How Does Cold Water Coffee Brewing Differ From Hot Water?

Coffee can be brewed with cold water, not only hot. Since the 1960s, Japan popularized a method of slowly drip-brewing grounds with ice water in a special ice drip pot, producing a full-bodied cup with almost no unpleasant bitterness. Ice drip extraction typically takes six to eight hours.

Cold water lacks thermal molecular movement, so extraction is slow, and the ice must be watched and replenished to keep the dripping water cold. Because each batch is small, ice drip coffee usually costs more. A simpler alternative is soaking grounds in cold water and refrigerating about twelve hours, which gives a slightly less clear but balanced cup with a clean coffee aroma.

Coffee doesn't have to be brewed with hot water—cold water can also extract stunning flavors. Since the 1960s, Japan has popularized a method of slowly drip-brewing coffee grounds with ice water using a special ice drip pot, producing a rich, full-bodied coffee liquid with almost no unpleasant bitterness. Because cold water lacks thermal molecular movement, the extraction time often takes six to eight hours, during which one must constantly monitor the melting of the ice and replenish it promptly to ensure the dripping water remains at a low temperature. Combined with limited output per batch, ice drip coffee is usually priced higher than other regular coffees. However, ice drip equipment is expensive, so some people switched to soaking coffee grounds in cold water and refrigerating for about twelve hours. Although this method is slightly inferior in clarity, it still yields a full, balanced coffee without unpleasant bitterness. This article will systematically clarify the essential differences between ice drip and cold brew, the flavor differences between cold water extraction and hot water extraction, and, using Front Street Coffee's practical experience as an example, detail the production methods and storage recommendations for both types of low-temperature coffee.

Can coffee only be brewed with hot water? Of course not! Cold water can also make delicious coffee. Since the 1960s, Japan has popularized a special ice drip coffee pot, resembling chemical apparatus, which extracts a rich, full-bodied coffee liquid without unpleasant bitterness by controlling the speed of ice water dripping through the coffee grounds.

Because cold water lacks thermal molecular movement, the extraction time for coffee is relatively long, typically requiring 6-8 hours. During this period, one must constantly monitor the melting of the ice and replenish it promptly to ensure the dripping water remains at a low temperature. Also, because the amount produced each time is small, ice drip coffee is more expensive than other regular coffee products.

However, ice drip coffee equipment is expensive. In an era when not all coffee equipment was fully widespread, the cost for ordinary households to make ice drip coffee at home was too high. So some people simply soaked coffee grounds thoroughly in cold water and then refrigerated them for about 12 hours. The coffee extracted this way may not be as clean-tasting as ice drip coffee (because fine particles cannot be filtered out), but the coffee overall is still very full and balanced, without unpleasant bitterness.

The difference between ice drip and cold brew

So the most essential difference between ice drip coffee and cold brew coffee is that the former uses ice water drip filtration to extract coffee liquid, while the latter uses ice water immersion to extract coffee liquid. In terms of taste, the former is rich and refreshing, while the latter is full and balanced.

What is the difference between coffee extracted with cold water and hot water?

Because cold water lacks thermal molecular movement, large molecules (bitterness) in coffee are not easily released, and only sweet and sour flavors can be extracted. Therefore, the coffee after extraction has a cleaner taste, but the downside is that the aroma is slightly weaker. Hot water, on the other hand, can more fully extract various aromatic substances in coffee, and the hot steam carries the coffee aroma upward, so more coffee aroma can be smelled.

How to make ice drip coffee and cold brew coffee?

To make low-temperature extracted coffee, Front Street Coffee recommends using coffee beans with prominent sweetness/acidity or outstanding flavor, such as the Ethiopian Yirgacheffe sun-dried Red Cherry coffee beans currently sold by Front Street Coffee, which have a full berry juice sensation, citrus-like acidity, soft fruit fermentation aroma, and black tea-like sweet aftertaste.

