Canning Food

By Charlotte King

Canning is a common method to preserve foods for very long periods, even years! Unfortunately, while home-canning has been steadily growing in popularity among homesteaders, it’s still considered too daunting to even try for many people.

Canning food is a science, not an art, and it has to be done perfectly and with care because there are risks involved. Yet, this doesn’t mean you have to miss out on the sheer joy of preserving your garden bounty!

I promise it gets easier the more you do it, and the results are completely worth the hassle.

If you want to learn how to can food, you first need to become familiar with the different canning methods, machines, equipment, and more. To help you with this, I’ve put together this extensive guide so that you can confidently try your hand at home canning.

Let’s jump in!

Benefits of Canning Food at Home

How to Can Food at home

Canned foods are often considered not to be as nutritious as fresh or frozen foods, but the truth is that canning preserves most nutrients in a food. A study has found that fruits and vegetables are just as rich in dietary fiber and vitamins, whether fresh, frozen, or canned.

Moreover, it’s been determined that, in some cases, canned products are richer in nutrients than their fresh or frozen counterparts. For example, the heating process that the food items undergo during canning seems to make the dietary fiber more soluble, and thus, easier to digest.

However, any product you want to preserve has to be handled and canned properly, following specific instructions even for their harvest, because several factors can affect the overall quality of the items and promote the deterioration of flavor, color, texture, and nutrients.

How Does Canning Work?

The food items typically go through three major steps during the canning process:

  • Processing: has to do with preparing the food by washing, peeling, slicing, chopping, pitting, shelling, or cooking the items according to the specific instructions. Then, the cans are filled with either water or juice and other necessary seasonings.
  • Sealing: requires transferring the food into cans and sealing the lids.
  • Heating: involves reaching a precise temperature for a specified amount of time to kill any enzymes and harmful bacteria in the food and prevent spoilage. After heating, the cans are quickly cooled.

Collectively, these steps remove oxygen, destroy enzymes in the food, and prevent the growth of bacteria, yeasts, and mold that are often the cause of spoilage.

Canning Terminology

Canning Jars

If you’re a beginner and are just taking your first steps into the canning journey for the first time, then you’ll probably come across some new terminology you’ll need to understand to do things right, and more importantly, safely.

Here are some of the most common terms you’ll find:

Low-Acid vs. High-Acid Foods

Understanding the acidity (pH) of the food you’re processing is important because it determines the method you can use. It’s not a matter of preference but rather one of safety.

In canning, high-acid foods are those that have a pH less than 4.6 and a high concentration of hydrogen ions. These hydrogen ions prevent the growth of common spoilage agents like most bacteria, fungi, and yeast and make them easier to kill at the temperature of boiling water.

For those reasons, high acid foods such as fruits, juices, pickled and fermented items are safely processed in a boiling-water bath canner.

On the other hand, low-acid foods have a pH greater than 4.6 that creates the perfect environment for Botulinum spores to grow. Killing these spores is crucial to make the food safe to consume, but, unfortunately, they’re quite resistant to boiling water temperatures.

Because of that, low-acid foods like meat, fish, and vegetables should be properly processed in a pressure canner.

Avoid mixing high- and low-acid foods because it can result in an overall mixture with a pH greater than 4.6, making it unsafe.

Cold Pack vs. Hot Pack

There are two different canning methods: cold- or raw-packing and hot-packing. So, which one is right for you and your food? Well, let’s see the differences between both methods first.

Raw-packing involves filling your canning jars tightly with freshly prepared but unheated pieces of food. In other words, the food is left as is, no cooking or blanching required. You obviously have to peel it and cut it into smaller pieces, though.

Then, boiling liquid is poured over the contents before sealing the jars. There will be bubbles or trapped air around the food pieces that you will have to release to prevent discoloration while in storage.

Raw-packing is the more suitable method for vegetables processed in a pressure canner.

