On Guard Against Spoilage
Don’t use canned food that shows any sign of spoilage. Look closely at each container before opening it. Bulging can ends, jar lids, or rings, or a leak—these may mean food has spoiled. When you open a container look for other signs—spurting liquid, an off odor, or mold.
It’s possible for canned vegetables to contain the poison causing botulism—a serious food poisoning—without showing signs of spoilage. There is no danger of botulism if pressure canner is in perfect order and every canning step is done correctly. But unless you’re absolutely sure of your gage and canning methods, boil home-canned vegetables before tasting. Heating usually makes any odor of spoilage more evident.
Bring vegetables to a rolling boil; then cover and boil for at least 10 minutes. Boil spinach and corn 20 minutes. If the food looks spoiled, foams, or has an off odor during heating, destroy it.
Burn spoiled vegetables, or dispose of the food so that it will not be eaten by humans or animals.