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

August 24, 2011(updated on October 3, 2018)

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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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458 thoughts on "Canning 101: Tomato Float, Sauce Separation and Loss of Liquid"

  • I noticed on my canned whole tomatoes a thin white line on the water line inside, just on the glass not like a film.
    Should I be concerned?

  • In regards to thenthin white line I have heard its from your hardware. Just add a glug on vinegar to your canning water.

    1. It’s typically from hard water, actually. The minerals in the water separate out and adhere to the jars and pot as the water boils down.

  • I canned tomatoes and the lids expanded as if fermentation was happening. I opened one and it looked and smelled normal. Do you think it’s safe to eat these or is it best to discard?

    1. What kind of film? I can’t really determine what’s going on with your tomatoes from a brief description. If what you’re seeing gives you pause, you should not eat the tomatoes.

    1. Typically, that cloudiness comes from the small bits of pulp. However, if you’re concerned about the safety of your tomatoes, you should not eat them.

  • Is it better to have more acid or less acid if you are canning things like a salsa tomato salsa blueberry salsa and I know it calls for earth acid but if you’re adding other ingredients other than straight by that recipe should it be a higher acid level or a lower acid level if it’s a If it’s a acid product like tomatoes or blueberries thank you

    1. Higher acid content is always desirable when canning anything in a water bath canner, because botulism spores cannot germinate in high acid environments.

  • When siphoning happens, sometimes bits of tomato get into the seal, but it still seems sealed. Is it safe to eat them if there are little tomato pieces hanging from the inside of the lid?

  • I canned tomatoes. Some looked very dark right after the canning process- the seals are good. Some looked like red tomatoes. The dark ones smell OK. Can I eat them?

    1. It sounds like perhaps the oxidized a little. That’s normal and as long as you followed a tested process and the seals are good, they should be fine.

  • Hi marisa! My tomato jars have a lot of bubbles in them, almost looks soapy. I have separation because I reheated them before canning. They all sealed without issue. I’m positive it’s not soap because I boiled the jars before filling them and the pot I used to cook the tomatoes was brand new and just rinsed out. I have 18 jars of these tomatoes, help!

    1. It’s natural to have some foam in the jars. I’d let them sit for a couple of days to see if it diminishes.

  • I have some tomatoes that my mom pressure canned 15 years ago. Was going to trash today & when I opened jar, they smelled wonderful. Jar was sealed tightly. Are they safe to eat?

  • I’ve been canning tomatoes in a old Aluminum pot. For about 35 years. Me and my spouse are in our early 80s. Nothing has happened to us yet. Is it OK to hand this the spot down to my children because they are in the canning also. I’ve heard you shouldn’t cook or can Tomatoes in aluminum. But this pot has worked for us for years and years. Making salsa every year and canning tomatoes in juice. Thank you for a comment

  • I pickled cherry tomatoes the recipe called for water, white wine vinegar and white distilled vinegar I didn’t have white wine vinegar so I used bottled lime juice, the liquid looks cloudy in the jars but everything sealed , did the lime juice cause the cloudiness or tomatoes splitting? My water is filtered so it’s not from that!

    1. I bet its from the split tomatoes. I wouldn’t worry about it unless you see other signs of spoilage.

  • My tomatoes are turning red on the vine in small batches (say 4-6 at a time). As you know this is not enough to make sauce. An their counter life is finite. Can I make small batches of sauce, refrigerate, and combine then reheat to a boil once I have enough to can 4+ quarts?

    Thank you!

  • I just canned 6 quarts of tomatoes. I planned to raw pack in own juice, but I read in usda canning book that quality of tomatoes is better if the tomatoes are simmered 5 minutes and hot packed. So thats what I did. After removing from WB after waiting 5 minutes, 4 of the 6 siphoned juice. Should I just freeze?

  • While making our yearly tomatoe sauce we cut the tomatoes the day before we cooked them and when we started boiling them the day after some of the tomatoes had a white film on them. We still booked them and jarred them. Do you think they’ll be safe to eat

    1. Were they refrigerated? If not, they may have started to mold overnight. Still, they should be okay since you boiled the sauce and processed the jars.

  • Hi, I’m a newbie to canning. I wanted to make a tomato purée, using just tomatoes nothing else. I used 32oz jars with a boiling canner. I set the timer for the time indicated and turned up the heat. The problem was that the water never came to a visible boil. The water temp went as high as 200 or so for the recommended time; I even heard the ping of the lids sealing while they cooled but I’m not sure if they’re safe to use.

    1. It might be that your stove is not sufficiently powered to process canned goods. You need to achieve a rolling boil for things to be safe.