On the other hand, hot-packing is the practice of heating food to boiling, then letting it simmer for 2 to 5 minutes before filling the jars. Partially cooking the food before packing helps remove the air out of the jar and reduce food floating. This comes in handy when canning tomatoes and firm fruits like pears and peaches.

Hot-packing is the best pack style for foods processed in a boiling-water canner.

While you might notice that the color of hot-packed foods might look no better than that of raw-packed foods at first, both the color and flavor of hot-packed products will be superior within a short storage period.

Choosing Canning Jars


Being cautious early on and taking the time to choose the right cans can save you a lot of frustration later. Always use jars that are approved for canning, and check each one for any cracks or chips. Cracks will always lead to broken jars in your canner, and even the smallest chip can cause a failed seal.

Mason jars are the most common choice when it comes to canning containers because, when used and handled carefully, they can be reused many times. However, they do require new lids each time.

The best choice are regular wide-mouth Mason-type home-canning jars with self-sealing lids like these ones here. Mason jars are usually available in ½ pint, pint, 1½ pint, quart, and ½ gallon sizes, with a standard jar mouth opening of about 2⅜ inches. On the other hand, Wide-mouth jars have openings of about 3 inches so that they can be easily filled and emptied.

Preparing the Canning Jars and Lids

Canning Food

Start with a careful and thorough examination of your jars, and discard any that have nicks, cracks, and rough edges. Such defects will prevent an airtight seal on the jar, leading to food spoilage. You can repurpose damaged jars for a craft project, but they’re not suitable for safe canning.

Then, wash your canning jars with soapy water, and rinse them well because detergent residues may affect the flavor and color of the food.

Once clean, make sure to keep your jars hot until you’re ready to fill them to prevent breakage. There are two ways you can do this:

  • Run them through a dishwasher cycle: preheat your jars by washing and drying them on a complete regular cycle. This only works if you keep the jars in the closed dishwasher until you need to fill them.
  • Submerge them in a stockpot or boiling-water canner: grab a large stockpot or your boiling-water canner if you have one and submerge your clean jars in enough water to cover them. Let the jars simmer (180 °F / 82 °C) until you’re ready to fill them with food.

However, if you’re going to process your filled jars for less than 10 minutes in a boiling water bath canner, preheating them is not enough; the jars need to be sterilized.

To sterilize your canning jars, place the canning rack in the bottom of a boiling-water canner and submerge the jars with the right side up. Fill the canner with warm water until it’s 1 inch (2.5 cm) above the top of the jars. Boil them for 10 minutes at altitudes of less than 1,000 ft (305 m) and an extra minute for each additional 1,000 ft elevation.

Once sterilized, keep the jars in hot water until ready to fill. It’s recommended that you remove the jars and fill them one at a time.

Jars that are going to be used for vegetables, meats, fruits, and thus, processed in a pressure canner, don’t need to be sterilized. The same applies to jars for fruits, tomatoes, and fermented or pickled foods that will be processed in a boiling water bath canner for more than 10 minutes.

Supplies You’re Going to Need

Supplies might vary depending on the type of food you want to preserve, but here are the most common ones:

How to Can

How to can food

As we’ve mentioned before, the canning method you choose will depend on the type of food you want to preserve. Remember to use a boiling-water bath canner for high-acid foods such as fruits, tomatoes, and pickles, and a pressure canner for low-acid foods like meat, fish, and vegetables.

If you’re in doubt, always verify that the recipe you’re following comes from a reliable source, or like I often do, double-check with the National Center for Home Food Preservation.

Most canners are designed to hold an average of 7 quart (1 L) jars or 8 to 9 pint-sized (500 ml) jars. Smaller pressure canners hold a load of 4 quart jars, whereas larger ones can hold 18 pint jars in two layers, and only 7 quart jars.

Before using your canner, whether it be a boiling-water or a pressure canner, take the time to read the manufacturer’s instructions because some of the steps can vary depending on each model.

