12 Factors that Affect the Quality of Your Espresso

factors that affect the quality of your coffee
A perfect espresso is rich and flavorful

Espresso is the foundation for a number of coffee drinks such as cappuccino, latte, macchiato, mochaccino, flat whites as well as iced coffees. It is, therefore, fair to state that the quality of your coffee drink depends on the quality of the espresso.

A perfectly extracted espresso is rich, dark, and sweet.

Espresso extraction is a process where an espresso machine uses pressure to force hot water, almost at boiling temperature, through compressed fine grounds of coffee beans to make espresso.

There are several mistakes to avoid to pull perfect espresso shots every time. When pulling espresso, watch out for the following factors that can affect the quality of the espresso:

1. The Quality of the Coffee Beans

Freshly roasted beans do not prime until after about five days from the roasting date. Brewing espresso with coffee beans immediately after roasting is undesirable because the beans still have a lot of trapped carbon dioxide that affects the pulling process.

The beans reach their highest quality between 7 and 14 days after roasting. However, exposure to heat, light, moisture, and oxygen will reduce the quality and shelflife of roasted beans.

Proper storage of coffee beans prolongs the shelf-life of roasted beans. For example, vacuum-packed beans as well as beans that are stored in airtight opaque jars have a shelf life of up to 12 months.

The vacuum packaging has a special air valve that allows the beans to gradually release carbon dioxide.

Once the packaging is opened, the shelf-life of the beans reduces significantly to between seven and fourteen days. Stale beans affect the consistency of your puck as well as the aroma and flavor of espresso.

Ensure proper storage of your roasted beans to safeguard them from going stale. See our separate guide on how to store roasted coffee beans.

2. The Quality of the Coffee Grounds

Grinding coffee beans long before you make the espresso results in the grounds becoming dry and old. Pre-ground coffee, if left exposed for a long time, loses its flavors and aromas.

Ground coffee loses its gases and flavors faster than whole beans because the grinds have more surface area to react with air (oxygen) than whole beans. The grounds become dry pretty fast when you expose them to air. The best practice, especially, for espresso is to grind coffee when you are ready to use it.

When I was a beginner barista, I would grind lots of extra grounds than I needed for my espressos. This becomes a problem, especially during days when business is slow. I was fairly new to espressos and so when new orders came in I would make the new orders using the “old grounds”. Yes, you guessed it! I had multiple complaints with comments that my coffee was stale, weak, and different (in a bad way).

3. Grind Size

Breaking the coffee beans down into tiny particles increases the surface area for the extraction of its flavors.

The calibration of your coffee grinder will determine how coarse or fine the grinds will be. Coarse grinds allow water to flow through much faster than desired while extracting fewer oils and soluble elements and flavors.

The result is an under-extracted espresso that is sour, watery, and lacks sweetness.

A finer grind causes over-extraction where water draws too much of the coffee elements and flavors resulting in an espresso that is bitter and dry. An extra fine size will block water from flowing through the puck and lead to spillage from the top of the portafilter.

A properly calibrated grinder gives perfect grinds for optimal extraction.

4. Dosage

The dosage for a single espresso is usually about 7-10 grams to produce about 1-1.5 oz of coffee. For a double shot, the dosage is 14-20 grams to generate about 2-2.5 fluid ounces. The ratio of grinds to coffee is 1:2

Under-dosing reduces the time of contact between water and the coffee grinds and leads to under-extraction. The resulting coffee is weak and watery and has less flavor.

Over-dosing reduces the speed at which water flows through the puck. This increases the extraction time and the espresso is bitter and dry.

To avoid dosage errors you are better off using a scoop or a weighing scale. There are available options for scoops that measure the exact amount of grounds for a single or a double shot of espresso.

Two scoops with a single-shot scoop will measure the grounds for a double shot. However, a weighing scale is the surest way to ensure consistent dosing. Some grinders feature an integrated scale.

5. Distribution And Tamping

When adding your ground coffee to the portafilter, the grounds do not fall evenly. Some grounds will be sitting higher than the others. If you tamper without leveling the grounds, the resulting puck will cause uneven extraction.

Another common tamping mistake is excessive tamping which leads to over-compression of the grinds and eventually causes over-extraction. Under tamping where the puck is not compacted enough will cause under-extraction.

Also, some people like to polish the puck by slightly turning the tamper when doing the final tamping. While it’s totally fine to polish the puck, over-polishing might loosen the grounds and compromise extraction.

How to Tamp Coffee Grounds on a Portafilter

  1. Add the correct dosage of grounds into the portafilter
  2. Use a portafilter distribution tool to spread the coffee evenly
  3. Place the portafilter on a tamping pad and use a weighted tamper to gently compact the grounds into an even puck
  4. Use a soft brush to remove the coffee grains that are on the sides of the filter
  5. Tamper again by applying a little of your weight while ensuring that the puck is level

We have discussed in a separate article, several coffee distribution methods to help you adapt and improve the method that you prefer. Fine-tuning coffee distribution will ultimately level up your overall espresso technique.

