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Everything You Want to Know About Canning

Canning, defined as a method of food preservation that uses storage containers and heat to create a vacuum seal was invented in France after a man by the name of Nicolas Appert responded to the request of the government for someone to figure out how to store food to be kept safely for use in the army and navy. Of course, canning was not the first method of food preservation, as people had been drying, fermenting, spicing, and smoking food for centuries before canning was invented. Still, it was an important part of our food preservation history and exists today relatively unchanged from how it started, only with better understanding of how to make the safest canned goods possible.


Some Definitions in Canning

To get the basics down, first you might want to learn a little bit about the language used in canning recipes. These three definitions may seem common sense at first but they can be confusing for someone who is just starting out with canning.

  1. Headspace - the space between the top of the food and the lid. The correct amount of headspace is necessary for the food to expand properly and the vacuum seal to form.
  2. Ring - the part of the top of the canning jar that you would screw on or off, depending on where you are in the canning process. This is removed when the process is finished. Rings are reusable and can be used for many years if they are cleaned properly and rust free.
  3. Lid - the part of the top of the canning jar that is held in place when a vacuum seal is successfully executed. This part remains on the jar after the ring has been unscrewed and must be removed to break the seal. The lid can only be used one time and must be replaced after each use.

What Do I Need to Start Canning?

It doesn't take much to begin your home canning journey. There are only a few things that you may not already have on hand, but these are easily purchased at a hardware store, online, in some grocery stores, or at farmer's markets, depending on the area.

  • Specialized tongs called a "jar lifter." What's the difference between regular tongs and jar lifters? Jar lifters are long, wide tongs designed to fit underneath the rim of the jar so it can be lifted out of hot water without burning the person doing the lifting. These are longer than and have a longer grip than regular tongs.
  • A wide-mouth funnel is necessary to work with your food quickly. You will want to work quickly as just a simple change in temperature will affect the quality of your vacuum seal and may be cause for the seal to not form at all.
  • A large ladle is perfect for pouring foods into the jars.
  • Clean towels or rags to wipe the rims of the jars clean before you place lids and rings onto the jars after they have been filled to the appropriate level.
  • Measuring cups of various sizes will come in handy when you are canning.
  • Spatulas are used to remove excess air bubbles or pockets from the jars after the food has been poured in. Typically, the spatula will be passed around the jar, disturbing and displacing any excess air, helping it escape.
  • A Stock Pot or a Canning Pot that is large enough to accommodate several jars and tall enough for the correct amount of water above the jars.
  • A Canning Rack to put at the bottom of the pot you will be using to can, as the jars cannot touch the bottom directly or the heat may shatter them.
  • Specialized canning jars are necessary for canning. You cannot recycle old jars for the purpose of canning. If you don't have them already, buy jars that were made for canning specifically. Some grocery stores carry them, and they are usually available at hardware stores as well. Canning jars come in a variety of sizes for your specific canning needs.
  • A timer is a good idea to have on hand as well because it will help you keep track of your food processing time. These recipes are extremely time sensitive, and it is necessary to keep an eye on the timer throughout the whole process.
  • Some people like to have a Lid Wand on hand as well, a specialized, magnetic tool designed to help remove lids and rings from the boiling water after they have been prepped for canning.

What Foods Can be Canned?

There are some limitations to what can be canned. It may seem like anything can be canned or stored in jars for a year or so, but there are some foods that aren't suitable for canning. You should try to can only whole foods if you are planning to keep them for a year or so. Fats and dairy do not can well. In the same vein, lean meats can better than fatty meats. Pastas will break down and become mushy. Oats, wheat, and flour products in general do not do well when they are canned. Some herbs, spices, or seasonings may have an effect on the acidity of the food, so you should always follow your recipe as closely as possible and not make any major changes or risk the integrity of your jars.


Can I Can on a Glass or Ceramic Top Stove?

This is a question with a tricky answer, because it can be either yes or no depending on what type of stove you have. To begin with, all flat top stoves are made with a glass ceramic blend, not a single type of material. For simplicity's sake, we will refer to this as a "glass top stove" throughout this piece. Some glass tops are fine for canning, others will shatter. First things first, contact the manufacturer of your stove and find out if it can be used for canning. If you do choose to can on your glass top stove, don't use a stock pot that exceeds the width of the actual burner circumference by more than an inch. If you do, the pot won't heat evenly and you risk making yourself sick with contaminated food or having your jars not seal properly.

Even with proper consideration and safety practices, your glass top stove may still shatter. If you have access to a different stove top, it may be best to use one of those instead. Don't use an enamel canner on a glass top stove as most will have indentations on the bottom and the bottom won't come in full contact with the stovetop. You will need a pot that has a completely flat bottom or else the pressure between the pot and the stove will cause cracking or break the top completely. Again, other stoves are much better for canning and you should not use a glass top stove for canning unless you are positive it is safe to do so and you are okay with the possibility of the stovetop shattering.


