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How to Prevent Under or Over Extraction?

24 February 2021
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Coffee extraction is the final, and one of the most important factors in determining whether your coffee tastes good, or not.

While the extraction process may seem like a simple and straightforward step, controlling the variables can result in a big improvement for your coffee.

If you want to brew the most flavourful and balanced tasting cup of coffee, here’s how to prevent under and over extraction.

What is Coffee Extraction?

Extraction occurs when water pulls out the flavours and aroma from coffee grounds. These flavours are made from a combination of the oils, sugar, and dissolved compounds that are present in coffee grounds.

The secret to perfecting coffee extraction lies in extracting the ideal amount of these flavours and aroma. Too much results in an over extracted and bitter brew. Too little and you will get an under extracted brew that tastes sour.

A lot of work goes into balancing the countless variables to extract a cup of deliciousness, but it’s well worth it. Here’s what a perfect cup of coffee tastes like.

Factors that Prevent Under or Over Extraction

Grind Size

Menu display on a coffee bean grinder
Adjust your grind size according to your brewing method. Featuring the De’Longhi Dedica Conical Burr Grinder. Photo from De’Longhi.

There are many factors that affect how your coffee tastes, but great coffee starts with using the right grind size for your brewing method.

The rule is simple: the finer the coffee grounds, the more flavours are extracted over the same period of time.

But here’s the tricky part: every brewing method requires a different grind size as the extraction time varies. This infographic will help you determine the ideal size for every brewing method.

To get the perfect grind, ensure that you use a reliable grinder for better grind uniformity and consistency. If you are looking to add a coffee grinder to your home or office, we recommend the following to get you started.

Pro tip: Don’t underestimate the importance of grinding and having a reliable coffee grinder. This will ensure that your coffee beans and grounds aren’t jeopardising the other variables and resulting brew.

Tamping

a person tamping coffee
A well-tamped espresso will ensure an even and consistent extraction. Photo from Ketut Subiyanto.

Home brewers often apply an inconsistent tamping pressure which results in an imperfect coffee puck.

However, a consistent flavour extraction requires not only a bed of grounds with even density, but also the perfect compactness.

To prevent under or over extraction, use a pressure of approximately 19-20kg for tamping. This ensures that excess air is eliminated, while perfectly compacting the grounds for water to flow through.

Pro tip: Before tamping, give the portafilter a quick tap on the table, then apply firm pressure on the coffee grounds while keeping the tamper perfectly level with the table.

The Golden Ratio

Imagine pouring a kettle full of hot water over a teaspoon of grounds – you will get an over extracted cup of coffee that contains unwanted solubles and bitter compounds from the grounds.

If you are unsure about the amount of water and coffee grounds to use, always stick to the golden ratio of 1:17. For every gram of coffee, use 17 grams of water to make that ideal cup.

Measuring the amount of grounds and water is the best and most foolproof method in controlling the strength and balance of your coffee. Nonetheless, gradually adjust and experiment with the ratio to suit your taste buds.

Water Temperature

pouring hot water from a gooseneck kettle onto coffee grounds
The ideal water temperature for coffee brewing is between 90-96 degrees. Featuring the De’Longhi Icona Café Gooseneck Kettle. Photo from De’Longhi.

If you have been wondering why your coffee has been tasting sour or bitter, water temperature is most likely the culprit.

Heat is a stimulant when it comes to extraction – the hotter your water, the more quickly it extracts flavours from coffee grounds.

Many make the mistake of using freshly boiled water for their brew. This results in over extraction as flavours are extracted too early and too fast, causing a lacklustre brew.

Similarly, lukewarm and cold water are unable to extract the ideal amount of flavours within the recommended brewing time, giving an under extracted cup of coffee.

Always ensure that the water temperature is slightly below the boiling point at 90-96 degrees.

Learn more about the importance of water in coffee making.

Brewing Time

Here’s a common misconception about brewing time: the shorter or longer the brewing time, the “weaker” or “stronger” the brew will be.

Caffeine levels are determined by other factors, such as the brewing method and type of coffee bean used. Here’s what you should be looking out for if you want a “stronger” or “weaker” brew.

Brewing beyond the recommended brewing time causes coffee grounds to release bitter chemicals (this applies to tea brewing too). Similarly, under extraction is a result of coffee grounds not having enough time to fully release its yummy flavours.

Here’s a guide on the recommended brewing time for five of the most popular coffee makers.

Save the Trouble

person pressing a button on a coffee machine
Let the coffee machine do all the work for you. Featuring the De’Longhi PrimaDonna Elite Experience. Photo from De’Longhi.

Perfecting a cup of coffee may seem like an arduous and daunting task. That is why technology-driven coffee machines have been making their way into homes and offices.

Today, there are a variety of automatic coffee machines that are precisely engineered to extract a café-quality shot of espresso. No fuss, no trouble. It’s all about enjoying convenience at one touch.

Browse De’Longhi’s range of fully automatic coffee machines here.