What can you water bath can?

The list: safe in a water bath

• Jams, jellies, preserves, marmalades and conserves — sugar and fruit acid, the most forgiving category in canning.
• Fruit butters — apple, pear, plum. Thick, but tested recipes exist for exactly this consistency.
• Whole and sliced fruit in syrup, juice or water — peaches, pears, plums, apples, cherries, apricots, berries.
• Apple sauce and other fruit sauces from a tested recipe.
• Pickles made with vinegar — cucumbers, beets, green beans as dilly beans, okra, carrots. The vinegar is what makes these safe, not the vegetable.
• Relishes, chutneys and pickled peppers from tested recipes.
• Salsa from a tested canning recipe — not a fresh salsa recipe, which has a different ratio.
• Tomatoes and tomato products, acidified with bottled lemon juice or citric acid in the amount the recipe specifies.
• Juices — tomato, grape, apple, from tested recipes.
• Pie fillings made with a tested recipe and Clear Jel, which is formulated for canning.

The list: never in a water bath

These are low-acid, and no water bath time makes them safe. They require a pressure canner. This is not a caution, it is the boundary the whole method sits behind.

• Green beans, including as a plain packed vegetable. Pickled dilly beans are a different food and are fine.
• Corn, in every form.
• Carrots, potatoes, beets, peas, squash, pumpkin, asparagus — plain packed. Pickled versions from tested recipes are fine.
• Meat, poultry, fish and seafood, in every form.
• Stock, broth, soups and stews.
• Beans and legumes, dried or fresh.
• Plain tomatoes with no added acid.
• Any mixed dish containing a low-acid ingredient — a salsa with too much onion for its acid, a soup, a sauce with meat.

Why acidity is the whole rule

Boiling water reaches 212°F at sea level and no higher. Clostridium botulinum spores survive that comfortably. What stops them causing harm in a jar of jam is not the heat — it is that below pH 4.6 the spores cannot germinate into the bacteria that produce toxin. The boiling water is dealing with molds, yeasts and spoilage bacteria and driving the air out to form a seal.

Take the acid away and there is nothing stopping germination in the anaerobic environment of a sealed jar. That is why the pressure canner exists: about 240°F is what destroys the spores themselves. The mechanism is set out in botulism and home canning, and SDSU Extension covers the same ground in its water bathing vs pressure canning guidance.

Tomatoes: the borderline case

Tomatoes are the food that generates the most confusion, and for a legitimate reason: they sit right at the boundary. Modern varieties hover close to pH 4.6 and vary by variety, ripeness and growing conditions, so they cannot be assumed acidic enough on their own.

Tested recipes therefore require added acid — a specified amount of bottled lemon juice or citric acid per jar — which brings them reliably below 4.6 and makes water bath processing safe. Bottled lemon juice specifically, because its acidity is standardized and a fresh lemon's is not. Skip the acid and tomatoes become a pressure-canning food.

The things that are not safe in any home canner

A short list worth knowing, because they come up constantly. Pureed pumpkin or winter squash is not recommended for home canning in any method — the density prevents reliable heat penetration, and the tested route is cubes in a pressure canner. Dairy, eggs, and thickened or floured sauces are likewise outside home canning guidance. Pesto and butter belong in a freezer.