Boiling-Water Bath Canning

Boiling-water bath canners are typically made of aluminum or porcelain-covered steel, and have perforated racks that can be removed at wish. The canner must be deep enough to ensure that at least 1 inch (2.5 cm) of boiling water remains over the top of the jars while processing.

You can use a boiling-water bath canner to preserve:

  • Fruits, and fruit juices
  • Tomatoes
  • Jams, and jellies
  • Salsas
  • Pickles and relishes
  • Chutneys, sauces, and pie fillings
  • Vinegars

How to Use a Boiling-Water Bath Canner

Water Bath Canner

The specific steps for using a boiling-water canner might vary depending on the model you own and the type of food you want to process, but in most cases, this is what you have to do:

  1. Fill the canner with enough clean water so there will be at least 1 inch (2.5 cm) over the top of the filled jars.
  2. Preheat the water to 140 °F (60 °C) for raw-packed foods and to 180°F (82 °C) for hot-packed foods. You can start preparing your food while you wait for the water to reach the required temperature.
  3. Place the filled jars with their tightened lids in the canner rack, and lower it into the water. Alternatively, you can use a jar lifter to fill the canner with the rack in the bottom. If you choose to use a jar lifter, make sure to keep the jar upright at all times to prevent spillage into the sealing area of the lid.
  4. Add more boiling water if necessary. If you’re going to process your jars for more than 30 minutes, the water level needs to be at least 2 inches (5 cm) above the tops of the jars.
  5. Turn the heat to the highest setting and place the lid on top of the canner.
  6. Once the water in the canner starts to boil vigorously, start a timer for the amount of time required for processing your food. Ensure that a complete boil is maintained for the entire process time, and, if needed, add more boiling water to keep the water level above the jars.
  7. Turn off the heat when your jars have boiled for the required amount of time.
  8. Remove the canner lid, and wait at least 5 minutes before removing the jars. Be mindful of the steam.
  9. Use a jar lifter to remove the jars and place them on top of a kitchen towel. Leave at least 11 inches (30 cm) between the jars to prevent any cracking.
  10. Allow the jars to sit undisturbed to cool at room temperature for 12 to 24 hours.

The jars will seal as they cool, and all you will have to do afterward is labeling and dating them before storing them.

Pressure Canning

Pressure canners are lightweight, thin-walled kettles with a jar rack, gasket, dial or weighted gauge, an automatic vent lock, a steam vent port, and a safety fuse.

Some people might think that it’s the pressure that kills the microorganisms in the food, but it’s the high temperatures the device can reach and maintain for a specific period. Pure steam, free of air, at sea level, can reach temperatures as high as 240°F (115 °C).

The canning recipe you follow should specify both the amount of time you have to leave the jars in the canner and the amount of pressure that’s required (in PSI, or pounds per square inch).

The process for using a pressure canner is similar to that of a boiling-water bath canner. The main difference is that, instead of being submerged, the jars will sit in just a few inches of water.

You can use a pressure canner to preserve:

  • Vegetables
  • Meats
  • Poultry
  • Seafood
  • Salsas
  • Chili

How to Use a Pressure Canner

Pressure Canner

To use a pressure canner to preserve your food, you usually have to follow these steps:

