Tuesday, July 29, 2008

Killer Canning, or How to Avoid Poisoning Anyone

Home canning is all the rage. Eating locally is in, and doing so year-round pretty much requires some kind of food preservation. No one's freezer space is unlimited, and home canning is a great way to preserve the harvest. It seems every food blogger is canning and offering recipes for the foods she's canned.



Unfortunately I'm seeing a large number of unsafe canning recipes posted on various food, recipe, and local eating blogs, and we aren't talking about just the kind of unsafe canning that gives you a few days of gastrointestinal misery. We're talking serious neurotoxins, botulism, paralysis, and death.



Here are a few key bits of knowledge, useful whether you're canning yourself or are the recipient of a home-canned gift.



Canning Fruits. In general, canned fruits are safe. Almost all fruits (exceptions include bananas, figs, and tomatoes) are high-acid, which means both that spoilage is less likely and that any spoilage is likely to be evident -- you'll see mold, or the jar when opened will have an off smell, or the seal will be broken. This is why so much home canning is about jams, jellies, marmalades, and other fruit spreads. HIgh-acid fruits are all safe to can in a boiling-water bath using a wide variety of recipes.



Canning Vegetables. This is where the serious food-safety issue comes in. All vegetables are low-acid foods and are unsafe to can in a boiling water bath unless sufficient high-acid ingredients, generally in the form of vinegar, bottled lemon juice, or citric acid, are added. The proportion of high-acid to low-acid ingredients must not be altered from that specified in the recipe. The problem is that often an experienced-cook-but-inexperienced-canner picks up a canning recipe and assumes her cooking experience can be used to adapt and improve the canning recipe. It can't.



Tested Recipes for Canning Vegetables. Unlike cooking recipes, which the cook can adapt to her own tastes -- increasing the proportion of one ingredient, omitting another entirely, using an unspecified technique such as sauteeing the veggies -- the canning of vegetables should be done using a tested recipe (that is, a recipe that has been tested by the USDA -- or the equivalent, in other countries -- and found to be safe for home canning) with no changes in the proportion of high-acid to low-acid foods. To be sure the recipe you are using is a tested recipe, use a trusted resource such as the Ball Blue Book (use a new edition, as canning recommendations have changed over the years), the Ball Complete Book of Home Preserving , the Complete Book of Small-Batch Preserving, or the National Center for Home Food Preservation.



When you discover a delicious-sounding boiling-water bath canning recipe online and think you'd like to try it, ask the person providing the recipe where he got it. (Most foodies are happy to talk about the source of their recipes and won't take this as an insult if you ask in a way that indicates curiosity rather than mistrust.) If he did not get the recipe from a trusted source, or if he adapted it in any way that changes the proportion of vegetables-to-acids, or if he added oils, fats, or animal products, don't use the recipe. Find another similar recipe from a trusted source and use that instead. The same goes for gifts of home canned vegetables, including combination recipes such as salsas, sauces, chutneys, and relishes. I cannot stress this enough. When canned vegetables go bad, one likely culprit is botulinum, which is the neurotoxin that causes botulism: if it doesn't kill you, it can leave you paralyzed. It is a seriously nasty bacteria and nothing to fool around with. Worse yet, unlike mold, you can't see, smell, or taste botulinum. The seal on the jar may not even be broken.



With the sharp increase in canning by inexperienced canners, we are likely also to see an increase in home canning-related food poisonings. Done properly, home canning is very safe and a great way to preserve the harvest so you can eat locally all year around. But do take the necessary steps to make sure you know what you're doing.



The National Center for Home Food Preservation is a great resource for home canners, new and experienced alike. The recipes posted there are all USDA-tested and approved, and they have a ton of information for home canners -- even a complete home-canning course you can download in pdf form.



Your county extension service is an excellent resource for information about canning. Many are offering canning classes geared to new canners.



Another great resource for canners is the Harvest Forum on GardenWeb. You can search the forum archives to find answers to many questions.



Originally posted at Eat.Drink.Better.

14 comments:

Jen (Modern Beet) said...

