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When Good Preserves Go Bad

Determining the Safety of Canned Foods -

Just like planning next year’s garden – This is the time of year when I start to think about next year’s canning season.

For me, part of that process is going through all the cupboards to dig out any of last year’s leftover preserves.

It is time to see:

  • How many jars are left to eat?
  • What did I make too much of? {I went a little plum crazy last year}
  • Are there any jars that need to be thrown out?

That last one is an important topic because sometimes good preserves go bad.

Assessing the safety of your canned goods is important to do every time you open a new jar.

But what exactly should you be looking for?

Well, here’s the scoop…

Common Sense:

As you look at the list below, you might be thinking, “Well many of these tips are common sense“.

That is so true.

But I have found that when it comes to homemade preserves, many people can totally lose their common sense. Ha!

Perhaps it is because we have put so much work into creating those preserves. Or maybe it is because in general, canners are a frugal bunch who hate waste.

But for whatever reason, for every sign of spoilage listed below I have had someone ask me if they could still eat the contents of those jars.

And they ask this with pleading eyes – hoping beyond hope that I will say yes. But I tell them no.

Don’t do it.

Don’t eat anything that is questionable. It’s not worth it.

Also, a Reminder:

You should always store your jars with the rings OFF. You’ll see why as your read below or you can go to this post on Why Remove Canning Rings to learn more.

Remove Canning Jar Ring -


7 Signs of Spoilage (Plus Tips):

1) An Unsealed Jar:

This is the most common scenario: You reach for a jar of preserves and the lid just falls off.

It’s not sealed.

If you just processed that jar (in the last 24 hours), you could reprocess it or refrigerate it and it would be okay.

But if it has been on the shelf for weeks or even months, you have no choice but to chuck it. You have no idea how long it has been open or more importantly…why.

Throw it out.

2) A Weird Smell:

If you ever open a jar of homemade preserves and it just smells off, rancid, or just plain “bad”, throw it out.

The rule of thumb is that if it smells bad, it IS bad.

Please, don’t taste it to be sure.

Just throw it out.

3) Mold:

If you find mold on the contents in the jar or on the lid of the jar, you need to throw the food out.

Yes, our grandparents would simply scrape off the “bad” parts and eat the rest. But here’s why I don’t recommend that:

First, we now know that mold grows with long tentacles that reach down into the food. Scraping off the top only removes the part you see. You may not be removing all the mold and some molds are carcinogenic.

Also, mold can change the pH of the food. If it has changed enough, you could have something much more dangerous than mold growing in there.

Throw it out.

4) A Funky or Slimy Texture:

Any time you open a jar and the texture of the contents is not as you expect, it can be a sign of spoilage.

Now, I am not talking about something just having a slightly softer texture than it had when fresh. All canned food will soften a bit during the canning process. This is because the canning process cooks it slightly.

But if you open a jar and the food is slimy and slippery or the texture is disintegrating, you need to toss out the food.

5) Bubbles Actively Rising in the Jar:

If you see bubbles moving inside the jar, it is a sign of bacterial activity and fermentation. Since you don’t know exactly what type of activity is happening, you need to throw it out.

If you have stored your jars without the rings (as you should), the jar will unseal (see #1 above) and you may never have to search for bubbles.

That is just another reason not to store jars with the rings on. Doing so allows you to know right away if something is happening inside that jar.

Note: This bubble thing can throw off new canners because there is one time when it IS okay to see a bubble move – and that is when you first process the jars.

You see, immediately after processing and for about 48 hours after, bubbles inside the jar can dislodge and rise to the top as the food cools and settles.

That is normal.

But if you see bubbles moving after a jar has been on the shelf (unmoved) for weeks/months, something else is going on in there and you need to throw it out.

6) A Bulging or Leaking Lid:

Again, this only happens if you have stored the jars with the rings on and bacteria activity builds up pressure inside the jar.

Look, you should never have pressure build up inside the jar. Instead, that jar should be under vacuum (the opposite of pressure).

So a bulging lid is a sign of spoilage.

Throw it out.

And next time, store the jars without the rings. (I won’t stop harping on that one…tee hee)

7) Spurting Liquid When Opened:

This too would only happen if you left on the rings and bacteria activity raised the pressure inside the jar.

Any jar that spurts out the contents when you open it should be thrown away as this means spoilage.

