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I have recently made a large batch of habanero jelly, and followed the recipe exactly (please see References). I am wondering, why is the final boil of the sealed jars necessary? I've already boiled the jars, lids, and locking mechanism, and the jelly itself is piping hot. Most recipes I've found insist that after sealing the jars, they need to be boiled, while sealed for five minutes. Is this to guarantee no micro organisms from the air remain?

References

  1. Habanero Jelly Recipe, Accessed 2014-03-31, <http://allrecipes.com/recipe/habanero-pepper-jelly/>
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    This is just how canning works - see the NCHFP site for some good general information. The boiling after filling is called processing.
    – Cascabel ♦
    Mar 31, 2014 at 17:11
  • @Jefromi Is it likely my jelly is going to spoil then? I pre-boiled the jars for about 8 minutes, and then boiled the jars after sealing them, but only for 8 minutes. The jars are very tiny (ie: one-third of a cup in size each).
    – Cloud
    Mar 31, 2014 at 17:15

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In terms of killing pathogens, it is a belt and suspenders thing.

The additional processing ensures that any pathogens that entered the jars while you were filling them are killed.

More importantly, as Jefromi has reminded us, the additional boiling with the assembled and lidded jars causes the header air to heat up, expanding in volume and raising the pressure, and so some of the air will bubble out past the seal. When the jars are cooled, the header air also cools, creating a partial vacuum, and pulling the lid down against the jar. This is what makes the permanent seal--the ring is only there to hold the lid in place long enough for the processing.

So the processing is necessary to seal the jars, even if the food is already rendered perfectly safe from pathogens.

For more information on canning safety, see NCHFP's processing guide.

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  • That's what I was thinking. Kind of like inoculating wine with sulfites.
    – Cloud
    Mar 31, 2014 at 17:10
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    It's not just this. The processing heats up the air in the headspace, and replaces some of it with steam, so that when the jar back cools down, the steam condenses and the air contracts, creating a tight vacuum seal on the air. (It may appear that you've gotten a good seal without this, but the seal is more likely to fail at some point during storage, resulting in spoilage.)
    – Cascabel ♦
    Mar 31, 2014 at 17:12
  • Is it likely my jelly is going to spoil then? I pre-boiled the jars for about 8 minutes, and then boiled the jars after sealing them, but only for 8 minutes. The jars are very tiny (ie: one-third of a cup in size each).
    – Cloud
    Mar 31, 2014 at 17:15
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    @Dogbert That's probably plenty of time - generally processing times are 5 minutes for half-pint jars, 5-10 minutes for pint jars and 10-15 minutes for quarts. I'm guessing you have half-cup jars, so the 8 minutes of processing time is a lot. If you've also left the correct headspace, everything will be fine. If it's too much or too little, the seal can be compromised. Too much headspace can also cause discoloration on top.
    – Cascabel ♦
    Mar 31, 2014 at 17:40
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    If you test the seals as described here: nchfp.uga.edu/how/general/cooling_jars_test_seals.html and they're good, and they're still good when you return to open them, everything's fine.
    – Cascabel ♦
    Mar 31, 2014 at 17:40

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