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Diagnosing bitterness

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  • Diagnosing bitterness

    Hello there,

    I'm a new member new brewer - I sincerely apologise if this has been covered already!

    I'm extracting week old roasted beans that have been stored in the sealed bag with pressure valve. In the last day or 2 I've noticed my latte tasting more bitter. Specifically, the drink starts out more bitter. By the time I've only got a third of a cup left it's not so bitter. Is this due to lower temperature rounding out the bitterness or my taste buds adapting to the flavour profile? Or perhaps less bitterness due to less microfoam by the time I approach the end of the drink??? I'm scratching my head...

    What are the number one things to look for in tackling bitterness? My extraction seems ok - 25 seconds roughly (but it never seems as syrupy as I've seen in videos). I've also ensured my milk is not overheated - erring on cooler than 60 degrees. Is it possible that beans can turn bitter in one week?


  • #2
    Hi Rowan,

    If it's an overly developed roast, or a roast with excessive defects like baking, scorching and unevenness (inside of bean darker than outside)

    you will be extracting bitter solids which will be suspended in the crema, a percentage of which will

    remain in the foam of the milk. If you leave the foam 'til last and then spoon it out, is it bitter?

    Bitterness can also come from water that is too hot and a grind that is too fine for the extraction temp.

    Bitterness is concentrated at the back of the palate, top of the throat.


    • #3
      I'll have to go make another brew to taste again
      My water temp is set at 93. Perhaps I should try a slightly courser grind but tamped a little harder?

      Here's a photo of the beans:


      • #4
        Hi Rowan

        Things I'd be looking at and asking:
        1. Have you ruled out channeling?
        2. No chanelling, try lowering the temp.
        3. Does the shot start off very dark? Possibly too fine a grind, course it up and pull another shot.

        Have fun


        • #5
          Hi Rowan
          In the photo the beans look quite oily - are they home roasted?
          If you are roasting yourself, and roasting well into 2C (which is where the oils will really start to flow to the outside of the bean soon after roasting ), you will have more bitterness, as the sugars are more darkly caramelised…
          Cheers Matt


          • #6
            Originally posted by gombul View Post
            I'll have to go make another brew to taste again
            My water temp is set at 93. Perhaps I should try a slightly courser grind but tamped a little harder?
            G'day Rowan...

            The roast doesn't look too bad (from that photo), the little bit of oil here and there shouldn't be an issue in my opinion. How sure are you that that 93C brew temp. is accurate, and what is being delivered to the top of the puck? Might be worth doing a measurement or three with a bead type t/couple on top of the puck to make sure.

            If the actual temp. is higher than that which you've selected, that will also produce pours that tend more towards bitterness. As an exercise, you could try lowering the brew temp. a couple of degrees and see how that turns out. If it works, you could try increasing the PID setting called Temperature Offset (for the brew water) by a couple of degrees. Wait for 15 minutes or so to allow the brew system to attain equilibrium, and then make another couple of brews to see what they taste like. If the excessive bitterness disappears, or is on the way to doing so, then you know you're on the right track.

            Worth doing as an exercise I believe...



            • #7
              As I type this, I am enjoying a cup of a blend I roasted on July 30. It is Panama, Yemen and Sulawesi in the ratio 45:30:25. I thought the roast went really well. Looked good, smelled great and the aroma lingered in my roastery (aka the laundry) for days.
              Opened the bag a week later and it was OK; the next couple of days the coffee was so sour I thought I must have stuffed up the roast somehow and almost binned it. It was somewhat better yesterday.
              Today, it is everything the blend promised: a range of flavours including raspberry jam, chocolate, almond. Sensational, but almost at the end of the bag.
              Try resting the coffee for 10 days before trying.
              Last edited by flynnaus; 10 August 2014, 03:10 PM. Reason: Meant sour, not bitter


              • #8
                What are the beans gombul?

                How are they roasted? (Method & profile)

                Have you sectioned a couple of beans to see the colour inside?


                • #9
                  Here's a photo of the beans:
                  Looking at the beans I would suggest they were roasted too fast and you are tasting sour, not bitter.
                  ...but please understand that diagnosing via a PC screen is a little hit and miss.


                  • #10
                    I was going to mention the bitter being mistaken for sourness opinion.
                    Do you know the end roast time and temp?

                    Assuming the coffee was roasted perfectly and you are mistaking bitterness for sourness, try a higher brew temp or finer grind.

                    If i were you though, i would brew the coffee using another method(or even 2 alternative) to rule the coffee out or confirm it.


                    • #11
                      Great feedback, thanks all. Bitterness vs sourness is an interesting one. I'm guessing there's info on CS explaining the two so I'll have a dig around. My tasting capability will surely mature over time. Reminds me of my first guitar which I thought sounded awesome until 12 months after playing.

                      The beans were roasted not by me but at a local roaster here in Canberra. I'm not sure of their methods but I'm now trying a different variety. It's a milder roast and I'm curious to see what differences there are after a week or so with same storage & brewing conditions.


                      • #12
                        Originally posted by chokkidog View Post
                        Hi Rowan,
                        Bitterness is concentrated at the back of the palate, top of the throat.
                        Bitterness will initiate the gag reflex.

                        Sourness is a front palate sensation which will also affect the inside of your mouth. Your tongue

                        will work overtime as your mouth puckers up and you want to expel the offending substance.

                        The two are pretty much opposites on your palate, though not confined to distinct zones.

                        Search 'palate' and 'tastebuds' in the search bar, there are a couple of good threads to be found.

                        p.s. some roast profile info will also help diagnose the likely issues...........
                        Last edited by chokkidog; 10 August 2014, 09:58 PM. Reason: add p.s.