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Just as hot brewed coffee can be made in many ways, people are experimenting with different ways to make cold brew coffee. This article reviews the main methods of making cold brew coffee, and a little experiment of my own at the end!
Let’s start with some of the principle variables in making cold brew coffee.
The effects of time, temperature and grind:
The temperature of the water used to brew will influence the final result. When making hot brew coffee, you don’t want to brew too long or the coffee will become overextracted. Overextraction creates bitter coffee.
When brewing with cold water, coffee needs to contact the water for an extended period of time. If the coffee is not brewed long enough, the grinds will be underextracted which results in a thin bodied and weak brew.
Cold brew coffee is technically not a cold brew, but a room temperature brew. Brewing at room temperature takes between 12-24 hours. I have experimented with brewing in the fridge, in which case I brew for 18-24 hours. Try both and see which one you like better, I go back and forth on this.
Time is a variable all on its own (independent of temperature). Longer brew times will lead to overextraction (marked by bitterness in both the coffee and the drinker!). Underextraction will produce coffees that do not have the full flavor of a properly brewed cup. The optimum brew time is 12-24 hours.
The degree of grind is closely linked to brew time as well. Finely ground coffee requires a shorter brew time while coarsely ground coffee needs a longer time to fully extract the coffee. Finely ground coffee that brews for too long will be overextracted. Coarsely ground coffee that does not brew for long enough will be underflavored.
Summing Up Temperature, Time and Grind:
- The colder the water, the longer the brew time needed.
- The longer the brew time, the more extracted the coffee grinds will be
- The coarser the grind, the longer the brew time needed.
How equipment affects cold brew:
Because of the long contact time in cold brew coffee, the type of container used to brew the coffee can make a difference in the final flavor. Glass or ceramic will be the most neutral. Paper and plastic are not recommended. Stainless steel is a bit of a gray area. I will drink coffee from a stainless steel cup, but I don’t steep my coffee in it. Personally, I feel after extended contact there is a slight metallic taste.
There are a few different ways to filter coffee. The type of filter will affect how many coffee oils make it into the final cup, as well as whether any sediment is at the bottom of your cup.
Cloth—Cloth filters include a variety of cotton or mesh products. Cotton products may absorb oils and be difficult to clean over time. These filters are okay for filtration but with brew in the bag immersion techniques they may impart flavors to coffee even after repeated washings. I experimented with organic cotton drawstring tea bags early in my coffee journey and quickly moved on. Despite boiling the bag before use and multiple washings, the coffee always tasted like sucking on a washcloth. Nylon mesh bags (for example nut milk bags) impart less flavor than cotton, but tends to allow more sediment into the cup.
Paper—Paper filters will produce the clearest coffee (little sediment). The downside of this is that it may also absorb the coffee oils, which can diminish the flavor profile of strained coffee. If you use paper filters, you should rinse them before use to rinse away some of the paper flavors.
The other factor is the great bleached vs. unbleached debate. Some tasters can’t tell the difference, while others claim they can. A tasting experiment done by Stumptown Roasters determined that oxygen bleached filters are the best choice.
French Press—French press coffee makers are a logical choice for cold brew. They have a built in sieve that pushes the grounds to the bottom of the container and holds them there. The mesh allows oils to make it into the coffee but also some sediment. Use coarser grinds with French Press to reduce sediment in your cup.
Metal mesh– Some coffee experts advise against coffee contacting metal so immersion with metal mesh is not recommended and may impart flavors to the coffee. For filtration, mesh filters will leave some fine sediment similar to nylon mesh bags.
What type of water is best?
No special water is required, but if your water is overly chlorinated you should use filtered water. Using bottled water can create a flatter brew as can overly hard water. As a rule of thumb, use water that tastes good to you on its own.
For both methods, a glass container is recommended as plastics or metals may cause off flavors. A mason jar is ideal and inexpensive.
With a filter: The simplest way to make cold brew is immersion with a filter. This can be a bag or pouch
- cotton drawstring bag (reusable)
- stainless steel mesh basket (reusable)
- nylon mesh bag (e.g. nut milk bag) (reusable)
- paper drawstring or heat seal tea bag (disposable)
With this method, the coffee grounds are placed in the filter and both the coffee and the filter soak for 12-24 hours. When brewing is complete, the filter is removed and the coffee is ready.
Cons: flavors from the filter can show up in the coffee
cleaning the reusable filter bags can be messy
Without a filter: This is similar to the first method but filtration occurs after brewing is complete. Only the coffee and water are present during the brewing process. Because filtration occurs at the end there is less contact with the filter so less chance for it to introduce flavors to the coffee.
Cons: need to clean grounds from brewing container and filter (if not disposable)
Cold brew drip systems like the Bruer allow water to drip through the machine one drop at a time. The rate can be adjusted, but you can have coffee with this machine in as little as 4 hours. The water will not contact the coffee for all 4 hours which begs the question will this coffee be under extracted? I plan to test this system in the near future to find out.
This is not strictly a cold brew method but rather a hot brew method for making cold coffee quickly. Some feel that certain coffee flavors can only be released with hot water. This method extracts the coffee with hot water and then immediately cools it drip by drip over ice. Detractors claim that the ice dilutes the coffee, however when proper equipment is used that control the rate of drip the ice does not melt very much.
Cold Brew Queen Experiment:
So, I had to wonder why no one had tried a true hybrid method? In this method I boiled water and let it sit for a couple minutes to let it cool slightly. Water boils at 212 Fahrenheit and ideal temperature for brewing coffee is 195-200 F. Then, I poured just enough coffee on the grounds to wet them. In essence I bloomed the grounds with some hot water. Then to cool everything quickly I topped off the container with cold water—ice cube optional depending how cold your water is. Then, I let it immerse for the usual time and strained. Two tasters sampled the results. Taster 1 preferred the hot bloomed coffee slightly citing a better body and interestingly less bitterness. Taster 2 (a hot coffee drinker usually) slightly preferred the room temperature brew stating the hot bloomed coffee had an off-taste on the finish. Taster 2 agreed the hot bloomed coffee had more body.