Where the coffee originated and why cold brew tastes smooth

Cold brew coffee tastes smooth rather than sour because ice water extracts slowly at low temperature, pulling fewer of the acidic and astringent compounds that hot water releases quickly. The result is a rounder mouthfeel, a pronounced sweet aftertaste, and noticeably lower acidity than hot-brewed coffee.

The method is credited to the Dutch, which is why it is also called Dutch-style drip coffee, and it uses a dropper structure that lets ice water drip through the grounds over an extended period. Traditional cold brew equipment often allows the drip rate to be adjusted by hand, unlike can you get drunk on coffee questions, which involve caffeine.

Cold brew coffee, with its unique low-temperature slow extraction process, presents a flavor profile entirely different from hot-brewed coffee—smooth in mouthfeel, with pronounced sweet aftertaste and relatively lower acidity and astringency. So why doesn't cold brew coffee taste sour? What price range do cold brew coffees sell for on the market, and how much should you spend on coffee beans to make it right? Drawing on the practical experience of Front Street Coffee, this article systematically explains the origins of cold brew coffee, its extraction principles, key production points, and the types of coffee beans suitable for making cold brew, helping coffee enthusiasts gain a comprehensive understanding of this slow-crafted beverage.

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Before we knew it, September has arrived again. Friends in the south are probably still dealing with the scorching sun and high temperatures day after day, and the summer heat won't subside anytime soon. For coffee lovers, the first thirst-quenching drink that comes to mind this season is naturally iced coffee. Walking into Front Street Coffee (FrontStreet Coffee), the first thing you notice upon entering is a coffee device that looks remarkably like chemical laboratory glassware—many customers curiously lean in to take a closer look. In fact, this apparatus is precisely what's used to make cold brew coffee. Today, Front Street will chat with you about what cold brew coffee actually is and how to make it at home.

The Origins of Cold Brew Coffee

Cold brew coffee is said to have originated with the Dutch, which is why it's also called Dutch-style drip coffee. Unlike brewing methods that require hot water, its core feature is using ice water throughout to extract coffee compounds. Because of the low temperature, the extraction time must be extended to slowly dissolve the aromatic substances in the coffee.

For this reason, cold brew apparatus uses a dropper structure similar to a chemistry experiment, letting ice water drip down drop by drop, slowly saturating and penetrating the coffee grounds layer. With traditional cold brew equipment commonly found on the market, the drip rate can usually be adjusted manually.

What Is the Extraction Principle of Cold Brew Coffee?

Cold brew coffee is a beverage that slowly develops over time. Brewing with different water temperatures produces noticeably different final coffee flavors. In a low-temperature environment, the compounds in coffee that bring astringency are not easily dissolved out. After extended extraction with ice water, the coffee liquid is then placed in the refrigerator to rest and ferment. Slightly fermented cold brew coffee carries a subtle fermentation aroma, and the mouthfeel becomes even richer. Because it doesn't undergo high-temperature extraction, relatively fewer impurities are released from the coffee, and the caffeine content is slightly lower as well.

Making cold brew is a lengthy process, typically taking 6 to 8 hours, and it uses more coffee grounds than regular brewing, so the price is naturally higher than an Americano. Front Street's cold brew coffee is priced at 40 yuan per cup.

What's the Difference Between Ice Water Extraction and Hot Water Extraction?

Temperature influences the breakdown speed of oils, acids, and sugars in coffee. Because these reactions occur at different rates, the coffee's aroma, taste, and mouthfeel end up very different. In other words, different extraction methods create coffees with different flavors and mouthfeels.

High-temperature extraction causes the tannic acid in coffee to rapidly break down into pyrogallic acid, bringing sour, sweet, and bitter notes—this is what Front Street often calls the coffee flavor release process. When the water temperature is too high, the coffee flavors are all released prematurely, and then the taste of the coffee beans' woody fiber begins to emerge—what we commonly call off-flavors, woody notes, and other unpleasant aromas.

Low-temperature extraction, on the other hand, lets water and coffee grounds stay in contact for a long time at low temperature. Only smaller-molecule flavor compounds (such as floral and fruity notes) can be extracted, while larger-molecule flavor compounds (such as smoky and roasted notes) are difficult to dissolve out. As a result, cold brew coffee more easily delivers the coffee beans' own flavors, with a smooth mouthfeel and very pronounced layering and sweet aftertaste.

Tips for Making Cold Brew Coffee

1. Grind Size

Just like with pour-over coffee, grind size needs attention when making cold brew. Grinding too fine creates dense channeling, easily leading to over-extraction and bitterness; grinding too coarse increases the likelihood of channeling, easily causing under-extraction and making the coffee taste weak. Front Street recommends a grind size slightly finer than pour-over, using a No. 20 standard sieve with a 75–85% pass rate as a reference—that is, a coarseness similar to granulated sugar.

