[Modernist Cuisine] Pressure Canning Tomatoes

[Anonymous Modernist 799]

Okay, so yesterday my husband and I spent a fruitful afternoon canning tomatoes and learning the ropes (so to speak)of pressure canning. Now we're wondering, what did we do wrong, and did we just waste 20 lb. of plum tomatoes?

Here's what we did: We packed raw tomatoes into one-litre jars, added the recommended amount of lemon juice, filled the jars with boiling water, sealed them, then processed them for 1.5 hr. I think that's an extraordinarily long processing time, but according to Modernist Cuisine, it's a fail-safe to ensure that everything reaches optimal temperature for killing any possible toxins. The instruction book that came with our pressure canner recommends 10 minutes at 10 lb. pressure.

Here's what we got: Bottles are only about 3/4 full, and there's evidence of leakage into the canner. After they came out of the pressure canner, the tomatoes were floating near the top of the jars, but have since settled to the bottom. The liquid and tomatoes fill only about 3/4 of the jars. They've also discoloured, indicating, to me at least, that they're seriously overcooked.

Okay, so I know that we didn't pack the tomatoes tightly enough. I have another case of tomatoes to can today, so will address that problem. What I need to know is, are the ones we've already canned safe to eat? Or is the air space likely to harbour any nasties, and should we just discard them?

[Chris Young]

pear tart said:

Okay, so yes­ter­day my hus­band and Ispent afruit­ful after­noon can­ning toma­toes and learn­ing the ropes (so to speak)of pres­sure can­ning. Now we‚’re won­der­ing, what did we do wrong, and did we just waste 20 lb. of plum tomatoes?

How full were the jars? It's important to leave enough headspace in the jars for expansion to happen during the heat up phase. And, yes, 1.5 hours is extraordinarily long. Can you send me the page reference you got that from? I think 1.5 hours is for a 1 liter jar of conductive food. For a 1 liter jar with tomatoes, which are acidic, I would estimate 10 to 15 minutes once the pressure has come up.

Here‚’s what we did: We packed raw toma­toes into one-litre jars, added the rec­om­mended amount of lemon juice, filled the jars with boil­ing water, sealed them, then processed them for 1.5hr. Ithink that‚’s an extra­or­di­nar­ily long pro­cess­ing time, but accord­ing to Modernist Cuisine, it‚’s afail-safe to ensure that every­thing reaches opti­mal tem­per­a­ture for killing any pos­si­ble tox­ins. The instruc­tion book that came with our pres­sure can­ner rec­om­mends 10min­utes at 10 lb. pressure.

Here‚’s what we got: Bottles are only about 3/4 full, and there‚’s evi­dence of leak­age into the can­ner. After they came out of the pres­sure can­ner, the toma­toes were float­ing near the top of the jars, but have since set­tled to the bot­tom. The liq­uid and toma­toes fill only about 3/4 of the jars. They‚’ve also dis­coloured, indi­cat­ing, to me at least, that they‚’re seri­ously overcooked.

A photo would help, but is sounds like air has remained (or leaked) in the jars and combined with the long, high temperature cooking you have degraded the lycopene (red pigment) of the tomato. I would guess the color is brick red to brown now, yes? This almost certainly occurred because the jars started out as much too full and overflowed during the heat up, preventing a good seal from forming during the cool down phase.

Okay, so Iknow that we didn‚’t pack the toma­toes tightly enough. Ihave another case of toma­toes to can today, so will address that prob­lem. What Ineed to know is, are the ones we‚’ve already canned safe to eat? Or is the air space likely to har­bour any nas­ties, and should we just dis­cardthem?

If you have refrigerated the failed jars then, yes, the tomatoes are fine for consumption. If not, the only ones I would use would be those that have a very firm seal when you open them, which indicates that you have a sterile seal.

edit: formatting

[Anonymous Modernist 799]

Chris, thank you for your response. I fully agree that 10 to 15 minutes is a much more reasonable processing time.

We followed instructions as precisely as we could, going so far as to ascertain the recommended 1" headroom with a ruler. If we did overfill the jars, it must have been with water. Other canning manuals advise that 20 lbs of tomatoes should yield about seven litres. In fact, we ended up with 10 one-litre jars. In the second batch of tomatoes that we canned, 20 lbs did fill just slightly more than seven jars. (These we processed for 40 minutes - still too long, and still some evidence of leakage, but the results were noticeably better).

As per Vol. 2, page 88, we assumed that tomatoes packed in water fell under the "conductive" category, so used the sterilization time as per the chart on page 89. Hence, 94 minutes. Even if we had opted for the "convecting" category, the processing time would still have been 40 minutes - a far cry from 10 to 15 minutes.

I have checked all the seals quite thoroughly, and so far all seem to be sound, so I have stored the tomatoes in our pantry. I will double-check any seals before use.Meanwhile, I'll be canning another case lot of tomatoes this afternoon, and will probably process them at 15 lb. for 15 minutes.

I'd be happy to add photos of this disaster, but don't know how to attach them in this forum. Instructions, anyone?

Again, thanks so much for your response.

[Judy Wilson]

Hi Pear Tart,

We're working on our photo gallery, but until then, what I've done for pics is to use imgur.com, and then directly put the forum link html into my post.

Judy

[Anonymous Modernist 799]

Thanks, Judy. Here we go, then:

[Anonymous Modernist 799]

Chris said:
 

I think 1.5 hours is for a 1 liter jar of conductive food. For a 1 liter jar with tomatoes, which are acidic, I would estimate 10 to 15 minutes once the pressure has come up. [Emphasis added]

 

 

Okay, now I'm really confused. What does acidity have to do with conductivity? One is a function of pH, the other of heat transfer. What we needed to know, and what the book does not make clear is the the amount of time for heat to transfer to a bunch of tomatoes. (And yes, I appreciate that you did answer that question in your response). Perhaps a more complete explanation of what constitutes a conductive food in the book would have been helpful. Or perhaps our reading comprehension is faulty.

In either event, we have learned that 10 minutes at Bar 15 is ample processing time for a liter jar of tomatoes, and since tomatoes are currently cheap at our green grocers, no great harm done.