home Forums Request Line Air removal

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  • #37925
    Anonymous
    Participant

    Laura, have you thought about including a page on here about air removal from a pressure cooker and how this affects pressure cooking? If the pressure cooker and its contents are cool or room temperature to start with, more air will be released before the lid seals shut and builds pressure. If the user starts with already-boiled water (e.g. from a kettle) or uses induction on too high heat, the cooker will reach pressure too fast and the food is very likely to under-cook. Also the trapped air (oxygen) will impair the flavour.

    It’s taken me a long time to learn that trying to rush the time to reach pressure is not worth it.

    #37937
    Laura Pazzaglia
    Keymaster

    I think it would be a good tech article to include – want to take a stab at writing it as a guest writer? : )

    One of our readers produced a handy chart to show HOW MUCH water is lowered when air is not properly vented that we used for this article..

    Pressure Canning Guide & FAQ: put ’em up! (update)

    Ciao,

    L

    #37950
    Anonymous
    Participant

    Good Hallowe’en picture. Hope you had a great Hallowe’en Laura?

    Some ideas of what you could include in a tech article about air removal, so readers can understand why air removal is important, especially newbies. If I think of anything else, I will add it to my next post. Imagine reading this from a newbie’s point of view:

      A pressure cooker takes around 8 – 10 minutes to reach pressure or even longer if fuller or when cold ingredients are used, especially frozen foods. During this time, air and oxygen are vented before a pin or rod automatically rises to seal the lid pressure-tight, provided the lid is correctly setup and locked into place. If the air is not removed, the internal temperature is lower, resulting in undercooked food, loss of nutrients, flavours and colour. Trying to rush and bring the cooker to pressure a few minutes faster (e.g. using hot water, less water, warming the pressure cooker first) is not recommended, the few minutes you may save has to be spent cooking the food for longer at the end.
      Oxygen is also replaced by steam, resulting in healthier food and almost no loss of colour and flavours.
      Old pressure cookers with weights: If there is only a steam pipe with a weight on the lid, the cook would place the weight over the pipe only when there’s a strong flow of steam being released, otherwise the cooker has trapped air.
      If cold water/liquid is substituted for hot, the cooker will not have as much time to exhaust the air. This can slightly undercook food, especially small quantities e.g. boiled eggs.
      Stovetop pressure cookers on induction should use a lower heat (link to page about induction). Induction heats much quicker and if the water comes to full boiling too fast, the pressure cooker will not have time to exhaust the air.
      Pressure canning requires all trapped air to be removed, but this is a separate topic (link to pressure canning page).
      If your recipes are regularly undercooked in a stovetop pressure cooker, trying using a slightly lower heat to bring to pressure in future.
    #37952
    Anonymous
    Participant

    If cold water/liquid is substituted for hot, the cooker will not have as much time to exhaust the air. This can slightly undercook food, especially small quantities e.g. boiled eggs.”

    I find this ambiguous. From the wording, I am not sure if you end up with hot or cold liquid.

    Better wording would be:
    “If you start with hot liquid instead of cold,…”

    #37953
    Anonymous
    Participant

    I agree Greg, your correction reads better.

    Indeed, it should read “If you start with hot liquid instead of cold”.

    I haven’t seen a recipe for pressure cooking which starts with hot liquid in a cold pressure cooker. As the cold liquid heats up, it produces more steam to warm up the pressure cooker and remove more air.

    Explain to readers why the pressure cooker appears to be doing nothing for several minutes as the liquid is boiling inside. So the liquid is boiling away and the pressure cooker appears to do nothing and not coming to pressure, just a small amount of steam venting from the lid. This is normal behaviour, air is being removed, this can take longer if the cooker is full or has frozen food. If the lid is locked in place correctly, the cooker will reach pressure eventually. When I first started pressure cooking, I could not figure out why this would happen, I had no idea it was venting air.

    #38032
    Annette
    Participant

    I’ve been using an induction-type stove for more than 17 years, I’ve been using it to pressure cook for almost that long, and I’m still having trouble recognizing what you’re talking about here.
    Sure I try getting my pot up to pressure as quickly as possible – I’ve never had any problems. (In general, I try to use as little liquid as I can get away with, so e.g. with soups I might add an extra cup of liquid after the cooking: this way, the food comes to pressure (and de-pressurizes) more quickly.)
    So: what kind of recipes are we talking about here?

    #38041
    Laura Pazzaglia
    Keymaster

    David, I love this discussion and once we get this pulled together into an article we should talk about how to credit you as the author.

    Annette, is right, perhaps there are A FEW things that might be more affected by this than others, for example Hardboiled Eggs and Pressure Cooker Pasta – in other words things that have a very short and precise cooking time.

