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  • Roast longevity

    OK, here's the preamble: For some time, my home roasts haven't been great from start to finish. I usually open after 10 days rest and 5 days later I more often than not discard the remainder (50-80g) because it loses its flavour.

    I recently bought a bag of CS Espresso Wow and it has been excellent from opening on Day 6 (post-roast) up to now, Day 19. While I'm never going to achieve the same quality as Andy's commercial roasts, I wonder what are the main factor/s affecting how long a roast remains palatable. Roast profile? Type of roaster? Storage (I only use 1-way valve zip lock bags)? Bean type? Bean age (I have several greens which exceed the 3 year 'limit')?

    So my question is how do I make my roasts last longer? Occasionally, I do get one that stays good to the last drop but not sure why.

  • #2
    Originally posted by flynnaus View Post
    OK, here's the preamble: For some time, my home roasts haven't been great from start to finish. I usually open after 10 days rest and 5 days later I more often than not discard the remainder (50-80g) because it loses its flavour.

    I recently bought a bag of CS Espresso Wow and it has been excellent from opening on Day 6 (post-roast) up to now, Day 19. While I'm never going to achieve the same quality as Andy's commercial roasts, I wonder what are the main factor/s affecting how long a roast remains palatable. Roast profile? Type of roaster? Storage (I only use 1-way valve zip lock bags)? Bean type? Bean age (I have several greens which exceed the 3 year 'limit')?

    So my question is how do I make my roasts last longer? Occasionally, I do get one that stays good to the last drop but not sure why.
    Not sure I can be of much help here Flynn.

    Couple of points, I roast batches of 750 grams green, I usually start using them 3 days post roast, a batch will last 7 to 10 days and usually continues to improve down to the last dose.

    I also store in one way valve bags, cool kitchen.

    Some of my green stash is getting on in age, probably past 2 years.

    I use a variety of beans from various origins, have a preference for African and South American, don't use beans from SE Asia, I dislike the earthy overtones.

    I roast quite dark, about CS9, use a Coretto, start from cold, approx 14 minutes to FC, approx 19 minutes to end, just before second crack.

    Don't use roasting software, monitor bean temp and time with a DMM and watch.

    Cool rapidly at end of roast and bag immediately.

    What roasting method are you using?

    Good luck.

    Comment


    • #3
      Everything else being equal, the roast profile will have the most significant effect, given that Andy's Wow is going the distance. Have found that the deeper one roasts, the shorter is the time for optimum and enjoyable consumption and in the case of dark espresso style roasts, these seem to better if opened earlier rather than wait too long. Different rules apply for Yemen Ismaili though...

      As Yelta mentions, knowing how you roast your batches will help us to know what might be happening and even better if you have a sample of Roast Profiles that also could be checked out.

      Mal.

      Comment


      • #4
        There’s really only three possible causes:

        1. Storage - you seem to have that sorted though.
        2. Roast depth - if you’re roasting quite dark this could happen. For a standard ‘espresso’ roast I’d suggest 3 days rest and 10-14 days of use. If you’re roasting lighter for filter or manual espresso then the most likely problem is......
        3. Green bean age - there are many factors that will influence this (green quality, processing, etc.) but generally once you reach the 12 month mark after harvest you’ll see fairly obvious deterioration unless you’re storing them in the freezer.

        Comment


        • #5
          Thanks Gents

          I use a KKTO and my roasts are stopped at the start of or just before second crack. I have to use roast monitoring software as a combination of an enclosed roast chamber and poor hearing means I can't hear the cracks. I'll try to upload a profile but my basic technique is to
          1. Preheat to 170 deg
          2. Add the beans (450 gm of SO or pre-blended)
          3. Maintain a RoR of 10 deg/min until 140 deg
          4. Drop back to 6-7 deg until 155 (for Maillard reaction)
          5. Turn up and continue at 10deg/min to 195 deg
          6. Drop back to 4-5 deg min until it reaches 220. Roast time is about 17-18 mins
          7. Dump the roast in my bean cooler and stir while cooling for about a minute.
          8. I split the roast into two 250g bags to try to keep one half fresh


          I wondered if my KKTO was the problem but had a similar longevity problem when I used a Behmor while my roasting lappy was out of action/ This is what led me to believe bean age might be the reason, reinforced by some of my older stock going flat in about 4-5 days. My next roast will be of newer beans to see if I can get better longevity.

