Redução de Molho

Reducing a sauce by volume

A reduction is just a liquid simmered down so the water boils off and the flavor gets stronger. To find how far you've taken it, use 1 − Vfinal / Vinitial. Bring 1 L down to 500 mL and that's a 50% reduction, with the flavor (and most of the non-volatile solutes) now concentrated 2×. A classic demi-glace goes much further, pulling stock down to about 25% of where it started, a 4× concentration. One thing to watch above all else: salt does not evaporate. Season early and the finished sauce ends up 2–4× saltier than the liquid you began with, so hold off and salt to taste after reducing. Timing isn't fixed either. Water and alcohol leave first while the sugars caramelize toward the end, so ease the heat down as the sauce thickens or it'll scorch on the bottom of the pan.

Applications and context

It's a backbone technique in classical gastronomy. You'll find it behind meat jus, demi-glace, glace de viande, balsamic strawberry glaze, the wine reductions that go with steak, and concentrated tomato sauce. It also turns up a lot on MasterChef and in culinary school exams, because knowing how to reduce well is one of the things that marks a beginner from a more seasoned cook.

FAQ

How do I measure the final volume without dirtying another container? Dip a wooden skewer or chopstick into the pan before you start and note where the liquid hits it, then work out the target depth from the ratio and mark that point too.

Why is my sauce bitter after reducing? Usually you've taken it too far, or solids have scorched on the bottom. Wine tannins and concentrated sugars start turning bitter once you pass 75% reduction, so strain and stop sooner.

Can I reduce with the lid on? No. A lid traps the steam and evaporation basically stops. Keep it uncovered, and use a wide pan so there's plenty of surface for the steam to escape.