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Old 08-19-2006, 09:46 AM   #21
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Quote:
Originally Posted by Michael in FtW
A pressure cooker and a pressure canner (sometimes called a canner/cooker) are essentially the same thing - except for the size. Some pressure cookers can only handle 4-5 pints for canning - while a small pressure canner can generally handle 5 quarts or 8-10 pints (depending on the rack they have). You just need to read the specs on the pot you want to purchase.
Michael -
Are you *sure* that a pressure cooker and a pressure canner are the same? I have read that an ordinary pressure cooker cannot achieve the higher heats required for safe processing of low acid foods.
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Old 08-19-2006, 11:19 AM   #22
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ayrton, the watermelon pickle looks like a good one--water bath it for 10 minutes to seal. (Follow the directions for water bath canning--a deep pot, deep enough to hold your jars plus an inch of water over the top, and room to bring to a rolling boil.)

I sent you a pm about the other recipes.
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Old 08-19-2006, 10:01 PM   #23
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Quote:
Originally Posted by subfuscpersona
Michael -
Are you *sure* that a pressure cooker and a pressure canner are the same? I have read that an ordinary pressure cooker cannot achieve the higher heats required for safe processing of low acid foods.
Let's look at what a pressure cooker and a pressure canner do, Sub. At a standard 1-Atmosphere of pressure (29.921 inHg) water boils at 212°-F. If you decrease the ambient pressure (like moving to the mountains of Colorado) - water boils at a lower temp .... if you increase the pressure (either by going down into a really deep hole, underwater, or using a pressure cooker to artifically increase the pressure) it boils at a higher temp.

So, a 2-qt pot with 1-qt of water in it will boil at the same temperature as a 12-qt pot with 8-qts of water in it. Increase the atmospheric pressure for both to the same level ... the boiling point will increase to the same temperature in both - unless there is some law of Physics of which I'm not aware. Pressure cookers and pressure canners are rated for the same pressure (about 10-15 psi).

Pressure cookers work on the same principle as pressure canners ... they are just too small to hold a significant amount (number/size of jars) for canning - although they will reach the same temp - they are just not economical or feasable for canning. Pressure vessels too small for canning are called pressure cookers ... pressure vessels large enough to do both canning and cooking are called pressure canner/cookers.

I do not doubt that you may have read that "an ordinary pressure cooker cannot achieve the higher heats required for safe processing of low acid foods" - but I would greatly appreciate a link to the site to figure out why they said that.
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Old 08-20-2006, 08:12 AM   #24
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Quote:
Originally Posted by Michael in FtW
I do not doubt that you may have read that "an ordinary pressure cooker cannot achieve the higher heats required for safe processing of low acid foods" - but I would greatly appreciate a link to the site to figure out why they said that.
Here's one www.wisc.edu/foodsafety/consumer/fact_sheets/pressurecannerandcooker.pdf
Here's another
www.vegsource.com/talk/pressure/messages/57769.html

color me confused
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Old 08-20-2006, 09:25 AM   #25
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Well, you learn something new everyday. I have a pressure cooker and a pressure canner, both made by the Mirro, and I would have thought they both would work for canning, except that the cooker would only hold a few pints or half pints.

I am sure the same book came with both of them, with canning instructions, but they are 25 years old, and canning has changed since then.
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Old 08-20-2006, 10:14 AM   #26
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I think they are the same. They just can't hold the same number of jars. Pressure increases temperature.
If you are canning something with enough acidity or sugar, pressure canning is not needed--water bath is sufficient.

The second post is "anecdotal" in my opinion--some one giving her opinion, just as I am.

The second says two things basically. If you know the pressure ofyour pressure cooker, it is safe.
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Old 08-20-2006, 05:05 PM   #27
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Maybe it is a matter of definition. The Extension publication says "pressure cookers do not come with pressure gauges, and cannot be used to safely can foods."

My smaller pressure cooker is made exactly like the big canner, and it probably would be fine. New ones that come with a high, medium, low control might not be, since you would not know what pressure you were using.

Gretchen, you are right about the "anecdotal" post. I have done a search of our Extension materials on line just now, and I don't see anything that says that length of heat-up time makes a difference in the canning process. You don't have to have a full canner load to can (2 quart jars would take less time to heat up than 7)--so why should a smaller cooker make a difference?
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Old 08-20-2006, 05:58 PM   #28
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Where IS the highest point in MO? I pass through (or used to) driving to Denver.
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Old 08-20-2006, 09:31 PM   #29
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Thanks for the links Sub - that helps explain your confusion ... especially when the second one contradicts some of the info in the first one (especially the part about pressure canners use lower psi than a pressure cooker).

The page from the Univ of Wisc is close ... but there is still a bit of misinformation IMHO. Some pressure cookers are made just like their bigger canner cousins - complete with pressure dial gauge or weighted gauge or a combination of both. Some modern pressure cookers would not be safe (not knowing the exact pressure) and using the "quick pressure release" that most of them now have would be a disaster (take a bottle or can of room temp soda and shake it up real hard and then open it ... it spews all over the place - the same thing would happen to the contents of the jars inside the pot if the pressure was suddenly released)! Another problem I have is that they allude to an assumption that you need a pressure canner to get 25-psi for canning ... that simply is not true (and I don't know what canner they are talking about that does 25-psi). If you look at the most popular canners, Mirro, Presto or All American - they are designed for use up to 15-psi! But, on the other hand, I don't fault them for warning people (who don't know what they are doing) away from using a pressure cooker which may not be adequate for the task. Canning guidelines are based on measurable standards ... and it would be impossible to publish guidelines for pots with "unknown" and "unmeasurable" pressure regulation!

So, back to the original question ... does a pressure cooker reach the same temp as a pressure canner ... yes. Can a pressure cooker be used as a pressure canner ... it depends on how it is made. Can a pressure canner be used as a pressure cooker ... yes. Would I use a pressure cooker for canning ... not if it was under 8-qts. even if it came with canning instructions - it's not economically feasible - it takes essentially the same amount of energy (gas/electricity) and the same amount of time as doing a larger batch in a larger canner.

The whole idea of pressure canning is to bring the food up to 240°F and hold it there for some period of time ... the time it takes depends on the food and the size of canning jar (could be anywhere from 30-mins to 2-hrs). Going back to the instructions in the Ball Blue Book ... you begin timing when you are up to pressure ... not when you turn the heat on.
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Old 08-21-2006, 10:33 AM   #30
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Highest point is Missouri is Taum Sauk Mountain, about 2 miles (as the crow flies southwest of me. I am in Iron County, which is about 70 miles south of St. Louis. (It is the orange one, shaped like a seven, towards the bottom right corner.)
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