Friday, February 22, 2013

Ask Granny... Vacuum Seal vs. Canning and Pressure Cooker vs. Pressure Canner

Q. I have the system that sucks air out of mason jar using a seal-a-meal. Does the water or canning process not only take the air out but sterilize the product? What I am asking is why can't you use just the seal a meal product that goes on mason jars and suck the air out?

A. Vacuum packaging or sealing and canning cannot be considered the same. Both the preservation methods involve the sealing of food in a container, but in canning the food that is sealed is heat-sterilized, which kills microorganisms. This is why there is no need to store canned food in the fridge. In the case of vacuum packaging, the food present inside the container is not sterile and microorganisms in the food are still present. But due to the removal of air from the storage container, the vacuum packaged food will stay fresh for a longer time in the fridge or freezer.

Q. What’s the difference between a pressure cooker and a pressure canner?

A. According to USDA, a pressure canner must be able to hold at least 4 quart jars, and have a gauge or weight to allow you to measure 5, 10, and 15 lbs. pressure. A pressure cooker is usually smaller and only has one pressure weight built in. You can cook in a pressure canner as well as can… but you can’t can in a pressure cooker.


  1. Actually, it is POSSIBLE to can foods using a pressure COOKER rather than a pressure CANNER, BUT IT IS AN INCREDIBLY BAD IDEA. I go around and around with some folks on this, as I teach canning to others.

    In order for food to be stored safely, without fear of botulism, etc., the food being canned MUST be heat-treated, as you point out, but heat must be held CONSISTENTLY at not less than 240 deg. F (10 lbs. pressure) for a specified period of time, depending on what you are canning. Both time and temp are critical; this is why the instructions tell us that if the temp falls below 240 deg. F (10 lbs. pressure) at any time, YOU MUST bring it back up to temp and start the count all over again.

    This temp also increases exponentially over 2000 ft. altitude.You must check your recipe for how much pressure to add, based on your altitude and the food being canned.

    Any less temp, or processing for less time than the specified length for the food being canned, at your altitude, is an invitation to food poisoning, and this is not always detected by looking at the food or smelling it. Even if it were, why would anyone go the expense and work required to can food, only to have to throw it out? Or worse, risk a life-threatening illness? Ever had food poisoning? I have (from "eating out", by the way); if it doesn't kill you, you may wish it would, at least temporarily.

    So, yes, it's POSSIBLE to can food using a pressure cooker. DON'T DO IT. Plain and simple. And I know of foolish people who have refused to heed the warning, because "grandma did it this way, and it worked just fine for grandma". Folks, grandma probably didn't have a choice; and grandma had YEARS of experience, and knew exactly what to do and how, for years before you became old enough to pay attention. Grandma would have loved the convenience of a modern pressure canner, I'm sure, but it was not an option for grandma. You're not your grandma. Don't try it.

    As to using the canner as a COOKER, obviously, this will work, but, I don't do that either. Canners are aluminum. Do you really want to eat food cooked in aluminum? I do not. I cook my food in glass cookware or stainless steel cooking pots (I've had the stainless Revere Ware for 40 years, and I steel love it!). Also, whatever you cook in aluminum, especially high acid foods, will enter the pores of the aluminum and discolor the metal, as well as taint the metal, so that it will leach into whatever you put in the canner next.

    So, no, I don't mix my cookers and canners. One is for COOKING, the other is for CANNING, and, in my personal opinion, never the twain shall meet! ; )

    Happy and safe canning, y'all!

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  2. Thank you for all this great info. I'm still new to canning doing jams and jellies.I really enjoy canning and may try pickles this year. What's your advice on making homemade pectin from apples? More work then what its worth?

    1. Actually making pectin (I've only done it from apples) is pretty simple... here's the link to how I did mine...

  3. Sooo when you make your pectin--are the potency results unique to each batch or are they consistent?

    And off topic--because I want to make you proud (and possibly pat myself on the back).
    I am in the middle of a kitchen renovation that I am doing all by my lonesome. I refinished the cabinets and tore out the ancient broken tile counters when I got a phone call. The fresh lemons I've been asking about at my local farmers market were in. The timing was bad--but they acquired these special for me--so I was obligated. Ended up with about 200 lemons. Made lemon squash (nearly 6 dozen pint jars)in my partial kitchen, with no counters--but have a working sink. Day 1 I juiced the lemons using your method. Day 2 I made my concentrate and canned. I had an 18"x24" table work area. All jars were covered and cooled on the dining room table. I figure If I can do this with the kitchen apart--I can do anything once the new kitchen is done! Can't wait to lazily sip lemonade this summer (at least until the garden explodes).
    Thank you for all your hard work--you have made it so much easier on me!

  4. what are the benefits of having a pressure canner over a water bath ?

    1. You can only can acidic foods like tomatoes, jams, and jellies using a water canner. To can vegetables, meat and everything else, you must use a pressure canner

  5. How lovely! Your tips were so helpful. thanks for sharing this. The next time can you give us some tips of using pressure cooker


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