When we brew, we are simply dissolving matter from the bean creating a solution of coffee and water.

The roasted coffee bean is comprised of fruit acids, oils/fats, simple sugars, caramelised sugars, and fibre (the woody structural bits holding everything else together). Each component tastes relatively unpleasant on its own. However, combining a little bit of everything is where the magic lies!

When dissolving (aka extracting) coffee, the acids extract first, followed by the oils/fats, then the sugars, and lastly, the fibre. If the barista extracts beyond the sugars, a great tasting espresso can quickly become bitter, ashy and dry. This is what we refer to as over-extraction. On the flipside, if you don’t extract enough from your coffee, the acids present at the start of the extraction will not be balanced by the sugars. This often results in an astringent and salty tasting espresso, which is referred to as under-extraction.

It is common for the average home-barista to mix up sour and bitter, with many consumers often reporting any negative flavour experienced when drinking coffee as ‘bitter’.  However, it is worth keeping an open mind and considering that the negative taste being experienced could be sour, as it is much easier to under-extract coffee than over-extract it (assuming your coffee beans are relatively fresh and from a reputable roaster).  

Bitter foods include bitter melon, beer, swiss chard, and citrus peels.  They have an unpleasant and disagreeable taste.  Examples of sour foods are lemon, orange, grape, melon, wine, and sour milk.  They have a sharp taste.

In addition, we all have a different sensitivity to ‘bitter’ taste.  If you are experiencing bitterness, try adding extra water.  If the bitter taste is no longer present, then it is likely the coffee was too concentrated or ‘strong’ for you, rather than being over-extracted.  If the bitterness remains, there are some simple ways to improve your extraction and achieve the coffee of your dreams.  

Espresso extraction is dependent on many variables.  I like to think of each variable as energy that can be dialled up or down to increase or decrease the extraction process.  To change your variables, they must be measurable – this requires some key equipment.

For variables including dose (grams of coffee used), water (grams of water used) and yield (grams of coffee beverage extracted – used primarily in espresso), a pair of kitchen or (better yet) dedicated coffee scales, capable of measuring to two decimal places are best.

Brew time can be measured using a kitchen timer or your smartphone. For the vast majority (coffee-nerds excluded) that don’t have a temperature-controlled kettle, you can use the boiled water temperature of 98-100C as a rough but effective gauge. Simply increase or decrease the increments of time that you wait after the water reaches boiling point before using it to brew coffee.

The above theory applies to all brew methods; however, it is important to change only one variable at a time, so it is clear the impact taking place.

While these rules apply to espresso brewing, a few extra considerations and observations apply.  

Channeling – a poorly prepared puck can result in channeling, creating an espresso that is both under and over-extracted.  This is where the water finds the path of least resistance, or 'channel' in the puck and uses this point to exit the puck, creating an uneven extraction.  You can often spot a channel as your extraction will start off watery, splash in the cup and be pale in colour. You might even see a hole in the spent puck when you take the portafilter out and inspect it.  Unfortunately, channeled espresso is best thrown away.

Visual indicators — how an espresso pours from the portafilter spout will give many clues about the extraction.  Water-like wavery shots will be under-extracted; shots that drip or ‘choke’ for several seconds will be over-extracted; and shots that act like olive oil or warm honey running off a spoon will be just right.

Coffee is about as complex as it gets when it comes to things we consume.  It is essential to remember that coffee is the seed of a plant constantly responding to its environment. The roaster deals with these seasonal changes and new crops every few months, and even after the coffee bean has roasted it continues to change over time. Although we promise delicious, well-roasted coffee, you need to be mindful constant changes are occurring.  This can be frustrating and gratifying at the same time.

Additionally, everyone has their own preferences, like wine or beer choices; however, coffee is exciting because you have control over how you brew it, meaning you can influence your brew to your preferences using the parameters above.  Some people may like a more acidic coffee while others maybe perfect the robustness of a heavily extracted espresso.

Now that you have mastered your coffee extraction at home, learn about coffee bean freshness and how to store them to keep them fresh on our blog How long do coffee beans last.

Thank you for getting this far. If you have questions, please feel free to email me at ali@whitewhalecoffee.com.au or ask one of our White Whale baristas, who are more than happy to share their knowledge!