Whether you’re a coffee aficionado or just someone who hangs out in cafés, there’s a good chance you’ve encountered cold brew coffee. This trendy beverage, also referred to as a cold water extract, is basically made by adding room-temperature or cold water to coffee grounds and letting the solution sit (“slow-steep”) for 10 to 20 hours or longer, after which it is filtered.
Though techniques and recipes vary, cold brewing calls for a higher coffee-to-water ratio (compared to hot brewing), which results in a concentrate that is then diluted with water or milk. Some people drink it straight for a potent espresso-like shot. Although it’s typically consumed “iced,” cold brew coffee is different from conventional iced coffee, which is made by pouring regular brewed coffee over ice.
The soluble compounds in coffee, including the oils and acids that give the hot beverage its signature taste and aroma, are less easily released in cold water than in hot water—hence the use of more ground coffee relative to water and the longer infusion time. If you let it steep for a very long time—say, more than 24 hours—you can still get flavors (and bitterness) similar to hot-brew methods.
But it’s impossible to make generalizations about cold brew coffee because there are so many variables involved in how it’s made and thus what ends up in it. Here’s a brief look at three aspects.
How much caffeine is extracted from coffee beans, whether cold- or hot-brewed, depends on several factors, including the relative amounts of grounds and water used, the temperature of the water, and the brewing time, along with the type of coffee (Arabica or Robusta) and grind size. Though more coffee grounds are used in cold brewing (which means a higher caffeine content), it’s also greatly diluted afterwards (which lowers the caffeine), so in the end there may not be that much of a difference. According to the Starbucks website, a 12-ounce serving of regular iced coffee contains 120 milligrams of caffeine, compared to 150 milligrams for an iced cold brew, which has steeped for 20 hours; other cold brews may contain more or less. Some companies sell decaffeinated cold brew.
Cold brew is being promoted as better, even “ideal,” for people who have acid reflux because, depending on the recipe, it can have a slightly higher pH, which means it’s less acidic. But that may not be true of all cold brews. In any case, whether acidic beverages (and foods) promote reflux is questionable; other things about the beverage, including whether there is also carbonation, caffeine, or alcohol in it—as well as other diet and lifestyle factors—probably play a bigger role in reflux. Still, if you have reflux that you think is exacerbated by regular coffee, you can try cold brew to see if that helps, but there’s no guarantee you will tolerate it better.
As noted in an article in Chemical & Engineering News in 2015, there’s no published research on exactly how this brewing method affects the molecular makeup, including the flavor molecules, of coffee. And there’s plenty of disagreement as to whether cold brew tastes better (it has been described as “smoother” and “sweeter”) or worse (“dead,” “dull,” “flat”) than hot brewed coffee. In general, however, unless it’s infused for a very long time, cold brew coffee tends to be less harsh, since the compounds that are less likely to be extracted tend to be the more bitter and “undesirable” ones. There is also less degradation and oxidation of the coffee solubles when the beans are processed in cold water.
Bottom line: Drink cold brew coffee if you like it—and don’t mind paying a premium price at cafes. Cold brew concentrates are also sold ready-made in large bottles for home use. Or you can make your own using a specialized device such as the Toddy system, a French press pot, or simply a jar, pitcher, or bowl plus some sort of filter. Many websites provide instructions, including Chowhound and the American Institute for Cancer Research, but you can experiment on your own to get the taste you prefer.
Also see Coffee: A Stimulating Friend of Millions.