Saturday, 17 January 2009

A Pressure Primer

by Sadge, at Firesign Farm
Our grandmothers may not have had a microwave (or even electricity), but they probably did have a time- and energy-saving cooking device in their kitchens - the pressure cooker. By cooking under pressure, they could turn even the toughest old bird or economy cut of meat into a succulent fork-tender meal, or take dried, unsoaked, beans from pantry to table in minutes instead of hours. Ready to learn more?

Sealed up under pressure, with only a small, controlled amount of steam escaping, the heat inside builds up much higher than the boiling point of water. I learned first-hand the value of pressure cooking during the years I lived in Leadville, Colorado, at 10,250 ft (3,125m) altitude - almost two miles high. At that altitude, the lower temperature of boiling water (remember your old science classes?) meant I had to boil quartered potatoes for at least an hour - if I wasn't watching, the water would boil away before the spuds were edible. But in a pressure cooker, potatoes take 8 minutes at 15 psi (pounds per square inch) pressure, regardless of elevation. And since the cooking is via pressurized steam instead of boiling, and coupled with a shorter cooking time, the nutrients and flavor stay in the food, not the cooking water.

In my kitchen, I use both my old pressure cooker, often, and the larger canner, only at harvest time. Most vegetables, and all meats and fish, must be canned under pressure. With its domed lid, my pressure cooker will hold four narrow-mouth canning jars. So I use the cooker when canning small amounts. With its tall, narrow shape, the pressure canner also works as my waterbath canner for tomatoes and fruit. If you are deciding between getting one or the other, a cooker would probably be your best value, and should be your first foray "under pressure" (sorry, I couldn't resist working that in).

If you're buying new, of course all the parts and instructions will be included. But quite often cookers and canners can be found in thrift shops and garage sales, albeit maybe missing a part or two. Since both have similar pieces, let's look at what they need to function.

On top, a weight regulates the amount of steam allowed to escape, and thus how much pressure builds up. On cookers, the weight will have various ways to adjust the amount of pressure - mine has holes labeled 5, 10, and 15 psi pressure, to be set over the steam stem, my mom's has a sliding pop-up piece with three marks denoting pressures. (Canners, on the other hand, have both a weight for the steam stem and a gauge denoting pressure; regulation of pressure is by adjusting the heat underneath. I, or my co-writers, will address the specifics of canning, at length, in some other posts.)

Maybe old horror stories, of exploding cookers and soup all over the ceiling, have you nervous about using a pressure cooker. By taking care to not overfill a cooker, and making sure the steam stem isn't blocked, this should never be an issue. Pressure cooker lids twist down to seal over flanges, and have pressure-sensitive blocks that prevent opening the lid if it's still under pressure. But just to be on the safe side, pressure cookers also have a little release button built into the lid - designed to give way if pressure builds up to unsafe levels. These are meant to be a replaceable part, so if it's missing don't worry. Check here to find one, and most other parts, even from defunct companies.

Inside the cooker, a rubber gasket fits inside the lid. On old cookers and canners, this is the part most likely to be problematic. Check to make sure the gasket isn't cracked or broken, or get a replacement (see link above). If the cooker doesn't seal tight, too much steam will be lost. You run the risk of not enough pressure or running out of water before the food is done, and canned foods may not be safe. For some recipes, and for all canning, you'll need a rack inside that keeps items off the bottom of the cooker. This isn't as essential - you might be able to substitute canning rings or a steamer basket.

I hope this post inspires you to think about using a pressure cooker in your kitchen. The shorter cooking time saves energy, and might also allow you to make more home-cooked meals. I've written about cooking dry beans here on my blog, here is a good place for all kinds of pressure cooking info, or use a search engine to find more pressure cooker recipes.