What is agitation and why we need it when brewing coffee? Is agitation a barista’s key to success? Can we make a brew without? If you are aiming to consistent extraction (and why wouldn’t you!), agitation is one of your tools to be the captain and not the co-pilot of the upcoming brews.
What is agitation in coffee brewing?
Close your eyes and imagine yourself in a plane. A sudden turbulence hits you - everyone is shaking up and down on their seats. Then it is over and you settle down again. Even though it sounds a bit funny, turbulence is also a tool when brewing coffee.
Turbulence (=movement) is created by agitation (=disturbance). And by agitation it is possible to enhance the extraction of coffee and what is even more important, maintain a consistent extraction.
When brewing coffee, we want to perceive the best flavors in the cup - repeatedly. Extraction is one of the main factors to get there. The more evenly the coffee grounds are exposed to water, the higher extraction rate we will achieve. Also, when other variables are hitting the bull’s eye, the brew will be well balanced.
When you choose the grind size for your brew, you only define the size of MOST of the coffee particles. There will always be also smaller particles (fines) and larger particles (boulders). This means you have unevenly sized particles, unless you use a sieving device.
Different particle sizes bring along two challenges.
- They are extracted differently. This means the acidity, bitterness and sweetness are not balanced as they are meant to be.
- They can create a phenomena called channeling. This means that water finds the easiest way through the coffee bed. That will prevent the coffee from extracted evenly.
If the coffee grounds are not extracted up to the same rate, you will not be able to fully control the flavor. And this will be haunting you when trying to replicate the recipe for you upcoming brews!
To achieve a consistent extraction despite the different size of particles, you need agitation.
Corner stones of brewing coffee
Extraction is a puzzle build up with several pieces.
Brewing time, water temperature, grind level, method and device, filter choice, pouring style (speed, direction, pulsing) as well as water quality have their own roles in the play called extraction.
Then of course dosing is there to effect on both extraction and the strength of the brew. Not to forget using fresh coffee of high quality!
How to agitate coffee?
By agitating the mixture of coffee grounds and water we can make a huge different to the final brew.
During the blooming, agitation happens naturally. CO2 bubbles out of the coffee grounds creating movement, ”blooming”. After that, the coffee bed is more even hence the grounds getting settled and dry ”pockets” getting wet.
It is recommended by many of the master baristas to stir the coffee bed right after the first pour before blooming. Instead of stirring with a spoon or a paddle, you can also swirl the whole filter by hand to create agitation.
DURING THE POUR
When starting pouring, we continue the agitation to ensure a balanced brew. This can be done in between the pours by stirring or swirling. Also the heaviness and the rate of the pour will effect on the extraction.
Pouring fast enhances turbulence and agitation which then extracts more.
After the final pour some baristas like to do a flush, meaning using the last drops of the water to flush down the ”high and dry” grounds. Stirring or swirling is recommended by many of the master baristas also at this stage. It is also possible to lift and tap the filter after final pour to make the coffee bed more even.
One very famous trick is ”Rao Spin”, named after a master barista Scott Rao, who actually did not invent this but still is the influencer behind. Rao spin means spinning the filter quickly after the final pour. According to master himself this ”minimizes channeling during the final drawdown and creates a flat bed every brew.”
Should you go for it?
Definitely. Agitation can and should be experimented in both home and coffee shop environments. Do two brews maintaining all the other variables same but use agitation on the other brew. Then go and taste the difference!