Cold brew methods are anything but new – and yet they exert a certain fascination. The cold brew method was likely invented by Dutch sailors in the 16th century to brew coffee on the high seas without a heat source.
But the exact details are unknown. What's far more interesting is the renaissance of this method. Many coffee lovers, as well as scientists, are intrigued by the significant sensory differences compared to hot brewed coffees. The key to the difference between cold brew and hot brewing methods (such as portafilter, moka pot, filter brewing, etc.) most likely lies in the volatility of the aromas and the shifted solubility limits of the coffee components.
The high brewing temperature of the water in the aforementioned hot extraction methods very efficiently dissolves volatile aromas as well as non-volatile solids of the ground coffee. The dissolved and non-volatile substances, such as caffeine, citric acid, or larger carbohydrate fragments, remain unchanged in the cup after extraction. The volatile aromatic compounds, however, are a double-edged sword: while the hot water temperatures help to extract the aromas very effectively, they also cause them to evaporate rapidly into the gaseous phase above the cup. This creates the wonderful aroma of coffee, but it also means that the aroma molecules will never return to the cup. An irreversible and fleeting pleasure – a real dilemma, one might think.
This is where the cold brew method comes in. This method favors very low temperatures between 0 and 7°C. This means the extraction time is longer to fully dissolve the desired components of the ground coffee. But the advantage is that the extracted aromas remain more in the extract and are not expelled as quickly. The cold brew method requires considerably more patience, but at the same time, the aromas don't dissipate as quickly into the atmosphere above the cup. In contrast, studies show that with the non-volatile alkaloid caffeine, equilibrium is reached after 6 to 7 hours of extraction – meaning the maximum caffeine extraction through solid-liquid extraction with water.
Cold brews are therefore veritable caffeine bombs. By comparison, a cup of espresso (25 mL) contains approximately 100 mg of caffeine (depending on the variety), while a serving of cold brew (200 mL) contains approximately 250 mg. Additionally, cold brews don't age as quickly as hot-brewed coffee extracts. Due to the high temperatures, there is a high oxidation rate in hot-brewed coffee; that is, the oxygen dissolved in and surrounding the liquid reacts with the flavor compounds (=aging) more quickly than when the temperature is kept low. Thus, cold brews offer several advantages, in addition to the refreshing sensation they provide on hot summer days.
Original article
"The Power of Delay: Cold Brew" | A SLIGHTLY DIFFERENT WAY TO PREPARE COFFEE