How-To Avoid and Fix Sour Espresso
Making delicious espresso at home can be tricky. Even experienced baristas sometimes end up with a sour, unpleasant shot of espresso.
Sour espresso is caused by underextraction, which happens when the hot water passes through the ground coffee too quickly and fails to extract enough soluble solids. This leaves you with a thin, weak, sour tasting shot.
Luckily, with a few tweaks to your technique and equipment, you can avoid sour shots and make restaurant-quality espresso drinks right in your own kitchen.
Here are some tips:
Avoiding Sour Espresso: Freshly Roasted, Quality Beans
The age and roast level of your beans can impact flavor. Old or stale coffee beans tend to lose their natural oils and aromatic compounds over time. This makes it difficult to extract enough flavor during the brief espresso brewing process.
On the other hand, very lightly roasted beans may not have developed enough soluble sugars and caramelized flavors yet.
For best results, choose beans roasted to a medium level within the past 1-2 weeks.
Purchase from a reputable roaster and pay attention to the roast date. Store beans in an airtight container out of sunlight.
Grind Coarser
One of the easiest ways to combat sourness in espresso is to grind your beans coarser.
Remember, espresso extraction happens under pressure in a matter of seconds.
So you need a perfectly balanced fine, powder-like grind to provide enough surface area for the water to extract sufficient soluble solids in that short timeframe.
If your grind is too fine, the water is not able to go through the coffee, resulting in over-extraction and a very compressed, small shot.
If your grind is too coarse, the water will just rush through without picking up enough coffee flavor and oils, resulting in a thin, weak shot of high volume.
Invest in a high-quality burr grinder that allows stepless grind size adjustment.
Dial in an appropriately fine setting for your machine by gradually adjusting finer until you achieve a balanced 25-30 second extraction time.
Espresso to sour? Use the Correct Dosage
The amount of ground coffee you use is also important. Too little coffee in the portafilter basket means less surface area for the water to extract from.
Start with the recommended dose for your basket size – usually around 15-18 grams.
You may need to adjust dosage slightly depending on the specifics of your equipment and bean varietal.
Weigh your dose for consistency using a small digital scale. Add or reduce in 0.5 gram increments to hone in the ideal dose for balanced flavor.
Distribute and Tamp
Be sure to distribute the grounds evenly and tamp consistently before locking the portafilter into your machine.
Use a distribution tool or simply stir the grounds with a chopstick to break up any clumps and spread them evenly.
Tamp evenly with about 30 lbs of pressure. Insufficient tamping can lead to channeling or uneven extraction.
Tamping too hard may over-restrict water flow. Finding the right tamping pressure for your grind setting is key.
Use a Bottomless Portafilter
If you can, pull your shot into a bottomless (naked) portafilter rather than using a spouted one.
This allows you to observe the extraction and diagnose issues like channeling that can lead to sourness.
Proper technique will result in an even, creamy, tiger-striped pour.
Spraying, blonding, or multiple streams indicate problems with grind, dose, distribution or tamping. Adjust your prep and try again.
Fixing Sour Espresso: Lower Your Dose
Sometimes overdosing the basket can cause problems.
If you’re already grinding fine enough and tamping well but your shots are still slow and sour, try lowering your dose by 0.5-1 gram.
This leaves more free space for the water to saturate the coffee bed. Just make sure to adjust grind coarser when lowering dose so extraction time remains in the target zone.
Try Pre-Infusion
Many modern espresso machines, like the Breville coffee makers offer pre-infusion capabilities.
This applies low pressure water to “bloom” the coffee for 5-10 seconds before ramping up to full pressure.
Pre-infusion helps saturate the grounds, reduce channeling, and extract more evenly for balanced flavor.
Machines without pre-infusion can sometimes be modded to add this feature.
You can even simulate it manually on less expensive machines by starting with the pump/lever off, then turning on after 5 seconds.
Increase Extraction Time
Experiment with grinding finer and/or using a higher dose to slow the shot and increase extraction time.
Stick within the widely recommended 25-30 second range, including pre-infusion.
This gives more opportunity for sweetness and acidity to balance out.
Be careful not to go too long or you may over-extract bitterness.
Dialing in extraction times in that ideal zone usually results in the best tasting shots.
Try a Longer Ratio
Traditionally, espresso shots are pulled short – around a 1:2 brew ratio.
This means 1 gram of ground coffee extracted into 2 grams of liquid espresso (a double shot is around 60ml including crema for a 15-18g dose).
However, longer ratios like 1:2.5 or 1:3 may help avoid sourness in some cases by increasing extraction and diluting acids.
Simply let the machine run longer to achieve your desired output volume. You may need to grind coarser to prevent over-extraction at longer ratios.
Adjust Water Chemistry
While it’s not commonly considered, adjusting your brewing water can impact espresso flavor.
Water naturally contains minerals that influence acidity and pH balances during brewing.
Try using bottled or filtered water to remove any off tastes, chlorine, or excess minerals from your tap water.
You can also look into adding mineral supplements to achieve the ideal water chemistry for balancing acidity and sweetness to your taste.
Vary Your Tamping Pressure
Tamping too lightly could lead to a fast, uneven extraction.
But excessive tamping pressure can over-restrict water flow, also causing under-extraction issues.
Try varying your tamping pressure in small increments. Increase if shots are blonding and sour.
Decrease pressure if you notice spurting or astringency from over-extraction with your current tamp.
There is a sweet spot you’ll have to discover for your specific equipment and grind setting.
Change Your Brew Temperature
Brewing at a higher temperature helps extract sweetness from the beans to balance acidity.
If possible with your machine, try increasing the boiler or grouphead temperature 5-10°F to achieve this.
Be careful not to scald the coffee however.
Lower temperatures can under-extract and accentuate sourness in light roasts especially.
But they may help tame bitterness in very dark roasts.
Play with your machine’s brew temp capabilities to find your ideal range.
Fixing sour espresso requires dialing in multiple variables
In conclusion, a perfectly pulled espresso requires dialing in multiple variables.
With quality beans and the right grind setting, dose, tamp, time, and temperature, you can eliminate sourness from underextraction.
Consistency and repeatability are key.
Vary just one factor at a time while keeping all others constant.
Take detailed notes each time you pull shots during the dialing in process.
With practice and patience, your taste buds will guide you toward sweet, balanced espresso bliss.
The effort is well worth the reward of avoiding sour shots and being able to enjoy cafe-caliber espresso drinks any time.
Nigel Hooijmans
I have tested over 20 espresso machines and tasted hundreds of kinds of specialty coffee. What is left is a lot of knowledge which I'd like to share. On BlackBlackCoffee.com you'll read honest opinions about real products.
