One of the biggest risks in home canning is botulism*. Not following directions precisely can be fatal, as was the case in Ohio this past April. The case involved 29 people who ate potato salad made with home-canned potatoes at a church potluck. Of the 29, one died of respiratory failure shortly after arriving at the emergency department.
The person who made the potato salad with the home-canned potatoes made a critical error. The person processed the jars in a boiling water canner instead of a pressure canner. A mistake that cost someone their life.
Low-acid vegetables such as potatoes, carrots, peas, and corn need to be processed in a pressure canner. Pressure canners process food at 240°F or higher. This temperature will eliminate C. botulism spores. A boiling water canner processes at approximately 212°F, not high enough to kill the spores.