How Does Coffee Extraction Change With Warm Water Cold Brew?

Using 40°C warm water instead of room-temperature water speeds up coffee extraction, because higher molecular thermal motion releases sweet and sour compounds faster. With 50 grams of coffee grounds and a 1:12 ratio (400 ml water plus 200 g ice), the brew needs only 4 to 5 hours instead of the usual 12 to 24. The result is a full-bodied cup with berry juice and caramel sweetness.

Grind slightly finer than for pour-over, targeting an 85% pass rate through a No. 20 standard sieve, since the water stays cooler than in pour-over brewing. Stir the grounds and water, seal the bottle, and chill. Standard cold brew sits 12 to 24 hours in the refrigerator, then filters and rests about 4 hours. Longer extraction is not automatically better, and taste remains subjective.

To enjoy a cup of cold brew coffee with outstanding sweetness at home, you actually don't need expensive equipment. Front Street Coffee, using 50 grams of coffee grounds as a baseline, shares the complete parameters from grind size and coffee-to-water ratio to refrigeration extraction time. Even more worth trying is using 40°C warm water instead of room-temperature water to make cold brew coffee—leveraging molecular thermal motion to accelerate the release of sweet and sour compounds, then transferring it to a low-temperature environment to suppress the extraction of bitterness. In just 4 to 5 hours, you get a full-bodied berry juice sensation and caramel sweetness. This article documents in detail the steps for warm water cold brew, flavor comparisons, and storage recommendations, suitable for every enthusiast who enjoys refreshing cold coffee.

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If you want to drink cold brew coffee but don't want to go out and buy it, then Front Street Coffee (FrontStreet Coffee) is here to teach you how to make cold brew coffee at home.

Cold brew coffee is a very easy-to-master brewing method. Front Street Coffee (FrontStreet Coffee)'s cold brew coffee uses 50 grams of coffee grounds as a baseline. In terms of grind size selection, because the water temperature in contact with the coffee grounds is lower than that of regular pour-over coffee, choose a slightly finer setting than pour-over coffee, that is, an 85% pass rate through a No. 20 standard sieve. Put the coffee grounds into a glass bottle, then add 400 ml of room-temperature water and 200 grams of hard ice cubes (totaling 600 grams of ice-water mixture), with a coffee-to-water ratio of 1:12. Then use a stirring rod to mix the coffee grounds and water evenly, seal it, and place it in the refrigerator to chill.

After 12 to 24 hours in the refrigerator, use filter paper to filter out the coffee grounds and obtain a clean coffee liquid. Then use a clean sealed bottle to store the coffee liquid and refrigerate it for about another 4 hours before drinking.

Here, Front Street Coffee (FrontStreet Coffee) needs to tell friends that cold brew coffee is not better the longer it is extracted; whether it tastes good or not is a very subjective matter. Some people like fresh and clean coffee, while others like bold coffee with a fermented feel. These all vary from person to person.

For friends who like a stronger fermented taste, Front Street Coffee (FrontStreet Coffee) recommends extending the extraction time a bit longer. As time extends, the fermented feel of the coffee liquid becomes stronger, but the coffee's concentration becomes richer and the mouthfeel layers become more complex. If when drinking it you feel the coffee liquid is too strong, you can add two ice cubes; as the ice cubes melt, the concentration of the coffee liquid will decrease accordingly.

Although there is now a type of coffee machine on the market that can speed up the release of coffee substances in a low-temperature environment through pressurization and produce good cold brew in only 2-3 hours, the price is really quite expensive. Warm water (that is, water that is not cold but also not too hot) can provide some heat to increase molecular motion. When molecular thermal motion competes with the attractive forces between solid molecules, the solid molecules disperse. At the same time, molecular thermal motion increases the number of contacts between water molecules and solid molecules (coffee particles), so when the coffee is ground finer, the solid molecules dissolve faster and more.

The release pattern of coffee substances is like this: sour-sweet-bitter. After 40°C warm water is poured into the coffee grounds and stirred evenly, the temperature of the warm water will gradually decrease. This can both prevent coffee particles from clumping together through molecular thermal motion, making the subsequent coffee extraction more even;

and also extract part of the sweet and sour substances more quickly, reducing the subsequent low-temperature soaking time. Then extracting for another 3-4 hours in a low-temperature environment is to allow the sweet and sour substances to be released more fully and also to suppress the precipitation of bitter substances.

The steps for making cold brew coffee with warm water are as follows:

This time Front Street uses sun-dried coffee beans from Ethiopia's Yirgacheffe Red Cherry Project. The biggest characteristic of Red Cherry Project coffee beans is: sweet! The sweetness is really excellent! Because they are 100% hand-picked fully ripe coffee cherries, then sun-dried as whole fruit, the sugar in the coffee pulp can be further absorbed by the coffee beans.

3 0g sun-dried Red Cherry coffee beans are ground to a medium-fine grind (73% passing through a Chinese No. 20 sieve). The approximate coarseness can be referenced in the picture below.

Then add them to a clean container that can be sealed and is resistant to both high and low temperatures. Next, pour in 390g of 40°C warm water (coffee-to-water ratio 1:13; if you want it stronger, you can try 1:12), then stir for half a minute and let it soak. (No need to cover with a lid)

After the coffee liquid in the container drops to 35°C (when making it, Front Street Coffee (FrontStreet Coffee)'s room temperature was 26°C, and it soaked for 16 minutes until reaching the desired temperature), it can be sealed and placed in the refrigerator to extract.

After 4-5 hours, take it out and use a filtering tool to filter out the coffee grounds, and then it is ready to taste. If you still feel the concentration is a bit high, you can add a small amount of ice cubes/cold water to dilute it.

How does the flavor of warm water + low-temperature extraction taste?

Under the same parameters, using room-temperature water + low-temperature extraction for about 12 hours, the flavor profile is: bright citrus acidity, with sweetness and tea-like notes even more pronounced, feeling like unsweetened lemon tea.

While warm water + low-temperature extraction for 4-5 hours has a flavor profile of: full-bodied berry juice sensation, very prominent caramel sweetness, with a black tea-like sweet aftertaste in the finish. The sweetness is really excellent!!!

However, it should be noted that cold brew made with warm water releases more flavor substances than soaking with room-temperature water, so it should not be stored for too long. If you also make it this way, Front Street recommends keeping it sealed in the refrigerator and drinking it within 4 days.

The above content is compiled by CoffeeHunters, a coffee news website.