Method guide · Acid & acidified foods
Atmospheric steam canning
Atmospheric steam
Natural or equilibrated pH ≤ 4.6
45 minutes or less including altitude adjustment
Continuous pure steam throughout processing
Foods and recipes that qualify
Current NCHFP guidance allows properly operated atmospheric steam canners for foods with a natural or equilibrated pH of 4.6 or below when a research-based boiling-water process is available.
Why the 45-minute limit matters
The limit relates to the water capacity in the canner base. The canner must maintain a continuous environment of pure steam throughout processing and cannot be opened to add water during the process.
Critical operating controls
- Preheat jars as directed so they enter the canner hot.
- Minimize cooling between filling jars and beginning processing.
- Vent air and establish a full atmosphere of steam before starting the timer.
- Confirm that steam remains at the temperature of boiling water throughout processing.
- Use the altitude adjustment required for the corresponding boiling-water process.
- Do not open the canner during processing.
- Allow jars to cool naturally in still air; do not force-cool them.
What steam canning cannot replace.
Atmospheric steam