A few days ago, a post was made about a "hamburger canning failure", based on attempted canning with an Instant Pot Viva. Some of the responses indicated that instant pots should not be used for pressure canning.
Actually, the situation is complicated. I have been researching this lately, and wanted to share what I've learned, including sources and links.
There has been a movement toward electric pressure cookers, usually computer-controlled and called "digital cookers". Many of these are relatively low pressure, not designed for pressure canning, and their manufacturers have not claimed they are adequate for pressure canning. Most Instant Pots, including the Viva, are in this category.
However, more recently, at least three digital canners have been designed with pressure canning in mind. These include the Instant Pot Max, the Presto Precise 2144 Digital Canner, and the Nesco NPC-9 Smart Electric Pressure Cooker and Canner. The Nesco is also sold as the Carey DPC-9SS, which is the same except for branding.
Contrary to popular belief, the USDA does not "approve" or "disapprove" pressure canners. What testing is done usually occurs at university extensions, and may result in "recommended" or "not recommended" status.
So what is known about canning in electric devices?
Utah State University Extension did a study that tested three different brands of electric pressure cooker, three low acid foods (raw green beans, cooked chicken strips, cooked pinto beans) at three different elevations (2,900 ft, 4,500 ft, and 7,100 ft). They reported that "in many cases, the food was under-processed."
A link to a brief summary of the study is available here:
https://extension.usu.edu/preserve-the-harvest/files/foodsafetyelectricpressurecookers.pdf
Unfortunately, there are several potential problems with this study that make it interesting but not conclusive. The Instant Pot Duo80 was not designed for pressure canning, and the manufacturer makes no claims or suggestions to use them as such. Consumers should not use it for canning. The Power Pressure Cooker XL is rated for pressure canning by the manufacturer only at elevations of 2,000 ft or less, which was not tested. The study shows that it is not safe for canning at 2,900 ft or higher, but did not test it at its rated elevation.
Like many pressure canners, the Nesco/Carey has two valves, one for 10 psi and one for 15 psi. The study doesn't clearly state whether they used the 15 psi valve, which is necessary at the elevations tested. If they did not, it would explain why the Nesco struggled to reach the required temperature for safety. Unfortunately, there is no way to tell what pressure was used in the test.
I am unaware of any formal, published studies done after the Utah work was published. In particular, I have not seen any formal research done on the Instant Pot Max or Presto Precise 2144 Digital Canner, both of which were explicitly designed for pressure canning. Even more unfortunately, there don't appear to be any plans to conduct more research that would answer these questions. The USDA and its extensions simply say "electric pressure canners are not recommended".
There is a lot of misinformation out there, with many people stating that no electric pressure canner is safe, based on the Utah study. Consumers have made errors in the other direction as well. For example, many Amazon comments on the Presto 2144 state something like, "At last an electric pressure canner that is USDA approved!" But the USDA doesn't approve canners, and hasn't tested the Preso 2144 at all. The claim made by Presto is that the canner follows USDA guidelines for pressure canning, not that the canner is USDA approved.
So has anyone tested these canners in a meaningful way?
The YouTube channel "RoseRed Homestead" has done some tests of her own, including using a digital temperature probe that logs temperatures every minute. She has done videos on the Presto 2144, Instant Pot Max, and Nesco/Carey, showing the testing process and the resulting data charts. Her conclusion was that these are safe at her altitude of 5,000 ft for the three recipes tested in the Utah study, and some of them have worked for other recipes as well. You can check her videos at the links below.
Links here:
https://www.youtube.com/watch?v=w62NdXOKROg
https://www.youtube.com/watch?v=aKLbe9oGde4&t=1s
https://www.youtube.com/watch?v=pvgIkkwYO7o&t=1s
The bottom line is that we are not likely to get the USDA or its university extensions to test the top three electric pressure canners in a formal, scientific study any time soon. Even if and when they do, they will not formally "approve" any of these canners.
Consumers will need to do their own research and decide how they want to proceed.
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