Guide for espresso machines
How to dial in espresso: sour, bitter, grind size and brew ratio
New beans, new taste, and suddenly your espresso is sharp or bitter? This guide shows you how to tell what's missing, which targets fit your roast and what to change first. It's the same logic the Mullino app uses.
The three levers
Dialing in is about how much the water dissolves from the coffee. Baristas call this extraction. Too little tastes sour, too much tastes bitter. Three things control it:
- Grind size
- The most important lever. A finer grind slows the water down, the shot runs longer and extracts more. A coarser grind lets water through faster.
- Dose
- The amount of ground coffee in the basket. It depends on your basket, usually 16 to 20 g for a double. Set it once and then rarely change it.
- Yield and brew ratio
- How much espresso ends up in the cup, weighed in grams. Its relation to the dose is the brew ratio: 18 g in, 36 g out is 1:2. A longer yield extracts more and tastes rounder but thinner. A shorter yield is more concentrated.
Depending on your machine, brew temperature and pre-infusion come on top. Both are fine-tuning once the three levers are right.
Sour or bitter? How to taste the difference
Sour: under-extracted
Sharp like lemon, sometimes a little salty, thin body, short finish. The shot often runs fast and the crema is pale and fades quickly.
Bitter: over-extracted
Dry and astringent in the mouth, hollow, with a long bitter aftertaste. The shot often runs slowly and the crema is dark and blotchy.
Not every acidity is a fault. Light roasts have a fruity acidity that's meant to be there. It's a fault when it turns sharp and unpleasant. That's why Mullino doesn't ask “sour: yes or no” but has two sliders from “none” to “very strong”.
Targets by roast level
Light roasts are denser and harder to extract. They need more water and more time. Dark roasts extract easily and turn bitter quickly.
| Roast | Brew Ratio | Example with 18 g | Shot time | Temperature, if adjustable |
|---|---|---|---|---|
| Light | 1:2.5 | 45 g | 27–35 s | hotter, about 93–96 °C |
| Medium | 1:2 | 36 g | 25–32 s | about 91–94 °C |
| Dark | 1:1.75 | 31.5 g | 22–30 s | cooler, about 88–92 °C |
Time counts from when the pump starts, not from the first drop.
Step by step to a good espresso
- Heat the machine properly. An E61 group needs about 25 to 30 minutes, even if the gauge says ready earlier. On thermoblock machines, a blank shot with the portafilter locked in warms up portafilter and cup.
- Pick a starting recipe. Weigh the dose and take the target yield for your roast from the table above.
- Prepare the puck. Distribute the grounds evenly, ideally with a WDT tool (fine needles), then tamp level. Tamping harder does little, tamping level does a lot.
- Pull with scale and timer. Cup on the scale, start the timer with the pump, stop at the target yield.
- Taste and rate. How sour, how bitter, how strong? Stir once before tasting, because crema and espresso separate into layers.
- Change exactly one thing. Use the troubleshooting table below. If you change two things at once, you won't know what worked.
- Repeat and write it down. You're usually there after three to five shots. Write the recipe down so you can skip the guessing with the next bag.
Troubleshooting: what to change
| What you taste or see | Likely cause | What to change |
|---|---|---|
| Sour, runs too fast | grind too coarse | grind finer |
| Sour, time is fine | too little water for these beans | increase yield, e.g. 36 to 40 g |
| Bitter, runs too slow | grind too fine | grind coarser |
| Bitter, time is fine | over-extracted | reduce yield, e.g. 36 to 32 g, or 1–2 °C cooler |
| Sour and bitter at once | channeling: water finds channels | distribute better (WDT), tamp level |
| Watery and thin | yield too long for this dose | reduce yield |
| Spurts, holes in the puck | uneven distribution | improve distribution, clean and dry basket |
| Same settings, suddenly different | beans ageing, machine not warm | check warm-up, mind the roast date |
Adjusting the grind the right way
- In small steps: one step on stepped grinders, a small turn on stepless ones. If the taste is way off, a double step is fine.
- Grinders with retention keep old grounds inside after an adjustment. Purge a few grams, or your next shot still uses the old setting. Single-dose grinders retain very little.
- Some manufacturers recommend adjusting finer only while the motor runs. Check your grinder's manual.
Bean freshness
Check the roast date on the bag. Very fresh beans, younger than about 5 days, still release a lot of carbon dioxide and run unevenly. From about 6 weeks after roasting, aroma fades and shots often run faster, so you'll need to grind finer. In between, espresso usually tastes most balanced.
Mullino does this for you
Log your shot, move two sliders for sourness and bitterness, and the app tells you what to change next, following exactly these rules. Matched to your machine, your grinder and your beans.
Frequently asked questions
How long should an espresso shot take?
For a medium roast, about 25 to 32 seconds from when the pump starts. Light roasts can run longer, about 27 to 35 seconds, dark roasts shorter, about 22 to 30 seconds. Time is a clue, taste is what counts.
What is the right brew ratio?
A good start is 1:2, twice as much espresso in the cup as ground coffee in the basket. A ristretto is closer to 1:1 to 1:1.5, a lungo 1:3 or more. Light roasts often taste better at 1:2.5, dark roasts at 1:1.75.
Why is my espresso sour?
It's under-extracted: the water dissolved too little. Usually the grind is too coarse or the yield too short. If it runs too fast, grind finer. If the time is fine, pull longer. A cold machine also makes espresso sour.
Why is my espresso bitter?
It's over-extracted: the water dissolved too much. If it runs too slowly, grind coarser. If the time is fine, pull a shorter yield or lower the temperature. Very dark roasts taste bold and bitter even when dialed in well.
How much coffee goes in a double basket?
Usually 16 to 20 g. Many baskets have their size stamped on them, otherwise check your machine's manual. Too much coffee touches the group head, too little leaves a wet, soft puck.
Do I need a scale?
Yes, a scale with 0.1 g resolution makes shots comparable. Without one, you can't tell whether the taste changed because of the grind or because of a different amount. In Mullino you enter the empty weight of portafilter and cup once, so you don't have to tare.