Home canning is experiencing a resurgence of interest. Imagine preserving the taste of vegetables and fruit at their peak to enjoy all-year long. From homemade pickles to tomato sauce and jams, canning captures the best flavors. See our introduction to canning for beginners to what canning is all about!
What Is Canning?
Think of canning as a form of cooking. Instead of cooking one meal for immediate consumption, you are cooking food that you can save and store away for months! Why do this? Because canning allows you to capture the best flavors at the peak of season—to enjoy all-year long! Imagine the amazing taste of garden-fresh tomato sauce in the middle of winter.
Canning is a method used to preserve fresh food in jars using high temperatures to kill microorganisms and inactivating enzymes that could cause food to spoil. The heating process pushes air from the jars, creating a vacuum seal as jars cool. Without air, the bacteria, yeasts, and mold will not grow and food won’t spoil.
The Two Canning Methods: Water-Bath and Pressure Canning
To can your produce properly and safely, follow one of these methods: water-bath canning or pressure canning.
Which method to use? This depends on the acidity of the food you are canning: Is the food you are canning high or low in acid? In other words, does the food have a high pH or a low pH? A pH of 4.6 is the dividing line; a pH higher than 4.6 means less acidity (“low-acid foods”) and a pH lower than 4.6 means more acidity (“high-acid foods”).
We don’t expect you to know the acidity level of every food so we’ll list this information below.
All you need to know is: Low-acid foods must be processed using pressure canning, while high-acid foods may be processed using either water-bath canning or pressure canning. You must use pressure canning for low-acid foods to prevent bacteria and toxins—which thrive in a low-acid environment—from surviving. Safety first!
Note: This pH scale from Clemson University Extension publication provides a good representation of common foods and where they fall with regard to pH. (The pH scale is not an endorsement of foods to preserve by water bath and pressure canning.)
1. Water-Bath Canning
Water-bath canning is the simpler of the two canning methods, as it involves boiling your food in glass jars in a big pot of water. There are pots specifically designed for this—called water-bath canners or boiling water canners—that consist of a large pot, a rack insert, and a lid. However, large, deep pot will do, as long as you have a rack that fits inside it and a lid.
Water-bath canning is a lower-temperature canning process (212°F), which makes it safe ONLY for high-acid vegetables and fruits. (Remember that low-acid foods must be processed in a pressure canner.)
- High-acid foods include fruits, pickles, tomatoes, sauerkraut, relishes, jams, jellies, salsas, marmalades, and fruit butters. It’s the acidity of these foods—in addition to time in a boiling water bath—which helps preserve them safely without the use of high pressure.
- If it’s your first time canning, start with the boiling water bath method! Make some pickles or a yummy berry jam!
Water-bath canning is not as big of an investment as pressure canning—and is more straightforward. Let’s call this “no pressure” canning!
To learn more about water-bath canning, see: Water-Bath Canning: Supplies and Getting Started
2. Pressure Canning
Pressure canning involves the use of a pressure canner, which is a device that consists of a large pot, a rack insert, and a fitted lid with a dial or pressure valve. The high pressure created inside the canner when it is heated allows the temperature inside to get much hotter (240°F) than it could in a water-bath canner. This kills off any harmful bacteria, toxins, molds and yeasts.
Low-acid vegetables such as green beans or corn MUST be processed at a higher temperature—240°F at sea level—to prevent the growth of bacteria, especially Clostridium botulinum. To maintain the higher temperatures for the proper length of time, you need to invest in a pressure canner which will get the job done.
- Vegetables that are low-acid include: artichokes, asparagus, carrots, corn, green beans, lima beans, mushrooms, okra, onions, peas, potatoes, pumpkin and winter squash (in chunks).
- Fruits that is low-acid includes: cantaloupe and watermelon. (All other fruit is high-acid including berries and cherries, grapes, nectarines, oranges, peaches, and plums.)
