Well I'm not sure I want to enter into a 3rd hand debate taking place somewhere else that I can't even access much less be quoted in it when I can't respond. Heaven knows there are sorts of canning forums out there on the web and they range from excellent right down to flat out dangerous in the info they provide. It is a user beware world out there. :)

So I guess I begin by saying that I am far from the only person that makes that statement, here or elsewhere. Most experienced home canners that make the effort to remain current with the guidelines know it, And anyone who has ever taken a certified canning course has certainly heard it.

Although "process for the time of the longest ingredient" was mentioned in some older books and while it is true that many recipes that include meat call for the meat processing times, not all do, it was never an official guideline.

It is simply an assumption made by long ago home canners that took on a life of its own. They noted that 90 min was the max time called for (except seafoods) so assumed that time would be good for anything. They reasoned that if X mins was good then XX minutes was even better. They used that assumption to allow them to make whatever changes they wanted to in the recipe. The greatly flawed "Gee, I can safely can anything I want to if I pressure can it long enough" assumption was the result and is still used by many today simply to justify disregarding the guidelines and making up their own recipes.

But all this was before the role of pH and density in canning were understood and when the resulting quality of the food was of little concern. Those issues should have put an end to the old assumption but didn't unfortunately.

So it is "guess work" because it encourages the canner to make up their own recipes and processing times and it disregards both pH and density of the mixed ingredients and the end quality. Tested recipes instead test to balance safety AND quality.

Good examples are in the NCHFP FAQs that address the "why can't I can my own recipe for ______" questions.

These are low-acid mixtures which could support the growth of bacteria that cause botulism, so a process cannot be estimated or made up. It must be a tested process known to kill these bacteria in this product.

Still it all boils down to personal choice, personal risk. Those that regularly advocate "time required for the longest ingredient" works are almost always doing it just to justify canning their own made-up recipes. That is their choice, their risk to take.

Hope this helps clarify.

Dave

That must be what the author of "Meals in a Jar" did - all the meat processing recipes say 90 minutes. In intro she mentions botulism and USDA, but not NCHFP, says "use current USDA guidelines" but gives pressure for dial gauge (11 lbs under 2000ft, increasing after that) only, says if you have weights just use 15 lbs for everything.. And then she proceeds to describe how she cans cheese, and many of the meat recipes contain large amounts of fat and flour. And pints of shrimp for 45 minutes?

Too bad b/c some recipes sound good (braised brisket has meat, vinegar, tomato paste, brown sugar, onions and garlic) but now I'm leery of all of them. What's worse, there's just enough mention of current USDA guidelines that an inexperienced canner may assume all recipes in the book are safe.

No, no, I'm not trying to involve anyone in a debate they don't have access to. It's just hard to know the meaning behind a single sentence quote. I think you've explained it as well as possible given the circumstances. Many thanks for answering.

If I may add to what Dave said, the NCHFP and others like Ball are concerned about both safety (obviously pre-eminent) and quality. So while it's hypothetically possible to process a mixture for the maximum time required for any individual ingredient in that mixture, the result, while possibly safe, may not be optimal in texture, flavor and/or retention of nutrients. And who wants to go to the trouble of processing just to achieve an unappealing and inferior product?

I think a lot of people are not aware that pH is not the only concern. Density affects heat penetration, and a very dense mixture might actually require a longer processing time than that called for with a single ingredient like beef which might be processed in cubes surrounded by broth.

Water activity is also a factor as botulism spores, for instance, require a low-acid, high water-activity, anaerobic environment. That proved to be an issue with pumpkin puree, which is no longer recommended for canning. Moisture levels in home-grown pumpkin were all over the chart and the pH of the samples tested varied so much it was impossible to come up with a reliable processing time which also yielded a quality product.

Canning may not be rocket science, but it is science and the opportunities for something to go awry are limitless.

Carol

Thanks for the further explanation, Carol. Much appreciated.

Facts About Botulism:

-- The toxins/spores produce by the bacteria can are fatal.

-- There has been 120 to 150 total cases of botulism reported ANNUALLY in US, of which 15% is food related (canning etc). That is 18 to 23 cases, in ALL USA in the course of one year. And from those not all of are caused by improper canning. .

-- It is the toxin/spores produced by the bacteria that is fatal , not the bacteria itself directly.

---Any food containing the spores/toxins boiled for 10 minutes or longer will destroy the toxin.

-- Any food item cooked at 250F( PC) will kill both the bacteria and the toxins, in just 3 minute. This means that the remotest part of food in the can MUST reach 250F and kept there for a minimum of 3 minutes.

Oh, so since the odds of us being one of the 18-23 who die or become seriously ill are slim we don't have to worry about it at all, right? Just as long as we pressure can our foods at 250 degrees for a minimum of 3 minutes, no problems.

Amazing. You make it sound so very simple. Simple but so wrong!!

That sort of gross over-simplification of the whole process is what misleads the under-informed into making dangerous assumptions about what is safe to do and what isn't.

Dave

This post was edited by digdirt on Sun, Jan 12, 14 at 22:25

CuriousCanner has been provided with information relevant to the question and can decide for him/herself how to apply it.

I have said before many many times that the CDC categorizes botulism as low-frequency high-risk. There's nothing new in that.

It's not that it occurs often; it's that when it occurs the consequences can be dire (though not necessarily fatal). But each home food processor decides the level of risk they are comfortable with.

I do agree that an untested canning recipe is not necessarily unsafe. It is an unknown. It is equally erroneous to consider it either safe or unsafe but considerably less risky to operate on the assumption it's the latter.

Carol

Sorry I should have said tested, not safe. 90 minutes at 15 psi for meat (not seafood) dish may be safe, but not sure it would be palatable - esp. since IIRC the recipes called for fully cooking everything first ;-)

I just listed the facts about botulism and did not express any personal opinion about it. It is up to every individual to prioritise.

Sure , I don't like to be one of the "one in 10,000,000" who dies of food related botulism but then I drive on the highways that tens of thousands die each year in traffic accidents.