How you open the pressure cooker is actually an important part of the recipe. Let’s review the four pressure cooker opening methods and how we’ve used them in this series so far. Then, we’re going to take a look at what is actually going on inside.
The Normal Release, also known as Quick-release, is when the pressure is released from the cooker all at once using the valve. We used this opening method for the hot water test, and the first recipe in this series (the Cauliflower Potato Mash).
The Slow Normal opening is when the pressure is released from the valve slooowly. Or, if that is not possible, in short bursts 10 seconds apart to keep foam and food from spraying out of the valve. We used that when we quick-soaked beans.
In the rice lesson, we use the 10-minute Natural Release. When cooking was finished we let the rice sit in the left-over heat and steam of the pressure cooker to continue cooking for 10 minutes. After that, if there was any residual pressure left that can be released.
And, finally, we used the Natural Release with the Black Bean Lentil Chili where we let the pressure cooker do its own thing until the pressure has completely dissipated naturally.
The benefits of each opening method will become clear when we take a closer look at exactly what is going on inside the pressure cooker when it’s reaching, maintaining and releasing pressure.
To do that, we have to first look at what happens when water boils without pressure.
When boiling conventionally, the water is heated, bubbles form, break to the surface and release vapor – steam! This is the exact same thing that happens in the pressure cooker before it starts to build pressure.
Except in a pressure cooker, when the valve closes the steam is trapped inside the pressure cooker. It pushes in all directions, including down onto the food and the cooking liquid. It is this steam that provides the physical push that is the pressure of pressure cooking.
This force is so strong that the bubbles from the boiling cannot rise and break to the surface, anymore. This is one of the unique properties of pressure cooking! The food is cooked at very high temperatures but, at the same time, it is not moving much. It’s not being tossed and jostled as it would have been boiling in an open pot.
So, any guesses what happens when pressure is released?
Well.. when steam is released from the valve the pressure inside decreases and the force that was suppressing the bubbles inside the pressure cooker is no longer there. And there is a lot of heat that wants to come out from the food and cooking liquid. So, this triggers a lot of movement and churning inside the pressure cooker. A lot more than from a pot of water at a rolling boil.
So, does it make sense now why some foods are torn to shreds or spray out of the valve when the wrong opening method is used?
Don’t worry, you can control the force of this “churn” by using different opening methods. Let’s re-visit the opening methods, this time taking a peek at what’s going on inside to understand which method is best for what kind of food, and why.
The Normal Pressure Release takes the least amount of time but also triggers the most movement inside the pressure cooker. This release method is best used for quick-cooking foods like vegetables, fish and eggs. It’s notorious for splashing things on the underside of the lid and gunking up the valves so you only want to use it with large pieces and NOT for thick recipes or those containing rice, grains or beans.
The Slow Normal Pressure Release can be used to hurry things along when it’s just not practical or convenient to wait for the full Natural Release. For example, when quick-soaking beans or opening the pressure cooker for an intermediate step to add ingredients. There is SOME movement but releasing pressure slowly or in spurts gives the foam inside a chance to settle down before it reaches the safety valves in the lid.
The 10-minute Natural Pressure Release is mostly used with rice and grains. When cooking time is up, the next 10 minutes, during which the heat is off and the pressure is not released, the food is absorbing the rest of the cooking liquid. So, if you did things right – like following the hip grain to liquid ratio – 10 minutes later there will be little no liquid left in the pressure cooker to actually bubble, boil, or spray out of the valve.
Finally, the Natural Pressure Release has the least amount of movement. Think of it as a very slow simmer. This opening method preserves the most flavor, too. That’s because a majority of the steam is not sprayed out of the valve; but, it hits the lid, condenses, and drips back into the recipe. It also gives the food time to come down in temperature from “pressure” to “boiling” – this is especially important for meats (I’ll explain why in detail in the next lesson).
OK, so I just threw A LOT of information your way. Don’t worry, you don’t have to remember it all! The hip pressure cooking time chart includes a column with my recommended opening method and its noted in all of my cookbook and website recipes, too.