ISO Guidance for Pressure-Canning Non-Acidulated Tomatoes

[slkinsey]

Most guidance for canning tomatoes is for acidulated tomatoes in a water bath.  I don't particularly care for that flavor and it strikes me that one ought to be able to pressure-can non-acidulated tomatoes just as safely.  Does anyone have any guidance on pressure-canning hot-packed tomatoes with no added acidity?

[MelissaH]

I found http://www.pickyourown.org/tomato_acidity.php, which talks about whether you need acid when you can tomatoes. Apparently, some varieties of tomatoes are not quite acidic enough to qualify as an "acidic" food, and that's why all the CYA instructions say to add lemon juice or vinegar. The link goes on to say that low-acid foods need temps of 240 to 250 °F to destroy botulism spores, attainable by using a pressure canner at 10 to 15 psi, and those temps need to be held "from 20 to 100 minutes" to destroy bacteria. But I would think that if you used whatever the canning directions for beans are, as that's definitely a low-acid food, that the time and pressure would be adequate to make tomatoes safe as well. A Washington Post article at https://www.washingtonpost.com/lifestyle/food/what-sold-me-on-pressure-canning-at-home/2015/01/26/4d365546-a2a3-11e4-9f89-561284a573f8_story.html says that for pint jars of cooked dry beans in their cooking liquid, leave an inch of headspace and process 75 minutes at 10 psi.

[Martin Fisher]

I also don't like adding acid.
I pressure can tomato sauce using the times for "Spaghetti Sauce without Meat."

[FauxPas]

Wow, I have been reading up on this and it's a job to straighten it all out. I don't have a pressure canner but vaguely thought I might be interested in one and so started reading up. This is what I understand:

 

Tomatoes (whether heirloom variety or not) can vary widely in their acidity. High acidity is below 4.6 pH. Anything 4.6 pH or above is considered low acid. Tomatoes tend to straddle this line. One study of heirloom varieties by U of Illinois found an average range of pH between 4.18 and 4.92 and almost 30% of the tomatoes were in the low acid range. (Brandywine was found to be a lower acid, higher pH variety and it's a very popular variety.)

 

Cited here:

https://foodsafety.wisc.edu/assets/preservation/UWEX_addacidtomatoes.pdf

 

But tomato pH can vary a lot due to growing conditions, soil/water/fertilizer pH and ripeness. Riper tomatoes have higher pH and lower acid. So even if someone gets a certain pH level in the same variety you grow/buy, your tomatoes may have a different pH level due to their specific conditions. 

 

Because of the difficulty of knowing the pH of the tomatoes that any one person is using for their canning, the USDA and extensions generally recommend the addition of acid to make sure the final product will fall within the safe pH level.

 

For water bath canning, extra acid is always recommended. However, extra acid is also often recommended for pressure canning since USDA feels the true required processing time would be so long as to make the non-acidified tomatoes undesirable (mush, I guess). So the recommended processing times, even for pressure canners, may not be sufficient to reduce the risk of botulism to what is considered safe. 

 

To ensure that pressure canned tomatoes without added acid are safe, it would require a longer processing time that would make the tomatoes far less appealing. (I'm guessing they would be mush?) Also, no one seems to know how long the safer processing time would be, so it may be better to just play it safe and add some acid. 

 

Some people think that citric acid affects the flavour less than concentrated lemon juice, though it still reduces the pH appropriately.

 

Still, some people choose not to add any acid when pressure canning. And some Extension sites may offer some support for this, such as is quoted here:

 

http://www.simplycanning.com/canning-tomatoes-safely.html

 

A good discussion here:

 

http://forums.gardenweb.com/discussions/1969930/pressure-canning-tomatoes

 

At the end of the day, I did not feel that there is a clear definitive answer on this but if I did go ahead and do some tomatoes in a pressure canner, I think I would just add citric acid. But others may disagree!!!!  

 

There are lots of opinions and discussions on this. I tried to find the best science I could and don't have all the citations anymore. I've forgotten some of the stuff I found but I think the summary above is pretty true to what I read overall. Not sure it will be of any help to you! 

[Martin Fisher]

To ensure that pressure canned tomatoes without added acid are safe, it would require a longer processing time that would make the tomatoes far less appealing.

 

No, not necessarily, let's not forget the most important point about pressure canning, the temperature is higher, time may or may not need to be longer, required time may even be shorter. 

The spaghetti sauce method I referenced above is basically tomato sauce with added high pH  (low-acid) ingredients and no added acid.

Edited September 6, 2015 by DiggingDogFarm (log)

[FauxPas]

I also don't like adding acid.

I pressure can tomato sauce using the times for "Spaghetti Sauce without Meat."

