any large losses in your equipment profile it wasn't that obvious.

    I've used kettle as the target exclusively since I worked that out. It ignores the losses in your equipment profile and just uses boil off rate for the calculations,

    I was going to check into the new approach to see if it was addressing the problem, but it was backed out before I had a chance to look in detail, so I'm back to only using kettle as the target.

    I think of batch as the amount packaged, but I can see that it doesn't really work for the calculator. I just have to accept that a batch of one beer needs to be bigger than another to fill the target package. Like the 1-2 litre difference between the hazy IPA and the witbier because of the huge difference in hopping.
     
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  14. J A

    J A Well-Known Member

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    It was worse, in fact pretty impossible. It didn't solve the problems that it addressed. It's still very wonky. All the parameters are a mess and there's no consistency as to what relates to what.
    It may be that they actually figure out a way to get back to full functionality but for now, I'm just bypassing it. I spent several hours yesterday putting together a brewing spreadsheet that actually works from desired batch size on down. I still have some work to do on it but I'll actually be able to trust that the ingredients I put together will give me the beer I'm trying to make. I should be able to use that to go back and fool the BF editor enough to maybe get some decent formulations for water additions since I've gotten used to using that. If not, I'll just start over with Bru'n Water.
    Here's how I've laid things out so far. Still need to do hop section/IBU calculation and ABV calculation.
    upload_2019-9-8_9-53-57.png
     

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