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Thread: Roast depth vs brew temp

  1. #1
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    Roast depth vs brew temp

    Was listening to a youtube video about coffee this morning on the way to work in the car, and something i'd wondered about but not really understood came up.

    Brew temp vs coffee roast depth. The guy speaking was reviewing a coffee machine with variable brew temperature control, and mentioned that you'd want a higher temperature for a lighter roast, and lower temp for darker roasts. For me it's interesting as i've gone from using a Gaggia Classic, generally brewing lighter roasts which were tasting strong enough in milk (I believe the gaggia was running very close to 98-100 from the grouphead), to a PID machine running at 93c where the same roasts were brewing very mild and not cutting the milk (although the flavour in the shot had more clarity i would say).

    Today i brewed a lighter PNG Waghi roast taken 6c past first crack, and increased the PID to 96 (the max the Breville will do), and found it cut the milk much better than at 93c.

    I'm sure many on here understand the relationship in results between brew temp and roast depth, thought it was worth mentioning though as i hadn't read anything previously which clarified how you would manage temp based on roast depth, just that different temperatures of brew temp would have different results in the cup and to try a range of temperatures on a bean to see which you like best.

  2. #2
    Mal Dimal's Avatar
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    Hiya Janus...

    Though it may prove true for some bean varietals (maybe even most), it can't really be used as a blanket rule for all beans, as playing with the Brew Temp. may actually highlight flavour traits that are undesirable in an inverse relationship to the one he described. I think you need to try it with the various beans you roast and take careful note of the flavours that are being promoted or retarded when varying the Brew Temp. in either direction.

    Mal.
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  3. #3
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    Roast depth vs brew temp

    Thanks Mal, if itís a rule of thumb subject to exception, I can live with that. Must say the Breville makes a better shot than the Gaggia, better flavour. Timed and weighed a shot this afternoon. Grinder is pretty much as tight as sheíll go, and I got 34ml in 23 seconds, a touch faster than Iím told is optimal. 17g coffee in the portafilter, will try 17.5g after dinner and see if that slows it a little. Shot was tasty as americano still. If I get through my evening jobs, and avoid the temptation of a battle royal on my Xbox, will roast some beans to start of 2nd crack to see how they go too.
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  4. #4
    Mal Dimal's Avatar
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    Good stuff mate...

    Mal.

  5. #5
    Senior Member LeroyC's Avatar
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    Behmor Brazen - $249 - Free Freight
    Yeah as Mal said itís a good basic rule of thumb, but doesnít always work based solely on roast level. The reason varying brew temperature based on roast level can work is because roast level affects the solubility of the coffee. The greater the solubility, the easier it will extract. So more developed roasts will extract more easily and therefore a higher brew temp may see them over extract too readily. Lowering the brew temp is one way to control this.
    However itís more complex than this as roast level isnít the only thing that affects solubility. Different types of coffee have different levels of solubility and roast level canít always be used to level the playing field so to speak. Generally lower grown, lower density coffees are more inclined to have greater solubility, but again thereís no blanket rule based solely on altitude as region and coffee variety play a part as well.
    Obviously grind setting affects solubility as well. The finer the grind, the greater the surface area and the therefore solubility. At the end of the day what youíre shooting for is the best level of extraction for the particular coffee youíre drinking. Roast level and brew temp and the way they relate to each other is one of the many ways to control this. And when it comes down to it, if it tastes good, youíre on the right track.

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