Pressure canning is also used to preserve low-acid foods such as meats, poultry, seafood, chili which also require a higher temperature to raise the heat inside the jars above boiling and long enough to kill harmful bacteria. Pressure canning can be fun and satisfying, but it does require a “canner” to get started and you need to follow direction—no ad-libbing!
If you’d like to preserve low-acid foods but don’t have access to a pressure canner, consider preserving them in other ways. Broccoli, corn, and green beans taste much better when frozen, and they will have better texture when prepared using your favorite recipes. For best results when freezing, blanch the produce briefly in boiling water, remove and cool down quickly in ice water, drain, and pack the produce in freezer bags or containers.
To learn more about pressure canning, see: Pressure Canning: How to Use a Pressure Canner
Canning Supplies
There are a few basic supplies which you’ll need in order to can at home:
- Canning jars, lids, and screw bands: Only use clean jars without cracks or nicks in them. We recommend using the tried-and-true Ball brand mason or Kerr brand jars.
- Water-bath canner or pressure canner:
- For water-bath canning, it isn’t necessary to purchase a special water-bath canner as long as you have a pot that has a fitted lid and is large enough to fully immerse the jars in water by 2 inches—and that will allow the water to boil when covered. You’ll also need a rack that fits inside the pot or canner—a cake cooling rack would do.
- For pressure canning, only use a pressure canner made specifically for canning (Presto or All American) and not a pressure cooker.
- Jar lifter: Large “tongs” that help to pick up hot jars and place safely in the pot with hot water and take them out of hot water after processing.
- Ladle: A ladle helps to spoon food into canning jars.
- Funnel: A wide-mouth canning funnel make it easier to fill your jars without spilling.
Image: Ball brand Mason jars at grocery store. Credit: David Tonelson/Shutterstock.
Where to Find Canning Supplies
Many websites, hardware stores, craft stores, and other retail outlets sell kits that incorporate most of these canning essentials, sometimes along with other handy tools such as magnetic lid lifters, headspace-measuring tools, plastic bubble removers, and jar scrubbers—all the equipment needed to be successful.
Except for single-use lids, which you must buy new every year, you can reuse mason jars, screw brands, the water-bath canner, food mill, and stockpot for many years. You’ll often find these items in good condition at thrift stores, yard sales, or in the basement of a friend or relative who’s given up on canning. If you find a nice canner with a domed cover but no rack, you can probably find one that fits your kettle in a local hardware store, farm store, or online.
Make sure you check each jar, especially the rim, for small cracks or chips each time you use it. Also, don’t attempt to use a rusty canner. I’ve learned the hard way that rust spots may spring leaks during processing, causing the flame on my gas burner to flicker or dousing it entirely, and leaving me scrambling to find a substitute canning pot.
10 Tips to Know Before You Start Canning:
- Always use fresh produce that’s in peak condition. Canning is not for overripe fruits or vegetables because they are on their way to spoiling!
- Gather all your ingredients and equipment and make sure you have everything you need before you start. Halfway through the process is no time to be running to the store.
- Follow recipes and directions exactly. No improvising because your family’s safety depends on doing this correctly.
- Sterilize the jars by washing and then keeping them hot in a pot of boiling water until you are ready to fill them. Using the dishwasher will also get the job done without the pot of boiling water!
- Use real canning jars (Ball or Kerr), screw bands, and new lids when you can. Lids on the market today do not need to be heated to activate the sealing compound before placing on the jar top.
- When you fill the jars, do not fill to the very top. This is called “head space” and can vary depending on your recipe (¼ inch or ½ inch). If you overfill the jars, the food may interfere with the lid’s sealing compound and your jars will not seal properly.
- Also, important is to wipe the jar rim and threads clean before putting on the lid and screw band. The band is tightened but only finger tight.
- Using the jar lifter, place each jar on the rack in the boiling water. Make sure that the jars are covered by at least 1 to 2 inches of water, cover with lid, and bring the pot to the boil. Start counting processing time once the water has returning to a boil.
