How do I know a jar of jam has gone bad, and how do I throw it out?

Check the jar before you open it and again as you open it. A jar has gone bad if the lid is loose, bulging or no longer curved down in the center, if dried streaks of food run down the outside from the rim, if you see rising bubbles, mold or an unnatural color, or if the contents spurt, fizz or smell fermented when the lid comes off [1][2]. Do not taste anything from a jar that shows one of these signs [1]. This page gives the check in order, separates spoilage from harmless flaws, explains how to throw a bad jar away without spreading the problem, and says when a jar needs the stricter handling used for low-acid foods.

The check, in order

NCHFP's spoilage check for home-canned food runs from the outside in [1].

1. The lid. With the band off, look and press. A good seal is tight and concave: "Lids with concave centers have good seals" [1]. A lid that flexes, lifts, or is domed upward has lost its vacuum.
2. The outside of the jar. Hold it upright at eye level and turn it. Look for streaks of dried food running down from the top of the jar, a sign it leaked [1].
3. The contents, through the glass. Look for rising air bubbles and unnatural color [1], and for mold on the surface. Bubbles that are fixed in the gel are trapped air; bubbles that move are not (bubbles in jam).
4. Opening it. Watch for liquid that spurts out, and for cotton-like mold, white, blue, black or green, on the surface or under the lid [1].
5. The smell. Note anything unnatural, including a fermented or alcohol-like smell [1][2]. If you have already seen mold, skip this step; FSIS advises against sniffing moldy food [3].

If the jar passes all five, it is good to eat. A typical full-sugar jam or jelly is considered safe as long as the seal is intact and there are no signs of mold or yeast [2].

Spoilage, and the flaws that only look like it

Several harmless quality problems look alarming in a jar. This table separates them.

A harmless flaw can hide a real problem, so a jar with syrup on top or crystals still has to pass the five checks.

Throwing out a jar of spoiled fruit jam

NCHFP's disposal steps for home-canned food separate jars that are still sealed from jars that are open or leaking [1].

Still sealed (including a jar with a bulging lid that has not opened): put it in a heavy garbage bag, close the bag, and put it in the regular trash or take it to a nearby landfill [1].

Already open, unsealed or leaking: for ordinary fruit jam made from a tested recipe, put the lid back on, bag the jar and put it in a covered trash can, as FSIS advises for moldy food [3]. Then clean any spill or drips and the shelf where it stood. Wear rubber or heavy plastic gloves, and wash your hands afterward.

When to handle a jar as a low-acid food

NCHFP's strictest procedure, detoxifying the jar before disposal, is written for low-acid foods, which can carry botulinum toxin with few signs or none [1]. Fruit jam from a tested recipe is a high-acid food. Some jars on a preserves shelf are not, and you should use the full procedure for any jar that is open or leaking if it holds:

• pepper jelly or any jelly or jam with peppers, onion or garlic (pepper jelly);
• pumpkin, squash, sweet potato or banana butter (pumpkin butter and other low-acid spreads);
• a recipe that was not tested, or a jar whose contents you cannot identify.

NCHFP's procedure [1]:

1. Put on disposable rubber or heavy plastic gloves.
2. Lay the jars and lids on their sides in a pot or boiling water canner of 8 quarts or larger.
3. Add water carefully, without splashing, until it covers the jars by at least 1 inch.
4. Cover the pot, bring it to a boil, and boil for 30 minutes.
5. Let it cool, then discard the jars, lids and food in the trash or a landfill.

To clean up a spill from one of these jars [1]:

1. Mix 1 part unscented household chlorine bleach (5 to 6 percent sodium hypochlorite) with 5 parts clean water. Make it fresh.
2. Spray or wet the counters, equipment and any clothing it touched, and let it stand 30 minutes.
3. Wipe up with paper towels, keeping the spill from spreading, and bag the towels before they go in the trash.
4. Apply the bleach solution again, let it stand another 30 minutes, then rinse.
5. Wash everything that was treated, and throw the gloves away.

NCHFP warns that botulinum toxin can be fatal if swallowed or if it enters through a break in the skin, and that bleach itself irritates skin and lungs [1].

If someone ate from a bad jar

If anyone who ate from a spoiled jar becomes ill, call Poison Help at 1-800-222-1222; it is free, confidential and staffed around the clock [5].

Botulism is an emergency. Its symptoms include trouble breathing, swallowing or speaking, dry mouth, muscle weakness, blurred or double vision, drooping eyelids, nausea, vomiting, abdominal cramps and paralysis, and they usually begin 12 to 36 hours after eating the food [5]. The Illinois Poison Center urges immediate medical attention if botulism is suspected, and calling 911 if someone is having trouble breathing [5]. If you still have the jar, bag it and set it aside rather than throwing it out, since doctors or health officials may ask about it.

Tracing why the jars spoiled

Throwing out a jar deals with the jar. If more than one spoiled, the cause is in how the batch was made, sealed or stored, and mold and fermentation in jam traces the usual ones. To understand which preserves carry a botulism risk and which do not, read can jam give you botulism?.

References

1. National Center for Home Food Preservation, *Identifying and Handling Spoiled Canned Food*, adapted from USDA, *Complete Guide to Home Canning*, rev. 2015 (accessed October 2026). https://nchfp.uga.edu/how/can/general-information/identifying-and-handling-spoiled-canned-food/
2. National Center for Home Food Preservation, *Storing Home Canned Jams and Jellies*, October 2005. https://nchfp.uga.edu/how/make-jam-jelly/jams-jellies-general-information/storing-home-canned-jams-and-jellies/
3. USDA Food Safety and Inspection Service, *Molds on Food: Are They Dangerous?*, rev. August 2013. https://www.fsis.usda.gov/sites/default/files/media_file/2021-02/Molds_on_Food.pdf
4. National Center for Home Food Preservation, *Causes and Possible Solutions for Problems with Jellied Fruit Products*, adapted from *So Easy to Preserve*, 6th ed., 2014 (accessed October 2026). https://nchfp.uga.edu/how/make-jam-jelly/jams-jellies-general-information/causes-and-possible-solutions-for-problems-with-jellied-fruit-products/
5. Illinois Poison Center, *Botulinum* (undated page, accessed October 2026). https://illinoispoisoncenter.org/health-safety/food-poisoning/botulinum