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From cold drip coffee to nitro brew, cold-brewed coffee has taken a larger and larger place at the national breakfast table. While brewing coffee with cold water may seem to be an affectation to the typical morning Joe lover, those who try cold brews invariably find that the resulting coffee drink is distinctly different from a good ol’ cuppa java. This isn’t just in their imagination, either. It turns out that there’s some serious science behind the difference in flavor and mouthfeel between regular coffee brewing and brewing coffee cold. Here are five things you should know about cold-brewed coffee.
The flavor in your coffee is created by a complex blend of chemicals that start in the coffee bean. Every decision you make about your coffee affects which of those chemicals – and how much of each of them – ends up in your coffee cup. The beans you choose, how fine your grind is, how long you steep them in water – and the temperature of the water – all play a role in how your coffee tastes. The water temperature, in particular, has a major effect on coffee flavor. That’s because many of the chemicals reactions that happen in brewing a cup of coffee are dependent on the temperature of the water. Hot water causes different chemical reactions than cold water. Higher temperatures extract more acidic compounds than lower temperatures, so a cup of coffee brewed with hot water is more acidic than a cup brewed with cold water – 67% less acidic, in fact. That results in coffee that’s naturally sweeter and richer. On the flip side, those acids are responsible for most of the fruity and floral flavors found in some highly prized coffees. Without those acids, for example, a cup of fruity Guatemalan coffee comes loses the bold berry and citrus flavors that are so prominent in its flavor profile.
As with any other type of cooking – or anything you do in life, really – the quality of your starting ingredients affects the quality of your finished product. Buy the best quality coffee beans you can afford, and you’ll be rewarded with the most delicious coffee. However, one of the benefits of making cold-brew is that freshness isn’t quite as important as it is when brewing with hot water. The reason that freshly roasted beans are preferable for making coffee is – again – a chemical one. Once the coffee is roasted, it starts losing chemicals to the surrounding air through oxidation, which reduces the chemicals available to flavor your coffee. The chemicals that are lost the soonest are those that create the fruity, floral notes that are so prized in specialty coffees – and that are less important in making cold-brew coffee.
Just like coffee starts going stale as soon as it’s roasted – and goes stale more quickly after it’s ground – coffee brewed in hot water starts going stale almost immediately. One of the reasons that single serve coffee makers have become so popular is that no one likes drinking coffee that’s been sitting in the pot for an hour. Even if you immediately put the rest of the pot on ice, the coffee still tastes stale and flat after an hour or so. Not so with cold-brewed coffee. Because the flavor compounds extracted with slow steeping in cold water are less volatile, the good flavors last longer. A batch of cold brew coffee will keep fresh in your refrigerator for up to two weeks.
There’s more to making cold-brew than soaking roasted coffee beans in water. Just as grind and exposure to water make a difference in brewing coffee with hot water, they also make a difference in cold-brew coffee – but those are just a few of the variations you can play on with cold brewing. There are elegant and sophisticated cold brew coffee drippers, many of them with mechanisms that allow you to set the drip rate of the water precisely. Contrast those with the simplest method of making cold-brew – stir coffee grounds into a pitcher of water and let them steep. Other methods of making cold brew coffee include the hot bloom method, which starts with hot water to bring out the high end fruit flavors, then switches to cold water for the remainder of brewing, and, of course, this season’s hottest cold coffee brew method, nitro brewing, which infuses cold-brewed coffee with nitrogen to create a creamy, rich coffee drink that mimics many of the qualities of a fine stout.
One of the beauties of cold brew coffee is that you really don’t need a fancy getup to get excellent results in your own kitchen. Just start with high-quality beans, a coarse ground and pure, fresh water and you really can’t go wrong.