Target OG consistently 10 points low

Discussion in 'General Brewing Discussions' started by lonelymtn, Feb 3, 2019.

  1. lonelymtn

    lonelymtn Member

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    Over the last two weeks, I have brewed three times and I keep running in to the same issue: my target OG is consistently 10 points lower than the recipe claims. I have been banging my head against the wall trying to troubleshoot the problem, but ultimately, I cannot figure out what is wrong. It is baffling, because all of my other numbers are either perfect or high, not low.

    Let's take yesterday's session for example, everything is looking great headed in to the boil:
    • Post-mash conversion = 96.3%, OG = 1.063
    • Pre-boil/post-sparge = 90%, OG = 1.056, estimated = 1.044 (so more efficient than expected)
    • Boil complete, OG = 1.061, estimated = 1.071 (drags brewhouse efficiency to 60%, estimated 70%)
    The first thing I think about is boil-off rate, as it seems I am not boiling off enough to get to my target OG. Yesterday, my pre-boil volume was 8.5 gallons and my final volume was 7.5 gallons, giving me a boil-off rate of 4 qt/hr. This is also higher than expected, as the boil-off rate in my equipment profile is listed at 3.5 qt/hr (tweaked after measuring several brew sessions). In fact, all of my volumes are spot on -- what went in to the fermentor, what was left behind in the kettle, etc.

    So, I'm stuck and hoping there is something glaring that I am just missing. Like I said, it has happened three brews in a row now, all different (grist, yeast, style)
     
  2. Mark Farrall

    Mark Farrall Well-Known Member

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    Generally lower attenuation is not getting enough activity from the beta amalayse. Biggest contributor to that would be not pushing the mash temp too high. Then keeping the pH on the lower side of the acceptable range. Then it's a matter of thinner mashes and/or longer mash time to give the beta more chance to do it's work.

    Though if you weren't having problems previously and you haven't changed these I may be barking up the wrong tree.
     
  3. lonelymtn

    lonelymtn Member

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    I appreciate the quick reply, Mark.

    Almost all of these boxes have been check off already. I tend to mash as thin as total volume of water+grist will allow (1.6-2.0 qt/lb) and I adjust to keep my pH near 5.2 (testing 15 minutes in & at the end of mash). My mash temp for the last three brews has been 151, 149, and 154 respectively; and I usually perform a 60 minute mash.

    I also perform an iodine test and measure the first runnings gravity before mashing out, leaving it if either isn't where it should be.

    But you bring up an interesting point regarding the Beta Amalayse, so the questions I have now are:
    • Can mash be judged to be done, per the typical tests, but the Beta Amalayse still have work to do?
    • If yes, would a longer mash theoretically "fix" the problem?
    I have a recirculating mash setup and I typically only mash for more than 60 minutes if I have either a low DP grist or my target OG is high. Makes me think, assuming the questions above are both true, that I should perform a longer mash on anything larger than 1.060 or so.
     
  4. Trialben

    Trialben Well-Known Member

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    I rutinely mash longer than 60 no matter the beer. Try adding 30mins to the mash and don't skip the sparge your gunna loose sugars to the grains otherwise.
     
  5. HighVoltageMan!

    HighVoltageMan! Well-Known Member

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    #5 HighVoltageMan!, Feb 3, 2019
    Last edited: Feb 4, 2019
    I guess I’m confused. If your mash efficiency is spot on, then it should translate into the boil.

    Evaporation rate change, unless you can exactly replicate every boil.

    If you have a mash efficiency of 85% or so and it’s plugged into the calculator at 85%, then the boil volume will be close to expectations. That’s why if I hit my mash efficiency, then I then boil for gravity only. If the recipe calls for 1.050, then I will shoot for that and ignore volume. If my efficiency is higher then I’ll have more volume, if it’s lower, then there will be less volume. My ending volume is usually very close to predicted.

    You shouldn’t loose any efficiency in the boil except to hops and hot/cold break.
     
  6. lonelymtn

    lonelymtn Member

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    This is why I am confused as well. Every step prior to the boil is either spot on or a little more efficient than expected. Yet, at the end of the expected boil duration, OG is more than a little low.

    And unless I completely dont understand starch conversion, high or low mash temp affects fermentability of the wort and not the SG as long as you manage to have good conversion, which I am.

    The math just doesnt add up. According to the recipe builder, I should have gone from 1.044 pre-boil to 1.071 post on a 60 minute boil. Instead, I went from 1.056 pre to 1.061 post and a predictable 1 gallon of total volume. I know the volume doesnt matter, but it is what is predicted.
     
  7. HighVoltageMan!

    HighVoltageMan! Well-Known Member

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    There must be something wrong somewhere, but I guess I’m not sure what it could be. Maybe what you should do is plugged into the calculator the actual efficiency you got from the last brew and go from there.
     
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  8. Nosybear

    Nosybear Well-Known Member

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    That's way too much of a change. 1.044 should have wound up at about 1.050. The numbers you got sound right. Something isn't right in your settings: You missed OG by 12 points low.you missed FG by 10 points low. What was your conversion efficiency?
     
