What is cold brew coffee?

Cold brew is coffee made by steeping coarsely ground beans in room-temperature or chilled water for 12 to 24 hours, then filtering. Cold extraction produces a naturally sweet, low-acid and very low-bitter cup because the acidic and bitter compounds stay largely insoluble in cold water.

Contrary to a common belief, cold brew is not a recent invention of the New York specialty scene. The oldest documented trace is Japanese, under the name 'Kyoto-style cold brew' or 'Dutch coffee', a slow cold drip method dating to the 17th century, when Dutch merchants in Nagasaki likely introduced the technique to Dutch sailors. The modern immersion version took hold in American cafés around 2010-2012 and went global via chains like Stumptown.

The chemistry explains the cup profile. Cold extraction is dramatically slower than hot: it takes 12 to 24 hours at 4-20 °C to reach an extraction comparable to 4 minutes of French press at 93 °C. But the slowness is selective: chlorogenic acids (responsible for acidity and, when degraded, bitterness) are less soluble in cold water. A cold brew typically carries 60 to 70 % of the titratable acidity of a regular filter coffee. It is often easier on sensitive stomachs.

Caffeine content in cold brew is not intrinsically higher than hot; it is all about ratio. Cold brew recipes use more concentrated ratios (1:4 to 1:8 for a concentrate to dilute, 1:15 to 1:17 for ready-to-drink) because the liquid often serves as a base, cut afterward with water, ice or milk. A 1:4 concentrate can hit 200-300 mg of caffeine per 100 ml, two to three times a regular filter by volume, though it gets diluted.

In Belgium, cold brew appeared in specialty bars around 2014-2015, first in Brussels (Saint-Gilles, Ixelles) and then Ghent and Antwerp. It is especially popular from May to September iced, sometimes with maple syrup or cane sugar, or topped with oat milk for a cold brew latte. Nitro cold brew, cold brew infused with nitrogen for a Guinness-like creamy texture, landed in Belgium around 2017-2018.

Cold brew vs iced coffee vs Japanese iced

How does cold water reshape the chemistry of the cup?

Cold brew is coffee made by steeping coarsely ground beans in room-temperature or chilled water for 12 to 24 hours, then filtering. Cold extraction produces a naturally sweet, low-acid and very low-bitter cup because the acidic and bitter compounds stay largely insoluble in cold water.

Cold brew coffee is one of the most striking demonstrations of how fundamentally temperature affects extraction chemistry. In hot brewing, the heat provides the energy needed to dissolve a wide range of chemical compounds from the coffee grounds quickly and efficiently: acids, bitter alkaloids, melanoidins, aromatic esters, and sugars all dissolve in minutes at 90-95 °C. In cold brewing, the absence of heat means only the most soluble compounds, primarily larger sugars and mild acids, dissolve in the cold water over an extended period, while the heat-sensitive aromatic compounds that define the volatile character of a hot-brewed specialty coffee are never generated and the harsh bitter compounds that require elevated temperature for dissolution remain in the grounds. The result is a chemically simpler beverage that is sweeter, lower in bitterness, and naturally lower in perceived acidity than its hot-brewed equivalent.

The concentrated format of most cold brew recipes (1:4 to 1:7 coffee to water, producing a concentrate for dilution) is practical rather than driven by any quality consideration: it allows more efficient use of the refrigerator space during the steep and produces a shelf-stable concentrate that can be diluted on demand over several weeks. The diluted final drink (typically 1:1 concentrate to water or milk) reaches approximately the same strength as a standard hot-brewed cup. Cold brew retains good freshness refrigerated for up to two weeks, far longer than hot-brewed coffee, making it a practical option for batch preparation in café or home contexts where daily brewing is inconvenient.

How do you brew and store a great cold brew at home?

For home cold brew, the most accessible method is the jar-and-strainer approach: 100g of coarsely ground coffee in a 1-litre jar with 600g of cold filtered water, stirred to saturate all grounds, covered and left at room temperature for 12-16 hours, then strained through cheesecloth or a paper filter into a clean jar. Refrigerate the strained concentrate immediately. The resulting concentrate will keep well for up to 14 days refrigerated. Dilute 1:1 with water or milk over ice for serving. For a smoother, cleaner concentrate, use the refrigerator steep method (longer time, 18-24 hours at 4 °C) which produces a less aromatic but more stable concentrate with less risk of over-fermentation in warm weather. Medium and dark roasts produce the most satisfying cold brew; very light roasts can produce a concentrate that is sharp rather than sweet due to the acid compounds that cold water does extract effectively.