Signs of Spoilage in Canning -

Final Important Tips:

  • Don’t taste anything to “test” it. It is not worth it.
  • Even if the contents are bad, you can save the jars. Just wash them thoroughly.
  • Remember to discard the used lids. They can only be used once anyway.
  • Store all your canned goods without the rings.
  • The USDA has very stringent clean up instructions if you suspect you have a jar with botulism inside. The process is called detoxification and is pretty extensive. You can go here to read on that.

My goal is to empower you with knowledge so that you have no fears. Canning season is coming soon!

So tell me…

Does this make you feel more nervous or more informed? Tell me in the comments!

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About the Author:

Theresa Loe is the founder of Living Homegrown® and the Canning Academy® and is the Co-Executive Producer & Canning Expert on the national PBS gardening series, Growing A Greener World®. Theresa homesteads on just 1/10th of an acre in Los Angeles with her husband, two teenage boys and several disorderly but totally adorable chickens. Learn more about Living Homegrown here and about the Canning Academy here.



    Made some “mimosa” jelly last year (using pectin) and it has separated in the jars. Seems the orange juice part solidified and the wine part did not. Aside from “mixing” in a cocktail, can you think of any uses for it? Sealed properly, tastes fine, too “runny” to put on toast or crackers – have eight half pint jars.

    • theresa says:

      Yes Jackie – I think that would make an excellent glaze on chicken! I would scoop out 1/4-1/2 cup and whisk it in a bowl with a little bit of water (if needed). Then brush it on roasted chicken during the last 30 minutes. YUM!

      Or if you make a lemon pound cake, you could take a 1/4 cup and warm it slightly (so that it gets runny) and drizzle it over a slice when you serve it.

      I think it would work as a glaze or sauce on anything that goes with citrus.

      Here is a link to some other posts using left over jam. You might get some ideas here:

  • Janet says:

    I pledge to go ringless this canning season! Even though I love how the jars look with all their rings so neat and tidy. Thanks for the great post.

    • theresa says:

      Yeah Janet!

      I hear ya on the look. I love it too and I used rings for years before I went through canning training. But going ringless really solved a lot of problems. Glad you liked the post!

  • Kimberly says:

    I understand all the reasons for not storing with the rings on… but I simply don’t have the storage for all those rings separate from jars. MY solution has been to leave them on the jars, barely threaded. So just enough to say they are “one” but not tight enough that you could pick them up that way. Doesn’t that work? Allowing the inner lids, if they must, to separate. So far, I’ve never had an issue.

    • theresa says:

      Yes Kimberly – I think that works. You are eliminating the issue of the ring being so tight that you can’t tell if there is a problem. As long as you look look carefully as you remove the lid to see if the jar is already open (and not that you caused the jar to open by twisting the ring off), then I think that is fine.

      • Darrell says:

        If the lid comes loose while taking off the ring you had a failed seal.
        The contents of the jar should be discarded only when it is an acid food. Low acid foods, because of the danger of botulism, should be discarded along with the container, lid, and ring as follows. Do not open it to examine the product.
        This from the National Center for Home Food Preservation:
        •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.
        Master Food Preserver
        UCCE Los Angeles County

        • theresa says:

          Hi Darrell,

          I am a trained Master Food Preserver as well. That is why I had linked to the NCHFP Detoxification Process in this post (it is at the end under “Important Notes”). Thank you for chiming in.

  • Sally says:

    Oh how timely this topic is – I love and hate your post! I have two jars of mouthwatering relish that sealed, but the lids came off easily — which is VERY different from what’s usual. The relish looks fine and smells fine… but I am leaning toward throwing it out (heartbreaking) just because getting sick is so awful… Thanks for your posts!

    • theresa says:

      So, so sorry to hear this Sally.

      If they required some force to take off (even a little), you probably just had a weakened seal – but a seal nonetheless. They might be okay. But if they basically fell off…well, then I would throw them out for sure.

      The thing with relish is that it has vinegar and is high acid. You do not have to worry about botulism here. Your worry is spoilage. Only you can determine if the lid fell off or just pulled off easily. It has to be your call. But I wanted you to have more to go on before throwing it all away.

    • Darrell says:

      Just remember that it is not just the risk of getting sick but getting permanently injured or dead.
      Todays food borne illnesses carry far reaching outcomes beyond the danger of botulism poisoning. The fruit category causes the most cases of illness with cantaloupe causing the most.
      When in ANY doubt, throw it out.

  • I write the canning date on the lids so I don’t get the used ones mixed up with the new. I use the “used” lids for storing things in the refrigerator that don’t need to be sealed, such as pickles, sauerkraut and fermented carrots.

