Canning Question

Just made Roasted Tomato Passata from Pam Corbin's River Cottage Preserves Handbook. It is processing in the water bath canner as we speak. Her recipe did not call for any lemon juice or citric acid, and I added it to be on the safe side. The recipe calls for roasting tomatoes, herbs, onions and garlic in a little olive oil and then running through food mill and then processing.

I am about to make a Roasted Garlic Marinara which calls for roasting garlic heads and red peppers. My question is would it be ok to roast the tomatoes also? This recipe came from a canning book that my friend has been using for years to make this recipe.

  • Posted by: SKK
  • August 6, 2014
  • 2518 views
  • 15 Comments

15 Comments

Keely M. September 24, 2014
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.
 
sfmiller September 24, 2014
The temperature at which the food is cooked and the internal temperature of the food being cooked are two VERY different things.

The air in an oven might be 350F, but that doesn't mean food cooked in that oven, even for a very long time, gets anywhere close to that temperature. Basically, as long as a food retains a considerable amount of water (as almost all food does), its
internal temperature won't exceed the boiling point of water.

So even after spending two hours in a 350F oven, the internal temperature of the ingredients in the tomato sauce won't go above 212F.
 
Eugenia B. August 7, 2014
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 August 7, 2014
Thank you so much!
 
Eugenia B. August 7, 2014
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 August 7, 2014
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. :)
 
Greenstuff August 7, 2014
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.
 
MrsWheelbarrow August 7, 2014
My guess, and really, it's not supported by any research, is the USDA Master Preserver program was doing everything possible to make every canner's results predictable. Waterbath canning jams and jellies is completely reliable.
 
Eugenia B. August 7, 2014
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.
 
SKK August 7, 2014
Thank you and this leads me to one more question. In Paul Virant's book The Preservation Kitchen, he says he uses a PH meter, and tests one jar from each batch. Your thoughts on this for a home cook?
 
MrsWheelbarrow August 7, 2014
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.
 
SKK August 7, 2014
Thanks, Cathy. Corbin's recipe calls for 4 and 1/2 pounds of tomatoes, 7 ounces shallots and 3 garlic cloves and 1/4 cup of olive oil. This is then roasted and put through the food mill and water bath canned. The second recipe calls for 12 pounds of tomatoes, 4 medium red peppers, 6 heads of garlic and 3 tablespoons of oil with lemon juice in each bottle. I am going to dispose of the Corbin recipe for sure, although the flavor is divine.
 
Diana B. August 7, 2014
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.
 

Voted the Best Reply!

Diana B. August 7, 2014
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.
 
SKK August 7, 2014
Thanks, Diana. Both of these recipes are from reputable canning books, not from Granny's. Pam Corbin is respected as a master canner in the U.K. and the second canning book is by a US author, also well respected. I have been canning for years, and am now wondering if there are different standards for different countries.
 
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