HOME CANNED FOOD SPOILAGE--WHAT WENT WRONG??

   1. Fresh food was decayed, unwashed, unpeeled or untrimmed. 
This results in a high microbial load.  A larger than normal
number of microorganisms can take a longer processing time for
complete sterilization than is usually recommended.

   2. Food packed too tightly in jars.  Temperature in the
geometric center of the jar was not high enough long enough to
result in complete sterilization of the food.  Pack food loosely,
prepare according to USDA Guidelines (1/2 inch slices, halves,
etc.) then use the recommended time, pressure, temperature.

   3. Jars became unsterile soon after being filled.  If lids are
not placed on jars and processing is not started immediately
after jars are filled, microorganisms may start to grow and reach
very high levels prior to processing.

   4. Inaccurate heat-processing time was used; this may occur if
old recommendations are used (food is underprocessed) or if the
timing was interrupted (power failure, pressure fluctuation,
etc.)

   5. Food was not processed at the correct temperature:
      A. Pressure Canner (240 F,115 C).       
      1. Failed to test dial gauge yearly.
      2. Failed to exhaust canner 10 min with full steam flow.
      3. Failed to make an adjustment for elevation (11 PSIG     
         versus 10 PSIG in Illinois due to average 1000 above sea
         level altitude)
      4. Failed to keep pressure accurate (high enough).

      B. Boiling Water Bath Canner
      1. Water was not covering jar tops by 1" or more.
      2. Water was not maintained at a rolling boil.
      3. Processing time was too short.
      4. Failed to make an adjustment for altitude (addition of 2
         minutes for every 1000 ft above sea level).

   6. Use of Open Kettle Canning, Microwave Canning, or Oven
Canning Methods.  These methods do not get the canned food hot
enough long enough to destroy microorganisms so the food may
spoil, may contain dangerous microorganisms and their toxins, or
both.


   7. Improper cooling of jars after processing:

      A. Failure to remove jars from canner at the end of
processing time or when gauge reads "0".  As jars cool, they may
suck water (containing microbes or spores) back into the food.

      B. Failure to properly cool jars.  Very slow or very rapid
cooling may interfere with formation of a seal.


   8. Use of paraffin to seal jelly jars.  Paraffin is no longer
recommended for sealing jams, jellies or preserves.  Mold, which
is the most common spoilerof sweet spreads, can send "roots" down
along the edge of the paraffin and produce toxic substances into
the spread.

   9. Improper storage of home-canned foods:

      A. Home canned foods which are exposed to temperatures in
excess of 95 degrees F may spoil.  Sterilization recommendations
used for home canning do not necessarily kill some of the
"thermophiles" or heat loving microorganisms.  These organisms
tolerate high temperatures and will grow at high temperatures. 
If they are still present, they may grow and spoil the food, or
alter the food so that other microorganisms can grow.

      B. Home canned foods which are stored in the sunlight may
get very hot inside--the light goes in, changes to heat as it is
absorbed by the  food, allows the air in the headspace to expand
breaking open the seal allowing microorganisms to come in.

      C. Keeping very acid foods (pickled or fermented products,
some juices) for a long period of time may give the food acid
time to eat away at and deteriorate the lid resulting in pinholes
which allow microorganisms to get into the jar.  Discard any home
canned food with damaged or flaking metal on the lid.

      D. Lids on home canned foods stored in a damp place may
rust through allowing microbes to get into the food.



Prepared by Susan Brewer
Foods and Nutrition Specialist
Revised,1992                                                      
     EHE-669