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Different loads - Same profile?

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  • Different loads - Same profile?

    Hi guys,

    This may be a completely ridiculous question but here goes....

    If I roast a FULL load of coffee at a specific profile, then roast HALF a load at the exact same profile..... Should the coffees taste the same?


  • #2
    Originally posted by CoffeeInZA View Post
    If I roast a FULL load of coffee at a specific profile, then roast HALF a load at the exact same profile..... Should the coffees taste the same?
    No, because of the heat.


    • #3
      If the profile is a reading of the actual bean temperature during roasting then yes. If the profile you are referring to is one of the preset Behmor profiles then no.

      Java "Definitions matter!" phile
      Toys! I must have new toys!!!


      • #4
        No because batch size determines the amount of heat required to achieve the same roast level, change the batch size and the parameters change.


        • #5
          This is an interesting question. Which roaster are you using?

          The Behmor, has a bean weight setting. I'm would assume that's the exact reason why they put this there, so you can change the charge weight and the roaster will automatically adjust the heat and time to provide relatively consistent results regardless of weight.

          Or is my understanding of this function incorrect?


          • #6
            Originally posted by MrFreddofrog View Post

            Or is my understanding of this function incorrect?
            Yes. Read Javaphile's post above again.


            • #7
              My bad. I interpreted his post incorrectly. Thx for pointing it out.


              • #8
                Thanks guys. I'm actually using a Has Garanti 5kg shop roaster. I'm reading the profile of the bean temp.


                • #9
                  I'm guessing that the thermodynamics will be very different for the two charges. There is a certain fixed amount of thermal energy sitting in the drum when the roaster is up and running and one has to significantly alter the mix of convective versus conductive energy to match the temperature curves. In other words, the half charge will have a higher proportion of conductive heat transfer compared to the full charge which will have a higher proportion of convective heat transfer. This is all theoretical though and it will be very interesting to hear what your results are and whether there is a discernible difference.


                  • #10
                    So here is the first part of the test:

                    I roasted 2.5kgs of a Kenya PBerry in a 5kg Has Garanti.
                    Result of this roast is disappointing. Coffee is noticeably under-developed. I'm assuming that this is because less heat is required upfront as well as the difference in convective vs conductive heat? Thoughts?

                    (Temps are in Celsius)

                    Full load test to follow next week....


                    • #11
                      What's your history with the Has Garanti? Are you completely comfortable with all of your roasting parameters on that roaster. Your curve shows that there is plenty of development time from start of first crack to drop but the temps are very flat from first crack and there isn't much temp increase to drop. Every roaster has different temps (my Quest M3 measures FC at about 10*C higher than my Proaster). Is it possible that the underdevelopment of the roast is purely attributable to degree of roast?

                      All of the above may be totally invalidated if you're a seasoned Has Garanti user of course!


                      • #12
                        Hi Kwantfm,

                        It is possible. I'm actually pretty new to Has Garanti's so maybe there are are few things I'm going to have to figure out, such as the degree-of-roast parameters.

                        Maybe I should hold off on this particular experiment for now... Will reply to this thread when I start it again.

                        Thanks all,


                        • #13
                          I'll be trying to replicate curves with different charge weights over the next month... I'll report any interesting in cup findings.


                          • #14
                            Firstly, I'm assuming when you use the term 'profile' you are referring to the time/temp graph you posted, not the particular air/gas/temp settings of your roaster.
                            If you roast 2.5kg of a particular bean, save the profile (the time/temp graph) then load up 5kg of beans and adjust your gas/air/drop temp settings and then roast the 5kg with a perfectly matching time/temp profile.. I believe the beans should taste exactly the same.
                            But as others have said too, your drop temp will need to be higher, the amount of gas used will need to be higher and your airflow adjustments will need to be greater as your dealing with a higher mass of beans.
                            That's the whole point (and the hardest part) of commercial roasting, replicating the flavour day in day out for the same bean regardless of how much you're roasting. That's where the practice and skill come in, knowing how much to increase/decrease your heat/gas/air to change the temp of the bean mass to be exactly what you want.
                            As for your underdeveloped flavour, the graph has very large intervals so it's hard to see what temps you're getting, but Kwantfm is on the right track, you have 4 mins between FC and dump but not much increase in temp. If your rate of rise is only 1 or 2 degrees for that long you're going to get flat, baked flavours.
                            Hope that helps.