  9. Mark Farrall

    Mark Farrall Well-Known Member

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    Yes it can, but I'm not feeling like that's your problem. And whether beta has more work to do is more a personal preference question than a yes/no question. I regularly mash longer to give the beta amalayse as much time as possible, but I like my beers fairly dry and that nearly always gives me over attenuation according to the recipe builder. I'm just about to start using custom attenuation rates for the batches where I mash longer, so I suspect this may be a red herring.

    Theoretically, but the attenuation rates of most yeasts would be targeted to someone with a process very much like yours.

    I missed that your OG was 12 points lower than expected and focused on the FG numbers. Yep, something very funky in the boil part of the equation.

    Looking at the boil off and dilution calculator your numbers tally up with that. Your 8.5 gallons @ 1.056 down to 7.5 gallons leads to an OG of 1.063. To get that OG up to 1.071 you'd need to lose 1.8 gallons according to the boil off and dilution calculator. Not sure where the recipe builder has that difference of 0.8 gallon to get the gravity up, especially as you're hitting the volume numbers. Anything in your water requirements other than the boil off losses after the boil starts?
     
  10. Trialben

    Trialben Well-Known Member

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    Your going to gain 8 points out of a 60 minute boil at best maybe 10 on a rare occasion. I get around 4-6 points now on my Electric element. I think your efficiency is set too high if your getting 96%extraction for an SG of 1.044 if that's my rig I'm expecting 1.050 and I'll call it Par for the course. Have you set your boil time to like 120 minutes then maybe your FG and Final Volume might line up.o_O

    Any chance of a recipie view for more detail pls I want to see your weight of fermentables in mash...
     
  11. lonelymtn

    lonelymtn Member

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    My pre-boil/post-sparge gravity was 12 points higher (1.056) than the recipe predicted (1.044), but my FG was 10 points low (1.061 instead of the predicted 1.071). And as you said, 1.044 to 1.071 is way too much of a change for a 60 minute boil, so I think there is a problem there -- if anything, my pre-boil gravity should have been in the 60s to reach 1.071.

    If you reference my original post, you can see that my conversion efficiency was 96.3% for a gravity of 1.063. Post-sparge, my gravity was 1.056. It is a real head scratcher, for sure.
     
  12. lonelymtn

    lonelymtn Member

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    Other than kettle dead space and hops absorption, no other losses.

    Regarding alpha/beta amalys, I did a bit or reading today and essentially confirmed what I already knew and what you have referenced. A longer mash at a higher temp does allow some time for the beta to do it's work, but only so much as the conditions that are favored by alpha tend to deactivate the beta (http://howtobrew.com/book/section-3/how-the-mash-works/manipulating-the-starch-conversion-rest). This affects fermentability, but shouldn't have any bearing on the target OG.
     
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  13. lonelymtn

    lonelymtn Member

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    That is much more in line with what I expect, 8 or so points an hour. I am really thinking there is something off with the Boil Gravity number in the recipe view (hit More button, under the Batch Stats section). Looking back over my last several recipes, and it always lists a number anywhere from 25 to 40 points below the target OG.

    I'm not quite ready to reveal the recipe as it is for a competition, but will later. For now, I can tell you that my fermentables came in at 15 lbs, even. 10.17 gal total water (7.25 in mash, 2.92 from sparge), 8.5 gal pre-boil and 7.5 gal post boil -- I hit those pre- and post-volume numbers almost exactly every time.
     
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  14. BOB357

    BOB357 Well-Known Member

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    Something is definitely wrong in the calculations.
     
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  15. Trialben

    Trialben Well-Known Member

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    Yep very suspect I'm always sitting a point or two or recipie calcs predicted preboil gravity. It's gotta be your water profile then Maybe something not set right in there? You hitting your desired fermentor Volume @lonelymtn ?
     
  16. Mase

    Mase Well-Known Member

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    “...Yesterday, my pre-boil volume was 8.5 gallons and my final volume was 7.5 gallons...”

    We’re you making a 7.5 gallon batch? Far more typical to have a 5 or 10 gallon batch.

    Without sharing the recipe, it’s gonna be tough to help you. Sounds like you have a flaw in your process
     
  17. dmtaylor

    dmtaylor New Member

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    This is totally completely entirely wrong. There's no way in hell you can get a 1.044 pre-boil to 1.071 post with 8.5 to 7.5 gallons. Your configuration in the recipe builder is wrong. What you should have expected starting with 1.056 is 56 * 8.5 / 7.5 = 1.063. Unless your volume and/or gravity measurements are way way off.
     
  18. lonelymtn

    lonelymtn Member

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    Answering you and @Trialben both -- I am hitting my target fermentor volume. I hae a Unibrau V.3 and it has been excellent. The one drawback is that it, along with the plate chiller, have almost 2 gallons of dead space unless you tilt. Seeing as how I don't want to disturb the trub cone post-whirpool, I don't tilt, so I have to accept the nearly 2 gallons of liquid left over. I'm not convinced it is a process problem as this is only a recent issue.
     
  19. lonelymtn

    lonelymtn Member

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    Yes, something is entirely wrong. I think I'm going to just have to ignore the Boil Gravity number for now and post a bug in Technical Issues.

    Does anyone else pay attention to that number? It is featured rather prominently on the Brew Day worksheet.
     
  20. Craigerrr

    Craigerrr Well-Known Member

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    I find that my boil gravity number is usually pretty close, and when it is not my volumes are off as well. I am still however dialing in my efficiency since switching from BIAB to All Grain.
     
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