What are Those Bubbles In My Pourover?

In my quest for brewing better coffee I've learned a lot about what brings out the flavor of the roasted bean. In a quest to improve the taste of my own coffee, I started hearing about "blooming" pourover coffee.  During some recent research on the science of coffee, brewing, and extraction it all began to make sense for me. I thought I would share a bit of what I learned.

Blooming is the initial “pre-wetting” of the bed of ground coffee in your brewing device. We want to bloom so co2 can release, and then move out of the way. When co2 escapes, you’re left with the desirable solubles that will bring out the flavors and carmelizations of the beans. The goal of the bloom is to get water working with the ground beans, not working with carbon dioxide.

When the co2 escapes, you should see bubbles forming on the bed of grounds. These bubbles can tell you how fresh the coffee is. Lots of bubbles (released co2) indicates really fresh coffee, minimal to none is more on the stale end.

Ideally your bloom should be measured on a gram scale. A good rule of thumb is to double your coffee dose. So a good example is my daily Kalita Wave. I use a dose of 23.5 grams of whole coffee beans.  With this dose, my bloom will be 47 grams of water. You typically want to wait 30 to 45 seconds after you’ve bloomed before you start your batch pours. This of course depends on batch size and your type of roast. Anything beyond 45 seconds and you can lose those good solubles that we want during our extraction.

When you don’t bloom and just do a continuous pour (i.e. auto-drip brewer or pourover) the escaping gasses push water away from the grounds, limiting the ability of the water to dissolve the coffee. So what you’re getting is a fair amount of co2 in the cup with less of the good stuff. And guess what...co2 is bitter. Anyone who’s had carbonated water will understand.

So now you’ve got it!  When you see those bubbles during the pour you know exactly what’s going on here and hopefully you’ll learn to bloom like I did to bring out more great flavor in your coffee.