  1. Fill the canner with 2 to 3 inches (5 to 7.6 cm) of hot water. Some foods might require that you start with more water in the canner, so check the recipe you’re following for how much you need exactly.
  2. Use the jar lifter to place your filled jars on the rack. Make sure to keep the jar upright at all times because tilting it can cause food to spill into the sealing area of the lid.
  3. Leave weight off the vent port and heat the canner at the highest setting until steam starts flowing freely from the vent port. Let the steam flow continuously for 10 minutes, and then place the weight back on the vent port.
  4. Let the canner pressurize for the next 3 to 5 minutes.
  5. Start timing the processing of the filled jars when the recommended pressure has been reached (you can find the pressure reading on the dial gauge) or when the weighted gauge begins to rock as indicated by the canner manufacturer.
  6. Make sure to keep the pressure steady to ensure the safety of the food you’re processing. If the pressure should go below the recommended amount, you need to bring the canner back to pressure and start the timing of the process back from the beginning.
  7. Turn off the heat when the timed process is over. Remove the canner from heat, if possible, and let the canner depressurize. Don’t try to force-cool the canner because it can result in unsafe food or spoilage, and many other issues.
  8. Remove the weight from the vent port once the canner is depressurized.
  9. Wait 10 minutes before carefully removing the lid. Always lift the lid away from you to keep the steam away from your face.
  10. Use a jar lifter to remove the jars. Place them on a kitchen towel on top of the counter, and make sure to leave a space of at least 1 inch (2.5 cm) between them while they’re cooling. Allow the jars to sit undisturbed to cool at room temperature for 12 to 24 hours.

The sealing of the jars occurs while they cool. Once that’s done, you can finally label and date them before storing them.

Storing Canned Food

When the jar lids are tightly vacuum sealed and the jars have cooled, you can remove the screw bands. Then, wash both the lids and jars under cool running water to remove any food residue. Finally, rinse and dry the jars.

Label and date your jars, and store them in a cool, dark, and dry place. They should never be stored in temperatures above 95 °F (35 °C), near hot pipes, a furnace, or under a sink. Avoid leaving your jars in an uninsulated attic or any place that gets direct sunlight as well.

All the conditions I’ve mentioned above will cause food to lose quality and spoil. Humidity can corrode metal lids, break seals, and even foster recontamination and spoilage.

While accidental freezing of the jars won’t spoil the food unless the seal is broken, freezing and thawing can soften the products. If you live in a cold climate, prevent jars from freezing by wrapping them in newspapers and covering them with more newspapers and blankets.

Potential Dangers of Home-Canning Food

Like in any area of life, prevention is the key to ensuring safety. Here’s a summary of some of the potential dangers associated with home-canning, along with what to look out for and tips on how to prevent them.


While this type of food poisoning is rare, it can be fatal. This is actually a big reason why many homesteaders are wary of home-canning. Botulism is caused by the Clostridium botulinum bacteria, which produces a deadly toxin in canned goods that haven’t been processed or sealed correctly. This toxin attacks the nervous system, paralyzing the body and causing death.

What makes the toxin even more dangerous is that it’s quite resistant to heat and can’t be detected by sight or smell.

The best—and probably the only—way to ensure that your home-canned goods don’t have botulism is to follow the proper canning and storing methods. Pressure canning is your best ally in fighting against this deadly toxin because it produces enough heat to kill the bacteria.  On the other hand, water bath canning methods can’t kill the bacteria in low-acid foods, which is why they’re not recommended.

Old lids

While you can always reuse canning jars and rings, lids must be replaced each time you want to can food. Each jar should have a brand new lid that includes a rubber ring around the inside bottom edge and helps to ensure a proper seal.

A reused lid won’t seal properly, and it can ruin your canned food and allow bacteria and toxins to enter the jar. Once you finish the contents of a jar, I recommend that you mark the lid so that you won’t get confused on which lid is new or old next time you want to can.

Old lids can either be recycled or used for crafts or to top other jars that will be kept in the fridge but never reused for canning.

Contaminated tools

Canning Set

Safe canning practices require that canning jars are sterile before filling for ultimate safety. Sorry, grandma, simply washing and drying the glass jars isn’t enough anymore. A completely sterile environment will minimize the risk of toxin or bacteria growth.

Clean and sterilize the jars, just as I’ve mentioned in the article’s section “Preparing the Canning Jars and Lids.” In short, you have to run them through a dishwasher cycle or submerge them in a stockpot or boiling-water canner if you’re going to process them for more than 10 minutes.

