How Does Yirgacheffe Cold Brew Coffee Extraction Work?

Cold brew uses water close to zero degrees instead of hot water, so flavor compounds volatilize less and much of the aroma stays locked in the liquid. As the coffee warms in the mouth, that aroma releases at the base of the tongue. Hot extraction brings out acidity, sweetness and bitterness fast, but can pull woody and off-flavors once those compounds are spent.

Bean choice shapes the cup: Yirgacheffe for dark berry notes, Kenya for a clean and crisp profile, and Mandheling for sweetness, with blending options between them. The method covers grind, ratio, production steps, fermentation duration and drinking recommendations, so a smooth, aromatic cold brew can be made at home.

Cold brew coffee, extracted through a slow low-temperature process, presents a flavor profile completely different from pour-over, and is deeply loved by coffee enthusiasts. Drawing on the practical experience of Front Street Coffee, this article systematically covers the origin of cold brew coffee, its extraction principles, bean selection, and operational key points, and shares several cold brew recipes centered on beans such as Yirgacheffe, Kenya, and Mandheling, covering dark berry types, clean and crisp types, sweet and delicious types, as well as blending ideas. The article also explains in detail the production steps, fermentation duration, and drinking recommendations, helping you make a cup of cold brew coffee with full aroma and smooth texture at home.

Pour-over coffee is certainly charming in flavor, but the premise is that every detail of each step must be handled properly. If you want to try something different, why not have a cup of cold brew coffee. Front Street's cold brew has always enjoyed a good reputation. A cup in midsummer is naturally refreshing, and even drinking it in slightly cool weather has its own kind of satisfaction.

Cold brew coffee, as the name suggests, is coffee extracted with low-temperature water. It is completely different from the hot water we use when making pour-over daily, and the operating logic of the two is entirely different. The advantage of high-temperature extraction is that it can quickly bring out the flavor substances in coffee, allowing tannic acid to decompose more quickly into pyrogallic acid, thereby presenting layers of acidity, sweetness, and bitterness. This is what Front Street often calls the flavor release process. But the shortcoming of high-temperature extraction is equally obvious: once the flavors have been fully released, the smell of the coffee bean's wood fiber begins to emerge, which is what we often call off-flavors, woody notes, and other unpleasant tastes.

Low-temperature extraction uses ice water close to zero degrees to extract coffee, allowing flavor substances to reduce volatilization in a low-temperature environment and locking as much aroma as possible into the coffee liquid. When the coffee liquid enters the mouth and the temperature gradually rises, the aroma originally stored inside bursts out suddenly, and the drinker can feel a strong fragrance at the base of the tongue. This aroma-burst experience often brings great satisfaction. Its drawback is that production takes a long time, and after dripping is completed it cannot be drunk immediately. It needs to be placed in the refrigerator and left to stand for more than 8 hours, allowing the flavor molecules extracted at low temperature to be fully released.

Where did cold brew coffee come from?

According to Front Street's understanding, cold brew coffee was invented by the Dutch, so it is also called Dutch-style drip coffee. Unlike other methods that require hot water brewing, its core feature is extraction with ice water. Under low-temperature conditions, it takes longer to dissolve the aromatic substances in coffee. Thus, a dropper device similar to a chemistry experiment is used, letting ice water fall drop by drop, slowly soaking and penetrating the coffee grounds layer. On traditional cold brew equipment, the speed at which the water drops fall can usually be adjusted. Cold brew coffee is also called water-drip coffee or ice-brewed coffee. It is a way of making coffee drinks, and the common cold coffee drip device consists of three to four layers of glass containers set on a wooden stand.

What is the extraction principle of cold brew coffee?

Pour-over coffee relies on specified water temperature, time, and coffee-to-water ratio to complete brewing, with simple operation and shorter time. Cold brew coffee, on the other hand, is a coffee slowly developed with time. We know that choosing different water temperatures for brewing will produce different coffee tastes, and in a low-temperature environment, the astringent substances in coffee are less likely to dissolve out. Extracting with ice water for a long time, then placing it in the refrigerator to ferment afterward, lightly fermented cold brew coffee will carry a faint fermentation aroma, and the mouthfeel also tends to become fuller. Because it has not undergone high-temperature extraction, relatively fewer impurities in the coffee are brought out, and the caffeine content is slightly lower. For friends affected by caffeine, Front Street believes cold brew coffee is a good choice. It is not too hard on the stomach, is lower in caffeine, and still has rich flavor layers.

What kind of coffee beans are suitable for making cold brew?

Pour-over coffee is relatively broad in its choice of beans. Almost any coffee bean can be used for pour-over; it is just that with different roast levels, the brewing technique needs to be adjusted accordingly. Espresso has certain requirements for beans, for example, the roast level should be darker than pour-over beans, that is, medium-dark roast is needed, otherwise the flavor of the espresso may be hard for people to accept. Of course, if someone prefers to use light-roasted beans for espresso, that is another matter.

Then what about cold brew coffee? Which beans are more suitable? Generally speaking, coffee beans used for pour-over can all be used to make cold brew. In fact, Front Street believes that making cold brew mainly depends on personal taste preference. However, Front Street still recommends using single-origin beans for cold brew, as this can effectively remove bitterness and tannic acid, giving a rich and smooth mouthfeel that is neither sour nor astringent and does not upset the stomach. Sometimes we also use two or more single-origin beans to combine for cold brew. Compared with cold brew coffee, cold brew coffee has a richer aroma and a more delicate and subtle taste.

