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🍲 The pressure cooker: raising the boiling point on purpose

An open pot is pinned at 100°C. A locked lid stacks extra atmosphere on the water, and dinner is what that extra heat can do.

5
lessons
~20 min
to learn
🔬 Science
subject
Adults
level
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What you’ll learn

  1. The pot that cannot climbSee boiling point as vapour pressure matching the air, and an open pot as pinned at 100°C at sea level.Extra heat in an open pot becomes steam, not a hotter stew. Altitude lowers that ceiling. Collagen is still waiting past it.
  2. Papin raises the ceilingConnect Papin's digester to gauge pressure, and read 10 and 15 psi as 116°C and 121°C.Raise the pressure sitting on water and the boil climbs. Stovetop 15 psi is about 121°C. Many electric High settings are closer to 116.
  3. What twenty-one degrees buySeparate hotter hydrolysis, stillness, and the lack of reduction as three different gifts of the sealed pot.Collagen and beans fail faster at 116–121°C. Stock can stay clear because it never rolls. Flavour may taste thin because nothing evaporated.
  4. How the pot holds the skyName regulator, lock, gasket and liquid, and explain why canners must vent and why low-acid food needs 240°F.Air in the headspace makes a gauge lie. C. botulinum spores survive a rolling boil. A Tuesday multi-cooker dinner is not a canning process.
  5. Tonight the valve talksHear the regulator as a temperature, choose a release for the food, and go run a water test.Altitude is a lower-pressure cooker you already own. Vent beans slowly. Tonight watch the lock pin rise.

Questions this course answers

In an open pot at sea level, why does water stop getting hotter once it boils?

Boiling point is the temperature at which vapour pressure equals surrounding pressure. In an open pot that is 100°C at sea level. Further heat makes more steam.

What has to match the surrounding pressure before water can boil?

Raise the pressure sitting on the liquid and you must raise the temperature until vapour pressure catches up. That is the whole cooker.

At about 15 psi gauge, roughly what temperature does water boil inside a cooker?

Fifteen pounds gauge is about one extra atmosphere. Saturated steam there sits near 121°C / 250°F, the classic stovetop and autoclave number.

Match each kitchen number to the boil it actually buys

NCHFP writes 240°F at 10.5 pounds in pure steam. Instant Pot lists High at 10.2–11.6 psi. Fifteen pounds is the hotter classic weight.

Put a safe cooker cycle in the order the physics requires

No liquid, no steam. Air left in a canner makes the gauge lie. The clock starts at pressure. The lid waits until the lock drops.

In your own words, why can a rolling boil not make low-acid green beans safe to can?

USDA FSIS and the CDC agree: boiling-water canners do not protect low-acid food. Electric multi-cookers are not a substitute unless they are tested canners.

Grounded in trusted sources

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