Canning 101: How to Prevent Jam Separation

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This time of year, lots of people are making and canning strawberry jam. Though it’s a universally loved preserve, I find it to be one of the trickier jams to get right, particularly for beginning jam makers. One of the reasons that people struggle with strawberries is that the finished jam has the tendency to separate into two layers* once it has cooled in the jars.

If you are one of the ones who have struggled with this two layer jam, worry not. It’s not a sign of danger or even that you did something wrong. It’s simply a sign that there is still some air trapped in the strawberries. They are lighter than the syrup and so rise to the tops of the jars.

I find that this jam separation happens primary in recipes that call for relatively short cooking times or very large pieces of fruit that have not been given a long maceration period.

You can work to prevent this two layer effect by chopping the fruit into smaller pieces, macerating it with the sugar overnight, mashing it with a potato masher during cooking (this action is best if you’re noticing big hunks of fruit bobbing around towards the end of cooking), and even extending the cooking period a bit.

If you’ve taken these actions and you’re still noticing that your jam is separating during the cooling stage, you can gently shake the cooling jars to reintegrate the fruit and the syrup.

My preferred method of dealing with this separation is simply to tell people that I meant it to be that way and that if you want a more integrated preserve, that they should stir the fruit into the now-set jelly when they open the jars.

*This can also happen with other varieties of fruit as well, but is simply most common with strawberries.

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20 responses to “Canning 101: How to Prevent Jam Separation”

  1. I had this happen with some strawberry jam this year and I reprocessed the batch with a bit more pectin, it came out better (maybe a little sweeter, but it is jam). I think I may have been trying to do too big a batch. I more often have the problem of the jam getting too hard – I have some very tasty strawberry vanilla jam from last year that is like fruit leather in a jar. I was thinking about melting it to use as flavor in ice cream base (I’m not going to throw it away!), but is there anyway to save it as jam?

  2. I’ve also tried letting the jam cool for an hour or so, then flipping the jars upside down for a half hour, followed by righting them til they cool. That seems to spread the fruit around a bit.

    • I try that technique as well, and it sorta works. I also have used the “shaking” method but then I sometimes find some seepage around the (otherwise good) seal. Strawberry jam simply remains my nemesis (tho’ strawberry rhubarb or strawberry plum or other blends I have made don’t seem to have this problem).

  3. If anybody makes any comments about something we canned, I just tell ’em: “If you don’t want it, hand it back. We’ll eat it!” The great flavor almost always wins out and we haven’t gotten anything back yet.

  4. Oh, how I wish I knew this last year when I threw away a batch of your strawberry-rhubarb butter. I saw the air bubble trapped with the fruit, and was already nervous about the thick product with low sugar…oh well. I just made a batch with this year’s fruit and I will trust it this time. 🙂 Thanks for the Canning 101 series. After canning for several years I still learn stuff and I ALWAYS point my new canning friends here for tips.

  5. Canned two types of sour cherry jam over the weekend and I had the same issue with separation. I made sure they sealed and then flipped them upside down for about 30 minutes. It pretty much took care of it. Now about the batch of Cherry Almond that didn’t set properly…I’m calling it ice cream topping and stirring it into seltzer water!

  6. What a great tip! This has happened to me a few times and I have drawn the same conclusion. As the true canner I am, I really enjoy reading your blog! You can always count on it for great inspiration!

  7. Thanks, Marisa! I’ve also noticed the top part of my strawberry jam turns from red to brown-ish over time. Any advice on this? I usually just stir it all together and it evens out, but it’s not very pretty to give as a gift!

    • Sadly, that’s just natural color loss. It happens more with lower sugar preserves than it does higher sugar ones. The only thing I know that helps prevent it is storing those jars in a very dark place. But even then, it happens a little.

  8. The best solution that I’ve found that works 95% of the time is to prepare the fruit, add sugar and lemon juice. Then let it sit for 8 hours or over night. This displaces the water in the fruit with sugar while making a ton of juice. Then cook as you normally would.

  9. Today I made a batch of your low-sugar strawberry vanilla jam and the maceration did the trick! No separating..woohoo! And then because the canning bug was on me I did the same recipe but with raspberries and no maceration and they did fine since they must not have so much air. My only gripe today was one jar that refused to seal. I processed it a total of 3 times and finally gave up…first time that has ever happened even after replacing the flat, finger tightening, feeling the jar edge. That jar is going in the garbage. lol

    Thanks for the great recipes, the tutelage and the general hand-holding Marisa!

    • You can always put the unsealed jar in the fridge and eat it over the next couple weeks. You don’t need to trash it.

      • That’s what I’m doing…I should have written that. It just seems that particular glass jar wouldn’t seal. I put some of the jam in hubbie’s yogurt for work today. It feels so good having a lower-sugar product to serve him so I don’t feel guilty about wrecking his blood sugar. Really looking forward to your next book and the natural sweeteners!

  10. I’ve had this problem with a peach jam recipe I like. I will chop finer (immersion blend maybe) and might try macerating it. I don’t comment often, but do enjoy your posts.

    I use your vanilla-bean strawberry jam recipe (from your book) and I’ve never had it separate (3 times). I did realize this time, however, that my thermometer is 10 degrees (F) off. Argh. Why bother making them if they are going to be so badly calibrated?

    • Thanks for reading and taking the time to leave a comment, Diane! And I secretly included steps to help prevent separation in the strawberry vanilla jam recipe in that book, so I’m glad to hear that it has worked for you. Too bad about your thermometer, though.

  11. I had the same problem with peach jam I made a couple years ago as well as the Strawberry jam I made this week. I will definitely try some of the tricks listed above going forward. 🙂 Thanks!

  12. When I made the strawberry vanilla jam from the web site, some of the juices boiled over so I lost some volume. That jam set up like a gummy bear. It tastes great and will, with effort, spread. ? No separation issues whatsoever.

    I will say that I used about a tablespoon in a strawberry balsamic vinaigrette and the vanilla and strawberries married beautifully with it.

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