The Science of Cold Brew: Why Temperature Changes Everything

The Basic Science

Coffee extraction is a chemical process. When water meets ground coffee, it dissolves and extracts hundreds of compounds — acids, sugars, oils, and bitter alkaloids — that collectively create what we perceive as flavor. The rate and selectivity of this extraction depend heavily on two variables: temperature and time.

Hot water extracts coffee compounds quickly. A typical espresso shot takes 25 to 30 seconds. A pour-over takes three to four minutes. Drip coffee takes five to six. At temperatures between 90 and 96 degrees Celsius, water is aggressive — it pulls out a wide spectrum of compounds rapidly, including the bright acids and bitter elements that give hot coffee its characteristic bite.

Cold water works differently. At temperatures between 2 and 20 degrees Celsius, extraction slows dramatically. Compounds that dissolve easily in hot water — particularly chlorogenic acids and certain bitter alkaloids — are extracted at much lower rates. The result is a fundamentally different chemical profile in the cup.

Why Cold Brew Tastes Smoother

The most noticeable difference between cold brew and hot-brewed coffee is acidity. Studies have shown that cold brew contains 60 to 70 percent less titratable acidity than hot coffee brewed from the same beans. For people who find hot coffee harsh on their stomachs, this reduced acidity can be a genuine quality-of-life improvement.

But reduced acidity does not mean reduced flavor. What cold brew lacks in brightness, it makes up for in body and sweetness. The slow extraction preferentially dissolves sugars and oils while leaving behind many of the harsher compounds. The resulting drink is smooth, naturally sweet, and has a syrupy mouthfeel that hot coffee rarely achieves.

The flavor profile also shifts. Where a hot-brewed Ethiopian coffee might taste of bright citrus and jasmine, the same beans cold-brewed might present as dark chocolate, stone fruit, and brown sugar. Neither is better — they are simply different expressions of the same raw material.

Cold Brew vs. Iced Coffee: The Actual Difference

This is one of the most common points of confusion. Iced coffee and cold brew are not the same thing.

Iced coffee is hot-brewed coffee that has been cooled down and poured over ice. It retains the full chemical profile of hot extraction — bright acids, bitter compounds, and all. The ice dilutes it, which can make it taste watery if the original brew is not concentrated enough.

Cold brew is never heated. Coffee grounds are steeped in cold or room-temperature water for 12 to 24 hours, then filtered. Because the extraction happens slowly at low temperatures, the chemical composition is different from the start. Cold brew is typically brewed as a concentrate that is diluted with water or milk before serving.

Neither method is objectively superior. If you love the bright, snappy flavor of a well-made iced pour-over, that is valid. If you prefer the smooth, chocolatey richness of cold brew, that is equally valid. The point is that they are different drinks, not different preparations of the same drink.

Our Cold Brew Process at Bean Brew

At Bean Brew & Beyond, we brew our cold brew using a coarse grind of our house blend, steeped in filtered water at 4 degrees Celsius for 18 hours. We tested steep times ranging from 12 to 24 hours before settling on 18 as the sweet spot — long enough to achieve full flavor development without extracting the astringent tannins that emerge in longer steeps.

The concentrate is filtered twice — once through a metal mesh to remove grounds and once through a paper filter to remove fine sediment and oils. This produces a clean, bright cold brew that works beautifully on its own or as the base for our flavored cold brew preparations.

Our cold brew menu includes both straight cold brew and flavored options like the Pistachio Cold Brew, where the concentrate is finished with house-made pistachio cream. The naturally sweet, low-acid character of our cold brew pairs especially well with nut-based flavors.

Making Cold Brew at Home

Cold brew is one of the easiest coffee preparations to make at home. You need coarsely ground coffee, cold filtered water, and patience. Use a ratio of 1 gram of coffee to 8 grams of water (or roughly 1 cup of grounds to 4 cups of water), steep in the refrigerator for 16 to 20 hours, and strain through a fine-mesh sieve or cheesecloth. The resulting concentrate can be diluted 1:1 with water or milk and stored in the refrigerator for up to two weeks.