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

  1. 201
    Kelsey says:

    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?

    • 201.1
      Marisa says:

      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. 202
    Andrea says:

    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.

    • 202.1
      Marisa says:

      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.

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