Releasing Pressure Part 1

How to release pressure naturally. (And a bit on why you might want to leave your cooker closed for longer than it takes to drop pressure too).

I promised last week that my next subject would be an in depth look at how to release pressure. Pressure cooker pressure, that is, not any kind of life pressure (although I think pressure cookers can help with the life pressures too. A bit).

So, pressure cooker pressure. Regardless of the type of pressure cooker you have, there are 2 main ways to release pressure as well as combinations of the two. They are:

Natural Pressure Release (known henceforth as NPR)

Fast Pressure Release (Some people use Quick Pressure Release, or QPR*, but I can’t see that acronym without thinking about football, corrupt councils and Death to Skylarks – it’s a local thing -  so I use FPR).

The type of pressure release you use depends mainly on what your recipe tells you to use – and of course once you understand which method to use, when, you will find you will easily be able to choose the right one when adapting conventional recipes or just making things up on the spot. But to give you a quick idea – you use FPR when you want short, precise cooking times – for example, when cooking something that can easily overcook if you leave it, such as green vegetables, pasta or rice. You use NPR for everything that doesn’t need such a precise cooking time OR because the time it takes to NPR is factored into the cooking time. I’m going to talk about FPR next week as there is quite a lot to say about it, this week I am focussing on NPR.

There are a lot of recipes which factor in NPR into the cooking time. This makes a great deal of sense when you think about it. When you remove a pressure cooker from the heat, it has to come down from a temperature of roughly 118-120C. So it will take minutes to come down to boiling point, let alone the kind of temperature you would expect from a slow simmer, or even a slow cooker. This type of cooking is good for a couple of reasons. Firstly if you are cooking meat, it gives it time to relax and means a much more tender result. The other main reason is one of cost and sustainability – this stage of the cooking is taking place off the heat and therefore using zero fuel.

As we talked about last week, the main 3 stages of pressure cooking are 1) the time it takes to come up to pressure, 2) the time it cooks at pressure and then 3) the time it takes to come down from pressure. To be as sustainable and fuel efficient as possible, you want to keep 1 and 2 to a minimum and NPR can help with that.  I am experimenting to push this as far as possible, with excellent results so far. The pressure cooker in effect turns into a souped up hay box** because it stays hot for a very long time once it is taken off the heat - as long as you don’t take off the lid. In a nutshell, the cooking continues in that residual heat until it has cooled down. While I have always factored NPR into my cooking times, I am now pushing it beyond the time when the cooker has actually dropped pressure, with excellent results. It has so far revolutionised how I cook beans and stock, and I fully expect to extend this as I continue to experiment.

This might seem obvious – it is, but it feels like a progression in how I use my pressure cookers. I had always taken advantage of the fact that pressure cookers stay hot for a very long time. For example, every Thursday night I have to take Adam (my son) to a class, just at the time I would normally be making dinner. So that night we usually eat something that I can cook at pressure, then leave off the heat until I get back – an hour and a half later it is still, amazingly piping hot. It didn’t occur to me for a long time that even though it was off the heat it was still cooking as well as keeping warm – and perfectly safely too, as there is no heat source involved. As soon as I made that connection – realised that every time I factored NPR into a recipe I was shaving off the amount of fuel I was using – it made sense to work on how far I could use it. Of course, there is a trade off – sometimes you just need something fast and might not want to wait an extra how ever long. But I like flexibility and being able to give people as many options on how to cook something as possible.

NPR is an option when using an electric pressure cooker as well, but of course the power is still on. You also have a keep warm function, which kicks in after natural pressure release if you want it to. But again, as the pot stays hot for a very long time – and actually is more insulated than a stove top – you don’t really need the keep warm function for at least an hour, probably much longer, so you may as well just switch the whole thing off.

The important thing to remember about all of this is that if you want your pressure cooker to continue to cook and keep your food hot for longer than it takes for the pressure to drop, you mustn’t take off the lid!

The other thing to mention about NPR is that that you will sometimes see an instruction in a recipe method, telling you to, for example, “NPR for 5 minutes, then fast release the remaining pressure.” This is combining NPR and FPR. More on this next week too.

And just to reiterate – NPR could not be easier – all you are doing is taking your pressure cooker off the heat and waiting for the pressure gauge to drop. Some pressure cookers do this gradually, some drop suddenly. You will also realise that you can again move the lid/handle because the seal will have relaxed.

*QPR: Many of you will know that QPR stands for Queens Park Rangers, a London football team. My council tried to give a piece of Metropolitan Open Land very close to where I live to QPR who intended to bring in around 50,000 tonnes of landfill to create a training ground – astroturf, floodlights, the lot. But in the meantime the site rewilded, long dormant acid grassland seeds germinated and the site attracted all kinds of rare species including skylarks. QPR eventually gave up, but the council are still determined to use a portion of the site for a sports ground again (there are good reasons it was neglected in the first place). More astroturf, bye bye skylarks. The site is Warren Farm:

https://www.warrenfarmnaturereserve.co.uk/

You may have seen photos of it on my Instagram - here’s one of fox and crow on a frosty February morning.

**Hayboxes. These are an old fashioned, sustainable slow cooker, perfect for anything you would put in a low oven. It is exactly as it sounds – a box lined with hay. You heat up your casserole, put it in the haybox, make sure it is well covered, then leave to cook for several hours. I first heard about them when I was a child and reading The Children Who Lived in a Barn. There are now all kinds of versions of these around, using different materials – search online and you will fall down a rabbit hole. Someone was telling me the other day about a community led initiative that involved providing people with the materials and know how to make a fabric version, as well as showing them how to use them. The details elude me, so if it was you who was telling me about this, please let me know? Thanks!