Why Your Café's Espresso Tastes Bitter or Sour, and How to Fix It

Written by Tiny Tiger Coffee

Written by Tiny Tiger Coffee

Has a regular customer ever pushed back a cappuccino and said it tastes "off"? Maybe the coffee tastes a little bitter this time, or maybe you can't taste the coffee at all. You can fix both if you work in the right order.

All you need to do is understand a single principle. Water pulls flavour out of coffee in stages: acids first, then sweetness, then bitterness. A sour shot stopped too early and a bitter shot went too far. You are aiming for the sweet middle.

How to fix it, step by step

1. Taste the shot without milk. Sharp, thin or salty means sour, so it is under-extracted. Harsh, drying or ashy means bitter, so it is over-extracted. Sour and harsh together usually means channelling (step 6).
2. Weigh and time it. Our house recipe is 18 g in, 30 to 40 g out, in 27 to 30 seconds.
3. Fix the grind first. Under 18 seconds, grind finer. Over 35 seconds, grind coarser. Move one small step, purge and pull again.
4. Fine-tune the yield. Once the time is right, let taste lead. Slightly sour? Let the yield increase by 2 or 3 g. Slightly bitter? Stop the shot 2 or 3 g earlier.
5. Change the dose only if you must. A gram less is easier to extract and helps a stubbornly sour shot. A gram more slows a shot that keeps running fast.
6. Check temperature and puck prep. Brew at about 90°C. A roasty, bitter finish on a shot that runs on time often means the water is too hot, so drop it 1 to 2°C. Good numbers but sour and harsh together means water is finding a shortcut through the puck: break up clumps, level the grounds and tamp flat.

Change one thing at a time, or you won't know which one worked.

Re-dial every day

Beans age, weather turns and burrs warm up in a rush, so yesterday's setting drifts. Pull a check shot every morning and after the lunch rush, and let new bags rest 10 days from roast. If you want an in-depth, step-by-step post explaining all of the theory behind dialling in a coffee, check out our guide to dialling in espresso grind size.

Stuck with one of our coffees? Send us your dose, yield, time and how it tastes on WhatsApp, and we'll help.

Common questions

Why does my espresso taste sour?

Sour espresso is under-extracted: the water stopped before it reached the coffee's sweetness. If the shot ran in under 18 seconds, grind finer. If the time is right, let 2 to 3 g more espresso run into the cup. Also check the beans are at least 10 days from their roast date, since very fresh coffee tastes sharp.

Why does my espresso taste bitter?

Bitter, drying espresso is over-extracted. If the shot took over 35 seconds, grind coarser. If the time is right, stop the shot 2 to 3 g earlier, or lower the brew temperature by 1 to 2°C. A dirty group head can also make every shot taste burnt, so backflush it regularly.

What is a good espresso recipe for a café?

A reliable starting recipe is 18 g of ground coffee in, 30 to 40 g of espresso out, in 27 to 30 seconds, with water at about 90°C. From there, let taste decide: finer or longer for sour, coarser or shorter for bitter.

What is the difference between acidity and sourness in coffee?

Acidity is a pleasant brightness, like orange or green apple, and it usually comes with sweetness. Sourness is sharp, thin and unpleasant, and it is a sign of under-extraction. Fruity, naturally processed coffees have lots of acidity even when brewed perfectly, so a customer who dislikes them may prefer a medium-dark coffee instead.

Can dirty equipment make espresso bitter?

Yes. Coffee oils build up on the shower screen, group head and baskets and turn rancid, giving every shot a burnt, ashy bitterness that no grind change will fix. Clean the group and baskets every day, backflush with detergent at least once a week, and deep clean at least every two weeks if you make more than 100 cups a day.