You may have seen advertisements for electric multi-cooker appliances now containing “canning” or “steam canning” buttons on their front panels. Before you make a purchase, we want you to be aware that we do not recommend our canning processes for use in electric multi-cookers at this time. We do not know if proper thermal process development work has been done in order to support the canning advice that is distributed with these multi-cooker appliances. The way the USDA, National Center for Home Food Preservation and University of Georgia process development work has been done would not yield results expected to be transferable to these electric cookers.
Our process directions for low-acid foods, for example, were developed for stovetop pressure canners which hold four or more quart-size jars standing upright. Even if there are referrals to the National Center for HFP in the instructions for canning in the manufacturer’s directions, we do not currently support the use of the USDA canning processes in electric, multi-cooker appliances. If you are canning low-acid foods and the proper amount of heat is not delivered to all parts of the food in the jars during the process, then the risk is botulism food poisoning in under-processed foods.
Some of the major reasons we cannot recommend using electric multi-cookers for canning:
- No USDA thermal process work has been done with jars inside an electric pressure cooker of any kind. Thermal process canning work relates the temperatures in the jars to the temperature inside the canner throughout the processing. It is not the temperature or pressure in just the canner that matters, but ultimately the temperature and heat distribution inside the jars is most important 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.
- What matters is temperature, not pressure. Even if a manufacturer says its cooker reaches the pressure required for canning, that does not prove the food in the jars is heated throughout at the same rate as in the canner used for process development. What is important is what temperature relates to the pressure reached in that cooker, and what the temperatures are throughout the whole canner environment. And does the temperature stay at the minimum required the whole process time? 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 as pure a steam environment inside the canner as possible.) How does the user adjust for altitude changes if the cooker is set to reach only one pressure? If the pressure actually obtained reaches a desired temperature, can the user actually verify the pressure reaches the stated description and stays there throughout the continuous process time? We do not know of ways in which these questions have been answered. (And unfortunately we do not have a budget to be able to buy and use all of the versions in the marketplace. We have been able to read some user manuals that do not answer these questions, however.)
- In order to ensure the safety of the final product, the temperature in the canner must stay at minimum throughout the process time, so do power surges or drops with an electric canner cause the temperature to drop too low? How will you know if that happens?
- USDA 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 0 pounds pressure before opening is used to advantage in calculating the total sterilizing value of the process to preserve some food quality. There is no way at this point in time to know exactly the percentage of contribution for each of the canning recommendations. Therefore, we emphasize that the canner size and steps in managing the pressure canning process from start to finish (heat up to cool down) are important to maintain. For example, if anything is done to shorten the cooling period, including using a very small cooker or force-cooling the canner, then the food could cool down more quickly than expected, and be under-processed. (This is one reason we recommend using only pressure canners that hold four or more filled quart-size jars, upright on a rack, with the lid fastened in place. It is a way to help judge that the cool down period will not be too short.) 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: 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 thermal process development done specific to that canner to support the recommendations with it.
Editor’s Note (February 12, 2015 ): We are aware that Jarden Home Brands will be releasing a new electric boiling water canner, multi-cooker appliance. More information will come as we learn about this new device.
For more information about canning in pressure cookers, please read “Burning Issue: Canning in Pressure Cookers”: http://nchfp.uga.edu/publications/nchfp/factsheets/pressurecookers.html