Food canning jars safety

Not all jars are made to be used for home canning.

Extension Educators teach many food preservation classes each year. During class, one question we ask participants is, “Why do they can food?” Responses vary, but common answers are because they have a garden, want to use local foods from farmers markets, they’re avoiding additives and preservatives, it is cost effective; or, like myself, they are sentimental canners. Sentimental canners often enjoy canning with family members because it brings back memories and flavored, home-cooked food during the cold, winter months.

One mistake a sentimental canner can make is not practicing safe preservation methods, beginning with canning jars. It is important to realize that not all jars are made to be used for home canning.

I have been the recipient of many canning jars that have been passed down through family or friends. My maiden name is “Ball,” so I am a collector of the many pretty, colored jars; blue, green, purple, red, square jars, zinc lids, bale lids and more! Many of these may have nicks and chips after years of use, making them weak, increasing the possibility that they will break. Breakage during canning could cause contaminants to get mixed into your food. If you’re holding onto these old jars because of their value, consider using them for dry storage or as decorative pieces.

Sometimes it may be difficult to distinguish new jars from the old jars. Over the last few years one jar manufacturer recently released “vintage style jars” in blue, green and purple, making it confusing to tell the difference between new and old jars. Examine your jars by looking for a commemorative stamp on the new editions, and keep them separated from the old ones.

If you are a bargain hunter, your finds may or may not be the best deal. You have no idea where or how the jars have been stored. If possible, ask the seller if they know the history of the jar and be sure to examine carefully for chips, cracks and nicks. If you are unsure, consider passing on the “deal.”

For years my family members saved and re-used mayonnaise jars when it came time to can. This practice is not recommended; these jars are created to hold commercially processed food and are not designed to be re-used to process home canned food, for several of reasons.

  • First, the rim of the commercial jar may not be flat like the canning jar; it is beveled or rounded, making it difficult for the compound of the canning lid to properly seal.
  • Second, the commercial jars are made different than canning jars, they have seams and weak spots that may result in breakage in your canner, something none of us want to have happen after working so hard to fill our jars with delicious food.
  • Finally, commercial jars may or may not be the same size or shape as quart and pint size jars. The times set for safely processing food is based on pint and quart jars, this could result in a product being improperly processed making it unsafe.

If you take care of your canning jars, protect them from extreme temperatures, chips and nicks, you can use them for many years. The National Center for Home Food Preservation recommends inspecting jars each year before you begin to can.

Michigan State University Extension suggests you practice safe canning using research tested recipes and up-to-date equipment. By doing this, you will enjoy the fresh flavors of summer all year long.

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