Adding sugar to boil kettle vs. fermenter

Discussion in 'General Brewing Discussions' started by Duchifat, Feb 12, 2021.

  1. Duchifat

    Duchifat Member

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    I was editing a recipe for a Tripel and noticed a big difference in the predicted ABV if I added the (cane) sugar to the boil kettle (10.5%) or to the fermentor (8.7%). This puzzles me: Why would I get different values? I'm practically just adding sucrose, a disaccharide that should be fermented totally in both cases. Can anybody please explain this to me?
    TIA,
    Michael
     
  2. Silver_Is_Money

    Silver_Is_Money Active Member

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    It appears that one (or perhaps both) ABV predictions math models are flawed.
     
  3. Head First

    Head First Well-Known Member

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    Not knowing the numbers you are working with, the recipe builder could be taking into account losing some sugar with your kettle losses. JUST a shot in the dark without more info. @Pricelessbrewing could maybe lay it out for you.
     
  4. Yooper

    Yooper Administrator
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    Could you give me a link and/or a screenshot of these? I need to dig into this.
     
  5. Duchifat

    Duchifat Member

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  6. Pricelessbrewing

    Pricelessbrewing QA Software Tester
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    @Duchifat, this is a known issue that we hope to get resolved as soon as some higher priority tickets get completed. @Yooper this is ticket #1496.

    Thanks for the ping, @Head First.

    In short: Late additions fermentor behaves as if the gravity reading is being taken after transfering to the fermentor, but before the sugars are added. As such, the FG decreases slightly (when compared to zero sugar addition) due to the 100% attenuation of the sugars, so the abv increases slightly. In comparison to the late addition: kettle, you're getting higher OG, with the same FG, and a higher abv% as a result. However, as @Head First alluded to, any kettle losses in your equipment profile will deduct the corresponding gravity points. If you have no kettle/misc losses, then a fermentable addition for late: kettle should behave (mathematically) the same as how late:fermentor should work after the update and is what I would recommend in the interim.
     
  7. Duchifat

    Duchifat Member

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    Thank for you explanations @Pricelessbrewing. I would like to make sure I understood you well and relate to the remark about losing gravity points in the kettle:
    1. Re the sugar addition, do you mean that in the 'fermenter late addition' the sugar quantity in the wort is not altered by the addition, but the 'nature' of the fermentables is changed (by altering attenuation), so that only the FG reached will be lower? And this is the reason for the small changes I see in ABV when adding sugar to the fermenter?
    2. Kettle losses, NOT including evaporation and shrinkage, should not alter s.g.: by losing wort in pipes and dead volumes etc, we are just losing 'future beer', but not changing s.g., so ABV should stay the same, but we get less beer. Am I seeing this wrong?
    I learn a lot from these discussions; this is the reason for my questions.
    TIA
     
  8. Pricelessbrewing

    Pricelessbrewing QA Software Tester
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    The issue is one of timing, since "OG" is defined as the gravity at the time of the transfer into the kettle, any gravity additions after that point aren't counted in the OG, but should be counted in the ABV formula. However at this time, the ABV is a function of the OG, and the FG, so your abv with any Late:Fermentor aren't being counted properly. This will be remedied.

    However, the apparent attenuation of the sugar additions are counted towards the expected FG.

    Kettle addition: (There's a bug here, the fg should be lower, bringing the abv up 0.2ish to match the fermentor vs no sugar differences).
    upload_2021-2-13_11-39-12.png

    Current Fermentor addition: (Almost the same as the no-sugar addition, but higher attenuation drives the FG down slightly, raising the abv).
    upload_2021-2-13_11-39-31.png

    No sugar addition:
    upload_2021-2-13_11-39-55.png

    After the update (approximately)
    OG: 1.089
    FG: 1.007
    abv: 10.70

    2) What I was referring to is that if you add 2.5 kg of sugar at 254 "points" to the wort. If you add these points to wort before losing some of the wort, then you're also losing some of the sugar points. VS adding it into the fermentor, where you will "keep" 100% of the sugar points so to speak.

    Example to keep the math easy:
    5 gallons (20.82 L) postboil volume, add 2 LB of sugar (0.91 kg), ie 92 points bringing the gravity up from 1.060 to 1.0784. If you then lose half a gallon (~2L), then you will also leave behind a corresponding percentage of that 92 points, or 9.2 points. The gravity doesn't change from 1.078 during the actual transfer, but if you would have added the sugar afterwards, then the you would have 1.0804 since the sugar was added to a smaller volume.
     