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          • #6
            I guess, by my own standards, those roast rates before and after the Maillard phase slow-down would be considered quite slow.
            Probably the slowest I ever use would 11.0C/Min but more usually, up around the 13-14.0C/Min. I don't pre-heat the BM Pan though, prefer to start from ambient temperature as pre-heating never realised any improvement in the cup and it doesn't really replicate what's going on in a commercial drum roaster - Much more Thermal Inertia to consider with them and the roaster must be pre-heated to a normal operating temperature in order to achieve any resemblance of an acceptable roast profile.

            What used to work best for me when I tried the KKTO, was to incorporate a 'drying phase' with the beans in the roaster and allowed to heat gradually to approx. 120.0C bean temperature and held there for approx. 3-4 minutes before starting the roast profile proper. Resulting roasts were always very sweet with no obvious flavour deterioration until the bag(s) were finished. Sure, the flavour profile does change over that time but always a very nice brew resulted.

            We keep our green stash stored in a cool location in the centre of the house at the bottom of a dark cupboard. Have successfully roasted beans that were two years+ from purchase date and observed no 'off tastes' in brews resulting from them. In fact, pretty well every roast batch was smack on the button of what I expected, and I'm pretty fussy. Sure, fresh is always best but there's no need to freeze the beans if you have a decent storage location set up in your house somewhere.

            Don't know if any of this useful to you Steve but maybe try sharpening up the temperature gradient as described and see what that does for you.

            All the best,
            Mal.

            Comment


            • #7
              Thanks Mal
              My KKTO struggles to get those temperature gradients but it still produces tasty roasts, some beautiful. I did try the drying phase early in the history of using my roaster but was still ending up with long roast times. I tried using a metal plate under the inner pot to reduce the roasting chamber volume with some success. Smaller batch size work but somewhat impractical andfound 430g is a happy medium.
              It wasn't until I resorted to preheating that I was able to get decent roast times. Yes, I understand it isn't a drum roaster but it still contains a significant quantity of metal.
              One of the problems with the KKTO is lag. When I turn up the heat after Maillard phase, it takes at least a minutes for the gradient to climb to 10 deg/min and doesn't rise above that until first crack exothermic kicks off.
              I've applied all the KK recommended mods over the years. I still have my old corretto; might be time to dust it off and gain a bit more control over the roast. It's a single pan BM but easily capable of 500g batches which is more than enough for my needs.
              Last edited by flynnaus; 30 April 2019, 11:37 AM. Reason: A bit more info abot post-Maillard phase

              Comment


              • #8
                Ah, no worries Steve...

                Sounds like you are roasting up against the limits of your KKTO setup.
                Don't know what's available re: TOs with more heating power, might be worth checking out...

                Cheers mate,
                Mal.

                Comment


                • #9
                  Just read your original post and I see your problem - 3 year old green coffee. This is waaaay past it’s best if it hasn’t been frozen. No reason you can’t still roast it and get a reasonable result, you just need to realise that moisture content and water activity will be really low and your expectations need to be realistic. You’re also roasting on the darker side so I’d suggest cracking open a bag after 24-48hrs rest at most and you’ll get a week out of it all going well.

                  Comment


                  • #10
                    Originally posted by Dimal View Post
                    Ah, no worries Steve...

                    Sounds like you are roasting up against the limits of your KKTO setup.
                    Don't know what's available re: TOs with more heating power, might be worth checking out...
                    Halogen ones are the go but hard to find a good one. KK recommended another mod of cutting out the centre of or drilling larger holes in the shield that covers the element which I've never tried.

