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The Ultimate Guide to Canning: Types of Canning and When to Use Them

Various types of vegetables being canned using airtight jars.

The Invention of Canned Food

Discover a healthy and delicious way of preserving food with this ultimate guide to canning where we give you the knowhow, history, the various types of canning, and when to use them.

It was 1795, and the French army was desperate for proper sustenance.

Long wars had spread their resources thin and there was no feasible way of feeding such large armies a proper, healthy meal. Their malnourished officers would often resort to foraging, but their efforts were usually unsuccessful. Conditions were looking bleak. In desperation, the French army offered the hefty sum of 12,000 francs to whoever could come up with an effective way of preserving large amounts of food in convenient packaging.

A historical illustration of French soldiers.

Nicolas Appert, a Parisian confectioner, vintner, chef, brewer, and pickle maker, came up with a brilliant solution. He packed cooked foods into champagne bottles, plugged the tops with corks, wire and sealing wax, and then boiled the jars. He proudly showed off his work; jars variously filled with roast, partridges, raspberries, peas, beans, broth, and gravy. The French military couldn’t have been more pleased. Appert was most pleased though. 12,000 francs in that day was no modest sum, and the recognition of such an innovation would grant its inventor some serious clout.

However, his innovation wasn’t perfect. It would be another 50 years until better jars would be made in the U.S. You see, Appert’s contraption was a tricky mix of cork, wire, and wax; it was too complex, too intricate. In 1858, Mason — a tinsmith from New Jersey — patented a much simpler jar design, which used a zinc screw cap. The jars were transparent, an aqua blue color which made it easier for homeowners to see the contents of their jars.

Although it is now dubbed the Mason jar, many other manufacturers would come up with more and more efficient designs of Mason’s original design. It’s a common conception to think that canning is done strictly in tin cans, but that isn’t always the case. Canning isn’t in any way defined by the type of container used. It can be done in both glass jars and tin cans.

A variety of canned food in tin cans.

But First, What is Canning?

Canning describes the process of placing food in airtight containers and heating them to kill all the bacteria. Creating a vacuum seal and removing all oxygen from inside the container makes it impossible for bacteria to live inside. The containers used in canning are airtight containers like mason jars and steel tin cans.

Some Notable Mentions

Canning is so effective that the shelf life of canned goods typically ranges from one to five years. In fact, under the right circumstances, canned food can last much longer. In 1974, samples of canned food recovered from the wreck of the Bertrand, a steamboat that sank in the Missouri river in 1865, were tested by the National Food Processors Association. Although no one in their right mind would eat 109-year old food, there was not a trace of microbial growth and that the samples were deemed safe to eat. Technically.

Canned foods have always been a vital part of expeditions, too. In his search for a Northwestern passage to India, Sir Edward Parry took canned beef and pea soup along with him. In 1829, Sir James Ross also took canned food along in his expedition to the Arctic. Canned food can last for long periods of time while remaining edible and nutritious.

Another Reason Why Canning is So Popular

Without refrigeration, dairy products will sour and fish will ooze. Without pickling, drying or bottling, perishable foods like okra, mangoes, and cabbage cannot stand the test of time. As much as drying, refrigeration, and other processes are great ways to preserve food, canning, because of the processes involved, has a desirable ‘side-effect’. Some canned goods taste better after they’ve been canned.

Here’s the reason:

The canning of organic matter may lead to the loss of semi permeability of cell membranes and solubilization and breakdown of pectic substances in the cell walls. The result is that the food loses its crispness and becomes softer. Chemical processes also alter the taste of the food and release flavors that weren’t present before. This is desirable as it makes the food more palatable. Also, because the food is softer, it makes the vegetables pliable enough to be packed tightly.

Although canned goods can last a long time, after a year, chemical processes slowly begin to alter their flavor, texture and nutritional value. To get the most out of your canned goods, always date the jars and make sure to use the older stock first.

Essential Equipment For Different Types of Canning

The first thing you need is a recipe book. As you’ll see later, recipes are the foundation that allows canning to be safe and effective.. You cannot preserve food properly without a tried and tested recipe. You should try to find the latest information from reputable sources. Avoid the dog-eared yellowing cooking pamphlet in your library; also avoid any homemade recipes or recipes from TV shows. You can get the most authentic information from publications made by the U.S Food and Agriculture Department, College Cooperative Extension services and major food processing equipment manufacturers.

Homemade strawberry jam being placed inside jars.

Apart from the canners themselves, there is a myriad of equipment needed to ensure that your produce is properly preserved. You’ll need either a water bath canner or a pressure canner — it depends on the type of food you’re canning. Both types should come with a rack. You’ll also need a:

  • long handled spoon
  • large measuring cup
  • timer or clock – important for accurate heat treatment times
  • lid wand – easier for removing lids from hot water
  • jar funnel
  • jar lifters (not totally necessary)
  • narrow, rubber spatula

As for the canning jars, they come in two styles; modern style jars with two-piece metal lids and older style jars with glass dome lids, a wire bail and a rubber gasket. The U.S Department of Agriculture recommends that you use the modern jars and new metal lids.

Various preserved vegetables placed inside jars.

Wide-mouth jars and regular jars work well for canning. Although wide-mouth jars are more expensive, they are easier to fill and they work really well with larger foods; whole fruits or pickles. When choosing your jar, make sure to check for nicks in the rims or cracks in the body. If your jar isn’t perfect, it won’t seal properly. And a perfect vacuum is what you want.

Types of Canning

There are two main types of canning:  water bath canning, and pressure canning.

Water Bath Canning

Water bath canning is a type of canning done by submerging the jars in boiling water and cooking them for a specified amount of time. A water canner is simply a large pot with a removable rack which holds all the jars. The rack keeps the jars off the bottom of the pot and allows the jars to be evenly spaced. It also allows the boiling water to flow around and underneath the jars for a more even heat treatment of the contents.

Canning jars being boiled in a pot to kill bacteria.

In the case that you do not have a canner, any large metal container would do. You only have to make sure it’s deep enough for 1 to 2 inches of bubbling boiling water to totally cover the jars. To make sure that all the jars are thoroughly heated, the diameter of the canner should be no more than 4 inches wider than the diameter of your stove’s burner and shouldn’t extend more than 2 inches on any side. In the case that you use an electric heater, make sure that the container has a flat bottom so that the canner is heated evenly.

Pressure Canning

Pressure canning is a type of canning method used in the processing of foods that need to be processed at higher temperatures. This method should be dedicated to food that is lower in acidity, like carrots and cucumbers. Water bath canning is not an effective way of heat treating low acidity produce.

Contrary to what many people think, pressure canning isn’t done in traditional pressure cookers. The pressure cooker is not an ideal option for temperature control, and it runs the risk of food not being heat treated properly, which is necessary in destroying the stubborn Botulism-causing bacteria. Besides, differences in the sizes of pressure cookers make it near impossible to adjust processing times safely.

An old pressure cooker on a white background.

Long story short, always use a pressure canner, never a pressure cooker.

Options of Pressure Canners

Unlike water bath canners, pressure canners will either have a weighted gauge or a dial gauge.

Dial gauge canners have a dial that indicates pressure. You must monitor the dial gauges so that the pressure doesn’t fall below the required level. At higher altitudes, dial-gauge canners are recommended because you can more easily monitor and adjust the pressure in the canner to compensate for higher altitudes.

Weighted-gauge canners on the other hand have small weights—anywhere from 5 to 15 pounds, that are placed over the vent. They rock or jiggle when the correct pressure is attained. At altitudes of more than 1,000 feet, dial gauge canners are recommended because you need to precisely increase the pressure at 5 pounds for every 3,000 feet.

Which one is best? The simple answer is ‘it depends’. But if you do choose to use a dial-gauge canner, it needs to be inspected annually to ensure its dial registers correctly and that the canner works well.

Choosing a Preferred Canning Method

Different foods have different acidic contents, and acidic content is by far the most important factor in determining the canning process you’ll use. Foods that have a higher PH-value have increased acidic content, which creates a more hostile environment for bacteria. Simply boiling them at the 100 degrees Celsius (212 F) is enough to kill off any microbes that may remain. Water bath canning is a sufficient method of food preservation for foods that are highly acidic, as there is less of a risk of bacteria surviving.

On the other hand, foods with a low PH-value are tourist destinations for bacteria. These foods have to be boiled at temperatures higher than 100 degrees Celsius, and the only way to raise the boiling point of water is by increasing the pressure. Hence the variety of canning called pressure canning.

A microorganism called Clostridium botulinum is why pressure canning is necessary. Although the cells of this bacteria die off at boiling temperatures, they may develop spores that can withstand boiling temperatures. These spores can grow uninhibited in low-acid foods and produce the deadly botulinum toxin.

An old jar of jam with mold spores on top.

Depending on the recipe, some low-acid foods can be canned with a water bath canner. Cucumbers, for instance, are naturally low in acid, but when you add vinegar to them to make pickles, they become a high-acid food that can be processed in a water bath canner.

Something to Consider

Just like cooking, canning is rewarding. But there are some differences in results.

With cooking, you can follow the recipe or play around with it, upgrade and swap out things as you like. You can leave out much of the garlic in the stew or add more nuts to the bread; you can adjust the whole thing to suit your own taste and make the recipe truly yours.

But with canning you cannot do this. You have to follow the recipe strictly. You cannot deviate as experimentation is dangerous. Too low a temperature or too little time may result in partial sterilization. On the other hand, too much time or too high temperatures may mean that you’re stripping the food of all its nutrients.

Follow the recipe.

A man consulting the cookbook while preparing food.

The main reason—no, the only reason you should follow the recipe is because of the real danger of botulism. Clostridium botulinum and its spores are everywhere; in the soil and in water. The spores are by themselves harmless; however, the spores will survive even boiling water temperatures. But at room temperature, in an oxygen-free, low-acid environment, the spores that survive boiling temperatures thrive and convert to growing cells. As these cells grow, they form a potent nerve toxin. When this toxin enters the human body, it bonds with the body’s nerve endings and fatally affects the nervous system. If untreated, it can lead to death.

Given that last bit of information, it’s important to note that this is a rather rare occurrence. It should not deter you from getting into the practice of canning, but it should make you pay close attention to the process.

Let the Canning Begin!

1. Read the Recipe

Before you start out, make sure you’ve read the recipe thoroughly and make sure you have all the ingredients at hand as well as all the necessary utensils.

2. Heat Jars & Lids

Before and during the preparation of your food, the containers and lids need to be heated. Submerge them in boiling water for at least 10 minutes. Let them sit there until they are needed. You may use a dishwasher (on a regular cycle) to clean the jars and keep them hot.

3. Fill the Containers

As soon as you begin reading any recipe, you’ll find that there are two methods of filling jars. Raw/cold packing, and hot packing.

Cold packing describes the process of putting cold uncooked food into a heated jar and then pouring a hot liquid over the food to fill the jar.

Homemade cherry jam being poured in a large jar.

In contrast, hot packing is when precooked food is poured into a hot jar. Hot packing is preferred because it softens the food and allows the content to be packed in with ease.

“Headspace”

Related: Types of canning racks

When fruits or vegetables are packed into jars, a certain amount of space must be allowed between the top of the foods and the lid of the jars; this space is called headspace.

It allows the food to expand during the canning process and this is crucial to creating the vacuum seal. It’s also important to leave the right amount of headspace, depending on the food you’re canning. If you leave too little headspace, the food may bubble out leaving deposits which interfere with the seal. Starchy foods like baked beans and pumpkins usually need a lot more headspace.

On the other hand, if you leave too much space, the jar may not seal properly as all the air may not be driven out of the jar. The rule of thumb is to leave an inch or so of headspace for low-acid foods, including meats and vegetables; one-half inch for acidic foods like tomatoes and one-fourth inch for things like jellies, relishes and juices.

4. Placing Jars in their Canners

Once the jars are filled, remove any air bubbles by inserting a nonmetal spatula or chopstick into the jar and gently agitating the contents. Clean the mouth of the jar with a moist cloth to remove any particles that may prevent a solid seal.

Tighten the lids on the jars and place the jars on the rack in the water bath canner or the pressure canner. In a water bath, about 1 inch of water must cover the tops of the jars. Start monitoring the processing time immediately the water begins to boil.

In the case of the pressure canner, fill the canner with 2 to 3 inches of simmering water. Cover it up and allow the stem to steadily vent through the petcock (the valve on the pressure canner’s lid) for 8-10 mins. Start monitoring the processing time when the pressure is brought to 10 pounds. You’ll know this when the weight rocks steadily.

Once the gauge reaches the appropriate pressure, you’ll have to adjust the heat source to maintain steady pressure.

Once the processing time is complete, turn off the heat, let the canner sit and allow the gauge to gradually fall to zero before removing the jars. When you remove the jars, space them well so they can cool properly. If a jar cools too rapidly, it can break. As the jars begin to cool, they’ll ‘pop’ when they are properly sealed. If you discover that a jar did not seal properly, simply refrigerate it and consume it as if it was fresh produce.

There is something very satisfying about seeing a pantry full of beautiful bright yellow, rich red and vibrant green jars full of nourishing food and knowing that you were involved in every step; from planting the first seed to harvesting and then canning.

You’ll also be confident that you have enough food for the Zombie apocalypse.

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