Every year or so my coffee obsession seems to peak and I try to really improve the quality of output I am getting.

I got to a certain point where a number of my shots were drinkable but they lacked finesse. Last year I went on some barista training and that made a huge difference (for a start it got me used to tasting decent espresso!).

I think this has given me the ability to know what tastes right and as a result I have noticed a bitter defect in almost every shot I make. My wife notices the defect in lattes as the brown part of the foam being bitter. Convinced it was my humble gaggia I tried the output from the aeropress and the defect remains (although it is muted by comparison). I think this eliminates the gaggia as a source of this defect which leaves me with a few other things:

Water:
Central scotland water is very soft and I believe slightly acidic, so I have tried volvic and (to get an extreme) evian. They reduce the bitterness but I can still taste the defect.

Coffee:
I can taste this defect in a number of fresh coffees from hasbean, including blends. Some seem more prone to it than others; the worst I have found lately is http://www.hasbean.co.uk/collections/am ... ed-natural which seems to go directly against the tasting notes!

Grinder:
I have a rocky and it is 18 months old. I would guess it has ground approx 20KG. It doesnt appear slow, the burr carrier is rock solid and I am not grinding excessively finely for most coffees (6-10 above 0). I also clean it regularly.


In general the pours look good and and are almost entirely crema which is persistent (possibly slightly dark suggesting some over extraction?). I normally aim for 60% yield but I have tried varying the dose and yield. The crotchless portafilter shows no obvious channeling or other issues.


At this point I can think of three things which might be causing the defect:
1. Grinder - I cannot eliminate this at this stage as I dont have a spare. I am thinking of replacing the burrs or buying a hand grinder which completely eliminates the grinder for testing. I think the burrs are showing signs of wear:

but is this likely to produce the defect with the aeropress?
2. Coffee - I buy decent coffee but I freeze it. I do this by taping over the valve and putting it in the freezer. It might be me joining the dots incorrectly (some weeks after my last delivery) but I think the first bag (non frozen) might have been better.
3. Rest time - I generally take the coffee out of the freezer and start using it the following day. Adding in the 1 day shipping that makes it 2 days post roast. It normally takes me 6-7 days to consume 250g and I don't think the defect changes much (although I guess this isn't the same as leaving the beans to rest unopened?).


Am I missing something obvious here or are these three likely to be the cause?



TIA,

You mention that there aren't any obvious issues with the bottomless portafilter, but your cups show signs of splatter... Are your pours too drippy?

I was going to say the same thing. That left cup has a lot of spatter in the cup which is a tale tale sign of channeling. On a side note, espresso can have a slight bitter as part of the flavor profile. Espresso is a balancing act, sweet with bitter.

another_jim wrote:Your set up is designed for Italian style shots, which will taste considerably better than any attempt at 3rd wave practices. Use 14 grams, grind fine enough to get your usual brew ratio, and give the machine a brief flush, 2 seconds or so, to avoid any boiling water, and to pull a slightly cooler shot.

Jim approximately what temperature are you talking about when you say "slightly cooler shot"? My understanding is that 200F is a typical temperature for espresso and a good starting point unless directed otherwise by a roaster or someone familiar with the blend.

For 6½ years I had a Rocky, I changed the burrs twice, and when it was sold it could have used another set. That would be 3 sets in 78 months or 26 months/set. I left the first set in too long as I had no idea at the time. For the price, you could do worse than changing the burrs. I noticed the difference with each set. While it is a sufficient grinder, the Rancilio burrs aren't the best nor the hardest, and like shock absorbers, you will realize how worn the current set is after you replace them. Worn burrs can increase bitterness by creating dust.

Dear James,
From the images, your burrs look completely blunt.
I'm not familiar with your grinder, but in mine, burrs have very sharp edges ...
Bad burrs produce bad grinds and, consequently, awful coffee.

Something I do with most coffees that are new to me is to brew at several different temps. I will normally brew at 190F, 195F, 200F, 205F for both brewed aeropress and espresso. Normally one temp will stand out when compared to the rest and I will fine tune from there. Mostly too bitter of coffee is from too hot of water. The smoothest and probably least bitter coffee you'll get is if you used 180F water, but it would lack a lot of the varietal flavors which make specialty coffee so delicious.

another_jim wrote:No idea; but if a shot is bitter, the most common cause is too much heat.

Thanks for the replies. This jolted my mind to something I hadnt considered:
Looking at the picture on the left (I had swirled it hence the apparent spatter) it looks overextracted, and the right under. Almost every shot I produce looks overextracted. I initially discounted the gaggia because I was getting the same bitterness when using the aeropress/cupping. However, reading this thread I suddenly realised I was probably burning the coffee in the aeropress as well by pouring water straight from the kettle.

I therefore setup some cups and tried tap, filtered and volic water (as per jims cupping guide) but I measured the water temp first and made sure it wasnt freshly boiling. The results were three much better cups, almost sickly sweet (I can still 'feel' the smell/taste in my nose now) and the bitterness was gone. All three cups were good, but the brita filtered one slightly sharper than tap or volvic.

I then managed to try one shot in the gaggia with a 3s cooling flush (@ 14g) before the beans were gone. The bitterness has all but gone and the sickly sweet (meant to be dried fruit I believe) presence was definitely there.