Warming up to Cold Brew
The brewing of coffee, that nectar of the gods, is steeped in tradition. The best and brightest of many a culture have been powered by this elixir, and many of them have devoted serious time to getting the perfect cup out of every brew. Of course, in the case of coffee, perfection is a relative term, or at least a subjective one. Even dip your toe into the vast pool of information available online about coffee brewing methods and you’ll find evangelists espousing their preferred method of brewing and spouting vitriol about others.
The big secret is that the best method for brewing coffee is the one that you like best. There are benefits to be considered for each method, and they range from ease to economy, health to heat, caffeine to convenience, and everything in between. As invariably as Earth’s axis tips our hemisphere towards the sun this time of year, warm weather always starts the conversation about cold coffee. Numerous options exist for making your daily cup cooler as temperatures climb, but one method that’s been steadily growing in popularity is cold brewing—and some take it hot. Its roots run deep, with devotees in the American South tracing their love for the stuff back generations. It’s not for everyone, but it might just be for you.
The Skinny on Cold Brew Coffee
In contrast to the relative speed with which a hot cup of coffee can be brewed, cold brewing coffee takes a time commitment of around twenty hours. As opposed to the aromatic, acidic coffee with a bite that hot brewing produces, cold brewing rewards your patience with smooth, sweet coffee concentrate. To understand why, it helps to understand some of the chemistry behind it.
Coffee beans are chock full of oils, acids, and aromatic compounds that are collectively referred to as coffee solubles. Every method of brewing involves releasing these coffee solubles into water, and variations in time, temperature, grind, and water-to-grounds ratio all contribute to different flavors coming out of the process. Each of these compounds has different degrees of solubility and volatility, which are basically the ability for the compound to dissolve into the water or be evaporated into the air, respectively.
Generally speaking, the ideal temperature range for extracting most coffee solubles is between 195 and 205 degrees Fahrenheit, which is why hot brewed coffee is often referred to as being more full-bodied than its colder counterpart. Solubility and volatility both increase with temperature, and it’s the latter that is responsible for the incredible aroma of a fresh brew. Also increased at higher temperatures are oxidization and degradation. Oxidized oils taste sour, and acids taste increasingly bitter as they degrade.
The decreased extraction rate of cold brewing is why the amount of grounds used is about double compared to a hot brew and the time it takes is hours longer. Oxidization and degradation are also slowed way down with the cold brewing process, and some compounds attributed with unfavorable tastes and many acids only dissolve at higher temperatures. As a result, cold brewed coffee is almost completely lacking in sourness and bitterness. With cold brew, chocolates, fruits, flowers, and nuts come through in the flavor profile, and there’s a certain sweetness in spite of the beans’ residual sugars not being fully extracted. Cold brew also only has about one-third of the acid, which makes it a lot easier on the teeth and stomachs of drinkers.
At this point, the question on everyone’s mind is, of course, “but what about the drugs?” Caffeine is extracted early in the brewing process, and brew time does not determine its concentration. By using twice the grounds, you’re effectively doubling the caffeine in the concentrate you make by cold brewing, but again, it’s meant to be a concentrate. You’re meant to be cutting it with water, milk, or whatever’s your pleasure, not drinking it straight. At the diluted level, you’re still getting your regular fix.
You Can Do It: How to Cold Brew It
For what seems to be a fairly straightforward and simple brew process, there are a staggering number of even more staggeringly expensive machines out there for making cold brew coffee. Of the devices specifically designed for the job, my favorite is the Toddy, which was developed by a chemist largely responsible for the popularity of cold brew outside of the South, where the traditional apparatus is a simple lidded Mason jar.
After many years of cold brewing, I’ve refined my own technique to suit my taste, but it’ll be good place for you to start and several of these techniques can be translated to other cold brewers, like the aforementioned Mason jar.
1. In a 38-ounce French press, add six ounces of cold, preferably filtered, water to the empty reservoir.
2. On top of this, weigh out 7.5 ounces of coarsely ground coffee (a little more coarse than a standard French Press Grind) and add that to your six ounces of cold water.
3. Add another 16 ounces of cold water, pouring it slowly over the grounds to moisten all of the coffee.
4. Wait five minutes for the coffee to bloom and soak up the water.
5. Add the final eight ounces of cold water slowly and steadily, taking care not agitate the grounds too much.
6. Cover loosely with a plastic bag, and let your concoction sit for 20 to 24 hours.
7. Just plunging the French press won’t get out all of the grounds, so have a secondary filter ready.
This produces the concentrated coffee mentioned above. You’ll want to mix this between 1:1 and 2:1 with water or milk to your personal taste (note: cold brew is known for going wonderfully with dairy—try pouring your concentrate over chocolate or vanilla ice cream; it’s fantastic). For hot coffee, mix concentrate with boiling water (don’t boil the concentrate itself!). Take some time to vary all of the elements at play here. Brew time, grind, even grounds-to-water ratio—all can be tweaked to net a cup of cold brew that is perfectly suited to your tastes.