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  • pour temperature question

    hey all
    i was wondering....i have read quite a lot about consistent temperature in extracting a wonderful shot.

    my question is: what would the difference be b/w a shot that began at 94c and then dropped to 84c by the end of the shot, as compared to a shot that stayed at 94c the whole way through?


    im asking from a theoretical / philosophical point of view.

    many thanks

    aaron


  • #2
    Re: pour temperature question

    If the brew temp is too cold the shot will be sour. Too hot and the shot will taste burnt/bitter.


    Java "Temperature is critical" phile
    Toys! I must have new toys!!!

    Comment


    • #3
      Re: pour temperature question

      thanks jp
      but what would the difference be b/w a shot that stayed at, say, 94c versus one that started at 94c and reduced to 90c for example?

      Comment


      • #4
        Re: pour temperature question

        In general as the temp drops from the ideal the brew becomes more sour. Exactly what will happen with any particular bean, machine, and temp can only be determined by brewing up a shot and tasting the result.


        Java "Let your taste buds tell the tale!" phile
        Toys! I must have new toys!!!

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        • #5
          Re: pour temperature question

          A lot of design effort goes into trying to produce a machine which will maintain a stable temperature throughout the 25" pour. Its a small amount of time for the water to be in contact with the ground coffee to produce an espresso. A small window of oppotrunity.

          If the temperature drops off, less than ideal conditions are prevalent, so less than ideal coffee is being pulled. Some beans, as Javaphile says, will turn out worse than others.

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          • #6
            Re: pour temperature question

            so from what im hearing the main problem with temp during the pour, is that the temp drops off somewhat, right?

            Comment


            • #7
              Re: pour temperature question

              roknee,

              That depends on the machine and the way it has been designed.....

              The larger commercials (like mine) dont drop at all, whereas poorly designed small single boiler machines do drop quite a bit as do thermoblock machines if the water flow is too high (rate of normal extraction is exceeded). And yet other boiler machines will drop just a little. A poorly designed machine can actually increase the temp during the pour.

              It is more a factor of the design of the machine and generally speaking the end user cant do anything about it (other than buy a quality machine and use it correctly).

              Comment


              • #8
                Re: pour temperature question

                thanks jb
                ive also wondered about the value of buying a dual boiler (ala expo minore) or hx with the easy ability to tweak opvs (which i understand changes pour temp) vs hxs that dont (or at least not easily..
                what are your thoughts?

                aaron

                Comment


                • #9
                  Re: pour temperature question

                  aaron,

                  There is no simple answer to what is a good design and what isnt.

                  The main reason for temperature drop during a shot is the cold water being forced in so that the heated water is displaced into the coffee grinds. This cold water (depending on design of the boiler) can reduce the extraction temperature....

                  So a large boiler will reduce the effect
                  Correct "injection" of cold water will reduce the effect
                  A heater circuit which responds quickly will reduce the effect

                  Commercial machines and prosumer class machines use pressurestats to control boiler pressure (and therefore temperature) and because they switch over a small range.... they maintain the temperature very well.

                  A PID fitted to smaller single boiler machines (and each boiler of multiple boiler machines - like a Synesso) do this very well also.

                  Multiple boilers arent necessarily better than single boilers - they are if correctly designed (again like the Synesso).... A large single boiler will be more stable than a small brew boiler and a larger steam boiler.

                  By the way the OPV changes brew pressure.... (Over Pressure Valve) adjusting the thermostat or PID on single boiler or the brew boiler (on multi boiler machines) adjusts the brew temperature..... as does adjusting the pressurestat on a commercial or prosumer........

                  In the case of a prosumer and especially a commercial - adjusting the pressurestat wont effect brew temperature that much.... there is a lot more in the design of these machines to make them stable.... the actual HX temperature being just one. Cooling flushes also pay an important role in setting brew temperature on these machines.

                  The only way to easily and repeatably adjust brew temperature is to have a machine where the boiler, or at least the brew boiler of multiple boiler machines, is under PID control.

