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Commerically canned foods will still be safe. Home preserved foods that were canned following up-to-date, tested recipes from reliable resources (USDA National Center for Home Food Preservation, So Easy to Preserve (U. of GA) or publications with PNW ### or SP50-### from Oregon State University Extension, WSU and U of ID) will also still be safe. Ball recipes from publications 2006 or newer) will be, too. Color, texture and nutrition begin to decline after a year with serious decline beginning after two years.
If you are not CERTAIN that home canned vegetables, salsas, pickles, meat, fish, poultry or wild game were preserved with safe methods you should treat them as having produced botulinum toxin and use a safe disposal method. If the jars are still sealed and you are not interested in salvaging the jars, you can write "Poison, Do Not Eat on the lid" then wrap in heavyweight garbage bag and seal it to go out in the regular trash or take it to the landfill. You can also detoxify the product, if you prefer. See the next paragraph for directions.
"Detoxification process: Wear rubber or heavy plastic gloves when handling suspect foods and cleaning up. Remove the jar lids and carefully place the suspect jars on their sides without splashing (along with the lids) in a stock pot, pan, or boiling water canner (8-quart volume or larger). Wash your gloved hands well. Carefully add water until the level is 1 inch above the jars. Put a lid on the pot and heat the water to boiling. Boil for 30 minutes to detoxify the food. Cool and discard the food and lids. Wash the jars and pot."
"Spray or wet contaminated surfaces (such as counters and cutting boards) with a household chlorine bleach solution (1 part unscented 5-6%s sodium hypochlorite bleach to 5 pars clean room temperature water and let stand for 30 minutes. Wipe up treated spills with paper towels and put them in a plastic bag before discarding in the trash. Rinse surfaces. Soak metal utensils in a mild chlorine solution (1 teaspoon bleach to 1 quart room temperature water ) for 30 minutes. Rinse."
If the food is suspect, do not feed it to your chickens or put it in your compost. Do not put detoxified food in your compost. Jams, jellies and pickles with have too much sugar or salt to put in compost. In fact, our Master Gardeners do not recommend putting any canned foods into the compost. Many canned products have salts, acids or other ingredients added that would not be healthy for your compost. Animal proteins should never be added to the compost.
This sounds like a big project. Good luck with this effort.