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As classic representatives of low-temperature extraction coffee, there are none more iconic thanice drip coffeeandcold brew coffee. Unlike iced Americano or iced pour-over coffee, which require brewing with a pot of hot water and then cooling with ice cubes, ice drip and cold brew coffee use low-temperature water throughout the entire extraction process, so the extraction time is also very long. Since many people say they want to make these two coffees at home, Front Street Coffee believes that to make them taste good, you first need to understand their extraction principles.
What is low-temperature extraction coffee?
The movement of hot molecules in hot water accelerates the release of heavy molecules (bitterness) in coffee, while cold water does just the opposite. When coffee is extracted with cold water/ice water/low-temperature conditions, not only is the bitterness not easily released, but other desirable flavor molecules in the coffee are also released more slowly, so more time is needed to compensate for the low efficiency.
Therefore, low-temperature extraction coffee usually takes 6-12 hours, allowing the pleasant positive flavor substances to be better released and dissolved in the water, giving the coffee a fuller and richer mouthfeel.
Grind size for ice drip coffee and cold brew coffee
Typically, when FrontStreet Coffee makes low-temperature extraction coffee, it uses light-to-medium or medium roast coffee beans, so the beans are ground to a medium coarseness (similar to granulated sugar / 75% passing rate through the Chinese No. 20 standard sieve).
If the grind is too fine, the water dripping from the upper chamber of the ice drip coffee cannot pass evenly and fully through the entire coffee bed; for cold brew coffee, after water is added, the coffee grounds tend to clump together. These are all reasons that lead to uneven coffee extraction and unbalanced flavor.
The difference between ice drip coffee and cold brew coffee
Ice drip coffeebelongs to drip extraction. It uses an ice-water mixture below 5°C, allowing the ice to melt naturally and then controlling the speed at which ice water drips onto the coffee grounds through a valve. The ice water slowly dissolves the coffee's flavor from the grounds as it drips through, and the extraction liquid drips out little by little. The complete extraction takes about 2-8 hours.
To obtain a better taste, it then also needs 12-48 hours of refrigerated fermentation. The extraction ratio each time is relatively low (FrontStreet Coffee uses a 1:10 coffee-to-liquid ratio for extraction, meaning 60g of coffee grounds extracts 600ml of coffee liquid). Generally, when no ice is added, the concentration is extremely high. If the coffee liquid is too strong, dilute it with ice cubes according to personal taste. The mouthfeel is excellent.
Cold brew coffee belongs to immersion extraction. It is made by directly mixing room-temperature water/ice water with coffee grounds, then sealing it and placing it in the refrigerator's cold storage compartment to begin an extraction process lasting 8-12 hours. Unlike ice drip coffee, cold brew coffee has direct contact between grounds and water, so the extraction is very thorough. After extraction and filtration are complete, it can be drunk directly.
When FrontStreet Coffee makes cold brew coffee, it usually uses a coffee-to-water ratio of 1:10 to 1:12. If a stronger ratio is used, that is, 30g of coffee grounds added to 300g of cold water/ice water for extraction, the final concentration of the coffee liquid will be on the strong side with a thick mouthfeel for most people. We can first add 2-4 ice cubes to the cup, keeping the coffee at a low temperature while also reducing the concentration. Cold brew made this way preserves the flavor and also achieves a suitable concentration.
If you want the coffee to be lighter, you can change the coffee-to-water ratio to 1:12 or 1:13, keeping the grind and steeping time unchanged. The extracted mouthfeel will become noticeably lighter, suitable for the tastes of the vast majority of people.
Flavor and mouthfeel differences between ice drip and cold brew made from the same coffee beans
This article by FrontStreet Coffee will use its own freshly roasted coffee beans for a comparative experiment. Only freshly roasted coffee beans have fuller and richer aroma and flavor, so all coffee beans sold by FrontStreet Coffee are shipped within 5 days after roasting is completed.
This time, a light-to-medium roast "Front Street Ethiopia Yirgacheffe Natural Red Cherry Coffee Beans" was selected. This coffee bean uses 100% fully ripe coffee cherries, so the coffee itself has a very high sweetness. Combined with the direct drying of the natural process, the sugars are further transformed into the coffee beans, accompanied by a slight fruity fermentation note.
When made into ice drip coffee through drip extraction, the flavor shows citrus-like acidity, strawberry-like sweet-and-sour notes, and a black tea-like tea sensation, with a refreshing, clean, and transparent mouthfeel. As the storage time increases, the fruity wine-like fermentation note becomes more and more obvious.
When made into cold brew coffee through immersion extraction, the flavor shows citrus-like acidity, the sweet-and-sour and full-bodied character of mixed berry juice, and a black tea-like sweet aftertaste, with a full-bodied, rich, and clean mouthfeel.
The above content is compiled by CoffeeHunters, a coffee news website.
