• Use a pressure canner: Unlike fruits and tomatoes, soup is a low-acid food and cannot be safely preserved using the boiling water bath method (and definitely not the upside-down jar method). The only safe way to can soup is with a pressure canner, which reaches temperatures high enough to kill bacteria and spores.
• Use a tested recipe: As tempting as it may be to put up your own concoction, canning experts strongly advise following recipes tested for the proper ingredients, processing time, and canner pressure. Master Food Preserver Rachael Narins recommends the books So Easy To Preserve and the Ball Blue Book of Canning. The Ball website also has some recipes.
• No pasta, rice, or thickeners: Don't can noodles, rice, flour, cream, milk, or other thickeners. If you want to add any of these ingredients to your soup, do it later, while reheating it.
• No dry beans: If your recipe includes beans or peas, make sure they are fully rehydrated first.
Have you ever preserved soup? There's no need to be intimidated, just be sure to use recommended recipes and equipment and you'll be on your way to stocking your pantry!