Do you have any info on canning olives in olive oil and red wine vinegar with raw vegetables? This is an old family recipe and we are now trying to market this product. I was just told by "Kerr" people that they do not recommend canning anything with olive oil. We have never had a problem with anyone getting sick, etc. How can we process this correctly?
We can't recommend canning this mixture at home. There would have to be a specifically tested process for the exact recipe and none exists.
Several relevant points:
- If it's black or ripe olives, they are low acid. So that product would be at risk for botulism if the olives weren't somehow acidified prior to canning. That would have to be a tested process itself. Without that, the olives would have to be canned as a low acid food under pressure, in a process specifically determined to kill botulism spores in that product.
- Oil in covering liquids presents a heat penetration problem. Oil can protect spores and bacteria from heat (it acts as an insulator), so if it's not accounted for in the process development, it can result in under-processing a food if added at will. The two or three products in the USDA canning guide with a little bit of oil were tested and the food (peppers, beans, etc.) is actually acidified prior to the mixture being canned with the oil in the jar, so C. bot. is not a risk.
- Even if it is green olives, they range in pH from about 3.6 to 4.6, which is borderline for botulism. So any smart thermal process expert would call for an acidification step prior to canning to make sure the pH stays well below 4.6...or commercially, the processor would be standardizing and verifying the pH of the olive prior to canning. And the oil issue still stands.
So, in the absence of a specific recipe and tested process for a worst-case scenario with this mixture, we have to say that this cannot be canned at home and the risk is botulism if the product is not canned properly.
Answered by Elizabeth L. Andress, Ph.D., Professor and Extension Food Safety Specialist Director, National Center for Home Food Preservation, Department of Foods and Nutrition, The University of Georgia
Last update: Monday, December 15, 2008