[Illustrated] Should Coffee Bloom Liquid Be Discarded? A Step-by-Step Guide to Coffee Blooming

Often when blooming coffee with twice the amount of hot water as coffee grounds, some coffee liquid will drip into the lower pot. Does this coffee liquid affect the flavor of the coffee, and should it be discarded?

Why does coffee liquid drip into the lower pot during blooming?

The water absorption rate of coffee grounds is twice their own weight, so when we inject twice the amount of water, theoretically there should be no excess coffee liquid dripping into the lower pot. The answer lies in the fact that the saturated water absorption rate of coffee grounds is twice their weight, and it takes time for water to penetrate the coffee grounds. When the coffee grounds are coarse, water hasn't fully penetrated and drips into the lower pot due to gravity.

Of course, this is also related to your blooming water injection method. Coarser coffee grounds paired with a larger water flow will result in slower penetration into the coffee particles, causing more coffee liquid to drip into the lower pot. If paired with a smaller water flow, giving more time for penetration into the coffee particles, although there will still be coffee liquid dripping, the amount will be less.

Some students might ask, can we use less water for blooming? Yes, provided you can ensure all coffee grounds are thoroughly wet. In reality, there are many people who use 1x or 1.5x the amount of water for blooming. However, compared to using 2x the amount of water, the former makes it more difficult to ensure all coffee grounds are thoroughly wet, meaning incomplete blooming. Therefore, if you're not confident, it's better to stick with using 2x the amount of water for blooming.

Should the blooming liquid be discarded?

FrontStreet Coffee conducted a comparative experiment on this topic, where one cup was brewed normally (retaining the coffee liquid), and the other group had the blooming coffee liquid discarded before normal brewing. The bean selection, brewing parameters, and technique were kept as consistent as possible.

For bean selection, we used FrontStreet Coffee's Panama Flower Butterfly for the comparative experiment. This is a high-value coffee bean containing 70% Geisha. FrontStreet Coffee used medium-light roasting to highlight citrus, honey, floral, and oolong tea flavors.

For parameters, we used 15g of coffee grounds with a theoretical coffee-to-water ratio of 1:15, a grind size of medium-fine for pour-over (80% pass rate through a #20 standard sieve), and water temperature of 91°C. V60#01 drippers were used for all, employing a three-stage pouring method.

Retaining Coffee Liquid

First, inject 30g of water and bloom for 30 seconds. Then for the second stage, pour 95g of water in a circular motion from the center outward, until the liquid level reaches the root of the V60's ribs. When the liquid level drops to the halfway point, proceed with the third stage, pouring 100g of water in a circular motion from the center outward. Remove the dripper once all coffee liquid has dripped into the lower pot, ending the extraction. Time: 2 minutes.

Discarding Blooming Coffee Liquid

First, inject 30g of water and bloom for 30 seconds. Around 20-23 seconds, when the blooming liquid has finished dripping into the lower pot, pour the coffee liquid into a container (for later use) and reset the electronic scale to zero. Then for the second stage, pour 95g of water in a circular motion from the center outward, until the liquid level reaches the root of the V60's ribs. When the liquid level drops to the halfway point, proceed with the third stage, pouring 100g of water in a circular motion from the center outward. Remove the dripper once all coffee liquid has dripped into the lower pot, ending the extraction. Time: 2 minutes.

Flavor Comparison

Retaining Coffee Liquid

Measured concentration: 1.39%. Flavors include citrus, honey notes, jasmine, tea aroma, etc. Clean and clear.

Discarding Blooming Coffee Liquid

Measured concentration: 1.22%. Weight of discarded blooming liquid: 14.6g. The coffee liquid was overall flat, with all flavors being weak and faint. There were citrus and honey flavors, but floral notes were not prominent.

We know that during the brewing process, the coffee liquid extracted at the beginning has a high concentration (high content of flavor compounds per unit), and as it approaches the end, fewer compounds are extracted. Therefore, the blooming coffee liquid contains a significant amount of flavor compounds and, of course, has a very high concentration. Discarding it will affect the flavor and texture of the coffee.

Of course, the less blooming liquid that drips, the better. The more it drips, the less water the coffee grounds absorb, making insufficient blooming more likely. A normal, ideal blooming state is to finish pouring 30ml of hot water in about 8 seconds, with small amounts of coffee liquid dripping into the lower pot one drop at a time around 13 seconds.

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