Otherwise, place the jars on the canning rack in the bottom of a boiling-water canner and submerge them with the right side up. Boil the canning jars for 10 minutes at altitudes of less than 1,000 ft (305 m) and an extra minute for each additional 1,000 ft elevation.

Make sure to keep the jars warm right until they’re ready to be filled to avoid compromising their sterile condition.

Many people often forget to ensure that the work area and other canning tools are sterile as well. Simply dipping your jar lifter and other tools into boiling water for a few seconds to avoid cross-contamination will do.

Using the Wrong Equipment

I’ve mentioned this many times already, I know, but it’s worth repeating once more: boiling-water bath canners should be used for high-acid foods, whereas pressure canners are ideal for low-acid foods, but these can be used for both.

What you should never, ever use is an electric, multi-cooker appliance. It doesn’t matter if it has a “canning” or “steam canning” button on the front panel.

Why? Because while electric multi-cooker manufacturers claim that their cooker reaches the pressure required for canning, it’s the temperature—not the pressure—that matters. The temperature in the canner has to stay at a constant minimum throughout the entire process time to ensure the safety of the final product.

With a canner placed on a stovetop, this is easy to control, but what happens with electric appliances during power surges or drops? Does the temperature stay constant? Hard to know, really.

If you want to know more about why it’s not safe to use an electric multi-cooker as a canning device, check the NCHPF’s article on the topic.

Keep an Eye Out for Spoilage

It’s important to know what to look for when checking your canned products for spoilage. Examine the jars closely before opening and don’t taste or use any that shows any of the following signs:

  • A bulging lid or leaking jar.
  • Broken seal. Lids with concave centers are properly sealed.
  • Spurting liquid and off-odor or mold on top of the surface or on the underside of the lid.
  • Rising air bubbles and unnatural color.

Low-acid foods may not show any signs of spoilage, but if you even suspect the jars might have been compromised, you should treat them as having produced the botulinum toxin and should handle them carefully in one of two ways:

  • If the jars or cans are still sealed, throw them into a a heavy garbage bag. Close tightly, and place the bag in your regular trash container.
  • If the jars or cans are unsealed, open, or leaking, you have to detoxify them before disposing of them. I’ll teach you how in the following section.

How to Detoxify Spoiled Canned Food

Canned Jam

The botulinum toxin can be fatal even if it enters through the skin, so be extremely careful not to contact the suspect food or liquid. Always wear disposable rubber or heavy plastic gloves, an apron, and long-sleeved clothes. Said apron and clothes, if contaminated, have to be bleached or thrown out.

Step-by-Step Instructions to Detoxify Canned Food

  1. Lay the jars and their lids on their sides in a large stockpot, pan, or boiling-water canner (don’t use your pressure canner for this!) Be very careful not to spill anything.
  2. Wash your gloved hands thoroughly with soapy water after handling the suspect jars.
  3. Add enough hot water to the pot to completely cover the containers. There should be a at least 1 inch (2.5 cm) of water above the jars. Do it slowly to avoid splashing any liquid.
  4. Cover the pot with a lid and bring the water to a boil.
  5. Let the food, jars, and lids boil for 30 minutes to detoxify them.
  6. Allow the containers to cool and discard everything (containers, their lids, and food) in the trash.

Be mindful of where you leave the jars to cool and keep them away from children and pets!

How to Deal with Contaminated Surfaces

Contaminated surfaces include any countertop and equipment (including can openers and clothing) that could have come in contact with suspect foods or liquids. Do the following to clean them up:

  1. Prepare a solution of 1 part unscented, liquid, household, chlorine bleach (5 to 6% sodium hypochlorite) to 5 parts clean water. Be careful when working with bleach and avoid inhaling it or having your bare skin come in contact with it.
  2. Spray or wet any contaminated surfaces with the mix and let sit for 30 minutes.
  3. Use paper towels to wipe the treated areas, and place them in a plastic bag before putting them in the trash.
  4. Do a second round of bleaching, and let sit for 30 minutes again before rinsing.
  5. Wash all detoxified surfaces and discard the palstic gloves when the cleaning process is complete.

