When a jar of canned food spoils or is found on the shelf unsealed, one needs to know how to dispose of it properly to protect themselves, children, and pets from exposure. Improperly processed food is usually the cause of a sealed jar to spoil. Lids my loosen due to various reasons. Food must be processed properly to kill bacteria that cause foodborne illness; in the case of low-acid foods, proper processing is needed to prevent the formation of the deadly toxin that can cause botulism. In all cases, the lid must have a secure vacuum seal to keep the processed food safe once it has been processed correctly.
What are the signs of spoiled food?
- Loose lid. Lids loosen for various reasons. In any case, a loose lid is a spoiled food. Loosening may be caused by improper processing allowing the growth of microorganisms to grow and produce gas which pressurizes the food, swells lids, and breaks the seals. Other causes of loosening might be a lid that was bumped causing the seal to break, air trapped in the jar, or storing the food at too warm of a temperature. It best to store jars without the rings or bands as it is easier to identify a jar with a loose lid.
- Air bubbles. There are two kinds of bubbles–stationary bubbles caused by air spaces in the food and bubbles that are moving. Stationary bubbles are benign. Moving or active bubbles are a sign that the product is fermenting or contaminated.
- Unnatural color. If there is an unexpected color change, that can be a signal that spoilage is present. Color change is not always an indicator of spoilage, however. Jars exposed to light may change color. Food pieces that float above the liquid, brine, or syrup at the top of a jar may discolor during storage. Some foods such as pickled cauliflower or garlic can turn pink or blue because the food may be immature or pigments in the food react with the acid in the pickling solution, causing color changes. While the latter examples exhibit color change, the food product is still safe to eat.
- Unnatural odors, mold growth on top of the food or bottom of the lid. Any canned food that is bulging, leaking, spurting or has an unnatural odor or appearance is a sign of spoilage and a potential health risk. Never taste food that show signs of spoilage. USDA and microbiologists now recommend against even scooping out the mold on jams and jelly products and using the remaining jam or jelly, even though that used to be suggested. Spoiled low-acid foods, including tomatoes, may exhibit different kinds of spoilage evidence or very little evidence. Therefore, all suspect containers of spoiled low-acid foods, including tomatoes, should be treated as having produced the botulinum toxin.
When in doubt, throw it out!
The National Center for Home Food Preservation recommends the following for properly disposing of spoiled canned foods:
- If the swollen metal cans or suspect glass jars are still sealed, place them in a heavy garbage bag. Close and place the bag in a regular trash container or dispose in a nearby landfill.
- If the suspect cans or glass jars are unsealed, open, or leaking, they should be detoxified before disposal.
Detoxification process: Wear disposable rubber or heavy plastic gloves. Carefully place the suspect containers and lids on their sides in an 8-quart volume or larger stock pot, pan, or boiling-water canner. Wash your hands with gloves thoroughly. Carefully add water to the pot and avoid splashing the water. The water should completely cover the containers with a minimum of a 1-inch level above the containers. Place a lid on the pot and heat the water to boiling. Boil 30 minutes to ensure detoxifying the food and all container components. Cool and discard the containers, their lids, and food in the trash or dispose in a nearby landfill.
Cleaning up the area: Contact with botulinum toxin can be fatal whether it is ingested or enters through any openings in the skin. Take care to avoid contact with suspect foods or liquids. Wear rubber or heavy plastic gloves when handling suspect foods or cleaning up contaminated work surfaces and equipment. A fresh solution of 1 part unscented liquid household chlorine bleach (5 to 6% sodium hypochlorite) to 5 parts clean water should be used to treat work surfaces, equipment, or other items, including can openers and clothing, that may have come in contact with suspect foods or liquids. Spray or wet contaminated surfaces with the bleach solution and let stand for 30 minutes. Wearing gloves, wipe up treated spills with paper towels being careful to minimize the spread of contamination. Dispose of these paper towels by placing them in a plastic bag before putting them in the trash. Next, apply the bleach solution to all surfaces and equipment again, and let stand for 30 minutes and rinse. As a last step, thoroughly wash all detoxified counters, containers, equipment, clothing, etc. Discard gloves when cleaning process is complete. (Note: Bleach is an irritant itself and should not be inhaled or allowed to come in contact with the skin.)
Composting. Composting of canned food is also possible with care. The botulism bacteria is anaerobic, so once exposed to the air, it will start to die. If added to a compost pile, the pile should be ‘working’ or hot enough so that the spoiled food breaks down quickly. Burying is also acceptable. In either case, one must make sure animals or children cannot get into or come in contact with the spoiled food. Follow sanitation and clean up as described above.
Food spoils. Glass is inert and does not spoil. Jars that are thoroughly cleaned and sterilized are safe to reuse. Bands are reusable if they show no signs of rust and are also thoroughly cleaned and sterilized. Flat lids are designed for single use only and should be discarded in the trash.
Spoilage in home canned food does happen. Make sure you examine jars of canned food carefully before serving to your family, friends, and pets.
_________________________________________
Old Canned Tomatoes–Ok to Composter? #451254. Ask Extension.
How can I dispose of spoiled food safely? USDA.
Discarding Spoiled Canned Foods Safely. Clemson University.
What Color Should Canned Foods Be? K-State Research and Extension.
Identifying and Handling Spoiled Canned Foods. National Center for Home Food Preservation.
Updated and reviewed, 3/2025, mg.
