(DONE) Custom Attenuation for Fermentables

Discussion in 'Feature Requests' started by ErockRPh, Nov 7, 2012.

  1. ErockRPh

    ErockRPh New Member

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    I'd love to have a setting on a per-ingredient basis that allows you to adjust how fermentable it is. At the very least, I would like to be able to mark something as 100% fermentable (for things like simple sugars, Candi Syrup, etc.). This would bypass the yeast's attenuation percentage calculation and would therefore have no impact on the calculated final gravity.

    A more advanced feature that I would like to see is a way to add a custom "fermentability factor" to fermentables that allows to adjust if an ingredient doesn't ferment out as fully as others. For example, I'd like to be able to mark certain Crystal malts or extracts with an attenuation factor of 90%, which would then multiply the yeast's attenuation percentage by 0.9 before calculating the FG. Something like lactose or maltodextrin could be set to an attenuation factor of 0% to indicate that it does not ferment at all.
     
  2. gelatin

    gelatin New Member

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    Re: Custom Attenuation for Fermentables

    I would also like to see this. I'm thinking about doing this with a locally hosted html and javascript file, though of course I can't save the results without writing the backend webapp.

    Looking into this, it's obvious that you'd need to edit the fmt_template and/or cfmt_template div to include a new parameter:
    <span><input type="text" name="custFermentability[]" id="custFermentability" value="" maxlength="6" style="width: 32px" /></span>

    The issue then becomes there's a whole lot of javascript that needs to be changed. You need to tie in the new parameter to the existing infrastructure, so then you need to modify the Fermentable function/class and then track down all of the things that are effected by this change, which doesn't look to be insignificant, and you're dealing with lightly obfuscated code so it's easy to make a possible mistake. The gravity methods are fairly easy changes though you'll need to pass in the fermentation data instead of just OG and attenuation to get FG.

    If BF does this, they'll also need to change their backend, and I'd bet it's going to be a little messy given their apparent current architecture, so I wouldn't count on this being down at a high priority given the work required for a couple of semi-uncommon ingredients.

    I'd be up to doing this work cheaply if BF wants to entertain that offer. I could do it a lot quicker with the un-obfuscated code.
     
  3. Kaiser

    Kaiser Member

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    Re: Custom Attenuation for Fermentables

    The problem with this approach is that the final attenuation combines both attenuation limit (wort fermentability) and the yeast's ability to get to this limit. The attenuation numbers published for yeasts have not been collected in a standardized enough way that allows for the separation of wort fermetability and the yeast's affect on the final attenuation.

    Your request is to provide for a way to predict wort fermentability based on the fermentability of the ingredients. But that cannot easily translated into final attenuation unless we know how much residual fermentable sugar the yeast is going to leave behind.

    BTW, I don't use the yeast attenuation numbers at all. I use the custom fermentability and enter an attenuation that I would expect based on the recipe, yeast used and past experience.

    Kai
     
  4. gelatin

    gelatin New Member

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    Re: Custom Attenuation for Fermentables

    Kai, a principle issue is that for things like significant amounts of lactose and maltodextrin, you are guaranteed to have a FG or OG that is way off. A pound of lactose may add 0.013 gravity points to OG and FG both, and there is no way to model this in the current recipes. You can add it in to get an accurate OG, but the FG is always wrong. Having adjustable fermentability allows us to fine tune the recipe so the calculator is matching reality.
     
  5. LarryBrewer

    LarryBrewer Active Member

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    Re: Custom Attenuation for Fermentables

    To be clear, FG is the only thing that would be impacted by this proposed change.

    FG is just a best guess. It depends on so many factors, including mash temperature, grain bill, yeast, fermentation temp, etc. No matter what we do with the FG equation, I get the sense it won't make everyone happy. Yes, accounting for maltodextrine would be a quick way to make the FG higher. Heck, we could just make an exception for that and lactose, and call it a day.

    The idea of putting in a % fermentability though, as Kaiser points out, doesn't translate through because there are additional variables in play. Take something like raw sugar, it might ferment 100% in some cases, but in others, if the yeast reach their alcohol limit, it would not - so it isn't that simple.