Because cold brew coffee uses a relatively long cold-water penetration extraction, Front Street suggests choosing varieties with stronger flavors when selecting beans, such as Front Street Kenya and Front Street Ethiopia Yirgacheffe, beans with distinctive character. The resulting coffee will be very recognizable.

Below is a share of the cold brew coffee recipes that Front Street Coffee (FrontStreet Coffee) often makes.

1. Dark berry type : Front Street Costa Rica Mozart 60g. This Front Street Mozart bean uses an anaerobic honey process and itself carries a very special raisin aroma. Used to make cold brew, it presents obvious blueberry, black grape, and wine-like fermented flavors, with a refreshing mouthfeel and a lingering fragrance on the palate.

2. Clean and crisp type : Front Street Kenya Asalia 60g. Asalia's acidity is very lively, overall like a glass of juice. Used to make cold brew, it carries the fresh fragrance of cherry tomatoes and grapefruit, and drinks as a refreshing, light acidity, very suitable for summer.

3. Sweet and delicious type : Front Street Indonesia Golden Mandheling 60g. Few shops use dark-roasted coffee to make cold brew. Those who have not tried it may think that dark-roasted beans will make cold brew very bitter, but in fact this is not the case. According to Front Street's cold brew method, after putting it in the refrigerator for 24 hours and then adding ice cubes, Front Street Golden Mandheling cold brew coffee shows sweetness with a hint of chocolate bitterness, overall very clear and transparent, and a rich fermented sensation that feels comfortable.

Front Street blended-bean cold brew coffee recipe:

In order to make each cold brew coffee's flavor more prominent and balanced, baristas usually choose two coffees to blend together for cold brew, with the aim of making the finished product highlight a certain flavor characteristic more strongly, with one bean providing aroma and one bean providing flavor.

For example:

20g [Front Street Coffee (FrontStreet Coffee) Honduras Litchi Orchid] + 40 [Front Street Coffee (FrontStreet Coffee) Gesha Village Red Label]

Barrel-treated Front Street Litchi Orchid plus sun-dried Front Street Gesha Village Red Label, with a faint brandy aroma, plum-like acidity paired with the sweetness of maple syrup.

Front Street Litchi Orchid treated in brandy barrels has a rich brandy aroma, a chocolate finish, and a honey aftertaste.

Front Street sun-dried Gesha Village Red Label has the fruity acidity of plum and citrus, with the sweetness of maple syrup and a creamy, smooth mouthfeel.

Made into cold brew, you will feel a faint brandy aroma, with rich fruity acidity leading the sweetness of honey and a creamy, smooth mouthfeel.

This time Front Street will use Front Street Gesha blend from Costa Rica Mirazu Estate and Front Street Sherry from Honduras whiskey barrel fermentation to demonstrate making iced coffee.

1. Place a round filter paper at the bottom of the powder cup, wet it with water so it sticks to the cup wall, add 60g of ground coffee powder (Front Street Coffee (FrontStreet Coffee) uses the Chinese standard No. 20 sieve, with a 75% pass rate; slightly coarser than the pour-over grind size is fine), then shake the coffee surface flat. You can also use the weight of the tamper to lightly press the powder layer, making the surface level.

2. Lay a piece of filter paper on top of the coffee powder layer. Because the tension of the filter paper allows water to be evenly distributed across the surface of the coffee powder layer for extraction. Without filter paper, long-term dripping will create a pit in the coffee bed.

3. Use ice water to "pre-infuse," evenly wetting the entire coffee powder layer with ice water. This step is like the blooming stage of pour-over coffee and can improve extraction efficiency and consistency of the final product.

4. Put a 1:1 mixture of ice and water into the water container, and adjust the valve to about 7 drops every 10 seconds.

5. After making it, pour the coffee liquid into a sealed glass bottle and then place it in the refrigerator to oxidize overnight, allowing the coffee's flavors to integrate. The taste will be better and easier to drink.

Pour-over coffee or espresso can be enjoyed immediately after making, so is cold brew coffee the same? The answer is: no.

After dripping is completed, cold brew coffee should be put in the refrigerator to ferment for more than 12 hours. Why? Front Street believes this is an oxidation process. Just like coffee beans that have just finished roasting, about 2% of their weight is carbon dioxide, and this large amount of carbon dioxide releases carbon dioxide depending on the storage environment, equipment, or method, making the pressure in the packaging higher than one atmosphere. The pressure helps the integration of aromatic substances and oils, bringing all the aromatic substances inside the coffee bean into a state where they are easy to extract.

The same is true for cold brew coffee. Due to long extraction, many flavor molecules have been extracted but have not been well released. So after cold brew coffee extraction is completed, put it in a sealed bottle and leave it still in the refrigerator for 12-24 hours, so that the carbon dioxide pressure generated inside the bottle causes the flavor molecules to be released. This is also why the longer cold brew coffee is kept in the refrigerator, the richer it tastes. Of course, this does not mean it can be kept for any length of time. Front Street does not advocate keeping cold brew for a week. After all, there are bacteria in the air or in the bottle, and it is hard to guarantee the coffee's condition after long storage. The recommended drinking period for cold brew is within 72 hours. If it has passed 72 hours, do not feel it is a waste; coffee kept that long may not be good for your body if drunk.

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