Topic Hub

Coffee Science

Coffee is one of the most chemically complex beverages in the world, with over 1,000 identified aroma compounds. This hub connects resources on extraction chemistry, roasting reactions, water chemistry, and the physics of brewing.

Curated by Keith E. Lyons·Author of The Complete World of Coffee

Overview

The science of coffee spans chemistry, physics, biology, and sensory science. At its core, brewing is a solvent extraction process: hot water dissolves soluble compounds from ground coffee. The key variables are grind size, water temperature, contact time, coffee-to-water ratio, and water chemistry.

Roasting drives the Maillard reaction and caramelization, creating hundreds of new compounds from the green coffee's sugars, amino acids, and acids. The roast profile determines which flavors are developed and which are lost.

Water makes up 98 percent of a brewed cup, and its mineral content dramatically affects extraction. Calcium and magnesium facilitate extraction of flavor compounds, while bicarbonate acts as a buffer that can mute acidity. Understanding water chemistry is one of the most impactful things a brewer can learn.