  • Hello! I canned some Romas last night, and was just taking off the rings and noticed a lot of tomato pulp had gotten up inside around the rings, and almost like it was trying to leak out where the lid meets the glass. I’ve never had this happen before. The lids are tightly on and have “popped,” so the seal worked, but are these tomatoes safe to keep canned? Thank you!

  • Using my Ball canning book, I made tomato soup that called for 2 tbls oil to saute onions garlic, and peppers. All jars sealed and while wiping them down after cooling, I noticed that there is a dark ring of liquid that looks like oil. I’ve used this recipe once before this year and checked the other jars for comparison. The other jars don’t have a dark ring at top. My first batch was thin soup, so I really cooked this 2nd batch down to thicken it. Could the color be a sign of something bad or over cooking. I will be heart broken if I ruined all this. Pls advise.

    1. If you followed the recipe as written (other than cooking it down a bit more), it should be okay. Sometimes tomato products discolor a little. It’s not typically a sign of spoilage unless there are other signs (like active bubbling or broken seals).

  • My tomatoes that have liquid on the bottom and crushed tomatoes up towards the lid I know are ok. How about the two jars I had that were crushed tomatoes on the bottom covered with liquid and the top two inches of jar have no liquid. Could have bubbled out during canning but wondered if those jars would be ok.

  • I have a white sediment in the bottom of the one jar. I have never seen this and the other jars don’t have that.
    What is this? Plus, they were separated but you answered that for me.

  • Hello Marissa,

    Last year, and this year, I have used raw pack with citrus acid for my tomatoes. And I noticed with the raw pack, I have tomatoes that have bubbles after the canning. The bubbles did not move and the tomatoes were fine. The floating – wide mouth/regular, I always get floating. Thank you for writing this column.

  • I made crushed tomatoes boiled for atleast 1 hr and added salt, it was late so I put into sterilized jars with lemon juice and kept in the fridge for 24-48 hrs before processing in a water bath.

    My tomatoes are looking separated. I’ve never had this happened. Are they still okay despite the appearance?

    Thanks so much for your help and time!


    1. This is addressed in this blog post. If you heat, cool, and then reheat tomato products, they will separate. This is not dangerous. You just broke the tomato pectin down. Use the tomatoes. They are fine.

  • So I canned a bunch of slightly blended tomatoes last week with basil and citric acid. BTW first time I used citric acid when water bathing tomatoes. At first, all of them were separated with liquid on the bottom, tomatoes on top. By the end of the day, I noticed that in some, the tomatoes were dropping and in one jar, bubbling and dropping were occurring. I unscrewed and checked that the seals were still fine. As a precaution, I took the one that had a lot of bubbly action and put it in the refrigerator as I didn’t want to waste the organic tomatoes!

    1. Active bubbling occurs when fermentation is taking place. I would be VERY surprised if your tomatoes started fermenting after less than a day out of the canning pot. It sounds to me like normal settling.

  • Thank you SO much. It was my first time canning tomatoes and when I saw the liquid on the bottom of the jar I thought “Josh Darn ” I ruined them. And all the time and effort!. You put my mind at ease and once I shook the jars they looked perfect. Thanks for giving me the confidence to do more canning.

  • Hi! I canned crushed tomatoes and water bathed them properly. They sealed well and sat on the table for a couple days. I went ti move one and jt exploded. Why?

  • Hi Marisa,
    I pureed tomatoes and did a water bath for 40mins in my sterilized jars. Upon opening the jars, the tomatoe puree has pushed to the top, and water is on the bottom. There is a small spot of white on the top of the puree, but the jars did pop when bathed, and when opening the jars the seal was tight. I am not sure if this is safe to eat

  • I canned pasta sauce. In the process sauce came over the jar .They did seal but does have sauce around the top. And have bubbles in the bottom. This has never happened before and Ive been canning for many years

    1. As long as the jars are sealed, they’re okay. I’m not sure why your sauce behaved like this, though.

    1. Did you process them half full? That’s not a great idea because they can float in the canner and break. Half full jars are also more prone to spoilage.

  • My daughter canned tomatoes this year with the same receipe we have used for years. This time she has eight jars that have a white film or residue in the middle of the jar. Looks like maybe she didn’t push the tomatoes down far enough and left an air pocket. Question is are these safe or contaminated and need to be thrown out?

    1. If they were properly acidified, processed for the proper amount of time, and the seals are good, they should be fine.

  • I have a white sediment on the bottom of the jars.
    Tomatoes were canned 14 months ago, I have used many jars and did not notice this sediment previously.
    Are they ruined?

  • The response to my question about a white sediment was not answered. I do not have float or separation. I have a white sediment, not much , but still visible.