Coffee Extraction: How To Make a Great Brew.

Every sip of coffee is a carefully balanced combination of different compounds, each contributing to its overall taste and mouthfeel:

• Bitterness – Extracted primarily from caffein. Caffeine has a longer extraction time, so leaving your coffee to brew for too long can lead to a bitter coffee extraction.
• Sourness – Derived from acids in the coffee bean. Some acidity is desirable, but insufficient brewing time can result in a sour coffee extraction that tastes sharp and weak.
• Viscosity (Texture) – Created by lipids, sugars, and carbohydrates, which contribute to body and mouthfeel. Espresso and French press taste “full bodied” because they don’t remove the natural oils from the coffee beans. Coffee preparation methods that use filters, on the other hand, remove up to 90% of the lipid content, producing a much lighter brew.

By controlling key variables like coffee extraction ratio, grind size, and brew time, we can manipulate these elements to create the ideal cup.

When you buy pre-ground coffee, it will often say on the bag what extraction method it has been ground for. This is because the grind size significantly impacts how water extracts flavour. Different brewing methods require different grind sizes:

• Coarse Grind: Ideal for methods involving steeping, such as French press or cold brew, as it slows down extraction for a more even process.
• Medium Grind: Best for pour-over and drip methods that combine steeping and light pressure.
• Fine Grind: Used in espresso coffee extraction and moka pots, where water is forced through coffee quickly under pressure.

It’s the process of drawing soluble compounds from coffee grounds using water. There are three main types of extraction: steeping, pressure percolation, and drip filtration, each influencing the final taste and texture of the coffee.

This method involves submerging coarse coffee grounds in hot water, allowing the flavours to infuse over time.

• French Press or Cafetiere: Coffee grounds and hot water are added to a jug and left to brew for 3-5 minutes. The coffee is then “pressed” using a plunger with a mesh filter. This method uses coarsely ground coffee and a wider mesh filter which stops the natural oils from being removed, resulting in a richer body and texture.
• Cold Brew: This method uses ground coffee steeped in cold water for around 12 to 14 hours, producing a smooth, low acidity concentrate.

Pressure percolating involves passing hot water through finely ground coffee under pressure. The result is a stronger, thicker product known as espresso. Espresso can be prepared by:

• Moka Pot: This stove-top coffee maker uses vapour pressure to pass hot water through finely ground coffee. A moka pot generates up to 3 bars of pressure.
• Espresso Machine: Uses 9 bars of pressure, producing a concentrated shot in 25–30 seconds. Precise coffee extraction measurement is key for consistency, as coffee ground too fine or packed too densely will be difficult for the water to pass through.

This method falls somewhere in the middle, as it relies on filter paper and gravity (pressure) to extract coffee, producing a clean and well-balanced brew. A funnel-shaped device, known as a Coffee Cone, is lined with a filter and placed over a jug. Ground coffee is added to the cone, then evenly saturated with hot water. As the water passes through the coffee, it gradually extracts the flavours before dripping smoothly into the jug below. Ensuring consistent saturation of the coffee grinds is essential to creating a balanced brew. A pocket of overly saturated grinds will allow the water to pass through too quickly, creating a weak and acidic brew. To assist with even pouring, many baristas will use a goose-neck kettle for optimal control.

Higher temperatures extract flavour faster, while lower temperatures slow extraction. The best temperature for coffee extraction is between 90-96 °C. Temperatures below this can lead to sour coffee extraction due to under-extraction, whereas higher temperatures can lead to bitter coffee extraction.

Water from a freshly boiled kettle can be unpredictable but will usually fall somewhere in this window if given a moment to cool. Coffee machines and dedicated water boilers can be more precise, allowing for more control over the extraction time.

The ideal coffee extraction time will depend on the extraction method used. To ensure consistency, professional baristas use coffee extraction equipment like timers to control how to time coffee extraction.

• Cold brew by far takes the longest, at 12-24 hours, as the cold temperature of the water is much slower at drawing out the flavours.
• French Press (Cafetiere) is second, taking 3-5 minutes to reach it’s optimally balanced flavour.
• Espresso, thanks to using a pressurised extraction method, generally takes about 25-30 seconds to produce a rich, velvety shot of coffee.

If your coffee tastes off, you may need to modify how to slow down coffee extraction or speed it up.

• To slow down extraction (coffee is too bitter): Use a coarser grind, lower temperature, or increase brew time.
• To speed up extraction (coffee is too acidic): Use a finer grind, higher temperature, or decrease brew time.

Achieving perfect coffee extraction is a blend of science and personal preference. By understanding coffee extraction chemistry, using the right coffee extraction equipment, and fine-tuning your grind size, water temperature and brew time, you can consistently craft an exceptional cup. Whether you love the boldness of espresso coffee extraction, the richness of a French press, or the smoothness of a cold brew, understanding and mastering these techniques will undoubtably improve your barista experience.

The process is better experienced than it is read, so refer to a coffee extraction diagram to visualise the coffee extraction process, experiment with the different variables, and find your best extraction method.