                    Here's my roast today of 420g of Zimbabwe Chimanimani (bought in Oct 2017). M=Maillard phase, F=First crack
                    Nice chocolatey aroma and stopped just shy of second crack. In fact, when I lifted the TO, I heard the single crack that announces 2C is imminent. Pleased with the result. Let's see how long it lasts

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                    Last edited by flynnaus; 30 April 2019, 04:16 PM.

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                    • #11
                      Originally posted by LeroyC View Post
                      Just read your original post and I see your problem - 3 year old green coffee. This is waaaay past it’s best if it hasn’t been frozen. No reason you can’t still roast it and get a reasonable result, you just need to realise that moisture content and water activity will be really low and your expectations need to be realistic. You’re also roasting on the darker side so I’d suggest cracking open a bag after 24-48hrs rest at most and you’ll get a week out of it all going well.
                      You're probably right Leroy. I've had to toss some old beans last year as they had nothing in them flavour- or aroma-wise..
                      Dark is a relative concept. As mentioned, I prefer to pull just shy of 2C. See my most recent roast in my previous post. That could be counted as dark by manual brewing standards. We'll see how it goes when I crack this one in a week's time.

                      Comment


                      • #12
                        Where does the idea that Maillard reactions only occur in a narrow temperature range come from?

                        I'm not trying to be fractious, it doesn't make sense to me which leads me to think either there is something I'm missing or some there's some serious misinformation out there.
                        Last edited by Lyrebird; 30 April 2019, 05:47 PM.

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                        • #13
                          Originally posted by Lyrebird View Post
                          Where does the idea that Maillard reactions stop at 155 oC come from?
                          It doesn't - according to this wikipedia article, it ranges from 140 to 165

                          https://en.wikipedia.org/wiki/Maillard_reaction

                          At 15, I turn up my thermostat because the lag means it will be ~ 165 when max temp is applied.

                          Comment


                          • #14
                            I think that's a serious misinterpretation. What the article should say is that it requires a minimum temperature of 140 - 165 to get rapid Maillard browning in a cooking process.

                            Maillard reactions occur at room temperature if you give them long enough. They occur more rapidly as the temperature gets higher until they are so fast that the reactions are substrate limited not temperature limited.

                            There are lots of ways of describing the change of reaction rate with temperature, Maillard reactions follow Arrhenius kinetics but that confuses most people since it's an exponential function. A simpler approximation is to use the concept of Q10, the rate increase that accompanies a 10 degree rise in temperature*. At coffee roasting temperatures a Q10 of x 1.5 (eg the Maiilard reactions increase by 50% for every 10oC rise in temperature) is a good approximation to the Arrhenius equation with an assumed Activation Energy of 100 kJ / mol (the literature values vary all over the place but they're mostly close to that figure).


                            * That's still an exponential equation by the way, it's just a way of saying it without using actual exponents.

                            I haven't been able to find any good information on substrate limiting during coffee roasting. A further complication is that substrate availability will be influenced by moisture level but there's even less info on that.
                            Last edited by Lyrebird; 30 April 2019, 06:48 PM.

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                            • #15
                              Originally posted by Lyrebird View Post
                              I think that's a serious misinterpretation. What the article should say is that it requires a minimum temperature of 140 - 165 to get rapid Maillard browning in a cooking process.
                              OK.
                              I'm not claiming to be an expert. Discussion on this site had it that the Maillard reaction for coffee occurs during the yellowing phase of roasting which was claimed to be in the range 140 to 160 degrees. I only know that I achieved a better result in the cup if I reduce the temperature gradient in that range so I've stuck with it rightly or wrongly.

                              I have to admit that when I next roast I won't be thinking about Arrhenius, Q10 or Activation energy. I will be using mostly my sense of sight and smell, Roast Monitor (on an ancient laptop) plus some basic principles learned on this site to produce a roast for my own consumption. My quest in this thread was to try to discover why Andy's beans were good to the end while my own roasts rarely went the distance.
                              Last edited by flynnaus; 30 April 2019, 07:44 PM.

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