Cold brew is everywhere. Just go to any supermarket and you are likely to find a number of brands selling their cold brew and cold brew concentrates. Typically sold in 16 or 32 oz bottles, some are flavored and some are not. So what exactly is "cold brew"?
The designation "Cold brew" is a general term often used for all sorts of cold versions of coffee: Immersion cold brew, slow drip kyoto, cold press, etc. One of the most popular, immersion cold brew, steeps ground coffee in water over a certain length of time, often from 12-24 hours. It can be done with room temp or cold water and can even be started with a hot bloom and finished with cool water. There are various filter options including metal filters or paper filters.
Flash chill or the Japanese method of iced coffee are methods using hot water. Japanese iced coffee is typically made using a pour-over device over ice. Rather than using the full amount of water, one would use half the amount of water and do the pour-over directly over ice as to immediately chill the coffee as it pours. Technically speaking, these methods aren't cold brew, but they are methods that produce iced coffee. It may seem like splitting hairs, but hopefully you will see by the end of this article that the distinction has some merit.
All of these methods attempt to address the question of turbulence, temperature and time. The extraction process looks very different for a cold brew than it does for a hot coffee. Coffee is made up of a number volatile and non-volatile compounds which make up the flavor, aroma and mouth-feel of the coffee. When brewed at hot temperatures of 195-205, these compounds are more readily released into the water or the air and contribute to the coffee's overall flavor profile and aroma (think sugar dissolving in hot or cold water). When brewed at lower temperatures, the flavor profile of any given coffee will be drastically different.
While giving a lecture at LA Coffee Con in 2015, George Howell described cold brew as having vanilla and woody notes derived from the cellular walls of the coffee. He considered cold brew a "concoction" not produced by terrior. Terrior is "the set of all environmental factors that affect a crop's epigenetic qualities, when the crop is grown in a specific habitat. Collectively, these environmental characteristics are said to have a character; terrior also refers to this character" (Wikipedia). Rather than reflecting the distinctive traits produced by terrior or the organic acids and compounds extracted with hot water, cold brew reflects the cellular walls of the coffee. Without hot water, cold brew makes up for this by an extended extraction process taking place slowly over time, but the final product still lacks some of the flavor profile that the coffee would have if it were brewed hot. Cold brew typically uses double the amount of coffee as another way to compensate for the lack of full extraction.
The Japanese method attempts to solve this problem by brewing with hot water. The problem is that this method only uses half the water, so you wouldn't have the same extraction as with a hot coffee. However, most of the extraction takes place in the beginning stages of brewing, so you will have extraction that comes close (19% rather than 21 or 22%). The science of iced coffee is still being considered by the best minds in the coffee industry, so improvements on the methods are forthcoming.
Cold brew does have some benefits over simply icing hot coffee. Those same compounds in hot coffee turn against the coffee flavor over time. Oils oxidize and acids degrade from Chlorogenic acid into Quinic and Caffeic acid when temperatures drop, making the coffee bitter and sour. Cold brewing avoids some of these negative effects. The Japanese method for iced coffee does as well.
Cold brewed coffee has an appealing taste to a large audience and often very powerful punch that satisfies the thirsty crave for coffee during hot months. Since more coffee is often used for the cold brewing process, it is loaded with caffeine. Since acidity isn't a notable characteristic of cold brewed coffee, the flavor profile is appealing to those looking for a chocolaty, caramel flavor profile. Cold brew has been growing in popularity over the past couple of years and will probably only continue to grow as coffee companies large and small continue to put their cold brews on the market.
One key part of cold brew that should never be neglected is freshness! Sure, you can get a bottle of cold brew at the super market, but the chances of it being fresh aren't very good. Cold brew is subject to oxidation from the very beginning of the brewing process, so after only a couple of days, the flavor quality of cold brew declines rapidly. For optimal flavor, we consider the best option to buy a growler of fresh cold brew and consuming it 1-3 days after purchase. We are now retailing Toddy Cold Brew systems for those who are interested in trying out their own cold brew. Here's the Toddy instruction booklet. We also retail 32 oz growlers that can be refilled for a very reasonable price with our 24 hour cold brew Toddy (immersion) or 8 hour Kyoto cold brew. The best part, we use some of the finest coffee around and you can get it fresh.