+ Reply to thread
Results 1 to 7 of 7

Thread: Tell me about pressure cookers.

  1. #1
    Free Exy Cluricaun's avatar
    Registered
    Feb 2009
    Location
    Elgin IL
    Posts
    3,641

    Default Tell me about pressure cookers.

    So I was doing some dinner last night and it occured to me that I hate waiting for some things, like rice, to cook. Half an hour? I can have two meals done in that time that don't include rice. So then I got to thinking about pressure cookers. They're pretty much like the convection ovens of the stove top, yes? They cook things much faster? I love cooking, but I also love economy of motion and time. I don't just want them for rice, so I don't care about rice cookers, I'm at this point mostly interested in speeding up all sorts of things. Real home cooking in 10 minutes flat.

    Does anyone have one, use one, know anything useful about them? They seem kind of pricey to take a flyer on, which is good because I'd imagine that a cheap pressure cooker is nothing more than a Stove Bomb and we wouldn't want that. Normally.
    Hell, if I didn't do things just because they made me feel a bit ridiculous, I wouldn't have much of a social life. - Santo Rugger.

  2. #2
    Stegodon Jaglavak's avatar
    Registered
    Mar 2009
    Posts
    360

    Default

    Pressure cookers operate by raising the pressure above a pool of boiling water to about 15 PSI. Due to the nature of water, this raises the boiling point to about 250 F. Stuff cooks 50% to 70% faster than regular boiling.

    I had one years ago and want to buy another one. Features to look for:

    1) Spend the cash and get a stainless unit. The alternative is aluminum, the corrosion products of which aren't good for you and may be a contributing factor in Alzheimer's. Also aluminum is soft and very susceptible to acidic conditions.
    2) I had the kind with the twist-on lid and prefer that style. A modern refinement prevents accidentally opening the unit under pressure, in case you ever get that drunk and stupid.
    3) It's only good for recipes with a fair amount of liquids
    4) It takes 10 - 15 minutes to heat up so it's not worth the time for small quantities.

    However if you can live with that, a pressure cooker can make an old army boot into fork-tender picadillo amazingly fast. For roasts and stuff like that you can't beat them.

  3. #3
    Elephant Myglaren's avatar
    Registered
    Apr 2009
    Location
    Washington, UK.
    Posts
    944

    Default

    My wife used one for years and swore by it. Recently bought a new one.

    Do be careful though. My mother thought it would be a good idea to make rice pudding in one, rather than the couple of hours in the oven.
    My dad spent several hours scraping rice pudding off the kitchen ceiling, then had to redecorate the kitchen.

    She did have another disaster with it too, but I can't remember now what it was.

  4. #4
    Stegodon Jaglavak's avatar
    Registered
    Mar 2009
    Posts
    360

    Default

    Oh yeah. Two reasons that steam is way better than air at transfering heat are:

    1) When steam condenses, it's volume is reduced by a factor of about 1000. This creates a slight low pressure area which draws in more steam. So steam is actively pulled to any cold spots.

    2) When steam condenses it releases a boatload of heat. Like around 950 BTU/lb. That's about 10 times the heat required to take that same pound of water from near-freezing to boiling.

    Steam under pressure, even more so. However the primary advantage over conventional steaming is the increased temperature. Say your target food temperature is 170 F. Heat transfer through solids is directly related to temperature difference.

    Steam at 0 PSI: 212 F - 170 F = 42 F temperature difference.
    Steam at 15 PSI: 250 F - 170 F = 80 F temperature difference.

    Approximately double the heating power. That and the efficiency of steam heat transfer are the main reason why pressure cookers work so slick.
    Last edited by Jaglavak; 19 Oct 2009 at 04:46 PM.

  5. #5
    Stegodon Jaglavak's avatar
    Registered
    Mar 2009
    Posts
    360

    Default

    Oh yeah again. If you ever get into using your pressure cooker for canning, be aware of superheated liquid explosions. Scope out the column for Liquid Cycles, note the bottom row.

    It's surprisingly hard to find good links on the subject. Basically at the end of a pressure cooker cycle containing of jars of liquid, you can end up with the liquid being very slightly superheated. That is, it's liquid at the moment but it contains enough internal energy to where it could just as well be steam. One bump and it partially flashes to steam with great force. You're supposed to wait 10 minutes after the pressure is released before you open the lid. That's one safety procedure I always follow.

  6. #6
    Stegodon Jaglavak's avatar
    Registered
    Mar 2009
    Posts
    360

    Default

    [QUOTE=Jaglavak;141053]2) When steam condenses it releases a boatload of heat. Like around 950 BTU/lb. That's about 10 times the heat required to take that same pound of water from near-freezing to boiling./QUOTE]

    AAAAAGGGGHHH!!! 950 BTU/lb is actually about 5 times the heat from freezing to boiling.

    I was converting from metric to english in my head! My finger slipped on the calculator! Honest... I ran out of gas. I, I had a flat tire. I didn't have enough money for cab fare. My tux didn't come back from the cleaners. An old friend came in from out of town. Someone stole my car. There was an earthquake. A terrible flood. Locusts. IT WASN'T MY FAULT, I SWEAR TO GOD!

    :: sigh ::
    Well, I'm off to fall on my mechanical pencil.

  7. #7
    Jesus F'ing Christ Glazer's avatar
    Registered
    Mar 2009
    Location
    Atlanta, Ga. U.S.A. (Male)
    Posts
    1,485

    Default

    [QUOTE=Jaglavak;141072]
    Quote Originally posted by Jaglavak View post
    2) When steam condenses it releases a boatload of heat. Like around 950 BTU/lb. That's about 10 times the heat required to take that same pound of water from near-freezing to boiling./QUOTE]

    AAAAAGGGGHHH!!! 950 BTU/lb is actually about 5 times the heat from freezing to boiling.

    I was converting from metric to english in my head! My finger slipped on the calculator! Honest... I ran out of gas. I, I had a flat tire. I didn't have enough money for cab fare. My tux didn't come back from the cleaners. An old friend came in from out of town. Someone stole my car. There was an earthquake. A terrible flood. Locusts. IT WASN'T MY FAULT, I SWEAR TO GOD!

    :: sigh ::
    Well, I'm off to fall on my mechanical pencil.
    Don't ya just love nerd humor?
    Welcome to Mellophant.

    We started with nothing and we still have most of it left.

+ Reply to thread

Posting rules

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts