Canning Question

I recently came across this recipe and plan to make it this weekend but had the same concerns about the lack of lemon juice. So these are my thoughts but I am not sure they are correct, so maybe someone here knows. A water bath canner brings the temperature up to 212F (boiling). This kills most things but does not kill botulism spores - hence the need for acidity. A pressure canner of course is designed to reach 240F hot enough to kill botulism spores if the processing time is long enough. The Passata recipe from the River Cottage Handbook calls for roasting all the ingredients at 350F for an hour. In an hours time I would expect all ingredients to reach 350F and hence be rendered not only sterile but botulism spore free. Is this what makes the recipe safe for waterbath canning? Unsure...just a thought. I would love to ask the author.

SKK: Regarding pH meters, they are useful tools in recipe development. I got mine, a digital pH meter, from the Cole-Palmer Instrument Company. Once you have made the recipe and canned it, then you mix the food with distilled water to make a slurry and insert the meter. You can't use pH sticks like the ones they sell to test the pH in your hot tub, unfortunately.

Keep in mind that when developing recipes a pH meter only determines acidity, not whether the food in the jar has come to heat for the appropriate amount of time.

SKK: Regarding pH meters, they are useful tools in recipe development. I got mine, a digital pH meter, from the Cole-Palmer Instrument Company. Once you have made the recipe and canned it, then you mix the food with distilled water to make a slurry and insert the meter. You can't use pH sticks like the ones they sell to test the pH in your hot tub, unfortunately.

Keep in mind that when developing recipes a pH meter only determines acidity, not whether the food in the jar has come to heat for the appropriate amount of time.

I very much appreciate all of your thoughtful responses! Thank you for sharing your time, experience and intelligence on this topic. I come away a more informed canner. :)

Thanks for this interesting discussion. There's not enough rational discourse on the subject. Just yesterday, I spent a whole lot of time looking for information--and real data--on why the US now recommends water baths for jams and jellies, and I felt like I never really did get a straight answer. I do know how serious botulism is, but I sometimes wonder if warnings without real information and data don't do us all a disservice.

SKK: Dr. Andress at the Center for Home Food Preservation told me years ago that up to a tablespoon of oil per pint jar is safe in water bath canning. Products packed in oil are not, for the reasons Diana stated. I agree with Cathy that your larger problem is acidity. Does the product in your jar have a pH of 4.5 or less? I am partial to canning recipes that state their safety credentials, but in situations where that info is not available, you can pressure can for the food product in the sauce that calls for the longest time. If you proceed with water bath canning, but then lose confidence in the product, you can always boil the food prior to eating in an open pot for 10 minutes (at sea level plus 1 minute for every 1,000 feet above sea level) and any spoilers present will be killed.

I have to say, I am less concerned about the oil in your recipe than the addition of onion, garlic and peppers, all of which are very low acid, further lowering the acidity (pH) of the sauce. With such low pH, this looks more like a pressure canning recipe than one to can using the water bath method.

As the OP noted, what is acceptable in other countries is not considered acceptably safe in the U.S. That said, I've been known to make small batches that might not be in the USDA safe zone. I do not serve them to others.

I think there are definitely different standards between the US and the rest of the world. Honestly, I often wonder about this myself. In the U.S., the National Center for Home Preservation is the arbiter of all things canning. Just as an example, for years, I sealed jellies with wax with no problem, but this is no longer recommended by them, so to some extent, I think their recommendations are an excess of caution. As an experienced (40 years) canner, I sometimes flaunt their recommendations, but I'm careful about it and careful about the instructions for use that I give anybody who receives a jar that I've been unconventional about processing.

In short, I'm giving you the National Center for Home Preservation's party line. You can't go wrong with following their recommendations, but they are very conservative and it's perfectly possible to can safely outside of their recommendations; you just need to know a lot more about canning that a novice. Sounds like you do!

With anything that contains oil, I'd suggest you keep the oil to a minimum, wipe jar lips with vinegar before applying the lid, and make sure the jars stay completely upright from the minute you seal them until you remove them from the waterbath. After the jars cool, take the bands off and test the seal by lifting the jar by the lid edges. If the seal's good, you're probably OK. Test the seal the same way at the time you go to use the jar; if it lets go, then the oil's likely to have compromised the seal and you should discard the product. Otherwise, you're probably OK, but "probably" is the key word.

Nothing with oil in it is safe for waterbath canning. As the National Center for Home Preservation points out, oil may protect botulism organisms trapped in a water droplet. Furthermore, oil may have a deleterious effect on lid gaskets and the at least one manufacturer of home canning lids recommends against it. Oil can creep up the sides of a jar and interfere with a safe seal, even if you wipe the lip of your jars with vinegar beforehand. I know there are recipes like this out there and I'm sure half a dozen folks will respond that they've been canning granny's fill-in-the-blank recipe with oil in it for years without a problem, but you're really playing roulette with botulism.

On the Roast Garlic Marinara, I don't know why it wouldn't be OK to roast the tomatoes, but again, if there's oil involved (I suspect there is), it's not safe for waterbath canning.