New research from UC Davis challenges conventional wisdom about cold brew coffee, suggesting that traditional long steep times may not be as critical as once thought—while roast level plays the biggest role in flavor.

Published in Scientific Reports, the study examined how brew time, temperature, and roast level affect the sensory qualities of full-immersion cold brew. Surprisingly, shorter steep times (such as 8 hours instead of 24) could produce similar flavors, potentially streamlining production for commercial coffee brands.

“Brew time had the least impact on sensory differences compared to roast level and temperature,” said lead researcher Jiexin (Jessie) Liang.

Roast Level Drives Flavor Most

The study found that roast level was the strongest factor in determining taste, followed by temperature, with brew time having the least influence. Researchers used light and medium-dark roast blends of Salvadoran and Nicaraguan arabica coffee, brewed at three temperatures (4°C, 22°C, and 92°C) and five time intervals—ranging from flash-chilled hot brew to extended cold brew.

A trained sensory panel evaluated 30 samples for acidity, pH, and flavor. The results showed that roast level dictated the most dramatic flavor shifts, with medium-dark roasts developing more bitter, burnt notes over time in cold and room-temperature brews, while light roasts retained brighter, citrusy qualities—especially at lower temperatures.

Key Takeaways for Brewers

• Shorter steep times may be just as effective as long ones for certain flavor profiles.
• Roast level is the biggest flavor driver, so coffee selection matters more than exact brewing parameters.
• Temperature plays a secondary role, with cold vs. hot brewing methods producing distinct but not necessarily “better” results.

The study, funded by Toddy LLC and supported by the Coffee Science Foundation, confirms there’s no single “right” way to make cold brew—only different paths to different flavors.

For coffee professionals, this means greater flexibility in production without sacrificing quality—as long as the roast is right.