The Presto Precise® Digital Pressure Canner is the first electric pressure canner to meet USDA home canning guidelines for safely processing meats, poultry, fish, vegetables, and other low acid foods.
While the USDA and the National Center for Home Food Preservation provide guidelines for home canning, neither agency certifies nor approves home canning equipment. Meeting their guidelines is key to safe canning. All Presto® canners, including our digital canner, meet those guidelines and our digital model is the first electric unit on the market to do so.
To appreciate the revolutionary nature of the Presto Precise® Digital Pressure Canner, one must understand the science of the pressure canning method. The U.S. Department of Agriculture Complete Guide to Home Canning, 2015 revision (available at https://nchfp.uga.edu/publications/publications_usda.html) explains that the temperature and time period used in pressure canning are the important variables:
Botulinum spores are very hard to destroy at boiling-water temperatures; the higher the canner temperature, the more easily they are destroyed. Therefore, all low-acid foods should be sterilized at temperatures of 240° to 250°F, attainable with pressure canners operated at 10 to 15 PSIG. PSIG means pounds per square inch of pressure as measured by gauge. The more familiar “PSI” designation is used hereafter in this publication. At temperatures of 240° to 250°F, the time needed to destroy bacteria in low-acid canned food ranges from 20 to 100 minutes. The exact time depends on the kind of food being canned, the way it is packed into jars, and the size of jars.1
Pressure does not destroy microorganisms, but high temperatures applied for an adequate period of time do kill microorganisms. The success of destroying all microorganisms capable of growing in canned food is based on the temperature obtained in pure steam, free of air, at sea level. At sea level, a canner operated at a gauge pressure of 10.5 lbs provides an internal temperature of 240°F.2
Because the required temperature is higher than the boiling point of water, for hundreds of years, the only way to obtain these temperatures was processing under pressure and using that pressure to control the temperature.
When developing the Presto Precise® Digital Pressure Canner, we incorporated a new innovative sensor technology that has the ability to hold the temperature in the digital canner between the 240° to 250°F required for safe pressure canning without regard to the pressure. As noted above, traditionally, pressure canners utilize the more basic but imprecise method of controlling temperature by regulating pressure, such as the use of a weighted gauge regulator (usually providing options of only 5, 10, and 15 pounds pressure) or a dial gauge (which needs to be regularly calibrated). Both methods require close watching and making the necessary heat adjustments to maintain the proper pressure and, therefore, temperature. Our Digital Pressure Canner instead directly monitors the actual temperature within the pressure chamber to control the unit itself. Therefore, traditional style “regulators” are not needed.
As a further benefit, because the temperature is controlled precisely without regard to pressure, the pressure canning process is not affected by elevation. The USDA Guide explains the difficulties presented by traditional pressure-based methods:
Water boils at lower temperatures as altitude increases. Lower boiling temperatures are less effective for killing bacteria. Increasing the process time or canner pressure compensates for lower boiling temperatures.3
During the development of the Presto Precise® Digital Pressure Canner the unit was tested utilizing multiple thermocouples to assess temperatures at many different locations inside the unit. This included one inside each jar of food being canned during each of the tests. The results of a multitude of tests on a many different low-acid food types confirm that the 240° to 250°F required for safe pressure canning had been achieved and maintained throughout the processing time.
This use of modern technology results in a much simpler pressure canning process yet results in canned foods that meet the USDA guidelines.
1 U.S. Department of Agriculture “Complete Guide to Home Canning,” Agriculture Information Bulletin No. 539 (Revised 2015). 1-8.
2 U.S. Department of Agriculture “Complete Guide to Home Canning,” Agriculture Information Bulletin No. 539 (Revised 2015). 1-19.
3 U.S. Department of Agriculture “Complete Guide to Home Canning,” Agriculture Information Bulletin No. 539 (Revised 2015). 1-10.