Well, first of all you can't PC "more or less any soup". ;) There are very specific guidelines on what can and cannot be included in soups, the amount of liquid required to prevent density issues (basically 1/2 water), no thickeners allowed, and long processing times to make them safe.

Same with tomato sauces - it is dense and borderline acidic so it's difficult to insure botulism spore killing. And that density varies from cook to cook preparation as do the type of tomatoes used.

So they add on the safety factor of "don't vary the amt of low acid ingredients" rule to try to insure that the recommended and tested processing times for the sauce will be safe in spite of those differing densities. Changing the ingredients could easily alter the processing time required and you'd have no way to know how much time to add. Remember it isn't just the pressure that makes it safe. it is the TIME under pressure that is vital. ;)

Why not post your recipe and let the folks here evaluate it for safety?

Dave

Hi, Dave! Here's the link for the NCHFP instructions that made people say (in another thread) that 'more or less any soup' could be PCd.

I'll post my recipe in another thread, thanks!

Val

Here is a link that might be useful: pressure canning soups at NCHFP

Hi Val - yeah I know the soup discussion you refer to but that statement was a very broad generalization ;) and could easily be misleading to those not familiar with the soup restrictions.

Generalizations when it comes to safe canning aren't a good idea but it does happen so it is always best to double check any recipe that doesn't come from a recognized, approved source such as NCHFP, BBB, Complete Book, etc.

I suppose one could say that per NCHFP you could PC "more or less any water-based soup as long as it contained no thickeners, dairy products, noodles, flour, rice, oil, or garlic cloves, and you only filled the jars 1/2 way with product and the rest with water" but what fun would that be? ;)

So, as i said above, when it comes to pressure canning, it is the time of processing that is just as important as the pressure itself. Changes in the recipe usually require changes in the time.

Risk, of course, is something we all have to evaluate for ourselves, and choose how much we are comfortable with but here we usually try to discourage unnecessary risk taking.

Dave

PS: for future reference you can just attach the recipe here so that the discussion remains in context. A new thread isn't necessary.

The processing times are kept as short as possible consistent with safety AND optimal quality. Mess with the ratio of low-acid ingredients and the processing time goes up. Ergo, quality goes down.

Theoretically you could pressure-can anything, I suppose, if you processed, say, three hours. But who would want to eat it?

As Dave said with the soup, there are limitations; you do have many options but not all options.

Carol

Dave, thanks for the pointer on where to post! I wasn't sure.

Got it, re: the soup. Why are garlic cloves a problem?

Carol, re: the overlong processing -- a lot of times I see on pressure vs. bwb canning that pressure canning a particular item will increase quality. I always wondered about that -- how could it? Intuitively it seems a shorter processing would be better if it were safe.

Hi Valereee,

Most written recommendations from NCFHP and this forum tend to be very conservative, as they should be. While I have not been able to find any reported cases of botulism in the USA from tomato products in recent years, why take any chances when prevention is so easy. Just adjust the acidity by adding a little citric acid (1/4 tsp per pint) or lemon juice (1 TBS per pint) before pressure canning. Citric acid has minimal effect on the taste and may even improve the balance.

TomNJ

Garlic cloves are one of the high risk botulism ingredients.

As to the question: see on pressure vs. bwb canning that pressure canning a particular item will increase quality it is because PC will usually reduce the processing time vs. BWB that same recipe. But when you change the ingredients in the recipe you throw the processing time out the window and when that change reduces the overall acidity the PC time - if there is one - ruins the product.

Dave

Dave, but I guess I figured that while it's reducing the processing time, it's increasing the processing temperature, which I guess I would have thought would also affect quality. Maybe not as much as a longer processing time does?

I'm wondering about the peaches I canned last week using BWB. They're good, but maybe I should try PC canning them, see if they're even better with the shorter-but-hotter PC time.

I have tried PC'ing my peaches before. I was not happy with them, they were too soft. Not sure if that would be your outcome or not, just giving you my personal experience with it.

Linda Lou, thanks. I guess it would make sense that it would be idiosyncratic to each product. For some items, hotter but shorter would be better, for others longer but lower would be better.

There are very few things that offer an approved choice of either type of processing. Basically it's peaches and some tomato products off the top of my head. Some food products can never be BWB and many can never be or never should be PC because of the damage done to the product.

That is one reason for the across the board recommendation to stick with approved recipes, to not modify recipes, and especially to not modify the form of recommended processing.

So it isn't an issue or choice that comes up all that often. But the chemistry behind it is confusing at times. Often it the addition of one ingredient such as sugar or dry herbs rather than fresh or one action such as pre-cooking that makes one recipe safe while another isn't.

And some times it is just a matter of taste. With the peaches they offer both options because both have been tested and because some prefer them BWB and some prefer them PC. Personally we like the PC ones. Try both and see which you prefer.

But many times it is just because there has been to scientific testing done on a certain food or recipe. In those cases, all we can do is use one that is approved. When the new, revised guidelines come out later this year (hopefully) there will likely be more changes to deal with. There are other legit sources besides NCHFP - Ball Blue Book, Ball Complete Book, Ellie Topp's book, among many discussed here. But never use "old family" or make-up-as-you-go-along or one of the how to preserve food in Alaska lady sites or ones from old cook and canning books without first having them vetted by those in the know. Be safe. ;)

Dave