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Johnson County

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Johnson County
11811 S. Sunset Drive
Suite 1500
Olathe, KS 66061

Office Hours:

Monday - Friday,
8:30 a.m. - 5 p.m.

(913) 715-7000
(913) 715-7005 fax

Map to our office

K-State Research and Extension is committed to making its services, activities and programs accessible to all participants. Reasonable accommodations for persons with disabilities may be requested by contacting Johnson County Extension at (913)715-7000. Notify staff of accommodation needs as early as possible.

Kansas State University Agricultural Experiment Station and Cooperative Extension Service

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Preserving Tradition – And the Summer

Canning Do's and Don'ts

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As I look out onto my garden that’s budding over with tomato plants, I see only one thing in my mind - jars. Jars of freshly preserved tomato sauce, tomato salsa, tomato jam, and lots and lots of jars full of diced tomatoes for future unknown recipes.  

Many remember canning at home this time of year with their mother or grandmother. I myself had never even heard of canning until I was an adult. But like many 30-something year-olds these days, I am hooked. Popping open a jar of home-preserved foods in the middle of winter brings a little bit of summer warmth to cold snowy days. My favorite thing about canning is knowing that I can enjoy my summer garden efforts all year long without wasting any of my crops and without having to rely on store-bought ingredients.

Preserving foods at home is not an easy task. It’s a very time-consuming process that requires a lot of equipment and a lot of patience. But for some reason, canning also inspires a willingness from others to help — especially children. I can never get my eight-year-old son to help me cook. But when I pull out my canning equipment and jars, he’s right there waiting and ready to assist.

There is one important thing to remember when canning. This is a process that must be respected. The essential act of canning is taking food — an item that is in a continual state of decay — and stopping that process. When you freeze life like this, you don’t want it incorrectly. There are two main points to remember when canning foods at home: 

  1. Use a current (not older than 8 –10 years) recipe from a credible source (Extension Office, USDA, National Center for Home Food Preservation, Ball).
  2. Follow the directions EXACTLY.

Canning is a science that changes over time

The hardest thing for many to understand is that canning is a science that’s continually being researched and updated, and over time. The rules change. The best way to stay updated on the rules is to only use current recipes from credible sources. If you ever have questions about a recipe, you can always call the Extension Office at 913-715-7000.

In addition to following an approved recipe, it’s important to use the proper equipment and methods.  Currently, there are only two approved methods for canning food: using either a water-boiling canner or a pressure canner.

Other canners and methods used in the past, like open-kettle and steam canning are no longer recommended. Open-kettle canning and the processing of freshly filled jars in conventional ovens, microwave ovens, and dishwashers are not recommended, because these practices do not prevent all risks of spoilage. Steam canners are not recommended because processing times for use with current models have not been adequately researched. Because steam canners do not heat foods in the same manner as boiling-water canners, their use with boiling-water process times may result in spoilage. So-called canning powders are useless as preservatives and do not replace the need for proper heat processing. 

Use proper canning containers

Food may be canned in glass jars or metal containers. Metal containers can be used only once. They require special sealing equipment and are much more costly than jars.

Regular and wide-mouth Mason-type, threaded, home-canning jars with 2-piece self-sealing lids are the best choice. They are available in ½ pint, pint, 1½ pint, quart, and ½ gallon sizes. The standard jar mouth opening is about 2-3/8 inches. Wide-mouth jars have openings of about 3 inches, making them more easily filled and emptied. Half-gallon jars may be used for canning very acid juices. Regular-mouth decorator jelly jars are available in 8 and 12 ounce sizes. With careful use and handling, Mason jars may be reused many times, requiring only new lids each time. When jars and lids are used properly, jar seals and vacuums are excellent and jar breakage is rare.

Most commercial pint- and quart-size mayonnaise or salad dressing jars may be used with new two-piece lids for canning acid foods. However, you should expect more seal failures and jar breakage. These jars have a narrower sealing surface and are tempered less than Mason jars, and may be weakened by repeated contact with metal spoons or knives used in dispensing mayonnaise or salad dressing. Seemingly insignificant scratches in glass may cause cracking and breakage while processing jars in a canner. Mayonnaise-type jars are not recommended for use with foods to be processed in a pressure canner because of excessive jar breakage. Other commercial jars with mouths that cannot be sealed with two-piece canning lids are not recommended for use in canning any food at home.

Jars with wire bails and glass caps make attractive antiques or storage containers for dry food ingredients but are not recommended for use in canning. One-piece zinc porcelain-lined caps are also no longer recommended. Both glass and zinc caps use flat rubber rings for sealing jars, but too often fail to seal properly. 

As you can see, canning is a very involved process. There are a lot of do’s and many don’ts, and it’s hard to keep track of them all. The best advice is to make sure you have credible recipes, follow them exactly, and call the Extension Office when you get confused. 

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Canning Classes

Johnson County has several canning classes for beginners this August. Click here for our class schedule.