    Ciao,

    L

    P.S. The Hip test kitchen is in dissaray at the moment we were robbed, for the first time two weeks ago, and just when we got new computers and phones robbed AGAIN last weekend. The details are too horrifying to discuss given that they entered our house, and bedroom, while we were sleeping. Right now we’re focused on surrounding the house with infra-red, loading the windows with sensors and the inner rooms with motion sensors. Thankfully we are all OK, and I only lost one month of work on the hip book – we keep almost everything on the cloud (so glad I had already uploaded the apple video to YouTube). They didn’t think to look in my underwear drawer so the photo and video cameras are OK. We drowned our sorrows in Halloween Candy and red wine the first time, pizza and beers the second. The kids have been busy setting booby traps around the house (metal pan lids tied with thread trip-wires) and I’m a little more motivated in my Goshindo Class (Karate for self defense) I think that punching bag will need to be replaced real soon!!! The first time I was shocked and scared, now I’m just really pissed.

    So apologies for not being as social as usual – but hopefully things will get back to a “new normal” soon!

    #38044
    Annette
    Participant

    First, oh my gosh – I’m shocked. This sort of taps into my deepest, darkest fears; I am glad you guys are ok!

    Re the air issue: maybe it’s because I use a stove-top PC with minimum amount of liquid (1/2 c), so it wouldn’t even occur to me to bring this to boil ahead of time for the hard-boiled eggs – it wouldn’t really make any difference, time-wise.

    And for pasta in the PC: of course I bring the water to boil, even before putting the pasta in; otherwise I’d have a bunch of Farfalle stuck to the bottom of the pot. So I just work from there, time-wise.

    Best wishes,
    A

    #38063
    Anonymous
    Participant

    Oh dear Laura, I’m very sorry to read. :'( Fingers crossed insurance recovers the loss. Please keep us updated.

    I hope plenty of video CCTV cameras (even a few dummy ones), along with CCTV stickers on doors and windows will help too. I’m glad you had backups of your work; I personally have TWO backups of files I never want to lose, saved on separate backup devices. Consider protecting your computers with with hard drive encryption and a BIOS password to power on the computer, these will render the computers useless to a thief and protects your confidential data, make sure you never forget the passwords otherwise you will be locked-out the computer forever! Sorry to type lots, I feel I have to help in some way. This must have been very upsetting!

    I’m glad you’re all OK.

    #38069
    Anonymous
    Participant

    Annette, sorry I didn’t to reply to you earlier.

    Air removal does appear to affect some recipes. Sliced carrots, low pressure for 5 minutes. When I used boiled water from the kettle, in an attempt to speed up the time to pressure, the carrots were always undercooked and firm. When I started to use cold water, the cooker would vent the steam for about 3 minutes longer and the carrots cook perfectly. Hard-boiled eggs are another good example: cold water + longer to pressure = perfectly set yolks, versus hot water + faster to reach pressure = slightly undercooked yolks in the centres.

    Yes less water is used in these examples, but pressure cooking generally uses small amounts of liquid compared to boiling etc.

    Bringing the water to the boil and then placing the lid on the pressure cooker will reach pressure very quickly, but again there will be trapped air inside and the results are never as good. Yes I’ve done this! Maybe some pressure cookers are engineered to remove more air first? Depends on how the pin or similar device is engineered to move up to seal the lid, once the steam has vented through it.

    When using induction for instance, starting with cold water and not using the maximum setting (or any power boost setting!), more steam is vented to remove air and oxygen, which preserves the colour and flavour of foods. Delicious! I have induction and I can tell you from experience there is a positive difference, bringing to pressure slowly vs break-neck speed. My induction can go well above 2kW and the bigger induction zone can go well above 3kW! Maybe yours is a lower wattage? Have you read Laura’s page about induction adjustments for pressure cooking:

    7 DO’s & DON’Ts of Pressure Cooking with Induction

    #38074
    HelenAdams
    Participant

    Interesting about the carrots. I usually add giant whole (Giant) carrots to a stew for the last 4 minutes. I find them slightly overcooked.

    Kind of like https://www.hippressurecooking.com/video-pressure-cooker-pot-roast-with-carrots-potatoes/ But carrots maybe 1 1/2 inch thick at top and 1 inch at bottom. And I use quick release.

    I have tried the experiments but not as persistently as you. Have given up on broccoli so I steam it, although cauliflower is easy to time and cook with hot or cold water. And potatoes are relatively foolproof.

    Keep up the good work, always enjoy reading about it

    #38300
    Anonymous
    Participant

    Air removal and why the pressure cooker appears to be doing nothing when the water inside is boiling away, for newbies it appears like that waiting takes forever! WHY?

    The user thinks that if they turn up the induction to maximum, the pressure is reached really quickly but the results are disappointing – undercooked.

    Explaining air removal will clear up the confusion. This could also be a good addition to a future version of Laura’s book. :)

    Think back to when you started pressure cooking, what was confusing at first? How could someone have explained the confusing bits to you?

    #38392
    HelenAdams
    Participant

    I was lucky in that I started here when I got my first pressure cooker. (Electric) I did the water test and then the potatoes in the school. Water test worked, potatoes I had to cook 3 times.
    Then I went on to many other things, bought a manual PC as well.

    I have read your threads and other articles on removing air and it all makes sense and good reading.

    Tried various methods and experiments. Totally inconclusive results and I actually kept a few notes and measured potatoes etc. I am interested and applaud your efforts but does not work for me.

    What would possibly have helped me now would be altitude adjustments or what the altitude of the recipe creator was, but probably not.

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