Effect of Mash Temp too high?

Discussion in 'General Brewing Discussions' started by Dirty Horse, Jan 19, 2018.

  1. Dirty Horse

    Dirty Horse New Member

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    Hi

    Brewed a vienna lager 2 weeks ago. Aiming for 1049 OG and achieved it.

    However, after nearly 2 weeks the hydrometer reading still only says its 1040 - still plenty of sugars in there and its been like that since 4 days after adding the yeast. I have upped the temp a little, given it a gentle stir and added more yeast but still no change. Yet there is still a layer of krausen on top.

    Experience would tell me that there is a lot of unfermentable sugars in there and i do remember that for some unknown reason my strike water went in at too high a temperature, 80 degrees Celcius acroding to my brewing unit. alarmed at this i gradually got the temp down over 20 mins to 64 degrees via some ice cubes and cold water.

    Is that enough of a high mash temp to warrant 30 points of unfermentable sugars? if so is there anything other than chuck it away and start again...??

    any help / advice much appreciated.
     
  2. Mase

    Mase Well-Known Member

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    176 degrees (f) for 20 minutes? I know that tannins (not good flavors) can be released above 170 (f), and from what I’ve read (never experienced), most of the conversion (starches to sugars) happens in the first 15-20 minutes of mash. You might have also denatured the grain/enzymes, thus inhibiting the starch to sugar conversion. Sorry, not much from me, but I’m sure the more experienced brewers here will shed more light on what may be happening.
     
  3. Johnwk

    Johnwk Member

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    #3 Johnwk, Jan 19, 2018
    Last edited: Jan 19, 2018
    For "strike water" that doesn't seem too high a temperature, since when it mixes with the grain, the combined temperature drops. Did you actually mean "mash" temperature? If so, then yes, you could have stopped much of the enzyme activity and have a lot of unfermentable sugars in your beer. Enzyme activity is usually stopped when the temperature gets over about 76 C.

    After two weeks of fermentation, the gravity should have dropped much lower than that if the beer was more fully fermentable.

    Here's some other uses for beer (it should make great beersicles):

    http://www.wisebread.com/21-great-uses-for-beer
     
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  4. The Green Man

    The Green Man Active Member

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    What a coincidence. I had a very similar experience with my last mash. The strike temp was obviously too low so to remedy this I upped the temp, but overshot and it went over 80c. Like you, I added ice cubes and got it down but I'm left with concerns. I over-pitched and the air lock went mad for 24 hours and has now calmed down. This is standard for S04 yeast. Not measured gravity yet. Will share when I do.
     
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  5. Dirty Horse

    Dirty Horse New Member

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    just been to my local HBS and asked - he suggested that it may be my yeast, cannot see that a mash decreasing from 80 - 65 in 20 mins would create that level of unfermanetables - although there will be some and i'll probaly end up around 1018 ish so it will be a sweet vienna lager!

    I was fermenting out at 11 degrees C and only went from 1049 - 1040 in 4 days. It's been nearly 2 weeks now and no change after adding more yeast.

    reckons i have killed the yeast off by not starting the yeast at 18C then dropping to 11C - instead i started at 11 and raised to 13 and as that has no effect yeast are probably dead.

    he suggested i could rescue it by scarping as much krausen off as possible - adding fresh batch of yeast at 18 degrees and then dropping down. if that doesnt work then its down the sink!
     
  6. Mase

    Mase Well-Known Member

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    So did he sell you another pack of yeast? I’m still thinking that you’ve denatured the grain/enzyme. But did you mash at 176 (f) or was that the strike water temp?
     
  7. J A

    J A Well-Known Member

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    You still have a layer of krausen on top? That wouldn't necessarily be the case if the yeast has become unviable or dormant. If you've pitched as low as you say and the temp has remained quite low, I'd try raising to 68F. Don't bother dropping the temp. You don't mention the kind of yeast and that's a big variable, but whatever it is, you don't have anything to lose by letting it rip at a higher temp.
     
  8. Dirty Horse

    Dirty Horse New Member

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    176 was strike temp and i got it down to 147 after around 20 mins.

    ha yes he did! Not just 1 packet but 2!! I was buying them regardless plus some other bits ready for this weekend of brewing.

    I'll let you know how i get on with the mystery Vienna...
     
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  9. Dirty Horse

    Dirty Horse New Member

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    yeast is a new one on the UK Home brew market - Bohemian lager yeast - by Bulldog(Hambleton Bard)

    i'll try that first then - thanks
     
  10. Johnwk

    Johnwk Member

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    #10 Johnwk, Jan 19, 2018
    Last edited: Jan 19, 2018
    If you have had a krausen, then the yeast you have is already working and should have dropped the gravity more than it did. By "strike" temperature, do you mean the temperature of the mash itself or the water you are adding to the mash? Usually the strike temperature refers to the temperature of the "strike water" or water you are adding your grain to (or the water you are adding to your grain). Once the two are combined, then the resulting temperature is the mash temperature. If this mash temperature gets over about 76 C, then it quickly starts to end enzymatic activity. Twenty, or even ten minutes at this temperature will certainly result in a lot of unfermnttable sugars.

    It certainly doesn't hurt to add more yeast. However if it's lager yeast, starting it at 11 C should create no problem at all. Many start it at about 8 C or lower, and then maintain it at 10 C or lower. Most of my lagers are fermented at about 9 C. The only time I have had slow fermentation is when the viable (healthy) yeast count is too low (old starters or starters with not enough yeast slurry). When making a lager, you should always make a yeast starter (or add 3 or more vials/packages of fresh liquid lager yeast). The vials/packages only come with 100 billion yeast cells (when fresh - deteriorates rapidly with time) and for a lager you need about 400 billion cells. I'm not sure why these manufacturers don't come out with packages that contain that amount. The packaging is the greatest expense, so a package of 400 billion cells would be much more practical and should cost much less than purchasing 4 separate packages.
     
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  11. Hawkbox

    Hawkbox Well-Known Member

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    When did you measure that high temperature?
     
  12. J A

    J A Well-Known Member

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    A likely the culprit is oxygen deficit. Lagers like a big pitch and a ton of oxygen to be able to work at low temps. My guess is that it would still have stalled short of target FG based on the high mash temp, but probably have gotten closer. Without more oxygen in solution, the new yeast won't do well and you probably won't get it much further. When you add new yeast you can try re-krausening with a very well areated (preferably bottled O2) starter that will allow for active reproduction and fermentation to start. Just sprinkling more dry yeast will probably not do much. Regarding the temp, I think most if not all dry lager yeasts are limited to a few strains that seem to do quite well at higher temps. Given that you're through the phase where a lot of esters would be produced, raising the temp as high as 70F would probably be fine.
     
  13. The Green Man

    The Green Man Active Member

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    Just to save binning it, what about dropping in Nottingham or a Kolsch yeast. California lager yeast is also a lager like ale yeast right. If I'm right, these are more robust and are happy with higher temps.
    If it works the result will be a little more ale like, but better than binning it. Of course, may not work though. What do brewfriends think?
     
  14. Dirty Horse

    Dirty Horse New Member

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    Added a bit more yeast, cranked it up to 18 degrees over night and it's dropped to 1032.

    Got it at 14 now and will drop to 12 later until finished ready for lagering.
     
  15. J A

    J A Well-Known Member

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    You'd probably do better leaving at a higher temp for a couple of days. The up and down may disrupt the yeast activity. I routinely finish the last several gravity points in the high 60F temp range.
     

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