Converting Pressure Cooker recipes for cookers with lower PSI

Question

Most of the recipes I'm using (mainly Modernist; stocks, caramelized vegetables, confit) suggest cooking at 15psi. My pressure cooker has two settings 12psi and 7psi. I've always had success just using 12psi in recipes where it says 15psi. However recently the 12psi mode has broken on my PC. I can now only cook at 7psi. How can I convert my recipes to use this lower pressure?

For example I would cook a chicken stock at 12psi for 90mins, I presume at 7psi the cooking time would need to be longer but by how much?

Answer 1

Here's a table that claims to give time equivalencies for cooking at different pressures. (This is from a website dedicated to pressure cooking information, so it's pretty standard.)

It doesn't go down to 7 psi, declaring 8 psi to be the lowest acceptable pressure, but the time increase for 8 psi is listed as 47%. Therefore, I'd try increasing the times by 50% or a little more than the recipe states.

Keep in mind that although this chart looks precise, it's really not. Pressure cooking at lower temperatures will significantly change extraction rates for various flavor components in you stock, for example. Some things will still cook out at roughly the same rate, while others will take a lot longer at the lower temperature. I'd guess that increasing cooking times by about 50% is a good place to start, but you may find that's too little or too much, or even that the result in some recipes just isn't right. (Sometimes boiling for too long alters flavors or textures in undesirable ways, so the fast cook in a high-pressure pot may be okay, but a slower longer cook may end up with just a boiled "overcooked" result.)

Answer 2

There's actually very little difference in cooking times between 15 and 12 psi. So if you get that mode working again, you would only need to make small adjustments.

Here is a pressure cooking time table by PSI (use the cooking times in the "Electric Pressure Cooker 10-12 PSI" column even if your pressure cooker is stovetop) in the chart here - as you can see the difference is a matter of minutes for most foods.

As for the conversion between "high" and "low" pressure cooking times it's pretty easy.

• High Pressure cooks foods three times as fast as conventional cooking
• Low Pressure (your psi) cooks food twice as fast as conventional cooking

So, just multiply the given pressure cooking time x3 and then divide it in half. For example, Modernist Cuisine's' 12psi for 90 minutes would be equivalent of 270 minutes (90x3) of conventional no-pressure cooking time. The low pressure cooking time equivalent is 135 minutes (270/2).

So to figure out the cooking time at "low pressure" for a "high pressure" increase the recommended time by 50% or just multiply the high pressure cooking time by 1.5.