Summary: Home-Canning Tips

Canned Food

If you’ve reached this far, I’m impressed! It means you’re really invested in learning how to properly can your food. So, as a reward, I will make a quick summary of the most important aspects of home-canning, along with some personal tips to achieve the best results.

  • Choose only fresh, firm produce to can. If it’s moldy or soft, throw it away! Even bruises on your food can affect the quality of the final product.
  • Never use lids that aren’t designed for home-canning. To play it safe, go for one of the three most common brands: Kerr, Mason, or Ball.
  • Never reuse canning lids. It can easily cause a failed seal, no matter how carefully you’ve removed them.
  • Wash and sterilize your canning lids before placing them on a jar.
  • Keep both the jars and the lids warm until ready to fill.
  • Don’t over-fill your jars. I know, you want to fit as much food as possible, but this will affect the quality of the seal and might lead to uneven processing. Fruits and most vegetables can be packed within ½ inch (1.3 cm) of the top (headspace). However, meat and some vegetables, like corn, beans, and peas, tend to swell while processing, so they require a 1 inch (2,5 cm) headspace. Raw packed meat requires even more space.
  • The rim of the jar should be wiped clean. Any pulp, grease, liquid, or bits of food can cause a failed seal.
  • Canning bands must be clean, rust-free. You should screw them down firmly by hand. Avoid overtightening them because it may break the jar while processing. The canner does the sealing, not you.
  • If you’re a beginner, I recommend that you start off with some of the easiest foods to can: fruits and tomatoes in a boiling-water canner. Once you gain more confidence, move on to some easy pressure-canned vegetables like carrots, mushrooms, rutabagas, and tomato sauces. If you want to try your hand at some of the “harder” foods, go for corn, salmon, pizza sauce, or chili.

Frequently Asked Questions

Canned Olives

What kind of containers can I use to can food?

Food is typically canned in glass jars, but you can also use metal containers. The difference is that metal containers are usually expensive, can be used only once, and require special sealing equipment. Honestly? They’re not worth it. Glass jars are much more convenient for home-canning purposes.

How do I know if my jars have sealed properly?

After allowing the jars to cool for 12 to 24 hours, you can test the seals in three different ways:

  • Option 1: Press the middle of the lid with your pointing finger and release it. If the lid gives in and springs up, then it’s unsealed.
  • Option 2: Grab a teaspoon andtap the lid with the bottom. An unsealed lid will make a dull sound,whereas a properly sealed one will make a ringing, high-pitched sound.
  • Option 3: Examine the lid closely, holding the jar at eye level. The lid should be slightly curved in the center, if it’s otherwise flat or bulging, it’s not sealed.

How long do canned foods last?

Properly canned and stored foods can last several years, but they start to lose nutrients and flavor after a year in storage. But if you’re preparing for a zombie apocalypse and don’t care about taste, then you can confidently stock up on canned foods for about 10 years!

What can I do if my jars don’t seal?

Don’t worry; a failed seal on a jar is not the end of the world. Simply remove the lid and check the rim of the container for tiny nicks or cracks. If you notice any, change the jar and lid, prepare them, and reprocess the food using the same processing time within 24 hours.

Another option involves adjusting the headspace in unsealed jars to 1½ inches (4 cm) to freeze them instead of reprocessing them. You could also store single unsealed jars in the refrigerator as long as you consume them within a week.


Canned Jam

As you can hopefully see by now, home-canning is not that difficult! However, knowledge is power, and knowing precisely the dangers involved in canning your food and how to prevent them is the first step to successful canning.

I’ve guided you through everything you need to know about this wonderful method for food preservation, from the benefits and specific terminology you’ll come across in recipes to how to choose the right containers, operate the different canners, and check for signs of spoilage.

All that’s left now is for you to try your hand at it and share your experience with me!

Check out our other Canning Guides!

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