canning – Fruition

June 26, 2025Flip and Michael Myers

Boiling Water Bath or Pressure Canning, which to use?

If you are new to food preservation, you might ask why there are two different processes for canning food: boiling water bath and pressure canning. What is the difference between them? This question often arises as individuals begin growing and preserving their own food. The decision process can seem intimidating, especially with the many differing viewpoints found on social media or stories of traditional methods passed down through generations. Fortunately, science can help us understand which methods are most effective to ensure our food is safely preserved.

The National Center for Home Food Preservation and the USDA can help take the guesswork out of your project. Their recipes have all been rigorously tested, taking into account factors such as food density, pH, and heat penetration in the jar. That’s why their guidelines are considered reliable and “approved”.

Returning to the original question: Why are some foods preserved using a water bath while others require pressure canning? The answer lies in the acidity, or pH, of the food. A basic understanding of the pH scale, often introduced in high school science classes, is helpful here. This scale measures the acidity or alkalinity of a substance, with 1 being highly acidic and 14 being highly alkaline. Water is at the center of the range with a neutral pH of approximately 7.

Understanding pH is crucial in food preservation because it directly affects food safety. The pH level determines how well spoilage microorganisms can grow and multiply in food. These microorganisms thrive in foods with a neutral pH. A higher acidity level creates an environment that inhibits their survival. The critical threshold for microbial growth in food is a pH of 4.6. Foods with a pH below 4.6 are classified as high-acid foods, while those with a pH of 4.6 or higher are considered low-acid foods. This distinction determines which canning method can be used.

From the USDA Guide to Home CanningHigh-acid foods and acidified foods are safely preserved using the boiling water bath method. High-acid foods, like berries, are naturally well below pH 4.6, so need no additional acid when combined with boiling water processing to safely prevent microbial growth. Acidified foods are naturally low-acid foods that have been preserved using a solution such as lemon or vinegar to reduce their pH below 4.6. A common example is pickling. This process involves submerging low acid foods, such as cucumbers or beans, in an acidic solution before canning. The combination of acidity and the boiling water bath process, which heats food to 212°F, prevents the growth of spoilage microorganisms.

Master Food Preserver volunteers hot filling jars of strawberry jam to be processed using a water bath canner.

February 15, 2024Kathryn Farr

The Food Preserver’s Garden

One of the great things about food preservation is the freedom to choose both foods and methods that suit our lifestyle. Over the years, I’ve enjoyed pickling vegetables, especially cucumbers, but then they sit on the shelf because I’m not excited about eating them. Nor do I usually eat the jams, jellies, or relishes I make and can. This year, I am focusing on choosing vegetables that I am confident I can preserve in ways that will appeal to me during the winter months. In this post, I’ll share some tricks I’ve learned over the years to grow and preserve foods I like. The Resources section at the end of this post includes links to get thinking about your garden.

Some preserving methods I’ve used in the past include both boiling water bath and pressure canning, pickling, dehydrating, freezing, and fermenting. I know right away that I’ll skip fermenting this year. I know, I know—probiotics, gut health, etc. I’ll get with the program someday, but not someday this year. Pickling is a tad up in the air, too, but I know for sure I will freeze many vegetables, with some canning and dehydrating thrown in the mix.

Last year I planted herbs for the first time in many years, and I was glad to freeze them to spice up winter meals. I prefer freezing herbs because they taste fresher than dried herbs, although I do have some dill and sage hanging around in the kitchen. I tried freezing herbs in a silicon mold and then storing them in baggies. I found I preferred these because they were not as messy as the loose herbs, which stick to my fingers when I use them. Plus, herbs frozen in molds [or ice cube trays] can be pre-measured.

silicon mold — These herb flowers are very convenient to drop into soups and sauces. And they’re cute.

Although technically not a “preservation” method, I dug up and repotted basil and parsley plants, both of which did well in my kitchen window. Snipping fresh herbs for recipes and garnish feels very Martha-like. This year, I will plant basil, parsley, and probably oregano with the intention of repotting them to my windowsill.

potted parsley — This parsley plant has provided fresh flavor to many recipes over the winter.

I also like to freeze what I call “flavor packs”, usually for use in soups. I prepare one-pint portions of recipe ingredients, including the vegetables, and leave out anything that does not freeze well, such as potatoes, pasta, and beans. I add those along with any thickening sauce, roux, milk, or cream when making the actual soup. I grow vegetables to make flavor packs for soups such as:

Is My Old Pressure Canner Safe to Use?

So, you spot a used pressure canner at a thrift store. Given the average price of a new pressure canner [around $200.00], that $25.00 price tag looks pretty good, but is the canner safe to use? What should you look for before using an older pressure canner? Extension employee Leslie Swartz recently posed that question to the Master Food Preserver group. Leslie had been gifted with a used Presto pressure canner and asked the group to evaluate it for safety.

The Master Food Preserver group evaluated this Presto pressure canner.

First Things First: When do I use a Pressure Canner?

A boiling water bath canner is fine for processing high acid foods like jams and pickles because molds, yeast, and enzymes are destroyed at temperatures below 212°F [the boiling point]. However, botulism spores can survive a boiling water bath, creeping inside the sealed jars of foods. Pressure canners use—well—pressure to heat the inside of the canner to 240 degrees. Water inside the canner is transformed into steam, which replaces the air in the canner, forcing the air out of jars and preventing bacteria from coming in. [The Cooperative Extension offers hands-on classes in how to use a pressure canner. See the Extension’s Events schedule.]

The Parts

The first thing the group asked was to see the canner’s user manual. We found the model number stamped into the side of the body and found the user manual online. The diagram below is an excerpt from How to Use and Care for Your Presto® Pressure Canner. Considering the critical functions of the various parts during the canning process, the group checked each part to see that it was in usable and working condition.

First Impressions

One MFP suggested checking the bottom of the canner body to see if it was perfectly flat because a warped canner bottom will prevent the canner from heating evenly. Our canner did not rock on a flat surface; its bottom was flat. Read more Is My Old Pressure Canner Safe to Use?