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As the spring and summer canning season approaches, those new to canning and seasoned food preservationists can benefit from a few safety tips from University of Tennessee canning expert Dr. Janie Burney.

Burney is a professor and food preservation specialist with the UT Extension Department of Family and Consumer Sciences, and in this column she reviews why using new recipes and guidelines can be essential to ensuring the safety of home-canned products.

Question: Why do I need to follow up-to-date recipes for canning?

Burney: As the science of home food preservation has developed, new foods have become popular, and new kinds of equipment have entered the marketplace. Recipes are continually updated by USDA to be sure they are safe and to ensure that the quality of the food is maintained for as long as possible.

Question: What are some examples?

Burney: Summer squash is a good example. It is no longer recommended for home canning. Recipes for canning summer squashes, including zucchini, are not found in recent USDA and university canning guides. The old recipes have been withdrawn due to uncertainty about the processing times. Squashes are low-acid vegetables and require pressure canning to destroy the bacteria that cause botulism, but documentation for the previous processing times cannot be found. Reports that are available do not support the old process. The reason is that slices or cubes of cooked summer squash will get quite soft and pack tightly into the jars, but the amount of squash filled into a jar will affect the heating pattern in that jar. This makes processing time too variable. It is best to freeze or pickle summer squashes, but they may also be dried.

Processing pumpkin butter or pureed pumpkin is also no longer considered safe. Home canning is not recommended for pumpkin butter or any mashed or pureed pumpkin or winter squash. According to the latest USDA publication, Complete Guide to Home Canning, published in 2009, the only directions for canning pumpkin and winter squash are for cubed pulp. In fact, the directions for preparing the product include the statement, "Caution: Do not mash or puree."

In addition to pumpkin and winter squashes, there are no home canning recommendations available for purees of figs, tomatoes, cantaloupe and other melons, papaya, ripe mango or coconut. No processing times have been established to ensure that purees made from these foods can be safely stored at room temperature without concern for growth of bacteria that cause botulism.

Question: Can I use the recipes for squash and pureed foods I find on the Internet?

Burney: If you use recipes from the Internet, or old family recipes, USDA and UT Extension cannot assure you that they are safe. A major concern is the growth of Clostridium botulinum bacteria that produce a deadly toxin that causes botulism. If foods are not processed at a high enough temperature for a long enough time, these bacteria can grow when food is stored at room temperature. Contact your Family and Consumer Sciences agent at your local Extension office for current recipes. You also can visit to print current recipes including USDA's Complete Guide to Home Canning. More recipes may be available on the national extension website: Just search the term "canning." Remember, recipes on web sites that end in ".com" may not be safe.

Question: I am interested in canning Asian pears. Are they processed like other pears?

Burney: New processing times have recently been established for Asian pears. This kind of pear is not as acidic as other pears. To prevent botulism, you will need to acidify them by adding 1 tablespoon bottled lemon juice per pint jar or 2 tablespoons per quart jar before filling jars with fruit. The only recommendation for processing at this time is the hot pack. Boil drained pears 5 minutes in syrup, juice or water then fill jars with hot fruit. Process them in a boiling-water canner for 20 minutes for pints and 25 minutes for quarts. If you live in an altitude from 1,001 to 3,000 feet, process them 5 minutes longer for pints or quarts.

UT Extension provides a gateway to the University of Tennessee as the outreach unit of the Institute of Agriculture. With an office in every Tennessee county, UT Extension delivers educational programs and research-based information to citizens throughout the state. In cooperation with Tennessee State University, UT Extension works with farmers, families, youth and communities to improve lives by addressing problems and issues at the local, state and national levels.

Carla Y. Bush, MVTE

UT Extension, Cannon County

Family and Consumer Sciences

614 Lehman Street

Woodbury, TN 37190


615-563-1285 - FAX

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Carla Bush
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