Is there a minimum load limit or guidance on the number of jars one must have for pressure canning?

Guidance has been given by the USDA and National Center for Home Food Preservation (NCHFP) regarding the minimum physical size requirements to be considered a pressure canner: the device must be large enough to hold at least 4 quart jars standing upright on a rack with the lid secure for USDA and NCHFP published recipes and processes.  Pressure canners meeting the specifications come in various sizes with either a dial gauge or a weighted gauge.

A minimum load for a pressure canner has not been specified by the USDA or NCHFP. In 2016, Ball canning issued guidance on a minimum pressure canner load stating, “To ensure proper pressure and temperature is achieved for safe processing, you must process at least 2 quart or 4 pint jars in the pressure canner at one time.” 

At this time, the USDA, NCHFP, university extensions, and contacted pressure canner manufacturers have not endorsed or tested the Ball recommendation regarding the 2 quarts/4 pints load minimum for safety. However, it may be a good practice. The more jars there are in a pressure canner, the more space is filled and the quicker it will vent (and the less time the food in the jars will be subjected to heat). UCCE Master Food Preservers of El Dorado County (CA) have found that a very small canner load can be difficult to bring up to required pressure and risks the water in the canner running dry. At any rate, canner load would have an effect on the warm-up and cool-down times, both of which are important to tested pressure canning processes.

When pressure canning a small batch, add jars of water (no lids necessary) to fill the canner space. The added jars will also prevent jars with food content from tipping over. Adding jars of water when water-bath or steam canning also helps with jars floating or tipping.

If you have canning questions, please do not hesitate to contact us by phone or e-mail. We are happy to help!

Sources:

¹The All New Ball Book Of Canning And Preserving, 2016, page 274.

²Pressure Canner Minimum Loads, UCCE Master Food Preservers of El Dorado County, December 2023.

Updated January 2024, mg.

Marlene Geiger

I am a graduate of the University of Nebraska-Lincoln with a BS in Home Economics Education and Extension and from Colorado State University with a MS in Textiles and Clothing. I enjoy spending time with family and friends, gardening, quilting, cooking, sewing, and sharing knowledge and experience with others.

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