    • theresa says:

      Perfect Linda. I put an X on my used ones. But I do sometimes write on the tops too – unless I have some cutie jar labels I’m using. 🙂

    • Kathy Hutton says:

      The new white plastic lids are great! They don’t rust or get icky very low cost. Dishwasher safe. I love them

  • Julie Korfhage says:

    Thanks for a timely reminder! I quit storing my jars with the rings on because they sometimes rusted (especially with pickles), but never thought about the great points you brought up. Love your blog–sooo many good hints and recipes. Thank you!

  • Mary says:

    I have quite a few quart jars of plain tomatoes (with canning salt) left from the 2013 canning season. They are all sealed, no sign of spoilage, and were water bathed properly. Are they still good to eat? I did use one quart for soup, and it tasted just like fresh tomatoes. I would like to use them if possible, as tomato crop last year failed due to drought. What is your opinion?

    • theresa says:

      Hi Mary,

      They are probably fine if the seal is good and you see no signs of spoilage. Most preserves will last past the year mark safely. The problem comes when they start to deteriorate in texture and flavor. I think they are probably okay. Just check those seals before opening.

    • Darrell says:

      Did you add acid to the jars of tomatoes? Either vinegar or citric acid ?
      If the tomatoes were properly acidified there is no danger provided they pass the usual visual inspections of the jar.

  • Mary says:

    Thank you Theresa, for your answer. I only added salt to the jar before filling,
    the tomatoes still look great, but I know how problems with them can sneak up

  • Gail says:

    Since I am new to canning I really appreciated this article! Going into my pantry to take off all the rings on my canned fruit and veggies!

  • Lynn says:

    As always, a timely post. I started today to collect jars from last year’s canning exercise before trying out a few new recipes this year — brandied peaches and green tomato chutney, to name a few. Thanks for seeming to read our collective minds. Onto those holiday gifts now with more confidence . . .

  • Barbara says:

    I’ve had jars stored with herbal tinctures, jams, pickled items for over a year now and have the rings on. My tinctures have a 10-year shelf life….jams and pickled items are fine as I use them. Do you recommend removing those rings now after a year?

  • Candace says:

    I am new to blogging and just recently found this one due to my daughters! The articles are timely and I’m learning ‘new’ things. Now I’ll take rings off for safety reasons! Growing up on a farm, we canned hundreds of jars of fruits and veggies. Mom took the rings off because we needed them for the next batch of canning. She was always careful about checking for spoiled jars too. I am wondering about adding acid to tomatoes when canning?? We never did and my 1975 Kerr canning book doesn’t mention it. My son-in-law told me his new canning book required adding acid due to different acidity levels of tomato varieties now.

  • Mona Brauer says:

    Help, I’ve been canning apricot halves for 3 days now and the results are mixed. The jars all appear to be sealed but some jars seem to have lost a large enough portion of the sugar syrup in the processing that the fruit isn’t totally covered. Yes, all jars were sticky when they were removed from the canner but in each batch, some did this and others didn’t. I made it a point to measure the 1/2 inch requirement for air space at the top. One: are they still viable with less syrup and two: why some jars and not others in the same batch?

  • Erin says:

    I recently made strawberry lemon marmalade dated 8 -2- 16. All 6 of my jelly jars sealed 15 to 20 minutes after taking them out of the canner lovely pop sound. I checked them in the pantry this morning and I have found small bubbles in my jar they are not moving around or Rising just sitting. I am new to canning and want to make sure that what I’ve made it safe to eat I follow directions to a tee and was very hygienic about it. Would love any kind of advice on the matter thank you.

    • theresa says:

      Hi Erin – As long as the bubble are not moving, you should be fine. It is common to have bubbles in jams, jellies and marmalade. It sounds like you did a fine job. I recommend storing the jars with the rings off on all your preserves. That way, if you ever do have an issue with a jar of something starting to ferment or grow bacteria, the lid should pop off. But in the case of your marmalade, I think you are just fine. Good job!

  • Dionne says:

    I made sugar free pear sauce about 3 weeks ago and followed all instructions for pear sauce only without sugar.
    The rings were loose and none of the lids have popped off, every one of my jars have bubbles in them that don’t rise and seem to go away when I shake the jar. Is it safe or shall I throw this all out? Hurts to think that the 12 hours it took me could allbe wasted until I can again. Thanks!!

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