ASANTE KNOWLEDGE

Water for Coffee: the invisible chemistry behind every cup

We talk a lot about origin, roast, and grind — but we forget the ingredient that makes up almost everything we drink. A cup of filtered coffee is about 98% water, and an espresso is around 90%. If the water is wrong, not even the best bean in the world can save it. This is the guide that explains what is dissolved in your water and why that determines the flavour.

Why water is the main ingredient

Soluble coffee — the acids, sugars, aromatic compounds — only passes from bean to cup because water dissolves and transports it. The mineral composition of water determines what it can extract and how efficiently. Two different waters, with the same coffee, the same grind, and the same recipe, produce cups that taste distinctly different. It's not magic: it's dissolution chemistry.

Two minerals do the heavy lifting. Magnesium tends to eagerly extract the most aromatic and acidic compounds — it enhances fruity acidity and complexity. Calcium extracts more gently and is associated with body and a rounder mouthfeel. The balance between the two shapes the cup profile.

Bicarbonate is the brake. Alkalinity (especially dissolved bicarbonate) acts as a buffer: it neutralizes coffee acids. A little protects against an overly sour cup; in excess, it flattens the coffee, leaving it dull, soft, and lifeless. It is the silent cause of many "flat" coffees made with hard tap water.

Essential vocabulary

Water TDS (total dissolved solids)

This is the total amount of dissolved minerals in water, measured in milligrams per liter (mg/L) or ppm. Do not confuse it with coffee TDS (the concentration of the prepared beverage): here we are talking about the starting point, the water before it touches the bean. Distilled water has near-zero TDS and extracts poorly; overly mineralized water extracts unevenly and encrusts equipment.