Canning 101: Tomato Float, Sauce Separation and Loss of Liquid

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Tomato canning season is here and so I’ve been getting a lot of questions from people who are canning their own tomatoes for the first time. They worry because their tomatoes are floating, their crushed tomatoes have separated or their jars have lost significant liquid in the canning process and now they’re not sure if their tomatoes are safe. Let’s take these three topics one by one and put your hearts at ease, shall we?

Tomato Float
Take a look at the jars on the left in the picture above. Those are the whole, peeled tomatoes that I canned last year. As you can see, the tomatoes are floating over a good inch of liquid and tomato sediment at the bottom of the jar. This one is absolutely no big deal.

Even the most seasoned canner is going to have some canned whole tomatoes that float. This is because there are air pockets inside those tomatoes and when you pack something with some internal trapped air in a liquid, it will float.

You can try to avoid float by using regular mouth jars (the shoulders of the jar help keep the fruit in place) and packing the jar as firmly as possible (without totally crushing the tomatoes). But really and truly, it’s no big deal.

Tomato Separation
Often, I will hear from people who are concerned because their crushed tomatoes have separated into a layer of liquid topped by a layer of solids. What happened here is that you heated your tomatoes for more than five minutes, let them cool and then heated them up again.

By doing this, you’ve broken down the pectin inside the tomatoes. In this situation, the pectin was there holding the structure of the cells together and once it goes, there’s nothing to maintain the integrity of the tomato flesh together and so pulp separates from the water.

I never worry about this one either. Just give the jar a good shake before using.

Liquid Loss
Back to the picture up at the top. Take a look at the quart jars on the right. You might notice that several of those jars lost a TON of liquid. I canned that particular batch in my pressure canner and during the cooling process, they siphoned like mad (that’s the official canning term for when liquid escapes).

Siphoning can be prevented by better bubbling of jars and a slower cooling process. However, even when you’re careful, it still happens sometimes. However, as long as your seals are good, jars with even significant liquid loss are still safe to eat.

You may experience some reduction of quality over time and when it happens to lighter colored foods (like peaches), the product that’s not submerged will begin to discolor. Put those jars at the front of the queue of jars to use and don’t worry about it.

Air Bubbles
Sometimes, you’ll preserve tomatoes and once the jars are sealed, you’ll notice that there are a few air pockets or bubbles in the finished product. As long as the lids remain sealed and those bubbles aren’t actively moving around on their own, the jars are fine. Once a jar is sealed, air pockets are only a problem if they seem to bubbling independently of you moving or tapping the jars, as that can be a sign of fermentation. Otherwise, all is well.

What other tomato questions do you guys have? Let’s hear it!

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393 responses to “Canning 101: Tomato Float, Sauce Separation and Loss of Liquid”

  1. Hi! I water bath canned some lilikoi (passion fruit) curd and by the next morning it was starting to separate into a thing layer of water on the bottom and the solids on top. I know this is quite different from tomato sauce, but could this be something similar to the sauce separation issue?

    • I don’t believe that passion fruit curd is high enough in acid to be safely canning in a water bath canner. Generally, curds don’t do well in a water bath. They tend to curdle.

  2. I have been canning for 40+ years with both the water bath method & pressure canning without any problems. Today I used my new pressure canner for the first time when processing my cold pack whole tomatoes. When I opened the canner I saw that on one jar both the lid and ring were completely off & there was a giant tomato mess everywhere. The other 6 quart jars sealed perfectly, although they were covered in tomatoes from the open jar. Any idea what caused the lid & ring to fly off?

    Thank you for this great site. Best practical information I have ever come across.

    • That happens occasionally when you haven’t tightened the rings tightly enough. You need to exert a little more force than with boiling water bath canning.

  3. I had canned 4 quart jars from my first harvest of our tomato plants. They were sealed, I thought, and put down cellar to be stored. About 4 days later i noticed some water under the jars. I picked them up and turned them up side down and more water came out. I checked the seals and they were loose. I tasted the contents of each and it did taste okay and there was no smell. However after reheating and sealing them again, I noticed that the liquid part that separated from the solids is cloudy. I have done several more quarts and all of those have clear liquid. Are these 4 quarts spoiled?

  4. Help, we have always timed the boiling/processing time, it would go off, we turn everything off, then raise the rack/jars carefully and put them on the wire rack to cool. Tonight, the timer went off, I turned off the stove and took off the lid and was going to have my husband help me lift out the rack and jars. We got distracted, the jars sat in the canner for like 25 minutes, the water cooled of course…. is this OK? Just making pints of stewed tomatoes..

  5. Your post is wonderful. I will subscribe. If you answer me how do I find this answer? Do I come back to this website and look for it or will you email me. I am new to canning tomatoes, I haven’t had any issues. My issue is I use Romas and Marzano‘s and I have tons of liquid left over. I fill the jars with crushed tomatoes and the liquid from the tomatoes in the pot. Hot packed whole tomatoes, and crushed tomatoes and both batches left me with well over 6 quarts each of tomato liquid after canning. Is this normal? I haven’t seen this question anywhere and I’ve been searching. Why do I have so much liquid? And since I’ve already boiled it to process tomatoes is it safe for me just go ahead and Can as tomato juice? Second question would be if I canned as tomato juice with citric acid in it can I use tomato juice as a liquid canning future tomatoes

  6. My question is when I cooked spaghetti sauce some of the cans had the sauce siphon out onto the exterior of the jar and you could tell sauce was underneath liid but the seal held, should I be concerned, or will it be safe

  7. I have been having problems with a lot of siphoning when I do my whole tomatos. I never use to have a problem and it seems to be a waste. You mentioned bubbling above…can you please explain that to me and if it helps. I was taught to cold pack them for 55 minutes but the local extention service advises 95 minutes so I changed to that time. Everything else that I bottle is fine. Thank you for any help that you can offer.

    • Bubbling your jars means to use a chopstick, plastic knife, or bubbling tool to remove the trapped air bubbles from your jars before processing. However, I think the issue is really the increased processing time. To reduce the siphoning, I suggest that when the processing time is up, you remove the lid from the canner and turn off the heat. Let the jars cool slowly in the pot for 10-15 minutes. This slower cooling process will reduce the amount of liquid that siphons from your jars.

  8. Hello, I so appreciate your time and kindness creating this helpful blog. I have read through most of the responses of the last five years, and I think you actually answered my question with your first, and the photo of various results of your own canning. But just to be sure….

    I just finished canning four quarts of tomatoes. I squished them into the jars but still, after cooking in a water bath, there is a very large head space, at least two inches in each jar, as the tomatoes dehydrated a bit during cooking. The tomatoes are san marzanos. I have one jar left to go.

    Will the tomatoes in the jars turn brown? Spoil? Should I open and repack them together, more tightly, creating less jars of them and recook? Thank you so very much.

    • Just leave them. You may experience some discoloration on the surface, but as long as the jars are sealed, they will be good.

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