As a quick overview, there are two commonly used methods used for home canning: water-bath canning (using a pot of boiling water) and high pressure canning (using a pressure canner). The purpose behind both is the same: 1. to heat the contents to a degree and for a length of time that kills microorganisms which could grow to dangerous levels in stored food, 2. to inactivate enzymes that cause food to deteriorate, and 3. to create a vacuum seal.
However, these two canning methods are not interchangeable. Food safety studies conducted by the USDA have established safe practices for canning every type of food you might imagine might be canned. These days, there are very clear guidelines, specific processing times, and other details to ensure food safety. This includes guidance of when it is necessary to use pressure canning and when it is preferable to use water-bath canning. For some foods (but not all!), you can use either method.
To boil it down to its essence, which method you use depends on the acidity (or pH) of the food you are canning. Pressure canning wins for being the most versatile; anything that can be canned at home can be safely pressure canned. Also, in some cases, pressure canning has a nutritional advantage; even though it brings the food to a higher temperature than water-bath canning, it requires considerably shorter processing times, so more nutrients are retained.
However, the advantage to water-bath canning is that no special equipment is needed; you can use a large stockpot instead of buying a pressure canner. Water-bath canning’s biggest limitation, though, is that it’s only safe for foods that have a high acidity—like fruits, jams, tomatoes, and pickled or brined recipes. Many foods just cannot safely be canned using the water-bath method.
Some folks hesitate to try pressure canning, but because it is the most versatile in terms of what foods can be safely canned using it, we want to help demystify the process. Once you try it, we feel confident you’ll see the tremendous benefits and make pressure canning a part of your food preservation skills.
Some foods must be high-pressure canned for safety, since pressure canning raises the temperature well beyond what can be achieved in boiling water-bath canning.
The high temperatures achieved during pressure canning are required for low-acid foods.
A “low acid food” is basically anything with a pH above 4.6, but you don’t have to guess because…
Any modern canning recipe will clearly tell you which method should be used. (Recipes are not interchangeable between water-bath and pressure methods.)
Which Foods Require High Pressure Canning vs. Water-Bath Canning
Water-bath canning (temp of 212 °F) | for (most) fruits and tomatoes; jams and jellies; broth; some pickled items |
High-pressure canning (temp of 240 °F) | required for veggies, legumes, all meats*, and recipes including any of these ingredients |
Not recommended for home canning (we know not everyone follows this rule, but we stand by the research for safety!) | NO dairy or pasta NO broccoli, cauliflower, or cabbage** NO summer squashes NO puréed or very dense foods like whole eggs*** |
*meats includes fish, shellfish, poultry and game birds, beef, pork, venison, game meat, etc. Any flesh meat.
**pickling with vinegar is a safe way to can these because vinegar makes them more acidic. Use modern recipes only, as commercial vinegar strength has weakened over recent decades.
***density must also be considered. Puréed beans and pumpkin, for example, should not be canned at home. Commercial canneries are able to safely can these because they can reach much higher temperatures than home canners. Pickling eggs is risky for home canning, though waterglassing is an option to consider for fresh eggs.
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