    For now the way to go about it is to adjust the yeast attenuation. Look for the custom attenuation checkbox in the yeast section. That allows fine tuning the FG.
     
  6. gelatin

    gelatin New Member

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    Re: Custom Attenuation for Fermentables

    OK, here's a guide to altering attenuation for unfermentables using only the yeast attenuation.

    First calculate the percentage of gravity the unfermentables contribute to OG. Suppose you are adding 1 pound of lactose to a 1.082 beer. As without the lactose the beer would be 1.069, the lactose contributes 0.013 out of the 0.082 gravity points over water, or 15.8% of the added gravity. Take 1 minus the 15.8% to get your attenuation adjustment, 84.2%. Finally, add a custom attenuation to your yeast and multiply the average attenuation given by your adjustment to get the attenuation you should enter.

    Example:
    http://www.brewersfriend.com/homebrew/r ... erry-graff
    15.8% gravity from lactose, adjusted average attenuation of S-04 by 84.2% to get 60.6%. Actual measured OG is 1.081 and FG is 1.031, essentially dead on.
     
  7. LarryBrewer

    LarryBrewer Active Member

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    Re: Custom Attenuation for Fermentables

    What other ingredients besides Lactose and Maltodextrine are non-fermentable? Instead of dealing with a change to the data model, and all the logic updates that involves, we could just program the FG calculator to recognize a list of special ingredients in this category. That would be the fast fix.
     
  8. gelatin

    gelatin New Member

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    Re: Custom Attenuation for Fermentables

    Those are the main two I know of.

    Maltodextrin isn't current on the built-in fermentables list (40 PPG and 1L).
     
  9. LarryBrewer

    LarryBrewer Active Member

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    Re: Custom Attenuation for Fermentables

    Good news!

    In the next release Maltodextrin and Lactose will fully contribute to FG and will not be reduced by the attenuation factor. In reality they do ferment a couple percent - a small limitation to live with considering the simplicity of the solution.

    The ppg listings were all over the place on the internet for both of these sugars. I could not find anything for lovibond. Here is what I settled on, open to updates:
    Maltodextrin - 43 ppg, lovibond 0
    Lactose - 35 ppg, lovibond 1

    Both will be listed in the fermentable drop down under the Sugar category. Milk Sugar will be renamed to "Lactose (Milk Sugar)" for clarity.

    Any custom ingredient that has the word Maltodextrin or Lactose in it (not case sensitive) will get this special treatment for purposes of calculating FG.
     
  10. Kaiser

    Kaiser Member

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    Re: Custom Attenuation for Fermentables

    That's odd. I would have expected lactose to have a ppg of ~43 since the lactose we buy is likely lactose monohydrate (95% lactose 5% water). And pure lactose should behave like table sugar when it comes to ppg. Maybe I'll have to buy some and experiment.

    Kai
     
  11. gelatin

    gelatin New Member

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    Re: Custom Attenuation for Fermentables

    This is great, thank you. I use maltodextrin and lactose quite a bit myself as I'm trying to perfect a sweet pumpkin amber and cherry graff (lactose), and I use maltodextrin when I want to boost the mouthfeel without touching ABV.

    I would run some hydrometer tests myself but mine is a general use one and not accurate enough to really pick up the difference unless I burn a lot of ingredients.
     
  12. LarryBrewer

    LarryBrewer Active Member

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    Re: Custom Attenuation for Fermentables

    I can pick some up at the home brew store this weekend and do some tests. I have a milligram scale. Should be fun to test. Still the ppg could vary by manufacturer...
     
  13. LarryBrewer

    LarryBrewer Active Member

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    Re: Custom Attenuation for Fermentables

    Just finished my experiment with measuring the ppg of maltodextrin and lactose. Was a good excuse to upgrade to a more precise hydrometer.

    Lactose came in at 41 ppg.
    Maltodextrine came in at 39 ppg.
    (revised after accounting for volume increase from sugar in solution)

    These values will be used in the recipe editor once this feature goes live.
     
  14. LarryBrewer

    LarryBrewer Active Member

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