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  • Free Rise

    I have heard about free rising fermentations. It involves pitching at a lower temperature but letting the cooling system kick in a few degrees higher.

    Who uses this, and why?

  • #2
    We use this on our Hefeweizen and some Belgian styles. Advantage is that the yeast is not slowed down by glycol kicking on before reaching high krausen. It can also help ester formation, and help prevent early stalls on some styles (maybe saison) which may be notorious for stalling. Much more isoamyl acetate (banana) and ethyl acetate (fruitiness) comes out when we free rise. Yeast has longer lag phase and exponential phase to build ester pre-cursor chemicals (acetaldehyde which reduces to acetic acid). The warmer conditions favor more fusel alcohol production, which are needed for ester formation. In the case of the two mentioned Ethyl alcohol or Isoamyl alcohol. These combine with acetic acid and form the isoamyl acetate or ethyl acetate.

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    • #3
      Originally posted by UnFermentable View Post
      We use this on our Hefeweizen and some Belgian styles. Advantage is that the yeast is not slowed down by glycol kicking on before reaching high krausen. It can also help ester formation, and help prevent early stalls on some styles (maybe saison) which may be notorious for stalling. Much more isoamyl acetate (banana) and ethyl acetate (fruitiness) comes out when we free rise. Yeast has longer lag phase and exponential phase to build ester pre-cursor chemicals (acetaldehyde which reduces to acetic acid). The warmer conditions favor more fusel alcohol production, which are needed for ester formation. In the case of the two mentioned Ethyl alcohol or Isoamyl alcohol. These combine with acetic acid and form the isoamyl acetate or ethyl acetate.
      At what temperature are you starting at. And what is your finish temp. I'd love to give this a try on a couple of our beers.

      Sent from my SAMSUNG-SM-G900A using Tapatalk
      Jon Sheldon
      Owner/Brewer/Chief Floor Mopper
      Bugnutty Brewing Company
      www.bugnutty.com

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      • #4
        We've been running the Westmalle-type strain for our Belgian styles and are still getting it figured out. Currently knock out at 64F and step up the controller 4F/day shooting for a max fermentation temp of 78F (I know that doesn't add up). I'm thinking of allowing it to rise a bit quicker since we often only see a max of 76F. Still produces a nice phenolic/ester blend. The "Brew Like a Monk" and "Yeast" books discuss this.
        Clarke Pelz
        Cynosure Brewing

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        • #5
          So why not just keep it at the higher temperature then? Seems if the desired temperature for the desired yeast characteristics are achieved at the higher temperature, why start artificially low, which should mean a slow start?

          Also, I was recommended this with a lager originally. Anyone any experience with that?

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          • #6
            My understanding is that rate of yeast growth effects the flavor profile. Cool initially favors phenols and minimizes fusel alcohols; warmer later favors ester production.
            Clarke Pelz
            Cynosure Brewing

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            • #7
              Originally posted by Brewberosa View Post
              So why not just keep it at the higher temperature then? Seems if the desired temperature for the desired yeast characteristics are achieved at the higher temperature, why start artificially low, which should mean a slow start?

              Also, I was recommended this with a lager originally. Anyone any experience with that?
              You sometimes want the slow start. It is a common misconception that you always want your beer to begin active fermentation very quickly. You want a proper lag (latent) phase if the yeast has been stored for any amount of time, or during a fresh pitch, so the yeast can uptake vital components before cellular division takes place. If you are pitching yeast that is in the log (exponential) phase (highest rate of cell division, think krausening) then you will have a very short lag phase.

              This practice of free rise is usually done to increase ester formation as warmer temperatures increase the likelihood of ester formation. There are however many, many, many factors at play. Nothing with yeast is a linear computation. As yeast metabolism occurs, there are a number of ester precursor compounds produced. Generally speaking, the more cell division that takes place, the more compounds are produced. It is thought by some that a shorter lag phase results in less precursor formation.

              The best advice is to try it. Try a warm fermentation, and then try a free rise. I would be willing to bet you will see a significant difference between the two. In my case on our weizen, a warmer starting temperature results in blow-off and less ester formation. I also find it to have more fusel note. We generally knock out at 17*C and "free rise" to 24*C.

              Lager brewing will typically knock out around 6-9*C and then be allowed to "free rise" to 9-13*C for primary. There are a number of methods for lager brewing but most of the methods fall within these guidelines. Some include later stepping or "free rise" to perform diacetyl rest and allow the yeast to cleanup after itself. Starting colder and allowing the yeast to warm to fermentation temperature prevents the yeast from a shock secretion. Yeast is very sensitive to cold temperatures and the glycol kicking on can cause undesirable effects.

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              • #8
                Thanks guys.

                How does one guesstimate what counts as too low?

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                • #9
                  I would suggest not starting more than a degree (*C) below the recommended temperature range for the yeast. Each strain has it's own specifics regarding temperature. Kolsch strains can be particularly finicky at low temperatures, so I wouldn't suggest going out of range on those. If you are too low, the yeast will just drop out of suspension. Even if you warm the liquid back up, the yeast may not behave well without being re-suspended in the wort.

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