How to Make Concentrated Cold Brew Coffee & Brewing Ratios? Cold Brew Coffee Bean Recommendations for Specialty Coffee Drinks

Understanding Coffee Grind Size for Cold Brew: Why Finer Isn't Always Better

Before writing this article, FrontStreet Coffee asked several coffee professionals and enthusiasts: "Under normal circumstances, when making cold brew coffee with the same water, coffee beans, coffee amount, extraction container, and extraction time, how would you increase the extraction concentration?" Like the respondents, you would likely answer: "Definitely grind finer!"

Indeed, since we began exploring coffee brewing, we've learned that: finer coffee grounds yield stronger flavor, while coarser grounds produce milder flavor. However, this theory has a premise: high-temperature extraction with coffee ground layer agitation. For cold brew coffee, which uses low-temperature static extraction, this theory doesn't apply. Why?

Impact of Water Temperature & Particle Movement on Coffee Extraction

During extraction, higher water temperature increases molecular movement. When thermal molecular motion counteracts the attraction between solid molecules, it causes solid molecules to disperse. Simultaneously, thermal molecular motion increases the contact frequency between water molecules and solid molecules (coffee particles). Therefore, when coffee is ground finer, solid molecules dissolve faster and in greater quantities.

When water extraction occurs at room temperature or near freezing, molecular movement decreases or stops. Without thermal molecular motion to counteract the attraction between solid molecules, coffee particles tend to "clump together," forming clumps. Therefore, when coffee is ground finer, the clumping becomes more significant, preventing the coffee powder in the center of these clumps from being fully extracted.

In pour-over coffee, high water temperature combined with the impact of water pouring causes the coffee bed to remain in constant agitation, rapidly increasing extraction efficiency. In this situation, if coffee is ground too fine, over-extraction can easily occur.

For cold brew/cold drip coffee, we add water and stir thoroughly before placing it in the refrigerator for over 12 hours. During this period, the temperature remains consistently low, so even with thorough stirring, some particles will still experience "clumped" extraction. This means that throughout the entire coffee extraction process, a small portion of coffee grounds doesn't get effectively extracted.

Can Using a Coarser Grind Effectively Improve Cold Brew Extraction Efficiency?

FrontStreet Coffee conducted a small experiment~

This cold brew was made using FrontStreet Coffee's Yirgacheffe Gedeb Cooperative coffee beans from Ethiopia. Using the same container and water quality at room temperature, 30g of coffee was steeped with a 1:10 coffee-to-water ratio. Two grind sizes were used: EK43s #9 (fine grind) and EK43s #10.5 (coarse grind), then both were placed in the refrigerator for low-temperature extraction for 16 hours.

After extraction, the coffee liquid was filtered using room temperature filter drippers, dry filter paper, and clean room temperature containers, then tested for concentration using a TDS meter.

The final test results showed that the fine grind cold brew had a TDS of 2.10%, while the coarse grind cold brew had a TDS of 2.20%. The fine grind cold brew displayed bright citrus acidity, honey notes, and a slight tea-like sensation; the coarse grind cold brew showed even brighter citrus acidity, with more pronounced sweetness and tea-like notes, resembling unsweetened lemon tea~

This experiment was primarily conducted because many people asked FrontStreet Coffee how to make cold brew stronger for creating specialty coffee drinks without having the coffee's aroma and flavors overly masked by other ingredients. If you want to extract cold brew with appropriate concentration that doesn't require dilution, FrontStreet Coffee recommends using a fine grind with a 1:13-1:15 coffee-to-water ratio for extraction.

Important Considerations

Although using a coarser grind can improve extraction efficiency and concentration, not all coffee beans or cold brew methods are suitable for this approach!

Very light or dark roasted coffee beans should not use this method to increase extraction efficiency and concentration, as it can easily produce harsh acidity or unpleasant bitterness.

Electric cold brew bottles are available on the market that can produce cold brew in a short time. The principle is that the device continuously shakes the filter screen up and down to keep the coffee bed moving. In this situation, using a finer grind is more suitable for extraction.

- This experiment was based on common cold brew coffee methods -

Important Notice :

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