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Completely Unscientific roasting experiment with interesting results

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  • Completely Unscientific roasting experiment with interesting results

    Hello esteemed coffee gurus!
    I was hoping I could pick your brains for a moment

    Let me start off by explaining why I bothered with this "experiment" of sorts...
    I have recently discovered the wonders of sous-vide cooking (Which is basically cooking stuff in a vacuum sealed bag in a water bath)..
    I proceeded to go on a rampage looking for different things I can sous-vide, I even sous-vide brewed a cup of coffee...
    Which led me to think... why not "sous vide" roast coffee?

    Since I could only sous-vide up to a max of 100 degrees Celsius, I knew you couldn't completely roast in the water bath.
    But I wondered if I could get some enzymatic reactions (to bring out more flavor) going in the bean if I held the beans for some time at enzyme favorable temps...
    and finish it off with my Heatgun+BM.

    With my limited knowledge of chemistry and biology, I tried to learn if enzymes play any role in coffee roasting and the literature suggests "not really"..
    Being stubborn as I have always been, I figured I would try it anyway since the worst case scenario would be that I start roasting the beans from a higher temperature...
    I then set aside two equal portions of Tanzanian Clouds of August and got to roasting one the normal way...
    I roasted it till the end of FC.

    The other portion, I vacuumed packed and set it in a water bath held at 65 degrees Celcius (an arbitrary temp, but one I use for beer brewing)...
    After 30 minutes in the bath, I roasted it normally with the external temp of the bean starting at 62 degrees...
    I pulled it out at pretty much the same time, and visually confirmed that they are of the same roast depth...

    I pulled a ristretto of each batch about 5 hours after roasting...
    And as expected, the normally roasted one was overly bright and I could not really taste much else...
    However, with the sous-vide treated coffee, I had the same initial acidic taste but it quickly dropped off and I tasted significant sweetness and ripe berry flavors...
    (my partner said apricots but I have never been able to distinguish flavors with much detail)...

    Now my question is, whether the water bath sped up the chemical changes in the bean? or I just have really inconsistent roasting methods and/or brewing methods...
    Either way, I have never been able to taste so much in a roast hours after roasting....
    Any thoughts on what has happened?

  • #2
    Originally posted by pernguin View Post
    Now my question is, whether the water bath sped up the chemical changes in the bean? or I just have really inconsistent roasting methods and/or brewing methods...
    Either way, I have never been able to taste so much in a roast hours after roasting....
    Any thoughts on what has happened?
    I would say you are a pioneer of this approach. I doubt if anyone has done studies on the effect of sous vide heating before using a more conventional roast method. There may well be conversion of oils or other components affecting brewed coffee characteristics.

    This article discusses the idea of two stage roasting. The first stage is slow cooking in an oven before first crack is reached followed by finishing the roast with more rapid heat on the burner. The heat applied initially in this method is much higher than what your sous vide provides but the end result may be similar.

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    • #3
      Thanks for providing that article, the concept seems to be pretty similar...
      though his objectives was only to get around using specialised equipment

      I am just really curious to see if they peak differently... (i'm really hoping they do... in a good way)

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      • #4
        Day 3 Update:

        Just pulled two more ristrettos....

        The "normally" roasted batch tasted a little less sharp than before but tasted warmly sweet after the acid subsided...
        But that was about it, with no subtle flavors or anything else...

        The sous-vide roasted batch tasted really sweet from the get-go...
        It almost completely hid how sharp it still was until you feel it go down the throat...
        the ripe berry notes have not changed much and if anything, are harder to detect over the strong sweetness...

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        • #5
          Hi pernguin

          Being of a scientific bent I'd like to see a blind experiment. You prepare some sous-vide beans and package as say beans "A" and non sous-vide and package as beans "B". Pass these onto someone in Coffee Snobs who can roast well enough to ensure repeatable roasts for identical beans. They must not know what "A" is or "B" is. They divide A and B into two lots and roast them all the same. These A1 and A2 should cup the same, likewise B1 and B2. These are passed along to a group of cuppers as lots 1 to 4. (The cuppers do not know how the 1-4 relate to the A & B) They cup them and we see if they can categorise them into two lots; a pair of A's and a pair of B's. What will be their cupping opinion?

          Mike

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          • #6
            Day 4 Update:

            Another two ristrettos...
            Sous-vide batch now tastes sweet with an undertone of acid...
            But has developed some nuttiness that I was not expecting...
            Overall impression is not great because it feels like it lost its complexity...

            The normally roasted batch however is coming into its own...
            Nice level of acidity on the initial hit with a hum of sweetness after...
            Also more pronounced berry flavors...
            IMO... a real pleasure to drink

            Originally posted by speleomike View Post
            Hi pernguin

            Being of a scientific bent I'd like to see a blind experiment. You prepare some sous-vide beans and package as say beans "A" and non sous-vide and package as beans "B". Pass these onto someone in Coffee Snobs who can roast well enough to ensure repeatable roasts for identical beans. They must not know what "A" is or "B" is. They divide A and B into two lots and roast them all the same. These A1 and A2 should cup the same, likewise B1 and B2. These are passed along to a group of cuppers as lots 1 to 4. (The cuppers do not know how the 1-4 relate to the A & B) They cup them and we see if they can categorise them into two lots; a pair of A's and a pair of B's. What will be their cupping opinion?

            Mike
            I'd be more than happy to hand over a pre sous-vide batch to a more accomplished roaster
            I'm very curious to see if there's any merit to this at all....
            Any takers in Melbourne?

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