Pressure cooker basics: whistles, timings and what not to do

The pressure cooker is the most useful object in an Indian kitchen and the one most people use by inherited instruction rather than by understanding. Knowing what is actually happening makes the timings portable to anything.

The core fact: pressure raises the boiling point of water from 100°C to about 120°C. Food does not cook faster because of the pressure itself. It cooks faster because the water is hotter than water can normally get.

What a whistle actually is

A whistle is the weight lifting to release excess steam once the pressure inside reaches the design limit. It is a signal that the cooker is at full pressure, not a unit of time.

This is why whistle counts are unreliable between kitchens. On a high flame a cooker whistles more often without the food cooking any faster, since the temperature is capped by the weight, not the heat. Two whistles on a roaring flame is less cooking than two whistles on a medium one.

The reliable method: bring it to the first whistle on medium-high, then drop to low and count time rather than whistles.

First whistle, then low heat, then time it
More gas does not mean faster cooking once it is up to pressure
A cooker that whistles constantly is wasting water and steam

Timings that work

From the first whistle, on low heat. Adjust down slightly if your cooker is small.

Moong dal: 3 whistles, no soaking
Toor dal: 4 whistles, no soaking
Chana dal: 3 whistles after 30 minutes soaking
Rajma: 5 to 6 whistles, soaked overnight
Chickpeas: 6 whistles, soaked overnight
Whole urad: 8 whistles plus 20 minutes on low, soaked overnight
Rice: 2 whistles
Chicken on the bone: 3 whistles
Mutton: 6 to 7 whistles

Natural release versus quick release

Natural release means taking the cooker off the heat and letting the pressure fall on its own, which takes ten to fifteen minutes. Cooking continues throughout, and it is part of the timing rather than a wait afterwards.

Quick release means lifting the weight to let steam out fast. Use it for anything that overcooks easily: vegetables, rice, fish.

Use natural release for pulses and meat. Forcing pressure down on beans splits their skins, and on meat it makes it seize and toughen.

Never quick-release something foamy like dal without a lid over it, unless you want dal on the ceiling.

Safety, briefly and seriously

Do not fill past two-thirds, or half for anything that foams: dals, rice, pasta. The space above the food is where the steam lives.

Replace the gasket every year or so. A gasket that has gone hard leaks pressure, which shows up as food that will not cook and a cooker that whistles reluctantly.

Keep the vent pipe clear. Check it against the light every few months, and clean it if you can see anything in it. The safety valve is the backup, and a backup you are relying on regularly is not a backup.

Never force a lid. If it will not turn, there is still pressure inside, no matter what the pin appears to be doing.

What it is bad at

Anything that wants browning. A cooker is a wet environment, so you cannot get a proper sear once the lid is on. Brown the onions or the meat first, with the lid off, then pressurise.

Anything delicate. Fish, greens and most vegetables turn to mush.

Basmati for biryani, where you want long separate grains. Pressure breaks them. Boil and drain instead.