Solutions for Pour-Over Coffee with Too Much Fine Powder: What to Do When Coffee Tastes Bitter from Over-Extraction?

Understanding Over-Extraction in Coffee Brewing

Many coffee enthusiasts have faced the frustration of over-extraction. While we can often avoid this situation by adjusting parameters or techniques, sometimes it's unavoidable due to equipment limitations, leaving us to silently endure becoming masters of over-extraction.

First, let's explain what "over-extraction" means. In coffee extraction theory, approximately 30% of coffee beans are water-soluble substances. However, not all soluble compounds create pleasant flavors. Over-extraction typically refers to dissolving excessive flavor compounds from the coffee grounds, resulting in coffee with unpleasant burnt bitterness and harsh astringency.

A common cause of over-extraction is inadequate grinder performance, leading to poor grinding quality with excessive fine particles that cause over-extraction and bitter flavors. Perhaps we could consider using some form of "intervention" to reduce the coffee extraction rate - is this feasible?

Variable Temperature Extraction as a Solution

Variable temperature extraction might be an excellent choice. FrontStreet Coffee previously introduced a stepped temperature reduction extraction method, starting with high water temperature and gradually decreasing. This approach enhances the coffee's sweetness and enriches flavor complexity. This brewing method primarily reduces extraction rates in the middle and later stages to avoid bitterness. Today, however, FrontStreet Coffee introduces using low-temperature water during the bloom stage.

Emi, the 2018 World Brewers Cup champion, also utilized low-temperature blooming in her extraction method. Her brewing approach was quite distinctive, using a dripper with a valve to alternate between immersion and drip extraction. Emi's pouring scheme consisted of three main stages: first, with the valve closed, she bloomed the coffee using 80°C hot water for immersion; second, with the valve open, she used 95°C hot water for drip extraction; third, she closed the valve again, using 80°C hot water for immersion extraction, and finally opened the valve to complete the drip process.

Emi explained that her rationale for using low-temperature blooming was to gently extract the coffee's sweetness while avoiding a dry aftertaste. In FrontStreet Coffee's view, this is essentially a measure to reduce the extraction rate. The combination of low temperature and immersion prevents water from passing through too quickly (which would cause under-extraction) while making it more difficult for bitter compounds to be released at lower temperatures.

If excessive fine particles are causing bitterness, could this method help prevent its occurrence?

Practical Testing with Ethiopian Coffee

This test used Ethiopian Guji coffee beans. FrontStreet Coffee used a hand grinder (in the 300 yuan price range) set to a grind size with 80% pass-through through a #20 sieve. Using FrontStreet Coffee's standard brewing parameters, the total extraction time was 2 minutes and 33 seconds. The slightly longer extraction time was due to a wide particle size distribution with a high percentage of fine particles (measured at 14% using a sieve tester), which slowed the water flow rate. The coffee presented balanced berry notes, tea-like characteristics, and a persistent dry bitterness.

FrontStreet Coffee first used 80°C water for the bloom stage, followed by 94°C water for the second and third stages. Other parameters remained unchanged (15g coffee, 1:16 ratio, three-stage pour volumes of 30/120/90ml respectively), with a total extraction time of 2 minutes and 40 seconds. Through tasting, the coffee flavor showed pronounced acidity with green astringency, somewhat reminiscent of unripe fruit. There was a hint of bitterness in the aftertaste.

Observing the behavior of the coffee bed during brewing, FrontStreet Coffee noted that the coffee grounds didn't expand significantly during blooming, and some bloom liquid had already flowed into the lower chamber. It was inferred that the green astringency resulted from insufficient blooming. The bitterness in the aftertaste might be due to the relatively high immersion water temperature. Therefore, FrontStreet Coffee made several adjustments based on these observations, with the final parameters as follows:

15g coffee, 1:16 ratio, grind size: hand grinder with 80% pass-through through #20 sieve (with many fine particles), three-stage pour volumes of 25/125/90ml respectively. The reduced bloom water volume was to minimize bloom liquid flowing prematurely into the lower chamber, but the pouring technique requires more precision to avoid leaving some coffee grounds dry.

First bloom stage used 83°C water with a 35-second bloom time to allow for better degassing. The second and third stages used 93°C water. The total time for all coffee liquid to drip through the filter was 2 minutes and 35 seconds. The resulting flavor presented rich berry sweetness and acidity, with overall balance, noticeable tea-like aftertaste, and no bitterness or astringency.

If you also struggle with over-extraction, you might want to try this approach (in principle). Note: don't copy the data exactly, as achieving identical grind settings is nearly impossible, and different levels of fine particles make the data substantially meaningless. You can reference the low-temperature blooming method, using water 2°C higher than usual for subsequent pours. Finally, make fine adjustments based on flavor results (bloom temperature, bloom time, extraction water temperature, etc.).

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473