If you’re considering picking up some of those electric pressure cookers at early summer garage sales thinking they’d be a handy, easy way to put up small batches of fresh produce for use next winter, think again.
It’s not the pre-owned status that should give you pause for thought, though. Even if you’re planning on buying a new countertop pressure cooker for a peck of backyard green beans, researchers and public health officials say the risk is too high.
Warnings about the cookers and the associated danger of botulism poisoning began a few years ago, almost as soon as various brands including Instant Pot and Power Pressure Cooker XL hit store shelves and the TV infomercial circuit. The warnings have continued, with another earlier this year from the National Center for Home Food Preservation.
Now, researchers at the Utah State University Extension service have released preliminary data showing the electric pressure cookers do not always reach high enough temperatures for the proper amount of time to safely can low-acid foods including vegetables, beans, meats, poultry, fish and soups.
The scientists in Utah focused on the use of such cookers at altitudes across their state, according to comments from Cathy Merrill, USU Extension faculty member and project lead on the research project.
“We knew from previous USU Extension research that altitude affects temperatures in electric pressure cookers, and we’ve heard rumors of community groups having classes about pressure canning in ‘smart cookers,’ so we knew it was time to do some research,” Merrill said in a news release about the project.
“The U.S. Department of Agriculture has recommended against electric pressure cookers being used for canning, and now we have our own data showing that they just don’t hit the high temperature needed for canning safely at our altitudes.”
Numerous Extension offices across the country have weighed in on the topic, including Penn State’s service less than a year ago, just as people were preparing to preserve the flavors of summer.
As in materials from other universities and public health officials at state and federal levels, the Penn State Extension Service warning stressed that a number of factors are involved in safe home canning. There hasn’t been any research by the USDA or a university to show that these electric multi-cookers can safely process low-acid food, according to the Penn State service.
“A common misconception about home canning is that the goal is to get the jar to seal. While having a strong seal is important, the most critical factor is whether the food inside the jar is safe to consume,” according to information from Penn State. “When food is heated inside the jar during the canning process, factors such as the density of the food, size of the food pieces, and size of the jar are figured into the process calculation.
“The entire thermal process including the heat-up to cool-down steps contribute to the destruction of harmful microorganisms. Electric multi-cookers tend to heat up and cool down quickly. Since heat transfer has not been specifically studied in this environment with this type of appliance, it is not recommended to use the canning feature of electric multi-cookers.”
Some manufacturers of electric multi-cooker appliances have been including directions for home canning with their products since they began marketing them, according to the National Center for Home Food Preservation. The companies have not done process development work to document temperatures throughout the units remain at a given pressure and throughout the whole process time, according to the Center.
The Center was established with funding from the Cooperative State Research, Education and Extension Service, U.S. Department of Agriculture (CSREES-USDA) to address food safety concerns for those who practice and teach home food preservation and processing methods.
“We do not know if proper thermal process development work has been done in order to justify the canning advice that is distributed with these pressure multi-cooker appliances. What we do know is that our canning processes are not recommended for use in electric pressure multi-cookers at this time,” according to the center.
The center does have instructions for the public on proper canning techniques using stove-top pressure cookers, but those instructions to not apply to electric multi-cooker appliances. Even if such cookers have buttons or settings for “canning” or “steam canning” the devices should not be used for such purposes.
“Bacteria are not killed in the food only during the process time; the time it takes the canner to come up to pressure, the process time, and the cool-down time all matter,” according to the center.
Some of the other “major reasons” the center cannot recommend using electric multi-cookers for pressure canning are:
- Thermal process canning work relates the temperatures in the jars to the temperature inside the canner throughout the processing. No USDA thermal process work has been done with jars inside an electric pressure cooker, tracking the actual temperatures inside the jars throughout the process. It is ultimately the temperature and heat distribution inside the jars that matters for the destruction of microorganism in the food product. The position of jars in the canner and flow of steam around them also impacts the temperature in the jars. For example, there would be expected differences in jars piled together on their sides from those standing upright on the canner base.
- One manufacturer says its cooker reaches the pressure required for canning, but that alone does not prove the food in the jars is heated throughout at the same rate. . . Just producing an interior pressure is not sufficient data for canning recommendations. For example, if air is mixed in the steam, the temperature is lower than the same pressure of pure steam. That’s why a proper venting process is so important in pressure canning — to obtain a pure steam environment inside the canner. Also, one has to know how to make adjustments in pressure readings at higher altitudes. The same pressure and process time combination cannot be used at all altitudes.
- In order to ensure the safety of the final product, the temperature in the canner must stay at minimum throughout the process time. Do power surges or drops with an electric canner cause the temperature to drop too low? How will you the user know if that happens with your cooker?
- One of the big concerns is that the USDA low-acid pressure process times rely on a combination of heat from the time the canner is coming to pressure, during the actual process time, and then during the early stages of cooling the canner and jars. Even after the heat is turned off under the canner, at the end of the recommended process time, the food remains at high enough temperatures for another period of time that can still contribute to killing of bacteria. This retained heat while the canner has to cool naturally to zero pounds pressure before opening is used to advantage in calculating the total sterilizing value of the process to preserve some food quality. If anything is done to shorten the cooling period, including using a very small cooker, then the food could cool down more quickly, and be under-processed. That is why we recommend using only pressure cookers that hold four or more quart-size jars. Bacteria are not killed in the food only during the process time; the time it takes the canner to come up to pressure, the process time, and the cool-down time all matter.
Please note, the center’s information about electric multi-purpose cookers includes the following disclaimer:
This statement about electric cookers does NOT include the Ball Automatic Home Canner for acid foods only, which is electric, but (1) is not a “multi-cooker”, but a dedicated canner, (2) comes with its own instructions and pre-set canning options for specific food preparations, and (3) has had proper thermal process development done to support the recommendations with it. Jarden Home Brands also sells an electric boiling water canner, but it is not a pressurized appliance and for canning purposes operates similar to a traditional boiling water canner. Directions from the manufacturer for this Ball canner, as well as for the Weck non-pressurized electric boiling water canners, should be followed to get them assembled and for managing temperature settings to achieve a boiling process.
Information about botulism poisoning
While a variety of illnesses can result from eating under-processed canned food, one of the most dangerous is botulism poisoning. Untreated, botulism can quickly paralyze the muscles needed for breathing, resulting in sudden death.
“In foodborne botulism, symptoms generally begin 18 to 36 hours after eating a contaminated food. However, symptoms can begin as soon as 6 hours after or up to 10 days later,” according to the CDC website.
The symptoms of botulism may include some of all of the following: double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, difficulty breathing, a thick-feeling tongue, dry mouth, and muscle weakness. People with botulism may not show all of these symptoms at once.
These symptoms all result from muscle paralysis caused by the toxin. If untreated, the disease may progress and symptoms may worsen to cause paralysis of certain muscles, including those used in breathing and those in the arms, legs, and the body from the neck to the pelvis area, also called the torso.
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