Restaurant green beans are bright green and crisp-tender, even when served an hour after they were cooked. The trick is blanching and shocking.
Key idea
Blanch: cook vegetables briefly in a large pot of well-salted, rapidly boiling water. Shock: move them at once into ice water to stop the cooking and set the color. Drain well. Later, they need only a quick reheat in butter or a hot pan.
- Use plenty of water (many cooks use about a gallon per pound) so the boil comes back fast.
- Cook in small batches; leave the lid off for green vegetables.
- Taste one: it should bend and still have a little bite.
- Blanching also loosens skins (tomatoes, peaches, almonds) and is the first step before freezing many vegetables.
Why it works
Green comes from chlorophyll. Long cooking, a lid that traps acids from the vegetable, or acid in the water turns it olive-drab. Fast cooking in lots of water, then ice, keeps it bright.
Worked example: Water
About how much water for 3 pounds of green beans at a gallon per pound?
- $3 \times 1 = 3$ gallons.
Answer: About 3 gallons (or cook in batches).
Common mistake
Blanching a big pile at once. The water stops boiling, the vegetables stew slowly, and they turn dull.
Practice at home
- Blanch two batches of green beans: one shocked in ice water, one left to cool on a plate. Compare color and crunch after 30 minutes.
- Peel tomatoes: score an X, blanch 20 to 30 seconds, shock, and slip off the skins.
In Meal Prep
- Recipes: vegetable sides that use blanching