- When processing time is done, turn off the heat and remove the lid venting the steam away from yourself. Remove each jar with the jar lifter and place upright and 1 to 2 inches apart on a cloth towel to cool. Let jars cool 12 to 24 hours.
- One sign that your jars have sealed properly is a “popping” or “pinging” sound” you hear as the jars cool. Jars that don’t seal can NOT be stored but rather place in the fridge and use within a few days.
- In general, your canned foods should last all year long, as long as they are stored in a cool, dry place. A broken seal is a sign air has gotten in. A bulging lid or a lid that seems corroded or rusty is also is a sign of spoilage.
- When you do open your cans, if you ever see mold or bubbles or a cloudiness, that is a sign that the seal popped and it’s spoiled. Do not eat!
Note: Guidelines for safe canning are always being updated. The National Center for Home Food Preservation is the trusted resource for canning regulations and more information.
Canning Safely
It’s important to know the food you’re planning on canning. More specifically, you need to know whether it is a low- or high-acid food, which dictates which canning method to use: water-bath or pressure canning.
The biggest concern is botulism poisoning. Botulism is an illness caused by the botulinum toxin, which is produced by Clostridium bacteria. These bacteria occur naturally in soil and don’t usually present a threat to people. However, they are a very hardy type of bacteria and thrive in low-acid, low-oxygen environments, like those created when we can foods. When food is canned improperly, the bacteria grow and produce their deadly toxin, botulin, making the food unfit for consumption. It’s critical that the environment inside the canned goods is inhospitable to the bacteria by using high heat (240° F) for low-acid foods or by high acidity to inactivate any toxin present.
If you are planning to pressure can, we also suggest that you have your pressure canner checked. Call your county extension office as many will check your pressure canner for a small fee.
Let’s Get Canning!
To avoid canning burnout, start with a small project at first. I love to can pickles. Most pickles need only 5 minutes processing in boiling water. Lift jars out, removing one jar at a time! Spread them out on a cloth towel or wooden countertop to cool. If you hear popping noises, it is the jars sealing. Once the jars are cool check the seal; the center of the lid should be depressed. If a jar doesn’t seal put it in the fridge to eat right away. The sealed jars can be labeled and stored in the pantry for winter.
The sight of those gleaming jars full of delicious food is very satisfying!
Ready to get started? See our beginner guides:
- Guide to Water-bath Canning (with recipes)
- Guide to Pressure Canning (with recipes)
For more information about food preservation, please check out the following resources:
USDA Complete Guide to Home Canning
So Easy to Preserve
Ball Complete Book of Home Preserving
National Center for Home Food Preservation
Your Local Cooperative Extension
This Canning Guide was updated and fact-checked as of July 2020, by Christina Ferroli, PhD, RDN, FAND. If interested in nutrition counseling and education practice to make healthier choices—or, simply stay up-to-date on the latest food, nutrition, and health topics—visit Christina’s Facebook page here.
Reader Comments
Leave a Comment
Photo Illustration
You may wish to reconsider including the picture of milk on the illustration of food to be canned - there is no safe, tested method for the home canner to can dairy products but many people do so anyway due to confusion about safety. This is not a good myth to support, even by accident. I run several local food preservation groups and would love to promote this article but would prefer not to introduce confusion about what foods can safely be canned.
pH scale
The pH scale references actually comes from Clemson University Extension publication. You can find a similar graphic from the Oklahoma State Extension publication on Importance of Food pH for Commercial Canning. Both graphics provide a good representation of common foods and where they fall with regard to pH. The pH scale is not an endorsement of foods to preserve by water bath and pressure canning. (It is not safe to process milk and milk products in a pressure canner.) We’ve added a caption clarifying the purpose of the graphic.
upside down jars
I've heard that if you turn your jars upside down after removing from canner they seal quicker. Is this true? I've been canning for 40+ years and have never done this.