6. Failure to Pre-heat Your Coffee Machine and Equipment

When you turn an espresso machine on, it will take some time to build up enough pressure and heat up the water. Some machines might take up to about 30 minutes to be ready for brewing.

Some espresso machines have pre-installed pressure and temperature meters that are easy to monitor. Others have settings that allow you to control water temperature.

Make sure your machine has warmed up properly, the pressure is about 9 Bars, and the water temperature is between 195-205 degrees Fahrenheit.

Preheating your portafilter and cup ensures that the espresso stays hot for longer. Run an espresso cycle without coffee by loading an empty filter into the machine and placing the espresso cup under the filter. Dry the portafilter before dosing.

7. Incorrectly Inserting the Portafilter into the Espresso Machine

When inserting the loaded portafilter into the group head, you run the risk of knocking the portafilter onto the head. This loosens or cracks the puck and leads to espresso channeling during extraction.

Locking the filter incorrectly or sideways leads to spillage over the sides of the portafilter and poor extraction. Correctly inserting and locking the portafilter in the group head is fairly easy but might require some practice for beginners.

8. Quality of the Water for Espresso

Water temperature affects the number of elements that are pulled out of the coffee grounds. The water temperature for making an espresso should be approximately between 195-205 degrees Fahrenheit (90.6-96 degrees Celcius). Boiling water is bad for espresso shots as it is likely to cause bitter and burnt flavors.

The chemical components in water affect how water extracts the compounds in coffee. Hard water leads to poor extraction and inferior coffee.

If your water is hard, it is important to install a filter and softening system to improve the quality of your water. Hard water can also lead to clogging and destruction of the coffee maker.

You may not want to make coffee with distilled water as it lacks several chemical and mineral elements and yields coffee that is bitter and flat. Distilled water may also corrode your coffee maker.

9. Calibration of the Coffee Machine

Poor calibration means that the espresso cycle is either too long or too fast leading to over-extraction or under-extraction respectively. An optimal cycle for a single shot is about 20-25 seconds and between 25-35 seconds for a double shot.

10. Care and Maintenance of Equipment

Flushing the group head of an espresso machine

It is important to properly clean and sanitize all the coffee equipment and machines and the whole workstation or kitchen.

Rinse the portafilter and filter basket in hot water after use. Use the filter pin to remove coffee particles that are stuck in the filter basket holes. Always dry the filter and the basket before dosing with coffee.

A build-up of coffee grounds and oil residues in the group head over time can compromise the taste and quality of your coffee. The grime can also damage the machine. A dirty machine gives an uneven extraction and the coffee can have a dirty after-taste.

Every time you make coffee, remove the portafilter and purge water through the group head for about three seconds to clean the group head. Regularly clean the shower screen and the rubber inside the group head using a nylon brush or a damp cloth.

At the close of business perform a backflush on the machine. Load a blind basket in the portafilter and carry out the backflush.

Perform a weekly or bi-weekly backflush with detergent. Remove the shower screen and shower block and soak them with the filter baskets and portafilters in detergent on a weekly schedule to remove coffee oils and residues.

Always wipe the steam wand with a damp cloth and purge the wand every time you use it to avoid clogging.

Keep a regular maintenance schedule of all machines and equipment, especially if operating in a commercial setting. Ensure that the burrs of your grinders are always sharp to avoid inconsistent and uneven grounds.

11. Swirling the Espresso

There are three profiles to an espresso:

  • the dark brown bottom
  • the middle layer is brown caramel in color
  • the crema; the blonde foamy top that is bitter

Crema floats on the espresso and constitutes the roasting flavors that are described as bitter. Mixing the three layers of espresso incorporates the bitter crema into the espresso and mixes the other complex flavors for a more balanced overall flavor.

The best way to mix the three layers of your espresso is by stirring with a spoon rather than swirling. Stirring is a more natural approach as compared to swirling.

Swirling might have some swagger to it but it does not mix the three parts of espresso properly. You also run the risk of spilling your coffee (an espresso cup is about 2-3 oz) and looking clumsy. Who knows, the drink might end up on your dress, your date, or on your computer.

So, let’s agree to stir our espresso and enjoy the rich flavors.

12. Sitting the Espresso for too Long

You can make the best espresso but like all good things, your espresso has a “Best By” time. The delicious volatile flavor and aroma will disappear and all you will have is caffeine, water, and the woody flavors. See how the espresso changes after pulling it.


Patrick is first a coffee lover and then a trained barista. His bucket list includes sky diving and sipping on Java in the Himalayas.

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