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Well, unfortunately the present my mom got me last Christmas turned out to be a pressure cooker and not a pressure canner. I've read that it is unsafe to can low acid foods using a pressure cooker.

But is it safe to can high acid foods in a pressure cooker? I'd like to do this because it uses a lot less water and a lot less energy than boiling water canning.

Does a pressure cooker actually cook to a lower temperature than a pressure canner? (My pressure cooker just has two settings (high and low) and I don't know what the PSI is on them.

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2 Answers 2

Pressure cookers and pressure canners are the same thing; with the canners being larger, and often having a pressure dial. Both can reach the same pressures and therefore temperatures if designed and manufactured correctly

The pressure canners dial gauge is more accurate for adjusting for food types and altitude, as you can get exact numbers not just 10 psi and 15 psi as with typical weight regulated pressure cookers. But for low acid foods you need 15 psi anyway

Pressure preserving is done because of the higher temperatures reached. This saves time and energy, and some food react better to a short 250°F (120°C) cook that an long 210°F (100°C) cook

Pressure preserving high acid food is worth doing as long as the food does not deteriorate quicker due to the high temperature (some soft fruits will)

For preserving low acid foods you need a known good pressure cooker that can reach 15 psi (103 Pa) and therefore 250°F (120°C)

With a commercially published recipe that has been acid level tested, you will have a published time that will be safe. For a home-made recipe you have to take the worst case scenario for the acid level of the main content, and cook for that. Your local government health department will most likely publish tables for this that you should be using. Remember to use altitude adjustments for timings too

Just relying on adding a teaspoon of vinegar or lemon juice per jar is not a safe and scientific method for raising the acid level, though many people do it, and have not come to any trouble with it?

You pressure cooker should come with a manual that confirms what it can or cannot do. Download a new copy if this has been lost

Also see What kinds of pressure cookers are there, and what are they good for?

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Good answer but that is 10 psi and 15 psi. Unless you use a different definition of "pound" down there. :) –  Sobachatina Aug 10 '12 at 23:27

For low acid foods the high and low settings are a problem. You really need to know what pressures those are.

You have to get to 15 PSI which will give you a boiling temperature of about 250F. Anything less and it won't get hot enough to kill botulism spores.

For most high acid foods the pressure cooker will be overkill. Most high acid foods such as fruit and jams process for only 10 minutes. At those small times there is not much water last and a pressure cooker will not save much time. Additionally the unnecessarily high temperature would damage the fruit.

Tomato sauce is an exception as it boils for much longer. In this case a pressure canner is actually preferred as cooking the sauce for 10 minutes will do less damage than the 30-45 that is required for a water bath.

Keep in mind that pure tomato sauce is not acidic enough to be processed with a boiling water bath. Extra acidification is required to be safe.

The above link has a table with cooking times for various pressures and altitudes. Your canner should be perfectly safe- if you are able to determine what the actual pressure it uses is.

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The pressure cooker cooks just fine at medium low on the stove and requires only 2-3 inches of water, none of which boils off or gets nasty. Boiling water canners have tons of water evaporate. (Also, I didn't say I'm cooking fruit, I'm doing tomato sauce, which requires a lengthy stay in the water). –  Peter Turner Aug 10 '12 at 20:08
From a quick search, I think you might mean 250F, not 150F. –  Jefromi Aug 10 '12 at 20:09
@Jefromi- you are quite right. Oops. –  Sobachatina Aug 10 '12 at 20:18
@PeterTurner- Indeed tomato sauce is an exception. In that case the pressure canner is actually preferred because even though it is at the higher temp it only cooks for 10 minutes instead of 30-45 so there is less damage. I'll amend my answer for your exceptional circumstances. –  Sobachatina Aug 10 '12 at 20:25

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