Iced coffees and teas should be some of summer’s simplest pleasures, especially when we just steep them in cold tap water, with no kitchen heat and next to no effort. But if you make even a desultory search for advice on cold brewing, you may find yourself mopping your brow deciding how, and even whether, to proceed.
Ratios of tea or coffee to water differ wildly from recipe to recipe; brewing times can be minutes or hours. And while some respected coffee authorities praise the virtues of cold-brewed coffee, others say it’s just not as good as brewing a fresh hot cup right onto the ice.
I’ve found it calming to take a leaf from China and Japan, where one batch of tea is briefly infused as many as seven or eight times and each infusion enjoyed for its particular qualities. Variety can be just as pleasing as consistency, and it can be a way to discover new sides of our most familiar ingredients.
When we brew coffee or tea, we’re doing a very basic thing: bringing plain water into contact with dried plant materials to imbue the water with flavour, colour and various active substances, like caffeine and antioxidant polyphenols. It is a basic process, but not a simple one.
As water moves into the coffee particles or tea leaves, it dissolves or suspends hundreds of different substances and extracts them from the solids. If the water is hot, it extracts more rapidly and completely. Hot water also cooks as it extracts, forcing chemical reactions that transform some of the extracted substances into other things, and driving some aroma substances out of the liquid. Cold water, in contrast, extracts more slowly and selectively, produces a simpler extract, and doesn’t change the original flavour substances as much.
So cold-brewed teas and coffees are chemically different from their hot counterparts. They tend to contain less caffeine and less acid. And, of course, they taste different. If the flavour of hot tea or coffee is your gold standard, then cold brews won’t measure up. If you think of hot and cold brews as different drinks, just as a lager isn’t the same as a pale ale, then you may find that you enjoy both.
There are a variety of specialized devices for cold-brewing coffee but you can improvise a cold-brewing system using a French-press pot or just a pitcher or bowl, with fine sieves, cheesecloth, or cloth or paper filters to strain out the grounds. Infuse coarsely ground coffee overnight in cold water, about five cups for every 227 grams of coffee, then press or filter the brew from the grounds. Cold-brewed coffee is controversial. To summarize the substance of many recent interviews and blog posts: Advocates praise its low acidity and lack of bitterness, and its intense but smooth flavour; detractors find it lacking in aroma and body and say they get more of both by starting with a double-strength hot pour-over or French press. The pour-over, or a Chemex brew, can be made directly over ice cubes, the French press coffee added immediately to ice. With each, the ice melts and dilutes the coffee to an appropriate drinking strength. Some automatic coffee makers now offer settings and pre-measured coffee doses for brewing strong coffee onto ice.
When it comes to tea, there’s less controversy and more flexibility. The standard proportions for Americans’ iced tea are about four teaspoons or two-gram bags per quart, with a brewing time of eight to 12 hours. In Taiwan, where cold-brewed tea has become increasingly popular in recent years and spurred studies of its chemistry, about twice that ratio of tea to water is used for a similarly long infusion. And one purveyor of fine Japanese teas in Kyoto recommends making small cups of cold sencha with five times that ratio, infusing first for 15 minutes, then for briefer times. The first couple of infusions are like no other version of green tea I’ve had, intensely grassy and bitter, with subsequent brews progressively milder and more refreshing.
Since cold infusion is a relatively slow and gentle process, proportions and times aren’t critical. There’s plenty of leeway for both. As a general rule, the more fragile the tea leaves, or the smaller the particles, the less tea and time you need to get a strong brew. If a cold brew infuses too slowly, just add more tea.
Two of my favourite cold-brewed teas come from Maricel Presilla, who serves a number of them at her Latin restaurant Zafra in Hoboken, New Jersey. One perennial on her list is a mojito iced tea, in which oolong tea scented with osmanthus flowers, or with a sliced peach and its pit, suggests the sweet aroma of white rum.
Presilla also makes an unadorned agua fresca de jamaica, the tart, deep-red sepals that surround the flower of a particular species of hibiscus.
Jamaica (pronounced ha-MY-ka) is especially rich in antioxidant polyphenolic compounds, including its anthocyanin pigments, and food chemists are investigating its potential as a nonalcoholic alternative to red wine. They have found that a two-hour cold infusion extracts as much of the pigments as a standard hot infusion, and that the flavour is fruitier and less marked by green-leaf, clove and cooked aromas.
Less heat may mean less flavour in coffees and teas, but not necessarily less pleasure.