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  9. Duchifat

    Duchifat Member

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  10. Silver_Is_Money

    Silver_Is_Money Active Member

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    #10 Silver_Is_Money, Feb 13, 2021
    Last edited: Feb 13, 2021
    As I presently understand it (subject to correction), the volume of the Wort increases by some nominal measure as table sugar is added to it, as opposed to the seemingly common and intuitive presumption that volume does not change when table sugar is added to water. The result of this (for water) has been variously reported that the SG gain will not be the commonly presumed 46.21 specific gravity points per gallon per pound of added table sugar, but rather the gain in specific gravity points may factually be closer to something on the order of ~43 points per gallon after the fact of now having more volume (more gallons) is recognized and factored in. But even this ballpark correction is for water, and not for Wort. Therefore what seems to be a necessary requisite before rushing in whereby to quasi-solve this matter is to actually quantify the volume gain measured when Kg.'s of table sugar are added into Worts of various Plato's (or SG's) as well as various initial volumes (as measured at room temperature).

    Short version: Intuition alone more often than not leads to bad science.
     
  11. Duchifat

    Duchifat Member

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    @Silver_Is_Money could you please point me to some calculator or formula so I can calculate this change in volume (for water and sugar would be good enough) instead of using intuition? As I understand, the relationship is probably not linear so I cannot figure it out using the numbers you mentioned.
    TIA
     
  12. Silver_Is_Money

    Silver_Is_Money Active Member

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    #12 Silver_Is_Money, Feb 13, 2021
    Last edited: Feb 13, 2021
    Having never undertaken the requisite science that I requested be done within my above paragraph, I can not in good faith present you with a viable extant calculator/software math model for the ABV. But my presumption as of right now would be to run with 43 gravity points per pound per gallon of fermenter volume for the sugar component.

    I will however interject that no math model precisely predicts true ABV. So even if there is full resolution for the ABV addition contributed by the sugar, you will merely only be able to approximate your beers ABV.
     
  13. Pricelessbrewing

    Pricelessbrewing QA Software Tester
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    Since PPG is defined as the points per pound per gallon of resultant wort, so as long as the measured property is accurate, this is already accounted for in the fermentables specs. Otherwise the ppg of extract would be different or we wouldn't hit the intended sg of our starters.

    However this is correct, and the amount of volume added is also non-linear, ie the volume increase for 1 lb of sugar is ever so slightly different at 1.030 vs 1.090.

    Starting from the PPG, the density of water, and the definitions of sg as a relative density, and plato/brix as a percentage of sugar weight, this can be derived from (almost) first principles.

    *Math is ... complicated*
     
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  14. Silver_Is_Money

    Silver_Is_Money Active Member

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    #14 Silver_Is_Money, Feb 14, 2021
    Last edited: Feb 14, 2021
    I did a rapid search of the net this morning and came across 3 figures for the volume increase witnessed for sugar additions before terminating my search. The agreement between them is abysmal. One said 0.41L of volume gain occurs when adding 1 Kg. of table sugar. Another said 1 Kg. of sugar increases volume by 0.5L, and the last said 0.625L. None of these reports mentioned the initial starting volume or SG, thus rendering them effectively useless.

    Despite my warning about intuition, I will intuitively speculate that as Wort SG increases, the rate of volume increase with additional sugars added goes up.
     
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  15. Pricelessbrewing

    Pricelessbrewing QA Software Tester
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    It's been a few years since I did the research, but I recall it being an inverse non-linear relationship, ie the volume added decreases as sg increases.
     
  16. Suga

    Suga Member

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    I may be way off here but wouldn't you expect higher OG if added to boil vs fermentor. Since the boil is concentrating the sugars?
     
  17. Silver_Is_Money

    Silver_Is_Money Active Member

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    #17 Silver_Is_Money, Feb 14, 2021
    Last edited: Feb 14, 2021
    It's still the same mass of sugar added either way. Boiling is not creating additional sugar mass, so the OG should be the same either way. But if 100% of that which is being boiled doesn't transfer, and some volume gets left behind, and that being left behind also contains sugar, the potential for an ABV increase in this case would favor direct addition of the sugar to the fermenter due to the same mass of sugar being added to less volume.
     
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  18. Suga

    Suga Member

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    Make sense, I had read about shorter boils and it said point of the boil was to concentrate the sugars/fermentables. So just followed that logic thinking the boil would increase the OG. Hadn't thought about the volume.
     
  19. Nosybear

    Nosybear Well-Known Member

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    Given a constant amount of sugar, gravity and volume are inversely proportional.
     
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