Thursday, August 12, 2010

Canning 101: Hot Packing and Headspace

I want to quickly cover 2 issues that come up with canning. The first is hot packing.


Many vegetables are able to be raw packed (since they are usually processed in a pressure canner) but most fruits require a hot pack. Why is this?
"Many fresh foods contain from 10-30 percent air. How long canned foods retain high quality depends on how much air is removed from food before the jars are sealed."
When you fail to hot pack your fruits you can end up with quite a bit of space in the bottom of your sealed jar as your fruit floats up at the top. Sometimes even as much as half the jar ends up being space instead of fruit!
To hot pack fruit, simmer it in boiling water for 2-5 minutes. With fruits such as peaches you can use that same water to create the syrup you add to the jars before processing. Pack your peaches well. You don't have the squish them all down into a peachy pulp but make sure you're utilizing as much jar space as possible. An added bonus, hot packed foods also retain better color and flavor over time.


Secondly, head space. "Head space" refers to the space above the food in a jar and below the lid. A general rule for head space is:
1/4" for jams and jellies
1/2" for fruits and tomatoes, processed in a HWB
1" for low acid foods, processed in a pressure canner
Head space is essential in jars to allow for the expansion of foods during processing and for forming the vacuum in cooled jars.
Foods canned in a pressure canner need more head space because as the temperature gets higher the air expands more.

I hope that some of this is helpful to those just starting to can or those that always wondered why their peaches always floated to the top. ;)

Don't forget to enter my canning book giveaway here!


Christa said...

Thank you for touching on the empty space in the peach jars. I know now what I've done wrong. I just warmed up my peaches in warm syrup for a half a minute or so. I guess it needs a lot more than that. I would love to get another load of peaches and try it your way.
Thanks again,


Brenda said...

Oh yeah those floating peaches. I canned peaches for the first time last year and picked the method of just dipping them in the liquid for a couple of minutes then covering. A lot of floating going on. I will try your method this year.

Cora said...

Thank you for this very useful info!

Laura Lane said...

Excellent explanation. It makes so much sense. Thanks so much.

City Sister said...

That happened with my dilly beans and tomatoes...I think I'll hot pack rather than raw pack to solve the problem. Thank you!

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