I added fresh basil to tomato sauce once it was bottled, just before sealing. Never done this before and I lost the whole batch within 2 weeks. Can fresh basil cause fermentation to continue? Should the basil have been cooked into the sauce before bottling?
Yes. The cooking sterilizes the sauce, but adding uncooked basil afterwards has contaminated the sauce again with germs.
Dry herbs and spices in canning are generally safe to play around with and change up. FRESH herbs on the other hand are not. Fresh herbs are considered low acid ingredients and will affect the acid level in whatever is being canned.
Without knowing more about how you canned the sauce, no one can say if it was or was-not ONLY the fault of the fresh herbs. They certainly played a part, however there could have also been other factors at play. Some of these may have been:
- Poor acid levels (did you acidify correctly?)
- Improper processing time or method
- Improper headspace in the jars
- A recipe that was not suitable/safe for canning
The acidification and/or recipe used and the possibility of improper processing are generally the main culprits when an entire batch goes off.