Our last blog: ‘Does the Grind Size Matter?’ examined the best ways to grind coffee, the various grind sizes and why they matter. This article follows on with a more in-depth look at the extraction of coffee, highlighting the importance of this process, with ambitions to educate you further.
What is coffee extraction?
When considering coffee, it’s rich history, the many methods of its production and the vast variety of flavours, coffee extraction is often overlooked. When, in fact, it’s arguably the most imperative part of coffee - without it, you don’t even have a cup of coffee!
The extraction element is everything that the water takes from the coffee and deposits into your cup. Although that sounds rather straightforward, the understanding and application of it can be complex.
The Chemistry of Coffee Extraction
As soon as water and coffee are combined, chemistry takes its toll. Without using too much scientific terminology, this is a dissolving/dissolution process. The flavours dissolved are what produce the end result in your cup. The rest remains undissolved.
If you were to toss the coffee beans into the water, as they are, there’s not much for the water to dissolve, due to the robustness of the coffee bean. All that would be extracted is the outer layer. Hence the need to grind, or open up the coffee bean, increasing its surface area and allowing the water to pass through it and maximise its flavour collection.
A roasted coffee bean is around 30% water-soluble. This means that you can extract about this much of the coffee bean’s mass in water. The rest is cellulose and other plant based stuff which forms the structure and integrity of the bean.
You may think that crushing the coffee beans into a fine grind and dumping it in hot water until it dissolves (like we do with instant coffee) would be enough to make the most amazing tasting coffee but its not. The only thing this will achieve is extreme bitterness. Unfortunately, not all the flavours coffee possess are nice. You must control the amounts of flavour you extract by measuring, weighing and timing the coffee grinding and extraction processes.
Extraction is a balancing process. Ideally, you want to avoid under or over extracted coffee - the best results sit somewhere in the middle.
Under Extracted Coffee
The key identifiers of an under extracted coffee are in its taste - sourness, a lack of sweetness and somewhat salty aftermath. If you are getting these end results, it’s because you haven’t extracted the coffee flavours for long enough. Let’s take a closer look at some of those underwhelming flavours...
Whilst we do champion acidity in coffee, it’s not to be confused with sourness. Although there is a confusion between the two because in some languages they are defined as the same thing.
Sourness should be identified as a flavour that dramatically alters your facial expression, as soon as you encounter it. Acidity is the blanket that unfolds flavours like sourness, sharpness and tartness, all of which can be wonderful in their own right. But if your coffee is too sour, you’ll know about it.
All coffee lovers search for sweetness on their pallet. Often, a lack of sweetness is due to other overpowering flavours such as sourness, due to an under extraction. To lose coffee’s natural sweetness is a crying shame. There should be no real need to add sugar or any other sweeteners, if you get the extraction of the particular coffee correct.
The overall finish of an under extracted coffee leaves you with minimal pleasantries. Not only do you not benefit from the expected flavours according to the descriptions but there will be no lingering aftertaste experience. It’s an abrupt and unsatisfactory coffee experience.
Over-extraction occurs when you take too much of the soluble flavours out of the coffee. This level of extraction results in unfavourable flavours.
Bitterness is a key component of the coffee flavour make-up. Having said that, it needs to be balanced alongside other predominant flavours for it to work in harmony. A lot of the bitterness in coffee comes from the caffeine. There are other chemical aspects that contribute towards bitterness, though, such as the roast itself.
You should be able to tell if your coffee has been over extracted. It will lack richness, smoothness and have no distinct mouthfeel. Instead, it will feel rough, dry and lacking in any sort of flavour or identity.
Over-Extracted Coffee Finish
If you identify elements from above in your coffee’s flavour and texture, it will no doubt be over-extracted. Flavours should be identifiable and not generic, especially if you’ve purchased a speciality coffee.
Perfectly Extracted Coffee
Everybodies ‘perfect’ coffee will differ slightly because of an individual's personal preference. However, a well extracted coffee is the ideal blend of nature and science and something to behold!
Imagine how a particular fruit ripens and transcends through its flavour profiles, (often tart to sweet), the same can be said for a coffee cherry. Sugars develop and become richer transferring more flavour to the coffee bean itself. This is why coffee harvesting and coffee processing methods are integral to flavour outcomes.
The final coffee extracted should have a degree of transparency and clarity. It should not be thickened or muddied by over or under extracting the chemicals. The texture and flavours should be consistent and in accordance to what you were expecting.
The sort of acidity you’re looking for in your coffee is one that carries the essence of, and reminds you of, a particular fruit. If you can easily identify several flavours matching the descriptors, you will have come close to getting the balance of acidity just right. Anything too intense and it’s gone too far.
A well finished coffee will leave a blanket of comfort and identifiable flavours on your palate. It will linger on, long after your coffee has gone!
Coffee Extraction at L&Y
Our specialist barista, Jamie Romp, works tirelessly daily dialling in the coffee machines, grinders and weighing and testing grind sizes to execute the perfect extraction!
In order to expand your knowledge further, you can enquire about our in-house City & Guilds L2 Barista Courses, just get in touch.