I’m going to go over a small piece of what you missed by not coming to coffee class today.
The perfect espresso has 5 requirements.
1. The proper dose. By dose, I mean the amount of ground coffee you’re starting with and 7 grams or 0.25 oz is what you want. This amount, when ground and extracted properly, will give you the right amount of caffeine (65-70 mg), which will keep you going for about 2 or 3 hours. Believe it or not, there’s less caffeine in your espresso than in drip coffee (over 100 mg) – when we get to timing, you’ll see why.
2. The correct water temperature. The water in your machine should be 90°C or 194°F. Notice that this is below boiling – boiling water makes for bitter coffee.
3. The right extraction pressure. The perfect espresso requires 9 bars. The pressure is what gives espresso that beautiful crema on top and distinguishes it from other coffee preparation methods. Most espresso machines will give you a pressure reading.
4. An exact percolation time. For a perfect espresso, you need 30 seconds – plus or minus 5 seconds is acceptable. Most drip coffee machines take at least 6 minutes, so think about what’s being extracted into your cup.
5. An acceptable volume. Your goal is 25 ml or 0.75 oz. This amount fills a standard espresso cup half-way.
I’m making several assumptions in order for these steps to work: your coffee is fresh and you’ve ground it properly; you’ve been cleaning your grinder and your espresso machine on a regular basis; you’ve tamped the espresso with the right amount of pressure – ideally, 20 kilos or 40 lbs. You have to put your body into it. Never use the tamper that’s attached to the grinder – you’ll never achieve the required pressure by using an up-motion.
Also, make sure to heat up your cups prior to serving. The top of the machine is warm and flat, making this one of the easier steps to follow.
You can end up with an underextracted espresso if: your dose is too small, the water temperature is too low, the pump pressure is below 9 bars and if your percolati0n time runs under 25 seconds. It could also be a result of coarse grinding (think water flowing through pebbles), light tamping or a cold cup. An underextracted espresso will taste overly acidic.
You can end up with overextracted espresso if: your dose is too large, the water temperature is too hot, the pump pressure is too high and if your percolation time runs over 35 seconds. Avoid excessive tamping or grinding too fine. Dirty or clogged filters and worn-out blades can also be culprits when it comes to overextracted espresso, which will taste more bitter and astringent than it should.
If you’ve done everything right, your espresso should be hazelnut to tawny in color. Sometimes there’s red streaks as well – think tiger stripes. The crema should be decently thick and should remain compact on the surface for at least two minutes.
Here’s what tamping looks like:
The first drops:
Now it’s going:
This is a decent cup:
Once you get all of this down, maybe we’ll move on to this: