Are You Making These Canning Mistakes?

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Canning isn't difficult. Let me repeat that: Canning ISN'T difficult! That is, as long as you follow recipes and directions from a reliable canning book (I recommend The Ball Complete Book of Home Preserving) or website (The National Center for Home Food Preservation is considered the gold standard). 

But if you learned to can years ago, or you learned from someone who isn't up on the latest and safest home canning practices, sometimes bad habits come into play. Some of these might not be considered a big deal; they will only waste money or time. But some errors can result in food that's unsafe to eat - possibly even creating food that has the potential to kill someone. Are you making any of these mistakes?

Mistake #1: Tweaking Recipes 

Canning recipes should be followed exactly. Changes can either make foods unsafe because the changes lower pH level, or because they make the food too dense to heat completely through for the required amount of time to kill pathogens. That said, there are a few things you can safely change about canning recipes: 

* Sugar preserves color and flavor, but doesn't make canned food safe to eat; therefore, it's safe to omit sugar in canning recipes. (See "Canning Without Sugar or Salt" for more information on this topic.)

* Salt is always optional in canning. 

* In any canning recipe, it's safe to omit dried herbs or replace them with different dried herbs. (It is not safe to use fresh herbs; they can change the density of the food, potentially causing it not to get heated through, leaving dangerous pathogens behind.) 

* It is fine to switch out pepper and onion types or varieties. Don't increase amounts, though.

 * It's safe to select smaller jars than what the recipe calls for - but don't reduce the processing time. For example, if you choose to can something in a jelly jar, but the smallest size jar the recipe calls for is a pint jar, use the pint jar processing time. (Never select a larger sized jar than the recipe mentions; this can lead to pathogens not getting killed off.)

Salt is always optional in canning recipes.

Mistake #2: Not Adjusting for Altitude 

If you live above 1,000 feet, you must adjust the processing time for your canned foods, or risk an unsafe end product. Home canning is largely about heating up food to a temperature that kills all pathogens; since water boils at lower temperatures as altitude increases and lower boiling temperatures kill pathogens less effectively, you'll have to process your jars for a longer period of time.

You can find the correct processing times for your elevation at The National Center for Home Food Preservation website. To prevent errors in this regard, I highly recommend penciling in the correct processing times for your location in every canning book you own.

Mistake #3: Using Incorrect Headspace 

Getting headspace right is easy - and also important for a safe end product.

Any safe canning recipe should explain how much headspace to use. (Headspace is the space between the top of the food and the top of the jar.) If you use too little headspace, the jars can't release air during processing, which leads to lid seal failures. Using too much headspace keeps air in the jar, causing food to darken over time; it may also eventually lead to food spoilage even though the jars sealed. 

Generally speaking, jams, jellies, and juice require 1/4-inch headspace, fruit requires 1/2-inch, things that go into a pressure canner (low acid foods) need 1-inch headspace, and pie fillings need 1 1/2 inches headspace. 

Don't worry if the headspace in your jars changes after canning. If you start out with the correct headspace when the jars go into the canner - and if the lids seal - the food inside the jars is safe. 

For more about headspace, see "The Importance of Headspace in Canning."

Mistake #4: Not Inspecting Jars 

While it's easy to overlook defects in jars, doing so increases the chances those jars will break during processing or that the jars will not seal. Therefore, I recommend inspecting each and every jar as you wash it in preparation for canning - and that you inspect once again before filling jars with food. Run your finger around the jar's edge, feeling for chips, cracks, or uneven surfaces that will cause seal failure. Also look for hairline fractures or any imperfections on the rest of the jar, which could lead to breakage during processing.

Mistake #5: Over-Tightening Lids 

Getting the lid screw band correctly applied is important.

When I started canning, for the life of me I couldn't figure out why canning books said to secure the jar rings until they were "fingertip tight." What the heck did "fingertip tight" mean?? Here's what I later learned: Turn the jar screwband until you just feel resistance. If you tighten it more than that, you can overtighten, which prevents air from escaping the jar during processing. This, in turn, leads to bucked or creased lids, which are not safe for storage.

EXCEPT...when you are using re-usable canning lids. In that case, always follow the manufacturers directions on how tight to apply jar rings. (For complete instructions on using Harvest Guard reusable canning lids, click here.)

Mistake #6: Not Using Enough Water 

Water bath and pressure canners require different amounts of water inside the pot in order to safely process jars. To know how much water to put in a pressure canner, consult your manual. For water bath canning, add enough water to cover the jar tops by 1 - 2 inches. Since some water will boil off during processing, I recommend aiming for 2 inches of water above the jars. This safety measure ensures the food gets heated evenly, killing all pathogens.

Mistake #7: Not Bubbling Jars

Some canned foods, like applesauce, will always have some bubbles in them, but it's important to try to remove as many bubbles as possible before processing.

Before putting a lid on your jars and processing them in a canner, it's important to "bubble" each and every one. This is accomplished by taking a wooden skewer or plastic spoon handle and running it between the jar and the food, removing air bubbles. (Never use metal utensils, since they can damage jars, resulting in hairline cracks.)