Water Bath Canning

The more common and approachable version of canning, this is the method to use in foods with high acidity. In this method, jars of food are heated under the cover of boiling water and cooked for the recipe specific amount of time. Low acid foods cannot safely be canned in a water bath.


Pressure Canning

This is a method of canning where jars of food are heated at a temperature of at least 240°F. This temperature is required to kill off any of the microorganism known as botulism, Clostridium botulinum, and any spores it may release. The bacteria can be killed at boiling temperatures, but the spores can survive much higher temperatures, necessitating this particularly high temperature in order to keep the food inside the jars safe. These spores thrive in low acid foods, but cannot survive in high acid foods, meaning that pressure canning is a necessary safety precaution when working with low acid foods. Botulism is deadly for humans.


How Do I Decide What Method of Canning I Should Use?

The acidity of the food will be the deciding factor for which type of canning you should use. Low acid foods like most vegetables, meats, soups, stews, and meat sauces, require pressure canning. High acid foods like fruits, pickled vegetables, chutneys, or fermented foods, require water bath canning.


Why Didn't My Canning Jars Seal?

There are several explanations as to why your jars didn't seal.

  • Perhaps there was a chip in the rim of your jar, making it impossible to form a truly airtight seal.
  • Maybe your jar was filled too much, and you didn't leave enough headspace for the right kind of seal to form.
  • Or the opposite is true, and you left too much headspace. This would make it impossible for the jar to seal because there is too much air inside the jar.
  • The top of the jar wasn't cleaned properly, causing an imperfect seal with the jar lid.
  • The ring was too tight. You are only supposed to tighten your ring to "fingertip tight" not fully. This means you want to be able to easily screw the lid on without much effort, and it could be easily twisted off without much effort either, if you wanted. This allows for proper pressure control as the jar is sealing itself.
  • The lid wasn't aligned with the rim correctly. Unlike rings, canning lids cannot be reused because they have a compound on them with helps them seal the jar. This compound can only be used in the canning process once.
  • The jars weren't processed for long enough or at the correct temperature. Keeping constant temperature and watching the recipe specific times of your canning adventure will help ensure proper sealing.
  • You didn't take altitude into consideration. Living at higher altitudes can alter how much or how little headspace you need in your recipe.
  • Finally, check out your supplies. Did you use a jar designed for canning? If you were trying to recycle an old pasta sauce or pickle jar, chances are you didn't use the right kind of jar. These are not made for canning, you want to use specialized, heat treated canning jars.

If your jars have not properly sealed, you can reprocess them or store the contents of whatever jars haven't sealed in the freezer for later use. There's only one jar that went unsealed, you could store it in the fridge and use it up quick!


Why Should I Remove the Rings from my Canning Jars After Processing is Finished?

Some people insist on keeping the rings on for aesthetic value, as you can see that most photographs in "canning" informationals include the ring. There are three reasons to remove the rings from your jars:

  1. Leaving the ring on creates a False Seal or even a sense of a false seal. The ring may artificially hold the lid down, so you will think it is sealed but it isn't.
  2. Rust may form between the ring and the jar, which could potentially break the seal. Unscrewing a rusty ring is also quite hard and may compromise your food inside if you break the seal while you are trying to unscrew the ring.
  3. Mold may form between the ring and the lid where food may have slipped out while the jar was processing. The mold will break the seal by growing and pushing on the lid, once again compromising the food inside the jar.

Simply remove the rings from your jars after they have naturally cooled from their heated state and carefully clean any residual food from the rims. Don't break the seal! If you do, you can store that jar in the fridge and use it up first, or you can reprocess the jar. If it turns out that you only need to reprocess one jar, you may find that storing the contents in the freezer instead is a more suitable option.

There is only one instance where you may need to keep the rings on your jars, and that is when entering them into competition. Each state and county fair has its own set of rules about what a canned good should look like, and some specify that you must have the rings on the jars. Please note that you can put the ring back on lightly for the day or days of the fair and remove it once more after the competition has ended. Never screw the rings back on too tightly or you risk damaging the seal, and always inspect the seal after you remove the ring from the jar later on.


How Will I Know if My Jars are Properly Sealed?

When you remove your jars from the water, your first sign of having done the whole process properly is the cooling down of the jars and the subsequent pinging or popping sounds you will hear as their temperature falls closer to room temperature. If this is your first time canning and you hear this, do not be alarmed! These sounds mean you've done it right. You should be more alarmed if you don't hear anything. After your jars have fully cooled, check visually for a good seal. The lid will be slightly indented if the jar is sealed properly.


How Should I Store My Jars?

Store your jars in a single row on the shelf. You should never store sealed jars on top of one another unless you've first laid down a thin piece of wood or a thick cloth to more evenly distribute the weight of the jars on the top row. The safest, surest way to reach for and find perfectly sealed jars every time is to keep them side by side, not stacked on top of one another.


Read More

The Difference Between Pickling and Fermenting
Canning Resources

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