I've received a number of customer emails recently asking about espresso extraction...
... these customers' extractions have either been too bitter or too sour. Here's a quick guide as to how I approach this.
My key philosophy on optimising extraction is that it's way easier to do if you can isolate a single variable which you change. The variables which you may be able to alter include: ground coffee dose, grind size, extraction output (the amount of coffee that is in your cup post-extraction), extraction time, preinfusion volume, preinfusion time, brew water temperature, flow rate, and portafilter basket type.
Let's concentrate on the few which are likely common to all espresso set ups:
- Dose
- Grind size
- Extraction output
- Extraction time
My approach is to fix dose and extraction output (what goes in and what comes out) and from that starting point I only alter grind size. I let extraction time do what it will and then I taste the result.
For my set up I fix the amount of coffee in the portafilter at 20 g and the amount of espresso in the cup at 32 g. I use a small whisk to stir the coffee grounds and then even them out before I tamp. This is an important step as it allows the grounds to be distributed randomly and evenly in the portafilter which facilitates an even extraction. Extraction time for those parameters (depending on grind size) can vary between 25 and 40 seconds. If the extraction time is in the low 30 seconds then I'll be pretty confident that the espresso will taste good.
If the espresso tastes sour then I tighten up the grind (make the grind finer), if the espresso tastes bitter then I loosen up the grind (make the grind coarser).
That's it. So the bottom line is that I'm a believer that having a small coffee weighing scale is the best gadget to optimise your espresso extractions.
Let me know if you think this has been helpful please!
To read a primer on espresso extraction click here
To read about pre-ground versus freshly ground coffee click here