Never taste canned food about which you have any doubt, or that shows gas pressure in the jar, that is mushy or gassy in appearance, that is moldy, or that has a disagreeable odor. A sour, rancid, or putrid odor is a warning but it is not always present in poisonous food.
TO HELP PREVENT BOTULISM
Use a pressure canner that has an accurate gauge for canning all low acid vegetables, meats, poultry and fish. Do no process for less that the prescribed time. If there is any doubt about the contents of the jar, do not taste the food. This applies to all home-canned, low-acid foods: vegetables, meats, poultry and fish.
To cook home-canned, low-acid food, empty the food into a pan and place directly over the heat, Stir the food. Break up any clumps. Bring to a boil, reduce to simmer, and simmer for 15 minutes at sea level and elevations up to 3,000 feet. Simmer greens, cream-style corn, meat and poultry for at least 20 minutes at those altitudes. At altitudes above 3,000 feet, simmer the product for at least 20 minutes, because the boiling temperature of water decreases with increase in altitude. If it is a tight pack, such as spinach or a thick product such as cream style corn or meat, simmer at least 30 minutes at altitudes above 3,000 feet. Add 5 minutes for each additional 1,000 feet.
Smell the product while simmering. The odor of botulism spoilage may not be detected in cold food. Any off-odor is made more noticeable by boiling. The odor is that of decomposition, usually somewhat putrid and cheesy or rancid.
It is not necessary to boil acid foods (fruits, tomatoes and pickles) unless you suspect spoilage.
Is it safe to use jam or jelly that is moldy on the surface
A thick, solid jam or jelly with a small amount of mold on the surface is safe to eat. (Pull out of jar with clean spoon and don’t double dip.) The high solid and high sugar content of the jam or jelly prevents the growth of botulism bacteria even if the mold has neutralized a little of the acid. Exceptions are fig, pear, or persimmon jams which are very low in acid. If any mold shows on these, the jam should be destroyed.
For canning do not use jars from other products in a pressure cooker, they are not strong enough to stand the high pressure they have to cook in. Use these jars for water bath canning only. Make sure they have no nicks or cracks, check them over carefully. They will make a mess in the canner if broken during cooking.