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Cold brew uses room-temperature or cold water (the latter will take longer) throughout the entire process, and extracts the coffee much more slowly, sometimes up to two days. The result is a richer, smoother, and less-diluted coffee concentrate that can be watered down or mixed with milk, while preserving the flavor of that coffee you paid good money for. \u201cIced coffee, on the other hand, is brewed hot and then cooled, or brewed directly over ice,\u201d Megan Biolsi, Manager of Coffee Education and Training at Sightglass Coffee, told me. \u201cBecause it uses hot water, it retains more brightness and acidity, resulting in a more vibrant and aromatic cup that is closer in profile to hot coffee.\u201d<\/p>\n
\u201cCold brew is essentially a long, gentle immersion brew,\u201d Biolsi explained. \u201cSimilar to a French press, the coffee grounds remain in contact with water throughout the entire process. Because of the lower extraction energy from colder temperatures, the contact time is extended to achieve proper extraction.\u201d<\/p>\n
Brewing coffee low and slow isn\u2019t pointless, in fact it\u2019s the whole point. \u201cAt these lower temperatures, the extraction of flavor, caffeine, and oils happens more slowly,\u201d Biolsi said. \u201cHowever, this extended steep time results in a smoother, sweeter, and lower acidity coffee, since many of the more acidic compounds are less soluble in cold water and remain behind.\u201d<\/p>\n
That\u2019s why we balk a bit at the machines that promises rapid, quick, or instant cold brew. As Major Cohen, an author and coffee educator at Cumulus Coffee, explained when I asked him to outline the difference he sees comparing the Cumulus process to some of the vacuum cold brew contraptions I’ll mention below, \u201cMost of these countertop machines are not creating cold brew. Rather they are brewing traditionally and then chilling the result, which is a different product flavor-wise.\u201d<\/p>\n
\u201cThe faster brew time allows more acidic compounds to be extracted compared to true cold brew, so the result won\u2019t have the same smooth, sweet, and balanced profile,\u201d Biolsi \u201cHowever, it may still be more full bodied than standard iced coffee.\u201d Hence, we\u2019ve included some of these quick cold brew machines in our reviews below.<\/p>\n
A simple immersion brewing method is similar to making iced tea: Coarse coffee grounds sit in cold water for a long period of time\u2014you could even just do this in a French press if you wanted. But a few brewers, including our winner, use gravity to gradually expose the water to the coffee grounds before filtering. We tend to prefer this style of cold brewer because most of the \u201csteeping\u201d methods rely on mesh or perforated metal filters that leave some unpleasant silt in your cup at best and, at worst, produce weak or bitter coffee.<\/p>\n
Frequently the directions that come with these cold brew makers produce cold brew concentrate (like for our winning Oxo pick), which can be watered down or mixed with milk to your preferred strength and liking. You\u2019ll want to experiment with your own ratios, but for concentrate, a coffee-to-water ratio of around 1:4 is a good place to start.<\/p>\n
\u201cUsing consistent brew ratios, fresh coffee, and controlled extraction times will yield the best results,\u201d Biolsi stressed, noting that precision is the name of the game. \u201cMeasure your coffee and grind it right before brewing whenever possible. Pre-ground coffee oxidizes more quickly due to increased surface area exposure. For grind size, use a coarse grind (similar to sea salt) to limit over extraction. If your brew tastes bitter (a dry sensation on the palate), adjust to a slightly coarser grind. If it tastes sour (a puckering or tingling sensation), adjust to a slightly finer grind.\u201d<\/p>\n<\/div>\n
Using the same whole beans and filtered water, I followed the brewing instructions, grind recommendation, and measurements for each individual coffee maker. Unless otherwise noted in the instructions, I brewed each system in the refrigerator for a full 24 hours. For a second round of testing, we brewed every system on the countertop at room temp for 18 hours. For \u201crapid\u201d cold brew makers that utilize battery-powered vacuum pumps, we brewed at any and all available extraction time settings. Testers tasted all of the resulting cold brew black and diluted with milk.<\/p>\n