Gosh, I've seen SO many methods described in the blogosphere -- it's hard to know what is good practice and what isn't.

I recently picked up the book 'Putting Food By', which has a lot of useful, readable information about food-borne pathogens, proper canning techniques, etc. Most of all, it addresses the WHY -- why you can't process low acid foods in a boiling water bath, why you should have an inch or more of water covering your jars in a boiling water bath etc...

valereee said...

Jen, I love books that do that! When I just get a rule, my first thought is, "But why?

valereee said...

Jen, just a heads up on Putting Food By -- I used to have that book but discarded it because it was over fifteen years old. I checked Amazon just now for a new version, and I'm not seeing one. If the version you have is the 1992 version, you might want to replace it with a newer book. Most of the canning books updated around 1995 to include the new recommendations from the USDA on canning of certain products. For instance, some tomatoes are now low-acid and need to have lemon juice added to bring them up to high-acid for BWB canning.

Tom said...

You know, I wonder if there would be a way for the local organic/locavore community to partner with the Hamilton County Fair to promote some of these ideas. My family attended the fair this afternoon and it really needs a shot in the arm.

valereee said...

Tom, I'd love to see the county fairs get the interest they're due. I can never seem to attend either the Hamilton Co Fair or the Ohio State Fair for various reasons. Maybe next year I'll put them both on my calendar and see if I can't plan to get there.

Debs said...

Thanks for this post. I'd like to learn more about canning, but will be cautious.

Do you know if there's any kind of home tester kit for the presence of botulism?

Debs
Food Is Love

valereee said...

Debs, I don't think so -- if you suspect a can is bad, you don't want to even open it. It's recommended you throw the entire thing away in some way that will prevent it from being eaten by animals. (Don't compost it, for instance.)

But don't let fear of botulism scare you from canning! It is not a common issue AT ALL, and if you can properly using a tested recipe, canning is safe. The concern comes when you can using a recipe that you don't know is a tested recipe or when you don't use a pressure canner when appropriate.

Debs said...

Thanks. Also, I remember in my college co-op, we were always told that we couldn't put an opened can of food in the fridge because it would cause botulism (and violated some health code because of this). It seems like a bad way to store food anyway, but do you happen to know if the bit about botulism from open cans in the fridge is true?

Debs
Food Is Love

valereee said...

Debs, I'm no expert in storage of food, but my understanding is that botulin needs an =anaerobic= atmosphere (that is, no oxygen, as in a sealed container) to grow. So I would assume an open can in the fridge isn't the kind of atmosphere botulin grows well in. But maybe other things grow in an opened can in the fridge? I do have some general feeling that an opened can in the fridge was 'dirty' though -- not sure why, but my gran always wanted us to decant into a storage container.

Tom said...

Valereee,

I would think there could be quite a bit of interest in an urban county fair if the fair marketed itself decently and actually tried recruiting the right people.

At the heart of a county fair is citizen participation. The folks running the fair need to attract major groups of the population. More and more people in the city are getting involved things like micro farming and sustainable lifestyles.

The fair's theme for this past year was "A County Fair for an Urban Society." It was a good idea, but there was no execution at all. However, there are a lot of things that both city and rural people engage in, like agriculture, baking, beer/wine making, quilting, knitting, etc....

Sorry, didn't mean to hijack this thread and turn it into boosterism for the fair.... I just see it as a great possible venue to pass along some green ideas....

maybelles parents said...

fantastic post. for some reason, I haven't visited you in ages. but I thought of you when I was in cincinnati a month ago...I wanted to source some of your local vodka as a gift for FiL, but next time.

valereee said...

Maybelle's, Woodstone Creek just announced another release: Straight Bourbon Whiskey

Kelly Brown said...

I recently starting home canning myself and I found the Blue Book of preserving by Ball very informative and helpful.

JunkerJunk said...

Good warnings for even the most experienced canner. I shudder in horror at most of the recipes I see on sites like Cooks.com which apparently has no moderation nor concern for the safety of the recipe. Scary.
(Im a Cinti boy from way back, now living in central Ohio, I grew up in Dillonvale/Deer Park. It was nice to see your site!)