Upside-Down Jars
We wouldn’t recommend it. Why mess with success? Plus, if an upside-down jar doesn’t seal correctly, you may end up with a big mess to clean up.
introduction to canning
awesome! i want to start canning and most pages are too complicated or not enough information. thank you for putting it all in one place without clicking all over the place.
Canning guide
Thanks, excellent canning guide. I have a lot of tomatoes this year so excited to try out canning.
What to do with so many large zuccini!
When I check for small ones there too small next check there giant. What can I dobesides feed to chickens.
what to do with so many large zucchini
Have you tried zucchini parmesan? Make same as eggplant parm, but use those giant zucchini!
Cauliflower and freezing
We freeze alot of our garden grown vegies...is there a trick to freezing cauliflower where it won't be mushy when you go to use them? Also would canning cauliflower be canned the same as pickles and other vegies?
how to freeze cauliflower
Hi, Angela. You’ll want to wash, then blanch your cauliflower before freezing. Cut the cauliflower into florets and then let it soak in salted water as you boil a pot of water. Also prepare a bowl with ice water. When the water in the pot is boiling, drop florets in and boil for no more than 5 minutes. Drain the cauliflower and then put in the ice water for 2 to 3 minutes. Drain again and dry. Lay the cauliflower in a single layer on a cookie sheet (or sheets) and put in the freezer. After 2 hours, transfer to resealable plastic bags or containers with lids. Eat the cauliflower within a year for best quality.
We have a Mustard Pickles recipe that uses cauliflower. You can find it in our pickling guide here: https://www.almanac.com/content/old-farmers-almanac-guides
Green beans
I am new at this. I misread the canning instructions for green beans and put 6 pints in a water bath. After they were in the canner I saw where it said pressure canner. I did leave them in for about 45 minutes. Are they already bad? It has been about a week. Thanks
canning green beans
Hi, Lynelle. When canning green beans, pressure canning is required. You could put your batch in the refrigerator and eat them soon, but they are not safe for storage.
Green beans
Thanks for your reply. Could I freeze them?
We would not recommend
We would not recommend freezing them.
Fear the can
Hi Robin, I so much want to can, but I'm scared to death of looking at my canning and to see only mold. What if I get it wrong..so nervous about canning the first time. I'm also not sure where you get new lids. They only come together in pairs (Lids with jar). Canning is a must, as waste of food cannot bring any kind of blessing. Thanks and regards,
Marina
Start small with something
Start small with something foolproof like pickles or jam and work your way up. Once you have some successes under your belt canning won’t seem so daunting.
Separate canning items
Marina,
As I was looking around your message, I discovered the date. Wow!
Regardless, besides so many places to order on-line, you can pick up individual items at any full-service, Menard's store.
c
Rings & lids to to put on Canning Jars
I have many jars to use, but no new lids and rings to seal them with. Where can I buy them? Can I buy them through you?
Hi Ann, Any store that sells
Hi Ann, Any store that sells jars should also carry lids and rings. Our local grocery store, hardware store, and garden center all have canning supplies.
canning applesauce
I been making and canning applesauce. I just read you can not do this on a glass stove? Is this really so? Said pan is too heavy and will break glass. I was using a regular stock pot that was heavier than the canner.
There are several problems
There are several problems with glass or ceramic cooktops. Many canners have concave bottoms that tend to form suction on flat glass tops. When you try to lift them the suction can be strong enough to crack the cooktop. Even if you use a flat bottomed pot, it can be too heavy when full, cracking the cooktop or scratching it if you drag the pot across it. A lot of glass cooktops have sensors that turn off when the temperature gets too hot or they cycle the heat on and off so your pot won’t boil steadily and maintain the temperature needed to safely process the food. Pots with a diameter greater than the burner by more than 1 inch can reflect heat onto part of the glass top not meant to get that hot causing it to discolor or crack. Check with the manufacturer of your cooktop before canning on it. You may have to invest in a simple electric or propane burner for canning purposes.