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Food Safety Feature Articles


Home canning questions — answered


Tammy Roberts, a nutrition specialist with University of Missouri Extension, has answers to the following questions about home food preservation and canning.


Q: Is it necessary to process pickles and jelly in a boiling water bath canner?
Yes. This helps assure that microorganisms that cause spoilage can be destroyed. It is possible that microorganisms can enter the jar as the food is transferred. Processing in a boiling water bath canner assures a strong seal on the jar.


Q: Can I can my yellow tomatoes? Can yellow, orange and red tomatoes be mixed?
Yellow and orange tomatoes can be canned using the same guidelines as for red tomatoes. It is also OK to mix yellow, orange and red tomatoes in the same jar.


To assure proper acidity, add 2 tablespoons of bottled lemon juice or teaspoon of citric acid per quart or 1 tablespoon of lemon juice or teaspoon of citric acid per pint of tomatoes when canning.


Q: Why are my jars losing liquid during processing?
There are several reasons liquid is lost during processing. They include:


  1. Not allowing the proper headspace. If jars are filled too full, liquid boils out of the jar during processing and a siphoning action is created. Packing food too tightly in the jar can have the same effect.
  2. Not venting the canner. Venting the canner allows the funnel of steam to flow from the petcock for 10 minutes before putting the weight on or closing the petcock.
  3. Pressure too high during the process.
  4. Fluctuation of pressure or sudden lowering of pressure. Do not force pressure down on the canner. For example, don’t run cool water over the canner to speed up cool down. Sudden lowering of pressure can also occur if you open the petcock before the gauge returns to zero.
  5. Raw packing vegetables increase the risk of losing liquid during processing.
  6. Starchy vegetables sometimes absorb liquid.


Foods from jars that have lost liquid are safe to eat. They should be the first you use since the exposed food will deteriorate quickly.


Q: Why are my tomatoes or fruit floating?
There are also several reasons this can occur. The reasons include: using overripe fruit, packing the fruit or tomatoes too loosely, syrup is too heavy for the fruit, raw packing tomatoes or processing too long or at too high of temperature.


For more information, see the MU Extension food preservation publications, specifically the Quality for Keeps series, or contact Tammy Roberts at (417) 682-3579.


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Last update: Monday, June 18, 2012