Home canning pressure cookers

Discussion in 'Back to Basics' started by stg58, Apr 27, 2013.


  1. stg58

    stg58 Monkey+++ Site Supporter+ Founding Member

    The recent terrorist attack with pressure cooker bombs has drawn my attention to pressure cookers.

    They claim 70% energy savings and usage for home canning.


    Any real feedback?
     
  2. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Just do NOT buy any Black Powder of Fireworks at the same time..........[lolol]
     
  3. chelloveck

    chelloveck Diabolus Causidicus

    Pressure cookers are a more energy efficient way of cooking and canning than using conventional methods of stove top cookery. There are some wrinkles that users need be aware of when using pressure cookers and pressure canners, so read and apply the operating instructions religiously!!

    Stainless steel cookers are preferred...aluminium cookers, although lighter and often cheaper react to acidic foods and may discolour and become pitted / corroded. There is a wealth of information on the internet about pressure cooking and pressure canning...including a number of Youtube film clips.

    Just remember...a pressure cooker, unlike a crockpot / slow cooker is not a set and forget piece of cookware....leave the pressure cooker on the stove top too long and you may find that your meal is a burned film of grunge at the bottom of the cooker....or your pressure cooked casserole may end up decorating your kitchen ceiling if the safety valve blows.

    Pressure Canning: A Step-By-Step Guide

    Tips on Buying a Pressure Cooker

    How to Pressure cooking - the complete how to guide - Cooking tips - Taste.com.au

     
    oldawg, kellory and tacmotusn like this.
  4. tacmotusn

    tacmotusn Mosquito Sailor

    Instead of hours, you can cook dry beans in 30 to 45 minutes. You can can (and cook at the same time) dry beans in pint or quart jars in about 75 to 90 minutes, and have fully cooked ready to just heat up beans just like the metal canned ones from the grocery store for about 1/8th the cost.
    .
    Chello was spot on for the statement about Stainless Steel if you are going to use your pressure cooker/canner for cooking. Acid in some foods will damage Aluminum. I have a couple smaller stainless steel pressure cookers (8 quart and 4 quart) I use only for cooking.
    .
    When it comes to pressure canning Aluminum is the least expensive way to get started and you can use a 15 to 22 quart pressure cooker/canner to do this. They will serve you quite well for $65 to $100 each. I have 2. I can in them only.
     
    VisuTrac and chelloveck like this.
  5. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Why? It's a closed system, independent of atmospheric pressure.
     
    chelloveck likes this.
  6. chelloveck

    chelloveck Diabolus Causidicus

    Sorry, I stand corrected...I am thinking of the waterbath method of canning.
     
  7. tacmotusn

    tacmotusn Mosquito Sailor

    Water boils at a lower temp at higher altitude. As I understand it 10 pounds pressure at sea level will give you 240F boiling water. This is what the USDA canning base standards are computed at. Next comes time (in canning, how long will it take to bring the contents of the canning jar up to 240F or whatever temp they are shooting for). Thus at high altitudes you either have to use the 15 pound weight or increase the time to obtain the same results. It is not a completely closed system. It has a pressure relief valve with a control weight. So if that is considered it is only a modified open pot.
     
    chelloveck likes this.
  8. Altoidfishfins

    Altoidfishfins Monkey++

    I used one regularly years ago. They work well to greatly reduce cooking time and that is where the energy savings come from. Some have a variable weight, effectively changing it (and affecting the internal pressure which directly affects cooking time) by repositioning a single weight on one of several studs. If you forget and leave your food on too long, even exceeding the recommended cooking time by two or three minutes, you can end up with the equivalent of baby food - mush. Never done presure canning.

    After what happened at the marathon I'm surprised that they are still legal, given the regime in power at the present time. It would follow their logic that they would release those responsible (who are still breathing) and ban pressure cookers, demanding a buy back on those already in possession.
     
  9. Clyde

    Clyde Jet Set Tourer Administrator Founding Member

    if I order 20 online, I think I will hit the watch list
     
  10. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    The altitude does not affect the weight in any measurable way. 10 psi at 10,000 feet is the same as 10 psi at sea level, thus the temp in the water will be dependent ONLY on the supplied heat as long as it comes fast enough to just wiggle the weight (boil water) at whatever the temperature is. There may be some other reason to raise the pressure, dunno about that, but the physics are pretty simple.

