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Direct fire: effect on colour and taste

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  • Direct fire: effect on colour and taste

    Considering to buy a direct fire system

    I've heard that direct fire tends to give a more caramelized taste as well as darkening the beer.

    Does this mean I'll have to forget beers under 4 SRM?

    Any experience/comparison anyone?

    Cheers,

    Zb

  • #2
    We've used direct fire at our smaller 7 Bbl Brewery for 11 or so years and have seen no issues in our lighter beers.

    Regards,

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    • #3
      So that "more caramelized taste" is a myth and doesn't have an impact on colour? Maybe with longer boil, then?

      Zb

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      • #4
        Like most "myths", there probably is some scientific basis in the phenomena. It's just that we perceive no issues on our system.

        A standard 60 min boil in a direct fire kettle for beers that are lighter in gravity and color has always been successful for us. In my honest opinion, I have seen more taste altering effects from yeast selection and clarification of the final product play more of a defining factor than kettle tub surface temperatures. "Caramelized flavors" can be emulated by a specific yeast throwing more diacetyl than the next and then hanging out in the finished product longer. I recall even getting a caramel apple taste from a geletin finig I was using at one time.

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        • #5
          caramel baby...

          What you have to remember is that heat plus sugar gives maillard products...darker color is always the result. Think about the temperature difference...gas combusts at about 1400 degrees F...while steam at 15 psi is only about 250 degrees F. you do the math. also, 60 mins may be enough but that's on the short side. Boil your light lager for 90 mins in a gas fired kettle and your color will be darker.

          that being said, with consideration you can make plenty of yellow beer with a gas fired kettle....just don't expect the color of Coors Light (not that you'd want it anyway)

          Cheers
          Larry Horwitz

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          • #6
            Good points for and against. I work on a direct fire system and have worked on a steam jacket as well. I make a very pale light ale on the direct fire with even a 90 minute boil. I would bet that a very objective scientific comparison would show that the direct fire gets more colour increase than the steam fired k-tel. But....I doubt it is more than 1 lovibond of colour (that being said, I also worked on a power flame system with direct heat loop that I believed would be hard to make a very pale beer on)....also I would imagine that with a higher gravity wort, the more caramelization/Maillard reactions would be a factor. When setting up your brewery and recipes, you factor for the colour loss, different for each brewery, but normally 20-30% from grist calculation after fermentation. You have to find out what your factor is for your brewery, then account for it in your recipes without throwing the flavours off. (excuse the British spelling, I have made alot of British style beers this month!)

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            • #7
              "Think about the temperature difference...gas combusts at about 1400 degrees F...while steam at 15 psi is only about 250 degrees F. you do the math"

              Larry - by this, you're not claiming that wort in a direct fired system is exposed to 1400 degree temperatures, are you? I mean aluminum melts at 14something I think - unless we're heating the kettle up before putting the liquid in, I don't think it's quite that high.

              Now, if we compare the smaller surface area of the fire box versus the typical steam jacket, I do agree that it's probably operating at a higher surface temp to achieve the same overall heating result. This was what I always thought was the limiting factor for the size of direct fired systems... surface area to volume ratio, requiring a hotter temp. Is this correct?

              The 60 vs. 90 minute boil is an interesting sideline here - starting another thread.

              Thanks,
              Scott

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              • #8
                I have no fixed objectives on colour; I was just curious to ear different point of views on the subject. Good point on immersed heat: my homebrew experience showed me that I could get more caramelized-coloured beer that those using direct fire under control.

                If you told me the difference was in the range of 5 Lovibond, then I would've taken that into consideration.This issue shouldn't be a factor in my purchase decision, then.

                Thanks everyone!

                Zb

                PS:
                Originally posted by beauxman
                When setting up your brewery and recipes, you factor for the colour loss, different for each brewery, but normally 20-30% from grist calculation after fermentation.
                I don't understand quite well what you are saying? (S'cuse my French, I've been drinking too much Quebec beers lately !)

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                • #9
                  not 1400F, there is loss of heat due to cP of the stainless, but waaaayyyy up there. 3-4 times 250F at least. Don't know what temp Alum melts at, but my kettle is stainless, and so are most.

                  BTW, my last gas fired kettle had more heating surface than my current steam kettle.

                  Cheers,
                  Larry Horwitz

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                  • #10
                    Wow. That surprises me - a surface of 316L stainless with a working temperature of 750-1000F. That just seems SO hot to me. I'm also puzzled by the heating surface (direct to steam) observation too - so maybe it's a matter of heat transfer RATES in one setup versus the other?

                    Sorry - of course, we're almost all probably using stainless - aluminum was just the number that stuck in my head from that casting class many years ago... and it was the wrong number too. More like 1220F.

                    Stainless is more like 1440F if this source is to be trusted... and since they make the stuff...
                    Stainless Steel There are various forms of stainless steels and we will briefly discuss the most common alloys produced by H. Cross Company. If the specific alloy you require is not listed contact us as we will fabricate your material or if the required quantity is large enough we can purchase and fabricate the material for ...


                    Anyway, I've taken us off topic a good bit here.
                    Scott
                    Last edited by Sir Brewsalot; 11-04-2005, 05:59 AM.

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                    • #11
                      The color loss I speak of is the calculated SRM for your beer using the malt analysis (Lovibond) vs. the actual SRM after fermentation and process. This value is typically 70-80% of the "calculated" value due to color loss.
                      -Beaux

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