Franklin County

   July 2009
 

Open kettle canning is open to food spoilage

If home-canned foods or community canned foods are to be stored on
the shelf, heat processing is essential to kill bacteria in the head space
of the jar, in the food itself, and provide a strong seal.

Even acidic foods like jams and jelly, apple butter, and tomato sauce must be heat processed in a boiling water bath canner to be safe. Low acid foods like green beans, corn and spaghetti sauce with meat must be processed in a pressure canner.

Many older canning or cookbooks from the 1930’s and
earlier often recommended open kettle cooking and canning without heat processing. These instructions are out-of-date and should not be used for home food preservation.

Why is open kettle canning not recommended?  In open kettle canning, food is cooked in an ordinary kettle, then packed into hot jars and sealed without processing. The temperatures obtained in open kettle canning are not high enough to destroy all spoilage and food poisoning organisms that may be in the food. Also, microorganisms can enter the food when it is transferred from the kettle to jar and cause spoilage.

Current research shows the open kettle method results in more spoilage and mold growth on the surface of the canned food and  results in a weaker seal. In addition, live bacteria can survive this canning process and cause deadly illness.

All current canning recipes are tested to ensure that the processing method and  processing time are correct and safe for each jarred food. All pints and half-pints of jams and jellies are processed in a water bath canner for 5 to 10 minutes. Pints of apple butter are processed for 10 to 15 minutes, depending on the recipe and size of jar. Pints of plain tomato sauce are processed for 35 minutes, quarts for 40 minutes in a boiling water bath canner. Tomato sauce may also be processed in a pressure canner if desire.

Current canning recipes can be obtained from the University of Missouri Extension http://extension.missouri.edu/xplor/hesguide/foodnut/gh1451.htm , Ball Blue Book, dated 1989 or more recent, or the National Center for Home Food Preservation http://www.uga.edu/nchfp/

Apple butter that is not heat processed should be stored in the refrigerator even if unopened.  Mold grows easily on home canned foods that are not heat processed since both the humidity and mold spore counts are very high in Missouri.

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		University of Missouri Extension Franklin County Site maintained by: Billie Jo Brenner, brennerbj@missouri.edu Last revised: 07/02/08