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Thread: Oat malt and weirdly viscous wort

  1. #1
    Join Date
    Jan 2013
    Location
    Seattle, WA, USA
    Posts
    15

    Oat malt and weirdly viscous wort

    So we've been pushing the envelope with our NE IPAs and decided to try hitting the oats a bit harder. Made a grist of 51% pale, 31% flaked oats, 9% Golden Naked Oats and 9% flaked barley. Run-off was terrible, but that's to be expected. We added a ton of rice hulls and reset the bed with another vorlauf twice before getting a decent lauter. We came in a touch low on expected efficiency, but extraction was not too far out of the ordinary. This was a bit of a surprise, since we only had about 1.5 lbs of hops per bbl in the kettle. Backflushed the chiller, restarted, clogged the chiller again. Repeated 4 times before getting it all into the fermenter.

    We typically get problems with clogging the heat ex around 2 lbs per bbl hopping in the kettle, and clogging can typically be resolved with a single backflush if it's an issue. After the first clog, I peeked into the kettle and the wort had a skin on it that was thick enough to collect with a spoon. It was so sticky that it took a good 30 seconds with really hot water to wash off my hands after touching a sample. After knock out finally finished up, a sample from the fermenter was like ropey beer in a pedio sick phase. Maybe even more viscous than that. Fermentation has gone from 15.7*P to 4.5*P in 2 days, so that's nice, but the beer is still thick as snot. Truly, the weirdest beer I've even made.

    In addition to the viscosity issue, it is intensely bitter. I'm assuming that the thickness of it prevented the hops and trub in the kettle from ever precipitating, which then clogged the heat ex. Presumably, a large percentage of the hops in the kettle made it through the heat ex into the FV, since samples run through a coffee filter (which takes at least a half hour for about an ounce to pass through) leaves hop residue all over the filter. I decided to go ahead and dry hop it today, ready to eat a big goose egg if I can't work something out with the end results.

    After a couple conversations, the only good theory I have at the moment is that there just wasn't enough enzymatic action to break down starches. This seems a little dubious because we've made beers with similar grain bills before and things have turned out great. We just did 50% pale, 24% flaked oats, 9% flaked barley, 9% flaked wheat, 7% Golden Naked Oats, and 1% crystal with no problems at all. Is there something peculiar about the particular blend of grist that we used that would create a glucanous snot wort? Maybe we just moved into a new crop year and something dramatic just changed? Perhaps the additional stirring from all the stuck mashes made the wort far more glucanous than it would naturally be in a typical mash?

    Thinking about tossing in some beta-glucanase to see if it will thin it out. Curious to see how the dry hop changes it, if perhaps any enzymes on the hops help at all, though this would likely take forever. If all else fails, might try blending it with a super dry IPA or tossing it in barrels to break down over time.

    Super baffled by this one. Has anyone seen anything like this or have any insight as to what happened here?

  2. #2
    Join Date
    May 2004
    Location
    St. John's, Newfoundland, Canada
    Posts
    830
    With high percentage oat beers:

    1/ mash and wort pH - pay close attention. Adjust accordingly. I find they run high. if not adjusted appropriately, will lead to an 'oily' hop expression poor hot break and a poor trub pile.
    2/ grist - undermilling can be a significant problem with such beers (different sized grains) leading to wort viscosity issues, turbid worts and possibly starch carryover
    3/ mash enzyme activity - if you can step mash, introduce a beta-glucan rest (all in at 40oC, immediately ramp to conversion temp target). Alternately, consider added beta-glucanase to the mash. will be denatured in boil. (Consider converting at a high temp to ensure gelatinization of the oat if unmalted or unflaked or otherwise, unprocessed)

    Expect long conversion times, slow runoffs, much lower efficiencies, less fermentable worts, huge yeast growth, lower head retention, big mouthfeel. Best of luck. Hope I may have stimulated more thought.

    Pax.

    Liam
    Liam McKenna
    www.yellowbellybrewery.com

  3. #3
    Join Date
    Jan 2013
    Location
    Seattle, WA, USA
    Posts
    15
    Thanks for the thoughts. Mash pH was actually quite low at 5.04, and extraction was considerably crappy, but that's to be expected when you're essentially batch sparging a glue ball. The grist was fine. We use sifters often to keep it on point, and the flakes don't go through the mill. Enzymes are definitely a potential culprit, but we can't step mash with our system. Definitely considering keeping glucanase around for the big oat beers.

    Interestingly, post fermentation it was still syrup beer, until the dry hop. Every day since then it has become less viscous and today it closely resembles a typical oated IPA beer. I can only assume that the enzymes in the huge dry hop are converting starches and glucans. Aside from looking like green cream and likely needing an extended lagering phase to get hop phenols to drop out, it's beginning to look like it's going to be a great beer!

    Quote Originally Posted by liammckenna View Post
    With high percentage oat beers:

    1/ mash and wort pH - pay close attention. Adjust accordingly. I find they run high. if not adjusted appropriately, will lead to an 'oily' hop expression poor hot break and a poor trub pile.
    2/ grist - undermilling can be a significant problem with such beers (different sized grains) leading to wort viscosity issues, turbid worts and possibly starch carryover
    3/ mash enzyme activity - if you can step mash, introduce a beta-glucan rest (all in at 40oC, immediately ramp to conversion temp target). Alternately, consider added beta-glucanase to the mash. will be denatured in boil. (Consider converting at a high temp to ensure gelatinization of the oat if unmalted or unflaked or otherwise, unprocessed)

    Expect long conversion times, slow runoffs, much lower efficiencies, less fermentable worts, huge yeast growth, lower head retention, big mouthfeel. Best of luck. Hope I may have stimulated more thought.

    Pax.

    Liam

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