I am a coffee roaster and am working through building a standard espresso profile for coffee shops in my area. I'm working with a particular shop that is interested in my coffee, but for some reason the espresso pulls extremely sour on their machine. I'm looking for ideas as to what might be going on. I've done quite a bit of research, so I'll add in what I have done thus far.
My Setup (Shots pull good)
- 18g grounds, pulling 2 fl oz with a final weight around 50g
- Machine is a Rocket Apartamento, nearly brand new. Water is filtered, non RO, boiler pressure is at 1.2-1.3 bar.
- Grinder is a Breville Dose Control Pro, also new.
- Shots are pulling in about 26-28 seconds
Espresso has good crema that stands up for longer than 1 minute and has rich orange / red tones. Shot is lively, but not sour with no hint of bitterness, and good heavy body. This isn't a fruit bomb blend or anything, I am more looking for something that a typical coffee shop customer would find palatable. Espresso stands up to milk very well. Personally, I almost feel like the roast may be slightly too dark since with milk, I start getting a hint of roasty-ness.
Shop Setup (Sour Shots)
- 18g grounds, pulling 36g output (supposedly this is 2 fl oz also, can't verify as I haven't seen markings on the glass they are pulling into. If anything, I would say it is probably a 2.5-3oz pull)
- Machine is A Nuevo Simonelli Aurelia 2. Boiler pressure 1.4 bar, pump pressure 9.5 to 10 later in the pull. Water is not filtered to my knowledge.
- Grinder is a used Mazzer, unknown burr wear (personally I'm thinking this is a likely culprit?)
- Shots are timed for a 27-30 second pull.
Shots pull extremely bright / sour, crema tends to be closer to a dirty brown color. This shot might blend with milk and be drinkable, but just barely.
Confusing points for me that may bear some explaination...
Longer pull (and thus probably a finer grind) results in sour coffee, not bitter.
Higher boiler pressure = higher water temp which tends to scorch if too high and impart more bitter qualities, yet this is sour.
Why is his 2 fl oz of extract such lower weight than my 2 fl oz. Crema production is heavy on both machines, but the weight difference almost seems to indicate that the crema on his machine is double or more than what my machine is producing which isn't the case.
Troubleshooting espresso via web forum is pretty difficult but I would appreciate any thoughts on how I might go about getting good shots out of this shop machine. Oh, btw, it wasn't me pulling the shots at the shop, so tamp could definitely be different between the two shots, but given that the pull times are pretty close together, and I did watch the tamp, I can say that technique is at the very minimum similar. I can say that both tamps appear to at least be even on a naked portafilter.