Coffee Bloom Explained

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Understanding what goes into creating a perfect cup of coffee may seem complicated but it’s really not. It’s about understanding the science behind the brew. One thing that will help you make your coffee taste better is the coffee bloom. What is it you ask? Well, this post is all about the coffee bloom, explained.

What is the Coffee Bloom?

The bloom is when the carbon dioxide gases produced during brewing are released. The carbon dioxide gets trapped during the roasting process because of the heat.

Coffee beans release this gas for two weeks or longer after they are roasted. The majority of it releases right after roasting but it still releases for 14 days after.

When you grind the beans, the rate of carbon dioxide rapidly increases because it increases the surface area of the bean. This is why you should grind your beans right before you brew.

Bean freshness is probably one of the most important factors to great tasting coffee. Although, other things can affect it as well.

kettle pouring water into pour over maker

Why it blooms

Fresh coffee that hasn’t had time to release a lot of carbon dioxide will be released when you put hot water on the grounds. It causes the grounds to swell up and bubble which is the gas trying to escape.

The carbon dioxide actually helps the coffee remain fresh before you brew it so it’s a good thing until then. If the gas isn’t released right before you brew, it will leave a sour taste.

But you can only avoid its sour taste by letting it bloom and release before you brew. The gas will keep the water from extracting all the good stuff from your cup of joe. And nobody wants that.

Things that affect the Bloom

So many things can affect the bloom.

Temperature:

Heat causes the gases to release faster, so this is why you should store the beans in a cool place.

Humidity:

You need the perfect balance of moisture because dry areas will cause the gas to release but high humidity will make the beans mold.

Roast:

The kind of roast it is makes a difference, darker roasts don’t release as much carbon dioxide as others.

How to Bloom

The bloom happens when you pour hot water over your coffee grinds like with the Pour Over method. You want to be sure that all the coffee gets wet and the bloom can occur for 30 seconds to a minute.

You will notice that it may continue to bubble as you pour

  • Put your fresh grounds into your maker
  • Pour the correct temperature water over the grounds. (you need to double the water to grounds ratio for this)
  • Wait for 30 to 60 seconds as the gas releases bubbles and your grounds puff up
  • Finish pouring your water as directed for the brew method

I use a gooseneck kettle to help control my pour.

kettle on stovetop
v60 with filter, water and grounds demonstrating bloom effect

You wouldn’t think so but the bloom affects the flavor of the coffee. When the gas is trapped and not allowed to escape, it can create a sour taste. The trapped gas keeps the water from properly extracting aromatics and oils in the bean.

If your coffee doesn’t bloom, it just indicates that it is not as fresh as it should be.

How to get the Freshest Beans

When you are looking for the freshest coffee beans, I would start by buying whole bean. Coffee that is ground ahead of time might seem convenient but it actually speeds up the carbon dioxide release.

Most coffee makers don’t put a roast date on their bag. The best way to make sure you are getting the freshest bean is to buy directly from the roaster. In my town, we have a local coffee roaster that I buy from weekly. This helps me get the freshest beans possible.

hands holding coffee beans

Grocery store coffee has a use by or expiration date. This is often a year from the roast date so you will want to stay away from those beans. I still strongly recommend buying directly from the roaster.

You will also want to make sure you keep your beans airtight and in a cool place. The air will start the oxidation process and heat will release carbon dioxide. You can store your coffee in an airtight container to help with this.

You can also try subscription coffee or have it mailed directly from the roaster. If you want to try a great coffee bean that is organic, fair trade beans, you need to try LifeBoost Coffee. They offer a subscription too. I promise you won’t be disappointed.

coffee bloom explained pinterest graphic

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