Home food preservation requires attention to altitude, as California’s elevation varies widely from 280 feet below sea level in Death Valley to 14,500 feet at Mt. Whitney. The altitude of a kitchen impacts the boiling point of water and thus affects cooking and canning times.
Maria Giovanni, a volunteer with the UC Master Food Preserver Online Program, highlights the importance of knowing your exact elevation before beginning food preservation. She advises home preservers to double-check their altitude using online tools.
As air pressure decreases with higher elevation, water boils at lower temperatures—212°F at sea level compared to 200°F in Truckee (5,820 feet). This means that foods take longer to cook or process in water at higher altitudes. “At higher altitudes, water boils at a lower temperature than at sea level, so the processing time or processing pressure must be increased to ensure the destruction of spoilage organisms and pathogens,” Giovanni states.
Canning recipes often specify adjustments for altitude; if they do not, users should refer to guidelines such as those found in university extension publications or reputable sources like the National Center for Home Food Preservation (https://nchfp.uga.edu/). Reliable recipes should always include these details because failing to make proper adjustments can result in unsafe preserved foods.
The article also notes that pressure canners allow adjustment by increasing internal pressure so temperatures reach levels necessary for destroying certain pathogens such as Clostridium botulinum spores.
Giovanni cautions: “Remember: you must know your altitude and make the required adjustments specified in the recipe, which should be a tested recipe from a reliable source, such as a University Cooperative Extension, the National Center for Home Food Preservation (https://nchfp.uga.edu/ ), or the Ball Blue Book. If a recipe does not include altitude adjustments, this might indicate that the recipe is untested and potentially unsafe to use.”
For further information on how altitude affects cooking and preserving food safely, resources are available through state university extensions and organizations focused on consumer food safety.