10 Rules for Safe Canning

By Diane Wright Hirsch, MPH
Senior Extension Educator/Food Safety

home canning with tomatoes
Photo: Diane Wright Hirsch

Even though some may feel home canning has gone the way of the dinosaurs, I regularly get questions posed to me by newbie and experience canners alike. Some want to know how to can tomatoes without potentially killing a loved one. Others want to know if there is anything new in the canning pipeline.

It seems as if more people are gardening these days so that they can have more control over their produce supply—they can grow what they like and minimize the use of chemical pesticides or fertilizers. A happy consequence of a successful garden is a bountiful supply of zucchini, tomatoes and peppers—maybe too bountiful! As a result, the gardener must now become a food processor. Home canning is not difficult, but, it IS important to do it right. Here are ten rules for canning to help you in your pursuit of a safe home canned food supply—whether you have been canning for years or this is your first time.

1) Make sure your jars/lids are in good shape.
 Use (or re-use) canning jars manufactured for home canning. Check for cracks or chips and throw out or recycle any jars that are not in good shape.
 Be sure the jar rings are not dented or rusty.
 Buy new jar lids. The sealing compound can disintegrate over time, especially in damp basements, so make sure that your supply is new or no more than one year         old. Do not reuse old lids. (If you still use rubber jar rings, these CAN be reused unless they are dry and/or cracked, though these jars may be more prone to failed seals.)

2) Use up to date canning guidelines. With the exception of jams and jellies, recipes that are older than 1996 should be relegated to the family album. A great resource for up to date guidelines and recipes is the National Center for Home Food Preservation at: www.uga.edu/nchfp. This site is the United States Department of Agriculture (USDA) approved site for home food preservation information. Go there and check out the latest recommendations. They are also great about addressing some questionable practices that are introduced over the years, such as canning food in the oven or canning bread in a jar.

3) Choose the right canner for the job.
 Water bath canners are for jams, jellies, relishes, pickles, fruits such as apples, apple sauce, peaches and tomatoes.
 Pressure canners are for all other vegetables, soups, meats, fish, and some tomato products, especially if they contain large amounts of low acid vegetables such as peppers, celery or onions. Some folks like to can tomatoes in a pressure canner because it takes much less time and uses less fuel/energy.

4) If using a pressure canner with a dial gauge, have it checked annually to make sure it is reading properly. Check with the manufacturer regarding gauge testing or call the Home and Garden Education Center.

5) If you are pressure canning, be sure that the gasket is still soft and pliable. If dry and/or cracked, you need to replace it.

6) Use high quality, just-ripe produce for canning. You will never end up with canned tomatoes (or any other produce) better than those you started with. Overripe strawberries can lead to a runny jam. Overripe, mushy or decayed tomatoes (often sold in baskets labeled “canning tomatoes” when they are really “tomatoes that we can’t sell for slicing because they are past their prime”) may have a lower acid level or higher pH, making the processing time inadequate for safety.

7) Make sure everything is clean before your start. Be sure to clean:
 Canners (often stored in a cobwebby corner of the basement)
 Jars, jar lifter, screw bands, etc.
 Counter tops or other work surfaces
 Your produce (wash with cold running water—no soap or bleach please)

8) Follow approved recipes to the letter. When you change the amount or type of ingredient, you risk upsetting the balance that would result in a safe, high quality product. Too little sugar will make jams too soft; cutting out the salt may make a pickle recipe unsafe; and throwing additional onions and peppers into a tomato sauce can increase the risk for botulism.

9) Adhere to processing times—even if they seem long. Processing canned foods in a water bath or pressure canner is what makes these products safe for on-the-shelf storage. Each product is assigned the processing time needed to destroy the spoilage organisms and/or pathogens (the kind of bugs that make us sick) that are most likely to be a problem in THAT product.
 The short processing times for jams and jellies destroy yeasts and mold spores that used to be common place when these products were not water-bathed, but covered in paraffin.
 The long processing times for tomatoes are needed because modern tomato varieties are often lower in acid than those in the past. If 45 minutes seems way to long to you (especially when you watch the electric meter ticking away), you might want to consider pressure canning them for 15 minutes at 6 pounds of pressure or 10 minutes at 11 pounds.

10) Allow your jars to cool naturally, right side up, for 12 hours or more before testing seals. Testing earlier may cause the new seal to break.
 Cool jars away from an open window to prevent breakage by cool evening breezes on hot jars.
 Remove screw bands, clean and dry them and store several in a convenient place for use later when you open a jar and need to refrigerate leftovers. (Screw bands should not be left on jars when storing. Food residue and moisture may collect and cause rusting or molding that can ruin a good seal.)
 Test seals, reprocess if needed.

Follow the rules and you will be well on your way to processing a safe, shelf-stable food supply for your household.

For more information about canning food safely at home, visit our website at www.foodsafety.uconn.edu, check out the National Center for Home Food Preservation, or contact the Home and Garden Education Center at ladybug@uconn.edu or 1-877-486-6271.

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