What is the principle behind cold brew coffee? Is cold brew coffee complex and difficult to make? Is Mandheling suitable for cold brew?

The joy of summer is being able to stay indoors, enjoy air conditioning, and sip on a refreshing cold brew coffee. Thanks to its simple preparation method, even those who don't know how to brew coffee can easily create a smooth, rich, and clean-tasting iced coffee that's perfect for summer.

Unlike common iced pour-over coffee and iced Americano, cold brew coffee uses low-temperature extraction throughout the entire brewing process. Pour-over coffee and Americano, on the other hand, are brewed by extracting concentrated coffee liquid at high temperatures, then adding ice for cooling and dilution.

In a coffee bean, coffee flavor only accounts for 30% of the whole, while the remaining 70% is woody fiber structure. And not all of this 30% flavor should be extracted, because over 10% consists of bitter compounds. Proper extraction of bitter compounds can give coffee appropriate richness and increase its body. Coffee lacking bitter compounds tastes thin, while coffee with too much bitterness tastes dry and astringent. We only need to extract 18%-22% of the coffee's flavor.

The advantage of high-temperature extraction is that the heat in water promotes molecular movement, allowing flavor molecules from coffee particles to be extracted in a short time. However, the drawback is that if water temperature and coffee particle grind size aren't properly controlled during brewing, it's easy to over-extract bitter compounds, causing varying degrees of bitterness in the coffee.

Low-temperature extraction, lacking heat to promote molecular movement, effectively inhibits the release of bitter compounds. However, due to the low temperature, the coffee flavor extraction time is relatively extended, usually requiring 6-12 hours to fully extract sweet and sour compounds. Therefore, cold brew coffee typically has rich sweet and sour notes, but if steeping time exceeds 12 hours, the woody fibers will release root-like flavors due to prolonged soaking. While these flavors aren't strongly bitter, they affect the overall aromatic performance.

To release the full flavor of cold brew coffee, the coffee particles should be ground slightly coarser than for pour-over coffee. For example: FrontStreet Coffee's Ethiopia Guji Coffee Bean has a grind size of 80% passing through a Chinese #20 standard sieve for pour-over brewing, but for cold brew coffee, it only needs 75% passing through.

Why does making cold brew coffee extraction stronger require adjusting to a coarser grind?

FrontStreet Coffee discovered through multiple cold brew preparations that coffee ground to pour-over grind size tends to clump during steeping. Using the same coffee beans, same steeping time, and same environmental conditions for extraction, different grind sizes were tested, comparing the concentration differences. The experimental results showed that coarser-ground coffee particles extracted higher concentration in a refined, low-temperature environment.

This is because when water temperature approaches room temperature/zero degrees for extraction, molecular movement also decreases/stops. Without molecular thermal motion to counteract the attraction between solid molecules, coffee particles will "clump together," forming lumps. So when coffee is ground finer, the clumping becomes more severe, preventing coffee powder in the middle of lumps from being fully extracted.

Making Cold Brew Coffee

To make cold brew coffee, you typically need a clean, oil-free, sealable container and materials for filtering coffee (coffee filter paper/tea bags/high-density filter screens/cloth bags all work). Then mix coffee grounds with ice water evenly and place in the refrigerator to steep for 8-12 hours. FrontStreet Coffee recommends using 30g of coffee grounds with a 1:13 coffee-to-water ratio (i.e., 30g of coffee grounds steeped in about 400g of water). After extraction is complete, filter out the coffee grounds to enjoy.

For cold brew coffee, FrontStreet Coffee uses coffee beans with strong sweet/sour profiles and rich flavors.

For example, lightly roasted coffee beans from Africa and Central/South America: Ethiopia Guji Coffee Bean (berry and fruit juice notes) sold at FrontStreet Coffee, Panama Butterfly Geisha Natural Blend (floral tea notes), and Costa Rica Mozart Coffee Bean (candied fruit notes) are all very suitable for making cold brew coffee.

Or specially processed coffee beans, such as Ethiopia Dorothy Coffee Bean (white peach oolong notes), Colombia Rose Valley Coffee Bean (fruit liquor-filled chocolate notes), and Honduras Sherry Barrel Fermented Coffee Bean (wine, vanilla, cream notes) sold at FrontStreet Coffee.

But if you normally prefer rich, strong black coffee, then you might want to try darker roasted beans, such as Indonesia PWN Golden Mandheling, Brazil Queen Estate Yellow Bourbon, and Papua New Guinea Bird of Paradise Coffee from FrontStreet Coffee's regular bean selection. Cold brew coffee made from these beans tends toward rich notes of nuts, caramel, and spices, with a finish that carries the sweetness of dark chocolate.

Tips for Cold Brew Brewing

In many high-temperature brewing methods, fresh roasting is often the first consideration for many people. First, beans past their prime period will have significantly diminished aroma - this is already a common consensus; second, gas release allows us to visually determine whether beans are fresh, such as the crema in espresso, blooming during pre-infusion, etc., while also indicating that the coffee is at its peak aromatic stage.

As coffee beans are continuously heated in the roaster, freshly roasted beans contain large amounts of carbon dioxide. To extract the internal aromatic compounds, these gases must be released first. Cold brew itself is a relatively static extraction state, and low-temperature water to some extent inhibits the release of these gases, making the brewed coffee easily become bland. Therefore, FrontStreet Coffee suggests choosing coffee beans roasted more than 10 days ago for making cold brew, which is more conducive to creating aromatic-rich coffee.

For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style)

For more specialty coffee beans, add FrontStreet Coffee on private WeChat, ID: qjcoffeex

Important Notice :

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FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473