Buying large to break down into small is not practical and possibly unsafe. 

Buying large tins of canned foods, such as tomatoes and vegetables, can certainly save a lot of money, but not if you can’t consume the product before it spoils. Buying in bulk with the intention of breaking the contents (or leftovers) down into smaller portions and re-canning them is also not practical – and may be unsafe.

From a cost perspective, the added expense of jars and lids, as well as the energy used to re-process the food (not to mention your own time), outweighs the savings of buying in bulk.

From a quality perspective, additional textural changes will be seen, and the heat of processing for a second time will further reduce the nutritional value of the food.

As far as safety, a significant concern is that previously canned food will be excessively soft and thus pack more densely into jars. Jars that are packed too densely will impact the penetration of heat throughout the jar, with the potential result of an under processed (and thus unsafe) product. Except for some tested recipes which may call for small amounts of previously canned products to be added to fresh ingredients, to date there has been no testing done to determine safe processing methods for re-canning previously canned commercial products.

For these reasons, re-canning commercially canned foods is not recommended.

Instead, purchase commercially canned foods in manageable sizes, and refrigerate or freeze leftovers that can’t be immediately consumed once opened.

For further information on canning visit the National Center for Home Food Preservation (NCHFP) at nchfp.uga.edu or contact your local Cooperative Extension office.
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Brought to you by the UCCE Master Food Preservers of El Dorado County
Last updated: July 2025