    The system is closed to the extent that the stuttering weight (actually a pressure control valve as you indicate) keeps the pressure "right" for the desired temp. As you say, an "open" system (boiling water in an open pot) cannot achieve the temp/time relationship for cooking at high altitude that you can do at sea level. I don't remember the numbers, but I do know that we cooked things a lot longer at 6500 feet in Wyoming than we did in Connecticut at under 50 feet. (And waiting for the cake to bake properly was a nuisance.)

    I've seen older pots with a real relief valve on the lids right next to the control weight. Due to the problems with calibration, they mostly have blowout plugs these days. The plugs are actually thermal reliefs that blow on temp, not pressure, and the plug alloy is easily and precisely formulated to melt if the temp gets too high in the pot; too high a temp is directly correlated to too high a pressure.
     
  11. tacmotusn

    tacmotusn Mosquito Sailor

    if water boils at say 200f at 5000ft it produces steam. at a certain point 10lb will be reached and the weight will allow excess pressure to bleed off. the boiling water is not at 240f (with the 10lb weight), but at some lesser point due to altitude (at sea level it would be at 240f). dispute that if you can. i am a bit busy right now but if neccessary i will find it in print at another source other than my own brain.
     
  12. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Easy to dispute on the back of a cocktail napkin. Even easier if you go to any convenient physics text or engineering handbook (I use Marks 8th edition, find it in Chapter 4). Basically, if (say) water boils at 200 degrees at 5000 feet in an open pot, then you close the pot, the pressure goes up because, and ONLY because the steam has no place to go until the wiggler wiggles. The temp follows the pressure for the same reason that water boils at a higher temp at sea level; increase the pressure on the boiling liquid, and boiling will be suppressed when you put the lid on, even if temp is held constant by controlling the burner.

    Be careful using cookbooks as sources for physics info. They are often in factual error in the interest of simplification for the LCD's benefit. :lol:
     
  13. tacmotusn

    tacmotusn Mosquito Sailor

    we seem to be in some form of agreement here. look, at sea level the 212F boiling water starts to produce steam, and you get a 28f rise to 240f if you cap it and allow the pressure to increase to 10lb. logically if you move the whole shebang to 5000ft altitude and water boils at say 200f and you pressurize to 10lb you should get a max temp increase to 228f not 240f correct?
     
  14. tacmotusn

    tacmotusn Mosquito Sailor

    and if i am not correct, then what is happening? is the steam which starts to produce at 5000ft and 200f somehow going to produce 240f at 10lb pressure anyway, and if so how?
     
  15. tacmotusn

    tacmotusn Mosquito Sailor

    at altitude, even baking temperature settings have to be adjusted, because the controls for sea level if say set at 350 may at 5000ft only attain 300-325f unless you adjust and crank it up to a higher heat setting.
     
    Motomom34 likes this.
  16. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    No, not correct; the delta T logic doesn't hold when the parameters are changed. When you put the lid and weight on, you close the system and divorce it from air (altitude) pressure. The temp change in a close system depends only on the heat addition, not the surrounding air pressure.
     
  17. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Not exactly. You still get the temp you want in thermostatically controlled stoves, but the baking is dependent on water in the mix as well as some minor alterations in the chemistry of the mix that are pressure dependent. I don't know enough about the ins and outs, but I do know that baking times have to be extended at altitude, using the same temps. There may be an increase in temp as well; that is beyond me.
     
  18. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    With the ten pound wiggler on, you get 240 F, regardless of altitude. Again, the wiggler closes the system.
     
  19. tacmotusn

    tacmotusn Mosquito Sailor

    one last feeble attempt. #1. whether at sea level or 5000ft, the weight does not go on until you have a good steam flow from the nipple where you are going to set the weight. before the weight goes on is it not still an open system? without the weight closing the system the lower atmosperic pressure at 5000ft causes the water to boil and produce steam at a lower temperature. even when you put the weight on, the pressure doesn't rocket to 10lb. It takes several minutes.
     
  20. tacmotusn

    tacmotusn Mosquito Sailor

    okay fine. I wouldn't bet the ranch on it either way. I will take your word, but not enough to bet one red cent .... sorry thats just me a tight olde Scots/Irish miser.
     
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