Brewing a cup of coffee is a ritual for many people. There are a number of variables that can affect the taste, including grind size and water temperature and how long the ground beans were exposed to hot water during extraction.
These variables can make or break your morning cup o' joe because under-extracted coffee might often taste salty and sour and over-extracted results in bitter brews. In this post I'll explore three signs that your next pot may have been under-extracted!
Important Variables During Brewing
Before explaining how under-extraction occurs it’s important to understand that there are a number of variables that can affect the taste of your morning brew. I've compiled them all here:
- The quality of the coffee beans
- The fineness that the coffee beans are ground
- The temperature of the water used to make the coffee
- The timing involved in adding the coffee grounds to the water, and removing it from contact with the heated element after a specific time interval.
Let's briefly explain all of these variables
The quality of the coffee beans
The quality of the coffee beans is a very important variable. If you use freshly roasted, high-quality Arabica beans, and grind them yourself just before brewing, then this will positively affect every cup that you drink from it.
You can tell how fresh your coffee is by looking at the "Roasted On" date on the bag. Coffee goes stale quickly after roasting – even more so once ground – and should be used within a few days for best results.
The fineness that the coffee beans
First, Imagine water running through a bed of small rocks then through a bed of sand. In which scenario will the water run through faster? If you thought bed or small rocks, then you are absolutely correct!
Such is the case with coffee, when you grind coarser the water passes through faster than when you grind finer. Choosing between the two of them is a little tricky, because it depends on which brewer you are using (French Press, Espresso machine, Moka Pot etc.) because each brewer will need a different approach.
The temperature of the water
The temperature of the water used to make the coffee affects how quickly the ground beans release their natural flavour into solution. I advise using heated water to preheat your ceramic dripper prior to brewing, and then allow the coffee to brew for a minute or two with the heated water.
After this time period (a total of about 3 minutes from start to finish) remove your ceramic dripper from contact with the heated element and pour yourself a cup. If you leave it on the element too long it will continue to extract, and become bitter
The overall brewing time
The timing involved in adding coffee grounds to the water, and removing it from contact with the heated element after a specific time interval is probably one of the most important variables during "pour over" style manual drip-style coffee brewing because it is essentially your recipe.
You know the way potatoes need a certain amount of time to bake in the oven, well, coffee is the same! It only needs a few minutes of contact with the water. This is why when brewing coffee it’s important to use a recipe.
3 Signs of Under-Extracted Coffee
Three signs of under-extracted coffee are when you brew tastes:
- Flat, thin, uninspiring cup
- Salty or sour with little depth of flavor
- Unbalanced or one-dimensional taste
3 Signs of Over-Extracted Coffee
Three signs of over-extracted coffee are when you brew tastes:
- Bitter, gritty cup
- Burnt flavors (e.g., charcoal) mixed with more pleasant characteristics
- Unbalanced or one-dimensional taste
Over-extraction vs. Under-extraction
The total dissolved solids (TDS) percentage of coffee brewed is the difference between the amount of water added to the grounds and the amount of final beverage that is produced.
If too much water was used then you are likely dealing with over-extracted coffee. On the other hand if too little water was used, then you are likely facing under-extraction.
There are three main variables that will affect how much water exactly is retained by the grounds during brewing: ratio, grind size and extraction time.
The ratio refers to how many grams of coffee there were to every 100 ml in your desired drink in total. For instance: a 12 oz cup served with a 1:15 time and a 22 g dose would be a 1:15 ratio. Another example would be a 16 oz serving at a 1:17 ratio and 26 grams of coffee in the brew.
The larger the grind size, the longer it takes for water to extract soluble components from the grounds (Solubles such as sugars, oils and caffeine).
Since large particles will require more time for extraction, there is also an increased chance that undesirable compounds may extract before desirable ones resulting in over-extracted flavors.
On the other hand, smaller particles result in faster extraction times and therefore decrease the risk of over-extraction . However if too little time is dedicated to extraction then you might end up with under-extracted results which we will discuss further below.
The extraction time refers to the time required for the entire brewing process starting from when water is added to the grounds until it is poured into your cup. Obviously, if too much time is dedicated to this step then you will end up with over-extracted coffee.
At the same time, an under-extracted shot means that you were unable to extract enough soluble material within your given timeframe. The problem occurs if there are grounds that require more or less extraction than others (which there definitely are).
For example, oil/fat soluble compounds (such as lipids) require a long extraction time because they are not very soluble in water. They need plenty of contact with hot water so would be among the last solubles to extract.
On the other hand, sugars are very soluble in water and dissolve easily. Therefore they require a short extraction time before being extracted from the grounds.
This might seem a bit too much information to you right now, but all it takes is practice and keeping these variables in mind when you brew.
Remember that in the end, all that matters is your own personal preference when it comes to coffee flavour. Some people might claim there is a right and wrong way of doing it but if you’re enjoying the end result then does it really matter? Happy Brewing!