Brewing · 10 min read
Cold brew coffee has evolved from a niche curiosity to a global category worth billions. Its appeal is intuitive — smooth, sweet, low-acid, refreshing — but the science behind these qualities is more nuanced than most drinkers realize.
The central principle of cold brew is kinetic: chemical reactions slow down at lower temperatures. The Arrhenius equation tells us that for every ten-degree Celsius decrease in temperature, reaction rates roughly halve. Brewing at room temperature instead of near-boiling therefore requires dramatically more time. Where a hot pour-over extracts in three to four minutes, cold brew typically steeps for 12 to 24 hours.
Chlorogenic acids, the primary source of perceived acidity and bitterness in hot-brewed coffee, are temperature-dependent in their extraction. Studies have demonstrated that cold brew extracts 30 to 50 percent fewer of these acids than hot brew methods. This explains the characteristic smoothness: fewer acidic compounds means a higher pH, reduced bitterness, and a perception of sweetness.
The role of lipids and oils in cold brew is underappreciated. Hot water is a far more effective solvent for coffee oils, which carry aromatic compounds and contribute to body. Cold brew extracts fewer oils, resulting in a cleaner but thinner body. Filtration method matters enormously: paper-filtered cold brew is almost oil-free, while metal-mesh filtered cold brew retains more oils.
Nitrogen infusion has added another dimension. Nitro cold brew produces a creamy, cascading pour reminiscent of a stout beer. Nitrogen bubbles are smaller than carbon dioxide bubbles, creating silkier texture. The creamy mouthfeel enhances sweetness and suppresses bitterness. From a scientific standpoint, nitro cold brew is proof that flavor is not merely chemical but deeply physical.