When opening a glass jar of prepared spaghetti sauce, (with the seal flat), and it makes a loud sound when opened, is that bad or good?

  • Hello Chris, your title and your body were two different questions. I would have suggested to choose one of them and edit the other to fit, but with having three answers answering the body, I changed the title. You can still open a second question, but it might be a duplicate.
    – rumtscho
    Feb 11, 2016 at 14:40

4 Answers 4


When being canned (or jarred as in this case) the ingredients are put into the jar hot before a lid is put on. When the ingredients cool it creates a suction that pulls the lid down. When you open the lid and hear a pop what is happening is that air is coming in to fill the low pressure inside, which indicates that there was a good seal. This is definitely a good thing.

If there is no pop that means that there is no longer low pressure in the jar, this could be because it was never sealed properly, or the contents have gone off despite the seal and created gas inside the jar. Either way it means that it's not safe to eat.

  • There was a pop. The seal was flat. Therefore it is safe to eat.
    – Marc Luxen
    Feb 11, 2016 at 13:02
  • 1
    That is what my answer says @MarcLuxen.
    – GdD
    Feb 11, 2016 at 13:38
  • The if there was no pop bit is irrelevant for the question and possibly confusing
    – Marc Luxen
    Feb 11, 2016 at 14:03
  • 10
    @MarcLuxen I couldn't disagree more. It's perfectly acceptable to expand on a scenario by offering the inverse. I found the answer interesting, in its entirety. +1
    – shennan
    Feb 11, 2016 at 14:13
  • 2
    @MarcLuxen shennan's right, of course, but really this isn't even expanding. It's just explaining - why is it good if it pops? Because of what it indicates didn't happen.
    – Cascabel
    Feb 11, 2016 at 16:13

The popping is used to indicate 1 of 2 different things have NOT occurred.

1) has it be opened previously or didn't have a good seal.

2) spoilage, even if the seal was perfect, if spoilage occurs it will create gasses that will increase the pressure inside the jar.

Caveat: we had one question in the past where someone opened a jar of sauce, used a small portion and within an hour or two fizz started pouring out of the jar from the unused portion, so spoilage can still occur without indicators. I think that was a 1:1,000,000 occurrence, but it can still happen.


A loud sound (like a pop) is the sound you get when the Jar has not previously been opened.

I define that as "good". The quality of the sauce, however, depends entirely on the brand and the ingredients.

  • Taking advantage of auto-migration to chat to clean up without deletion. (ping me there if you have further concerns.)
    – Cascabel
    Feb 11, 2016 at 16:11

The pop is vacuum sealed for freshness through heating, steaming, homogenizing, pasturizing. It pops when you break the seal like popping a can of coke or pepsi. No pop, no seal, not fresh (probably spoiled). There are pops for both vacuum seals and pressure seals.

Vacuum seals suck the air out. A pressure seal is hot food, sealed, then placed in cold bath.

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