 

I understand what you are saying and it makes sense to me (and to others). However, there are still some folks who say that the sauce is a different animal than plain tomatoes. For example (from the GardenWeb forum referenced above):

 

 

I agree that it's weird that tomato sauce requires lemon juice and spaghetti sauce doesn't. But to me, it does make sense. Notice that the "spaghetti sauce without meat" recipe says "Simmer uncovered, until thick enough for serving. At this time the initial volume will have been reduced by nearly one-half." This is a very important step. The thickening and the added sugar reduce the amount of water available, which makes the environment less hospitable to botulism. Also, the processing time would be 5 minutes longer at the same pressure (20 min at 10 lbs for spaghetti sauce, 15 min at 10 lbs for tomato sauce). That's not much but it does factor into the safety.

I am not recommending this, but I would think that in theory you could follow the spaghetti sauce recipe, leave out the other veg, and still process like spaghetti sauce, without lemon juice. The key requirements would be adding the sugar and salt as in the spaghetti sauce recipe, and cooking it down until reduced by half. Again, I don't know whether that's actually safe and I wouldn't risk it, I'm just trying to point out the big differences between the recipes that makes one not need lemon juice while the other does.

If the spaghetti sauce were not reduced to half its original volume, I wouldn't feel safe canning it without added acid.

 

So the spaghetti sauce recipe requires a much longer cooking time prior to processing which reduces the water content, plus generally has a longer processing time and added sugar. 

 

 

 

Remove cores and quarter tomatoes. Boil 20 minutes, uncovered, in large saucepan. Put through food mill or sieve. Saute onions, garlic, celery or peppers, and mushrooms (if desired) in vegetable oil until tender. Combine sauteed vegetables andtomatoes and add remainder of spices, salt, and sugar. Bring to a boil. Simmer uncovered, until thick enough for serving. At this time the initial volume will have been reduced by nearly one-half.

 

http://nchfp.uga.edu/how/can_03/spaghetti_sauce.html

 

DiggingDogFarm, just wondering - when you process your tomatoes, do you just follow the processing times for the sauce or do you also cook the tomatoes down prior to processing? 

 

Again, I have never even used a pressure canner, so this is just of general interest to me, and I don't want to claim that I have found the best or the only answers. Only that I can see the reasoning on both sides. 

[Martin Fisher]

Yes, plain tomatoes and sauce are different animals, that's why I specifically stated "sauce."

The tomato sauce I can is somewhat concentrated, although, nowadays I usually just freeze whatever little tomato products I preserve.

 

Unfortunately, there are no "tested recipes" for pressure canning various forms of tomatoes without added acid...this has been a BIG complaint of mine for the past 35 years, but, it is what it is.

[FauxPas]

Yes, plain tomatoes and sauce are different animals, that's why I specifically stated "sauce."

The tomato sauce I can is somewhat concentrated, although, nowadays I usually just freeze whatever little tomato products I preserve.

 

Unfortunately, there are no "tested recipes" for pressure canning various forms of tomatoes without added acid...this has been a BIG complaint of mine for the past 35 years, but, it is what it is.

 My bad, I misread your earlier post! I thought you were processing tomatoes as if they were sauce, but now I see that I didn't see what I thought I did.  

 

Yes, the lack of tested recipes is frustrating for sure!

 

Thanks for clarifying. 

[Jon Savage]

I understand what you are saying and it makes sense to me (and to others). However, there are still some folks who say that the sauce is a different animal than plain tomatoes. For example (from the GardenWeb forum referenced above):

 

 

So the spaghetti sauce recipe requires a much longer cooking time prior to processing which reduces the water content, plus generally has a longer processing time and added sugar. 

 

 

http://nchfp.uga.edu/how/can_03/spaghetti_sauce.html

 

DiggingDogFarm, just wondering - when you process your tomatoes, do you just follow the processing times for the sauce or do you also cook the tomatoes down prior to processing? 

 

Again, I have never even used a pressure canner, so this is just of general interest to me, and I don't want to claim that I have found the best or the only answers. Only that I can see the reasoning on both sides. 

I see both sides of this argument. I myself am comfortable pressure canning tomato (products) @ unacidulated for 15 minutes @ 10 PSI at sea level. YMMV,  as always be safe and discard anything that looks wonky. We have only ever had one thing look that way & it was Pinto Beans that had gone awry. It was pretty obvious with that one jar.

 

--edit obviously one should always use tested recipes.

Edited September 8, 2015 by Jon Savage (log)

[ElainaA]

After spending a (very painful) week in hospital with food poisoning due to badly stored leftovers a family party, I am fanatic about food safety. Adding 2 tablespoons of lemon juice to a quart of canned tomatoes ensures safety. Why would anyone not do it? 

From the CDC (Center for Disease Control):
 

Botulism is a rare but potentially life-threatening bacterial illness. Clostridium Botulinum bacteria grows on food and produces toxins that, when ingested, cause paralysis. Botulism poisoning is extremely rare, but so dangerous that each case is considered a public health emergency. Studies have shown that there is a 35 to 65 percent chance of death for patients who are not treated immediately and effectively with botulism antitoxin. 

Most of the botulism cases reported each year come from foods that are not canned properly at home. 

[Martin Fisher]

Some folks don't like pickled tomato sauce.

What I posted above is just suggestions based on many years of experience and research. Don't do anything you're not comfortable doing.

Edited September 8, 2015 by DiggingDogFarm (log)