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All recipes call for simmering a dish if you wish to reduce. I know that if for example if I wish to reduce wine, it will take me double the time or even more if I simmer instead of just cranking the heat up to a boil. But there must be a reason for this - what is that? There is only a 6c difference between a simmer and a boil.

I also presume boiling is more permissive in some cases than others, so an ability to distinguish the importance of simmering is necessary to know when you can crank the heat up to save time.

Bar Akiva
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2 Answers2

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There's another reason for not boiling liquids, besides the possibility of making a mess (boiling over) or ruining it (scorching, etc.).

You actually reduce the amount of flavor by boiling. As Kenji explains on Serious Eats :

But here's the deal: when simmering, water is not the only thing escaping. Ever notice how when you come home to a pot of sauce simmering on the stovetop or perhaps a beautiful pot roast braising in the oven, your entire home smells of it?

Guess what: if those flavorful aromatic compounds are reaching your nose, it means they are leaving the pot.

So ... if the only goal was to make there be less liquid, boiling's fine. But if you actually want to concentrate the flavors, you want a slow simmer.

The article also goes into more details about reducing alcohol, and some problems with boiling tomato sauce (which I believe applies to most pectin & other hydrocolloid thickened sauces).

Community
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Joe
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As you pointed out, liquids reduce a lot faster when you crank up the heat compared to when you leave it at a gentle simmer. The reason is simply that you're introducing a lot more thermal energy into the liquid when you crank it up to the max. Once the liquid reaches the boiling point, any extra heat you provide will be canceled out by the cooling effect of evaporation. So adding more heat to a boiling liquid causes the evaporation rate to go up while the temperature stays the same.

As for the reason to use a simmer, that's going to depend on the liquid. Some liquids handle heat a lot better than others. A simmer is nice to avoid burning, curdling, boiling over, etc. But if you're reducing something that can take the heat, feel free to crank it up.

Liquids that shouldn't be boiled include: anything with a lot of milk (can scorch or boil over), anything with a lot of starch (can boil over), emulsified sauces (can break), chocolate (can scorch), oil (very hazardous when boiling), and custard (can curdle). Some people also prefer not to boil stock because it can become cloudy, but that doesn't necessarily ruin it.

mrog
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