                  Comment


                  • #10
                    Re: pour temperature question

                    hi jb
                    thanks so much for going into the detail you did. v. helpful. and i now have a better understanding of why temps drop...

                    so, if i go back to basic lingo for a minute (easier on my noggin)...i can recall that some machines like the expo minoreII have a digital control panel on them where you can adjust brew temp. would this facilitate better extraction as compared to a machine like the expo office, as temp could be adjusted according to the blend, bean etc?

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                    • #11
                      Re: pour temperature question

                      aaron,

                      In theory .... it might.

                      I dont know the expo minoreII, but if the digital display is actually a PID then it should make quite some difference. There are however some other forms of digital display which arent really a PID (but a cut down version of one) and they wouldnt be quite as good.

                      A machine can have a digital display, and the temperature still droop during extraction whilst one without a display could be very temperature stable - but not easily adjustable. Generally speaking..... it costs money to design a quality machine.... and that cost is passed on to the purchaser....

                      With coffee machines - the more you pay, the better the machine will be designed and the closer it will maintain the correct temperature.... that is a sweeping generalisation.... but pretty accurate. Also most machines can be "tweaked" to perform even better. If you buy your machine from a reputable dealer (like a site sponsor).... this will be done for you pre sale.

                      It is generally not a good idea to try and "tweak" a machine yourself unless you really, really know what you are doing and how the changes will affect the tuning of the machine (PID adjustment of course excepted)

                      Comment


                      • #12
                        Re: pour temperature question

                        Originally posted by JavaB link=1197367483/0#10 date=1197434288
                        I dont know the expo minoreII, but if the digital display is actually a PID then it should make quite some difference. There are however some other forms of digital display which arent really a PID (but a cut down version of one) and they wouldnt be quite as good.
                        Gday JB,

                        From what Ive been able to find out mate, the control on a Minore II, etc is a simple Proportional Controller and so long as you know the degree of error (for setpoint purposes), it can manage the boiler temp quite well ,

                        Mal.

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                        • #13
                          Re: pour temperature question

                          as well as an add-on PID?

                          aaron

                          Comment


                          • #14
                            Re: pour temperature question

                            Originally posted by roknee link=1197367483/0#12 date=1197437988
                            as well as an add-on PID?

                            aaron
                            Not sure if youre referring to my post above roknee but in case you are..... As you may know, PID represents and acronym for a controller with Proportional, Integral and Derivative control elements.

                            In the case of the Minore, it uses a simple Proportional only controller and thus allows for the existence of a constant error between the SetPoint and the Process Variable. By adjusting the gain of the controller (probably preset in the case of the Minore) it is possible to achieve quite acceptable levels of control, as owners of the Minore can testify to. So long as the error between the SP and the PV is known, it is a simple matter of accruing the error quantity into the SP and the PV will be maintained at this setting.

                            Hope this helps you out....

                            Mal.

                            Comment


                            • #15
                              Re: pour temperature question

                              Originally posted by Mal link=1197367483/0#13 date=1197442925
                              Originally posted by roknee link=1197367483/0#12 date=1197437988
                              as well as an add-on PID?

                              aaron
                              Not sure if youre referring to my post above roknee but in case you are..... As you may know, PID represents and acronym for a controller with Proportional, Integral and Derivative control elements.

                              In the case of the Minore, it uses a simple Proportional only controller and thus allows for the existence of a constant error between the SetPoint and the Process Variable. By adjusting the gain of the controller (probably preset in the case of the Minore) it is possible to achieve quite acceptable levels of control, as owners of the Minore can testify to. So long as the error between the SP and the PV is known, it is a simple matter of accruing the error quantity into the SP and the PV will be maintained at this setting.

                              Hope this helps you out....

                              Mal.
                              hey Mal
                              thanks, I was referring to your prev post!

                              so i take it that the expo has a simplified version of a pid? and therefore somewhat less stable temps??

                              am i on the right track here?  :-?

                              ta

                              aaron

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