Bloom My Coffee?
What is Bloom?
You may have heard the term “coffee bloom” or “blooming your coffee.” Coffee blooms when a small amount of hot water is poured over freshly ground, fresh-roasted coffee. Carbon dioxide gas (CO2), generated in the roasting process and trapped in microscopic voids inside the coffee bean, is energized by the hot water and released. The coffee bubbles, foams, and swells in size as the CO2 is released, often forming a small dome.
The CO2 itself does not affect the flavor of the coffee, but its diminution over time does negatively affect the coffee's flavor. Oxygen, on the other hand, is a bad actor toward fresh coffee. It stales the coffee, robbing it of its flavor.
CO2 helps keep your coffee fresh by filling the voids inside the coffee beans so oxygen can’t get in there. And as the CO2 seeps from the tiny nooks and crannies inside the bean, it displaces oxygen inside the coffee container, again protecting the coffee.
As roasted coffee ages and CO2 escapes, its flavor diminishes dramatically. For unopened whole-bean coffee, the CO2 is normally gone by 4 to 7 weeks after roasting. Coffee ground at the roastery loses all its CO2 quicker, normally within 3 to 4 weeks after roasting.
To Bloom or Not to Bloom
The main reason to bloom your coffee is that the CO2 released from the coffee can hinder the brewing process, especially for pour-over and drip brewing. The CO2 can hinder the water from wetting all the coffee evenly. When that happens, your cup will be a mixture of some well-extracted coffee and some under-extracted coffee. The result is a weaker cup with compromised flavor.
For full-infusion brewing, such as French press and AeroPress, blooming the coffee is not as important or, arguably, necessary. That’s because you normally pour in enough water fast enough that all the coffee is wetted quickly. Even so, I sometimes bloom a French press and AeroPress. Try blooming them and see if you can tell any difference.
Blooming Blossoms Flavor
It is easy to bloom your pour-over and your drip brew, and the flavor in the cup will reward you for it.
Blooming a pour-over is easy. Here is a quick guide:
- If you use paper filters, rinse your bleached or unbleached filter in place with hot water and discard the water.
- Put your properly ground coffee (ground about the size of kosher salt) in the filter just before you are ready to add water.
- Pour 200° - 205° F water, approximately 3 times the weight of the ground coffee, in a circular motion over the ground coffee, attempting to wet it all. Avoid pouring water around the filter edges.
- Start a timer for four minutes.
- Let the coffee bloom for 30 to 45 seconds.
- Pour water onto the coffee bed in a circular motion, avoiding the edges.
- Stop pouring when the level reaches the level of the original bloom.
- Let most of the water drain and repeat steps 6 and 7 as many times as needed.
- A good rule of thumb is to have all the water poured onto the coffee bed with one minute remaining on the timer.
- When the timer goes off, remove the coffee filter or basket and dump the grounds.
This procedure should work great for pour-overs between 20g and 40g of coffee (approximately 2 to 4 standard coffee scoops). For smaller pour-overs, you might have to reduce the amount of time remaining on the timer for the last pour (step 9). That is, stretch out the time you pour while keeping the total brew time at 4 minutes.
For larger pour-overs, you may have to increase the amount of water with each pour so the level rises above the original bloom level.
Adjust your total brew time to best match your particular grind.
Blooming a Drip Brew
There are a few drip brewers that have an automatic bloom. If you have some spare change, I recommend the Oxo 9 Cup coffee maker. It runs $200 wherever you buy it, but it makes a great cup of coffee and has a nice, stainless steel thermal carafe instead of a heat plate, so it doesn't cook your coffee.
You can find it at multiple places online. Kohls ships for free https://www.kohls.com/product/prd-2344459/oxo-barista-brain-9-cup-programmable-coffee-brewing-system.jsp?skuid=33283929&ci_mcc=ci&utm_campaign=SMALL%20ELECTRICS&utm_medium=CSE&utm_source=google&utm_product=33283929&CID=shopping15&utm_campaignid=6889977295&pid=googleadwords_int&af_channel=CSE&gclid=EAIaIQobChMIm7f04rXH6AIVBpSzCh3K-AmfEAQYBCABEgJE_fD_BwE&gclsrc=aw.ds
I have a commercial Bunn drip brewer I use to brew 64-ounce pots when I need lots of coffee. My coffee is so fresh that if I do not bloom the coffee, the coffee basket will overflow from the coffee's natural bloom - and it makes a huge mess! I bloom my commercial Bunn with approximately 14 to 16 ounces of water and let it bloom for about 20 seconds. I physically rotate the filter basket during the bloom pour to get better water distribution in the basket.
I use 14 to 16 ounces of water because less water is not enough to start the flow through the machine. It just dribbles. I bloom for 20 seconds, instead of 30 to 45 seconds, because that seems to get the overall brew time to where it works great with the little-bit-courser grind I use. If you have a drip brewer that doesn't have a bloom setting, try my manual process to bloom your coffee.
Man, that is a LOT of information – a LOT of words. Let me know if this is helpful!