INGREDIENTS

INSTRUCTIONS

Growth of the bacterium Clostridium botulinum in canned food may cause
botulism--a deadly form of food poisoning. These bacteria exist  either
as spores or as vegetative cells. The spores, which are  comparable to
plant seeds, can survive harmlessly in soil and water  for many years.
When ideal conditions exist for growth, the spores  produce vegetative
cells which multiply rapidly and may produce a  deadly toxin within 3
to 4 days of growth in an environment  consisting of:  a moist,
low-acid food * a temperature between 40 degrees F and 120  degrees F *
less than 2 percent oxygen  Botulinum spores are on most fresh food
surfaces. Because they grow  only in the absence of air, they are
harmless on fresh foods.  Most bacteria, yeasts, and molds are
difficult to remove from food  surfaces. Washing fresh food reduces
their numbers only slightly.  Peeling root crops, underground stem
crops, and tomatoes reduces  their numbers greatly. Blanching also
helps, but the vital controls  are the method of canning and making
sure the recommended  research-based process times, found in these
guides, are used.  The processing times in these guides ensure
destruction of the largest  expected number of heat-resistant
microorganisms in home-canned foods.  Properly sterilized canned food
will be free of spoilage if lids seal  and jars are stored below 95
degrees F. Storing jars at 50 degrees F  to 70 degrees F enhances
retention of quality.  FOOD ACIDITY AND PROCESSING METHODS  Whether
food should be processed in a pressure canner or boiling-water  canner
to control botulinum bacteria depends on the acidity in the  food.
Acidity may be natural, as in most fruits, or added, as in  pickled
food. Low-acid canned foods contain too little acidity to  prevent the
growth of these bacteria. Acid foods contain enough  acidity to block
their growth, or destroy them more rapidly when  heated The term "pH"
is a measure of acidity; the lower its value,  the more acid the food.
The acidity level in foods can be increased  by adding lemon juice,
citric acid, or vinegar.  Low-acid foods have pH values higher than
4.6. They include red meats,  seafood, poultry, milk, and all fresh
vegetables except for most  tomatoes. Most mixtures of low-acid and
acid foods also have pH  values above 4.6 unless their recipes include
enough lemon juice,  citric acid, or vinegar to make them acid foods.
Acid foods have a pH  of 4.6 or lower. They include fruits, pickles,
sauerkraut, jams,  jellies, marmalades, and fruit butters.  Although
tomatoes usually are considered an acid food, some are now  known to
have pH values slightly above 4.6. Figs also have pH values  slightly
above 4.6. Therefore, if they are to be canned as acid  foods, these
products must be acidified to a pH of 4.6 or lower with  lemon juice or
citric acid. Properly acidified tomatoes and figs are  acid foods and
can be safely processed in a boiling-water canner.  Botulinum spores
are very hard to destroy at boiling-water  temperatures; the higher the
canner temperature, the more easily they  are destroyed. Therefore, all
low-acid foods should be sterilized at  temperatures of 240 degrees to
250 degrees F, attainable with  pressure canners operated at 10 to 15
PSIG. PSIG means pounds per  square inch of pressure as measured by
gauge. The more familiar  "PSIG" designation is used hereafter in this
publication. At  temperatures of 240 degrees to 250 degrees F, the time
needed to  destroy bacteria in low-acid canned food ranges from 20 to
100  minutes. The exact time depends on the kind of food being canned,
the  way it is packed into jars, and the size of jars. The time needed
to  safely process low-acid foods in a boiling-water canner ranges from
7  to 11 hours; the time needed to process acid foods in boiling water
varies from 5 to 85 minutes.  PROCESS ADJUSTMENTS AT HIGH ALTITUDES
Using the process time for canning food at sea level may result in
spoilage if you live at altitudes of 1,000 feet or more (Plate 2).
Water boils at lower temperatures as altitude increases. Lower  boiling
temperatures are less effective for killing bacteria.  Increasing the
process time or canner pressure compensates for lower  boiling
temperatures.  Therefore, when following canning directions in this
series, select  the proper processing time or canner pressure for the
altitude where  you live. If you do not know the altitude, contact your
local county  Extension agent. An alternative source of information
would be the  local district conservationist with the Soil Conservation
Service.  ======================================================= === *
USDA  Agriculture Information Bulletin No. 539 (rev. 1994) *
Meal-Master  format courtesy of Karen Mintzias  From Gemini's MASSIVE
MealMaster collection at www.synapse.com/~gemini

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