Reduction

Reduction is the process of simmering or boiling a liquid so that water evaporates and the remaining liquid becomes more concentrated in flavour and often thicker. The term also refers to the concentrated liquid produced by this process. Reduction is a fundamental technique in sauce making.

How reduction works

As water evaporates, dissolved flavour compounds, sugars, acids and salt become more concentrated. The final texture depends on the liquid’s composition, the amount of evaporation and any gelatin, starch or other thickening components present.

Common culinary examples

• Reducing red wine and aromatics for a Bordelaise-style sauce.
• Reducing shallot and vinegar mixtures for Béarnaise or other sauces.
• Reducing stock to a concentrated glaze or glace.
• Reducing fruit purées, juices or cooking liquids for a concentrated finish.

Technique

Use a pan with enough surface area for the desired evaporation rate and maintain a controlled simmer. Stir when needed to prevent scorching, especially as the liquid thickens.

Chef’s tip: Season carefully toward the end. Salt and acidity can become more pronounced as water evaporates, so a sauce that tastes balanced before reduction may become too salty or sharp afterward.

Key distinction: Reduction concentrates a liquid by evaporation; thickening with a roux or starch adds a thickening agent rather than relying only on water loss.