This article originally published in The Sturbridge Times, July 2018
By Elvis Dyer, Owner/Roaster, Sturbridge Coffee Roasters
How the coffee bean is roasted and ground makes a big difference in how your coffee drink smells and feels. However, the way it’s brewed makes a huge contribution to that final taste. There are two basic brewing methods – temperature and time – that really impact how your coffee tastes.
Hot-brewed drip coffee is usually what we visualize when we think of hot coffee. Whether it’s percolating in a coffee pot or utilizing a pour-over method of drizzling hot water over coffee grounds and letting it drip into a cup. This method of hot water extraction over ground coffee is also how ice coffee is brewed.
Cold brew on the other hand is made by soaking coffee grounds in room-temperature or cold water and letting it sit and steep for hours or days. After steeping, the resulting coffee is strained from what is often referred to as sludge-like solid. This cold brew is a concentrate that is then served over ice. Both beverages arise from the same starting materials, coffee grounds and water, but differ wildly in taste.
The brewing method for cold brew results in a deeper, less acidic and more subtle taste. The distinctively smooth and sweet taste of a cold brew are what distinguishes it from a hot cup of conventionally-brewed coffee.
The Chemistry Behind Cold Brew
When you mix coffee grounds with water, chemical reactions take place that pull solubles from the grounds, resulting in the coffee taste and smell. These solubles dissolve best around 200 degrees Fahrenheit, so coffee brewed with hot water has a more full-bodied, flavorful taste profile than cold brew. Hot water also pulls the soluble chemicals out of the grounds quickly, and makes them more volatile. This means that they evaporate into the air more easily which is why there is such a strong sweet-smelling aroma.
However, increased solubility isn’t always a good thing. Boiling water causes coffee’s chemical compounds to degrade and oxidize, causing that sour and bitter taste. Oxidation and degradation do happen when you brew your coffee cold, but it happens at a slower pace. Therefore, cold brew almost never tastes acidic or bitter. And, it’s why cold brew stays fresher than hot-brewed coffee. Cold brew can last 2-4 weeks refrigerated, whereas hot coffee usually goes stale after about a day. The water temperature of cold brew is below the optimal temperature to drag out those flavorful oily, acidic solubles, as it must sit for longer to create a strong brew. And, since cold brew is made as a concentrate, many more grounds are added to cold brew versus conventional brew, which helps increase the concentration of solubles in the final product. Since cold and room temperature liquid doesn’t volatize the aromatic compounds, cold brew has a duller smell when compared to hot coffee. That sweeter and smoother taste in cold brew is because the grounds are never exposed to high temperatures.
In addition to cold brew’s water brewing temperature, it also takes much more time and more coffee grounds to make.
Cold Brew Recipe
For a delicious cup of cold brew, you need a solid set of instructions. However, there are hundreds of different ratios for coffee-to-water, and just as many options for how long you should soak your brew. So, the real recipe is up to each person as they fine tune the right ratio of coffee-to-water, and the right brewing time. Start with coarsely ground coffee as finely ground coffee beans can result in a sludgy outcome, because it’s impossible to filter out the small particles. The exact measurements vary anywhere from 1 gallon of water with ½ pound of coffee up to 1 gallon of water and 2 pounds of coffee, and anywhere in between. Each consumer needs to find the right ratio of water to soak the coffee grounds in until it has reached their desired strength.
And it’s also worth noting that this cold brew concentrate will wake you up, as it has about twice the caffeine per ounce as a regular cup.
Cold Brew Brewing Methods
Cold brew can be made using a French press, in which you would place the coffee grounds in the bottom of the French press, add the water, let it sit, and then using the plunger, push all the grounds to the bottom. Or, you could use a mason jar with the same process, except instead of using the plunger, you pour the cold brew concentrate through a fine-mesh sieve. Or, there are commercial cold-brew machines available through local or on-line retailers. Whatever method you choose, they are all essentially the same – a vessel for the coffee grounds and the water, and a way to strain the coffee grounds out of the concentrate once you’re done soaking them.
Before you pour yourself a glass, remember, this is a cold brew concentrate. You should dilute with cold water or ice. A general measurement is 1-part cold brew concentrate (again, depending on how much coffee you used during the brewing process) to 1-part water. Add milk, cream or sugar to taste and enjoy!