If you don't like too obvious acidity, you can try the Costa Rican Musician Series Mozart raisin coffee beans, which have a rich raisin aroma, soft sweet orange acidity, slight fruit fermentation aroma, and caramel-like sweetness.

In this article, Front Street Coffee uses freshly roasted Mozart coffee beans to make ice drip and cold brew coffee. Only freshly roasted coffee beans can extract rich-flavored coffee, so all coffee beans sold by Front Street Coffee are shipped within 5 days after roasting, and the optimal flavor period for coffee beans is 4-35 days after roasting.

The method for making ice drip coffee is as follows:

For grind size, Front Street generally chooses the same grind size as for iced pour-over. Because low-temperature water reduces the extraction rate, the coffee is ground finer to improve extraction. For this bean, a 85% passing rate through the Chinese No. 20 standard sieve is chosen. According to Front Street's store grind size, this is a 9 setting on the ek-43s grinder.

Generally, we first calculate the extraction parameters, using a coffee-to-liquid ratio of 1:10, extracting 600g of coffee liquid from 60g of coffee. The ratio of ice to water mixture is 1:1, and the valve flow rate is controlled at 7 drops per 10 seconds. The drip filtration is usually completed within 6-8 hours. (Typically the ice drip ratio is 1:10-1:12; you can adjust according to your own taste.)

At the bottom of the middle pot, place a circular filter paper moistened with water, then grind the coffee beans into powder and pour them in. Be careful to spread them flat to ensure even extraction. Place another circular filter paper on the surface of the coffee bed to prevent water droplets from disrupting the bed. Before dripping, wet the coffee bed with cold water first; this both saves extraction time and avoids uneven extraction at the beginning.

Place the coffee powder cup on the rack and start adding the ice-water mixture, usually half ice and half water. Adjust the valve flow rate to 7 drops/10 seconds, mainly aligning the dripping water droplets with the position where the coffee liquid filters out. After the drip filtration is complete, pour the liquid from the lower pot into an airtight container—Front Street uses a glass bottle—and put it in the refrigerator to ferment for more than 12 hours. It is usually ready to drink the next day.

The method for making cold brew coffee is as follows:

The grind size used for cold brew coffee is the same as for ice drip. Then, when making it, you only need to prepare a clean, sealed container and extract using a coffee-to-water ratio of 1:11, i.e., add 11g of cold water to 1g of coffee powder. Then stir with a tool to fully contact the coffee powder with water, seal it, and place it in the refrigerator's cold storage. After low-temperature extraction for 12-16 hours, use a filtering tool to remove the coffee grounds and it is ready to drink.

Front Street has noticed that many convenience-seeking friends will soak a large pot of coffee at once and store it in the refrigerator, pouring it out whenever they want to drink. This also leads to the problem that, if not marked, it's easy to forget how many days the coffee has been in the refrigerator and whether it might have spoiled.

First, the fermentation process of low-temperature extraction cannot be interrupted. Refrigeration only slows down the fermentation rate of coffee, and as time passes, the substances dissolved in the water continuously change, eventually leading to spoilage. In addition, every time we open the bottle cap, the coffee liquid comes into contact with air, which not only causes the aroma to dissipate but may also introduce bacteria into the container.

To understand the effect of cold brew storage days on flavor, Front Street recorded two pots of cold brew, tasting them just after making, after refrigerating for 1-2 days, 3-4 days, 5-6 days, and 7-8 days. Finally, it was found that the coffee taste was best within the 1-4 day refrigeration range.

Generally, for the sake of flavor experience and health safety, whether ice drip or cold brew, for any extraction method conducted in a low-temperature environment, Front Street recommends drinking it within 5 days (counting from the production day).

If you follow the method in Front Street's past articles, using warm water to quickly make cold brew, the optimal flavor period is shorter. Because higher water temperature increases the release rate of flavor substances, compared to cold brew made with room-temperature water, warm water cold brew is more prone to breeding microorganisms in the refrigerator. Therefore, Front Street believes it is best to drink it within 2 days to avoid gastrointestinal discomfort.

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