Cold brew marketing promises a smoother, less acidic, naturally sweeter cup. The lab results half-agree — and the interesting half is which half. The thesis from extraction chemistry: cold brew differs from hot brew less in pH than in which acids and antioxidants make the trip — time compensates for temperature selectively, not completely.

What the measurements show

Across origins and roasts, cold and hot brews land at remarkably similar pH (4.85–5.13 in one six-origin study, Rao & Fuller, PMC). But pH isn’t the whole acidity story: hot brews carry significantly higher titratable acidity — more total acid molecules, including larger, temperature-dependent ones — and higher antioxidant capacity. A roast-interaction study (Rao, Fuller & Grim, 2020) found cold brew’s antioxidant extraction fades as roast darkens, while hot brew holds steady; the bean matrix simply surrenders different compounds to cold water, especially heavy melanoidins.

Kinetics research (Fuller & Rao, Scientific Reports) adds the timetable: caffeine and chlorogenic acid reach equilibrium in ~400 minutes (under 7 hours), not the 12–24 hours recipes suggest — and grind size barely matters at these timescales, since hours of steeping erase diffusion differences that dominate espresso’s seconds. Longer steeping past equilibrium mostly extracts slow, harsh catechol oligomers: over-brewed cold brew turns bitter, not stronger.

The counterpoint: perception isn’t titration

Drinkers do taste cold brew as smoother — partly real (fewer bitter acids, lower TDS), partly contextual (served cold, often diluted, expectations set by marketing). And “less acidic” cuts both ways: acids carry brightness and origin character; cold brew’s softness can read as flatness with delicate washed coffees. Light roasts keep the most antioxidants in both methods — roast matters more than method for chemistry.

Takeaway

Brew 7–10 hours coarse at room temp (not 24), favor medium-light roasts for character, and dilute to taste — concentrate is a choice, not a requirement. Cold brew isn’t better chemistry. It’s different chemistry: gentler acids, quieter aromatics, patience doing what heat usually does.