Failing to bubble can cause you to think the headspace in your jar is correct - but once air works its way out of the jar during processing, the contents will collapse, leaving too much headspace behind. 

BUT...even if you bubble your jars correctly, you may still discover air bubbles in them after processing. The idea behind bubbling is simply to remove as much air as possible; some small amount may be left behind, especially when canning dense foods like applesauce.

Mistake #8: Sterilizing Jars 

My husband's grandmother taught me to can, and part of her education in preserving was to sterilize canning jars - boiling them before filling them with food. Years ago, when certain items like jams and jelly didn't get processed in a canner, this type of jar sterilization was necessary. But it also left plenty of room for error, and sometimes resulted in food that was sealed in a jar, but still went bad. (Botulism spores and other pathogens are everywhere, so sterilizing before processing simply doesn't cut it.) 

These days, all safe canning recipes should include processing times; therefore, sterilizing jars is completely unnecessary. If there are pathogens in your jars, in your equipment, or in your food, running the jars through the canner kills them. 

Mistake #9: Using a Pressure Cooker 

Low acid foods must be processed in a pressure canner, unless they are pickled.

Some pressure canners can be used as pressure cookers, but pressure cookers should never be used as pressure canners - despite what some pressure cooker manufacturers claim. The reason is simple: Pressure cookers cannot hold enough water to safely bring jar contents to a temperature that kills harmful and deadly pathogens. 

In addition, pressure cookers are made of thinner metal than pressure canners, which means the time it takes them to come to pressure (and to cool down) is shorter than what a pressure canner experiences. This, in turn, means the canned food doesn't stay hot long enough to fully kill pathogens during processing. For more on this topic, see "Pressure Canners vs. Pressure Cookers."

Mistake #10: Using a Water Bath Canner 

There is a growing group of people who are using water bath canners to preserve everything - even low acid foods like meat and vegetables (which are foods that, let me be clear, should only be canned with a pressure canner...unless they are pickled). They claim "this is how it was done in the old days." But there is a myriad of problems with this idea. 

First, it's incorrect that water bath canning of every type of food was ever widespread. I happen to have a large collection of old household guides dating back to the early 19th century. All of these old books say only fruits, jams, and jellies should be processed at home. in a water bath canner. Of those books published after pressure canners became available, every one stresses that low acid foods (meat and vegetables) can be preserved through home canning - but only by using a pressure canner. 

Second, among those few people who did practice unsafe water bath canning of low acid foods, certain measures were taken to help prevent illness. For example, the jars were stored in a refrigerator-like location (a cold root cellar) and the food was always boiled (sometimes for an hour or more) before eating. This helped kill many pathogens - although botulism can survive the temperatures of a water bath canner, even after hours of boiling. 

Honestly, why anyone want to eat low acid foods canned in a water bath canner? According to its proponents, the processing times are quite long (over an hour). Boiling food for this long greatly reduces nutrients and makes it mushy. Why not just learn to pressure can? It's the only truly safe way to can low acid foods.

For more science behind the pressure canner vs. water bath canner debate, see "What You Need to Know About Botulism and Home Canning" and "Everything You Need to Know to Start Home Canning."

Mistake #11: Using Liquid and Powdered Pectin Interchangeably

Understanding pectin will make your jams and jellies taste better.

When making jams and jellies, don't use liquid pectin when powdered pectin is what the recipe calls for - and vice versa. Liquid and powdered pectin are used in different ways and are not interchangeable. 

Always follow the manufacturer's instructions on how to use whatever store-bought pectin you buy. For more about this topic, including how to use homemade pectin, see "Understanding Pectin."

Mistake #12: Not Cleaning Processed Jars 

After all the work of prepping food, getting it into jars, and processing it in a canner, it's tempting to immediately put finished jars in your cupboard. This is a mistake. Not only should processed jars sit completely undisturbed for 12 - 24 hours (while sitting at least 1 inch apart), but it's important to make sure there's no food on the outside of the jars before tucking them away in your pantry. 

And yes, food can end up on the outside of your jars because some of the contents leaked out during processing. Usually, this leaves only a bit of sticky residue behind, but sometimes you might even see particles of food on the exterior of jars. Either way, dirty jars result in mold and pathogens that could make you ill. To avoid this, simply wash processed jars in warm, soapy water and dry them with a towel before putting them into storage. 

Mistake #13: Throwing Out Old Jars of Food 

How long home canned food stays safe to eat is a question often asked and often misunderstood. But the truth is, home canned food remains safe to eat as long as a scientifically tested recipe was used and the lid is still sealed. 

Slowly, over time, canned food loses nutrients, color, and flavor, but this is a quality issue, not a safety issue. The 1 year recommendation oft quoted is a "best by" date that will ensure you eat the food when it's at its peak of nutrition. It is not an expiration date or an indication that the food will spoil after that time. For more on this topic, see "How Long Do Home Canned Foods Last?"

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