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Gravity Calculations for Low Temp Mash

Discussion in 'All Grain Brewing' started by cpsmusic, 8/11/18.

 

  1. cpsmusic

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    Posted 8/11/18
    Hi Folks,

    As I mentioned in another post, I'm interested in making an ESB using Danstar London ESB yeast.

    This yeast doesn't ferment maltotriose so it's recommended that the mash temperature be lowered so that the wort attenuates properly.

    What I'm not clear about is how this affects my OG/FGs. If I mash at 64 rather than 67 will I get a different OG? Also, how do I figure out the FG?

    Since I've been doing AG brewing I've used recipes from other brewers (thanks Dr Smurto!) but I was wondering whether any brewing software takes into account mash temp and yeast type in calculating gravities?

    Cheers,

    Chris
     
  2. ABG

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    Posted 9/11/18
    Mashing at a higher temperature will leave you with more unfermentables and by and large, a sweeter, lower ABV beer. Your OG should be the same, but FG will be lower on the beer mashed at lower temps. Brulosophy ran an Xbeeriment on this http://brulosophy.com/2015/10/12/the-mash-high-vs-low-temperature-exbeeriment-results/ I'm not sure what software takes this into account, but I'd be surprised if the main players like Brewsmith didn't. No doubt, someone with more experience and wisdom than me can give you a more definitive answer.
     
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  3. shacked

    I like beer

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    Posted 9/11/18
    Are you sure the Danstar ESB yeast can't ferment maltotriose? I know that CBC-1 from Danstar can't but that's designed for cask conditioning and fermenting dextrose.
     
  4. cpsmusic

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    Posted 9/11/18
    >London ESB does not utilize the sugar maltotriose (a molecule composed of 3 glucose
    >units). Maltotriose is present in wort in an average 10-15% of all malt worts. The result
    >will be fuller body and residual sweetness in beer. Be advised to adjust gravities and
    >mash temperatures according to desired result.
     
  5. gap

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    Posted 9/11/18
    I cant understand why you want to use a yeast which will perform in a way which you find unsuitable.
     
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  6. cpsmusic

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    Posted 9/11/18
    I'd like to make a classic ESB and Danstar London ESB is one of the recommended yeasts. The yeast isn't unsuitable, in fact, quite the opposite. It just requires a slightly different brewing process.
     
  7. keine_ahnung

    joeblogsbier.com

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    Posted 11/11/18 at 7:32 PM
    For me it also begs the question, why use a yeast which seems to make life harder. BUT if it's what you want to do, do it. Worst case scenario: you're beer won't be quite as good as you hoped, but you'll learn something firsthand that will only make you a better brewer. :)

    Suggestion, hold the mash at 68-69 deg for a while, then sink the temp back down into the beta-amylase temp range.
    I haven't tried this, but based on how enzymes and the entire mash process works, this should allow the alpha-amylase to do a bit of work (endo-amylase: cuts carbohydrate chains through the middle = makes more avaible ends for the Bete-amylase...quickly!). Then by dropping back down to around 65deg, you can optimise life for the Beta-amylase again and break down as many of the remaining dextrines as possible into maltose and maltotriose.
    However! be aware that the beta-amylase starts becoming rapidly and irreversibly deactivated at and above 70degC
     
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  8. ABG

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    Posted 11/11/18 at 10:15 PM
    Any reason you recommend dropping temperature rather than doing a more typical step mash, say starting at around 60, then ramp up to 65 and finally ramp to 69? Wouldn't both methods allow both alpha amylase and beta amylase enzymes do their work? Is there an advantage in letting the alpha amylase process activate first, then letting the beta amylase process proceed?
     
  9. pcmfisher

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    Posted 12/11/18 at 12:00 AM
    And how does one drop mash temperature?
     
  10. Lionman

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    Posted 12/11/18 at 3:50 AM
    I think the main reason for this approach is that its faster. The beta amylase only really works on already cut down carbohydrates that the alpha has already trimmed. At the lower temps, the alpha works much more slowly so the beta, while being highly active in the slightly lower temp range, wont have as much feed stock available and essentially 'waits' for the slower alpha to work. It still does work with the traditional step mash regime but its a slower process.

    By reversing it you move more logically through the mash process. I haven't ever tried this either but in theory, as I understand it, it should work.

    Easiest way is to add cold water, just like the traditional way to increase mash temp in an infusion tun is to add hot water.
     
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  11. altone

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    Posted 12/11/18 at 5:43 AM
    See, the cooling bit - I was thinking of recirculating it through an ice/water bath.
    Thought I could use the Guten chiller that's still wrapped in it's plastic :)
     
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  12. keine_ahnung

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    Posted 12/11/18 at 7:20 AM
    Yeah @Lionman has pretty much hit the nail on the head here.
    Firstly, the easiest way to do it would just be to start with a slightly thicker mash, than cool it with a bit of water.

    The reason I'd recommend this "reverse" mash direction is due to how the different enzymes physically breakdown carbohydrate-chains.
    The Beta-amylase can only attack the carbohydrate-chains from free ends, and chops off disaccharides (= Maltose).
    The Alpha-amylase chops these chains in the middle ----> creating more free ends.

    So logically, if it were possible, the best way to most thoroughly and quickly break down carbohydrate chains would be to go 72deg, then 62deg. However due to the very sensitive denaturation temp of the Beta-amyalse (70degC !!), this is unfortunately impossible.
    (On a commercial scale, it'd also be horrrible energy inefficient to heat and cool and reheat thousands of litres of mash).

    Like I said, the above is just an idea based on the logic of the enzymatic processes.
    But on a homebrew scale, why not give it a go :) You may just revolutionise brewing for the rest of us! :D
     
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  13. Lionman

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    Posted 12/11/18 at 7:26 AM
    The most you would ever expect is a faster conversion time. Not sure how much faster, but maybe you could comfortable get away with 15-20mins each step? would need to try it to be sure, and periodically do iodine tests to gauge when full conversion is reached.
     

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