The Buzz on Flash Brew vs. Cold Brew Coffee

Both cold brew coffee and flash brew have been gaining popularity. Why should you try these methods, and what equipment do you need to get started?

Cold brew coffee has been gaining popularity. According to the coffee drinkers who swear by this brewing method, the taste is superior to hot brew coffee. But flash brew, or Japanese style iced coffee, has its fans too. In this post, we’ll look at the reasons to consider flash brew and cold brew coffee, along with what equipment you’ll need for each method.

The Chemistry of Coffee

We promise to keep this simple. Brewing coffee involves solubility, volatility and oxidation. Solubility means how well compounds dissolve in water. Volatility means how well compounds evaporate into the air. Oxidation means how compounds react to oxygen in the air. Solubility, volatility and oxidation all increase with temperature.

Coffee brewed with hot water means more compounds will dissolve, giving a greater range of flavors. Likewise, the delicious smell of hot coffee is a result of evaporating compounds. Unfortunately, oxidation also occurs quickly with hot coffee, which is why it develops a stale or bitter taste. The effect of temperature on solubility, volatility and oxidation is what makes hot coffee different from flash brew and cold brew coffee.

Cold Brew Coffee

Cold brew coffee is made much the same way as cold brew iced tea: it "brews" over several hours in the refrigerator. The longer brewing time gives all of those soluble compounds more time to fully dissolve. Therefore, the water absorbs more flavor in spite of the lower brewing temperature.

Cold brew coffee is made much the same way as cold brew iced tea: it “brews” over several hours in the refrigerator. The longer brewing time gives all of those soluble compounds more time to fully dissolve. Therefore, the water absorbs more flavor in spite of the lower brewing temperature. Of course cold brew doesn’t have the same delicious smell as hot coffee, but cold brew oxidizes more slowly and keeps longer. Also, the flavor profile of cold brew differs from hot coffee. In general, cold brew is less acidic, with a deeper and more mellow flavor.

We recommend the OXO Good Grips Cold Brew Coffee Maker to make cold brew as simple as possible. But if you’d like to try out cold brew coffee before buying a machine, we like this workaround from Instructables. Either way, it’s helpful to have a digital kitchen scale to ensure you get the proportions right.

Flash Brew Coffee

Flash brew coffee, or Japanese style iced coffee, is brewed hot and served cold. Instead of dripping into an empty carafe, flash brew drips over a precise amount of ice which immediately cools the hot coffee. The primary advantages of flash brew over cold brew are that it’s more flavorful and only takes a few minutes to make. You can flash brew coffee using the pour-over method or with an automatic coffee maker.

Check out this video from Quartz to see how easy it is to flash brew a cup. The key is to measure your ingredients carefully, so a kitchen scale is essential, but we’ll forego the keg, the nitrogen and the refractometer.

While flash brew hasn’t gotten the same amount of attention as cold brew, it’s been around for years and has devoted fans. Flash brew aficionados maintain that it has a brighter, more refreshing flavor, especially for drinking cold. On the other hand, cold brew fans may not necessarily taste a difference. We leave it up to your personal tastes.

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