2. Coffee-to-Water Ratio

Whether cold brew coffee tastes good is closely related to the coffee-to-water ratio. Front Street recommends a range of 1:10 to 1:12. At this ratio, the brewed coffee can be drunk directly or diluted with ice cubes to a moderate concentration before tasting.

3. Before dripping, wet the coffee grounds first, and remember to place a filter paper on top of the coffee grounds layer.

Wetting the coffee grounds puts the grounds layer in a water-saturated state before extraction begins, facilitating a smooth drip extraction. Also, don't forget to cover the grounds layer with a piece of filter paper—this filter paper allows water droplets to spread evenly across the coffee grounds surface; otherwise, the final product may taste weak.

4. Cold brew coffee tastes better after resting in the refrigerator overnight.

Front Street generally starts steeping the night before, controlling the time to about 12–14 hours, so that by the time we arrive at the shop the next day, we can take it out and filter out the coffee grounds to obtain the finished coffee liquid. Front Street has also, due to forgetting, let the steeping time exceed a full day, resulting in coffee liquid that was bitter and harsh—so everyone must be careful to control the extraction time and avoid wasting it. Additionally, the space where coffee is stored will absorb various odors from the air. If storing it in a home refrigerator, Front Street recommends using a well-sealed container to avoid the flavor being affected.

Why does cold brew coffee need to be refrigerated and fermented for more than 12 hours after drip extraction is complete? Is this process really called fermentation?

Actually, rather than calling this step fermentation, it's more of an oxidation process. Just like freshly roasted coffee beans, about 2% of their weight is carbon dioxide. This large amount of carbon dioxide is released depending on the storage environment, equipment, or method, making the pressure inside the packaging higher than one atmosphere. The pressure helps aromatic substances and oils integrate, bringing all the aromatic substances inside the coffee beans to a state where they are easily extracted.

The same principle applies to cold brew coffee. Extended extraction allows many flavor molecules to be extracted, but they haven't yet been well released. So after cold brew extraction is complete, pour it into a sealed bottle and let it rest in the refrigerator for 12–24 hours. The carbon dioxide pressure generated inside the bottle prompts the release of flavor molecules—this is also why cold brew coffee tastes richer the longer it sits in the refrigerator. Of course, Front Street doesn't advocate keeping cold brew for a week, since there are bacteria in the air or in the bottle, and it's hard to guarantee the coffee's condition after too long. The recommended drinking window for cold brew is within 72 hours. For cold brew older than 72 hours, don't feel it's a waste to toss it—coffee kept that long offers no benefit when drunk.

What Beans Are Suitable for Cold Brew Coffee?

Reading this far, many friends might think that finding a flavor bean they like is all it takes. Indeed, making it with coffee beans you enjoy is perfectly fine. Because of their low-temperature extraction characteristics, cold brew and cold drip can highlight the winey notes and fruity fermentation sensations in coffee, making them very suitable for flavor-forward coffee beans. Front Street believes that medium-roast and medium-light-roast coffee beans presenting rich floral-fruity aromas or fermented notes are all suitable for cold brew—for example, the Costa Rica Musician Series and Honduras wine-barrel-processed coffee beans.

At Front Street Coffee (FrontStreet Coffee), to make each cold brew coffee's flavor more pronounced and balanced, baristas typically blend two coffee beans together for cold brew. The purpose is to make the finished product more vividly highlight a particular flavor characteristic—one bean provides the aroma, and the other provides the flavor. This time, Front Street will use Costa Rica Mirazu Estate Geisha blend and Honduras whiskey-barrel-fermented Sherry to make iced coffee for demonstration.

Front Street Coffee (FrontStreet Coffee) production parameters: Coffee grounds: 60g (20g Geisha blend : 40g Sherry) Coffee-to-water ratio: 1:10

Ice-water 1:1 mixture, 600ml total

1. Place a circular filter paper at the bottom of the coffee grounds cup, wet it with water so it adheres to the cup wall, add the ground 60g of coffee (Front Street Coffee (FrontStreet Coffee) uses the China standard No. 20 sieve, with a 78% pass rate), then shake the coffee surface flat. You can also use the tamper's own weight to lightly press the grounds layer, making the surface level.

2. Lay a piece of filter paper on top of the coffee grounds layer. The tension of the filter paper allows water to distribute evenly across the coffee grounds surface for extraction. Without the filter paper, prolonged dripping will dig a pit into the grounds bed, affecting subsequent extraction.

3. First, evenly wet the entire coffee grounds layer with water for "pre-infusion." This step is like the blooming stage in pour-over coffee, improving extraction effectiveness and consistency of the final product.

4. Add the 1:1 ice-water mixture to the upper pot, then adjust the valve so the drip rate is about 7 drops per 10 seconds. The cold brew apparatus is best placed in a cool, dry place, and protected from being bumped.

5. Pour the finished coffee liquid into a sealed glass bottle, then place it in the refrigerator to oxidize overnight, allowing the coffee's flavors to meld together for a better taste.

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