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Food Failures: When Home Canning Goes Wrong


This is SCIENCE FRIDAY. I'm Ira Flatow.


BILL: Ooh, there it goes. Cool.


LINDA: Ooh, I love it.


LINDA: It makes me giggle every time.

FLATOW: Oh, they're happy people. They're Bill and Linda, two home cantors on YouTube. If you can your own pickles and salsas and jams, I'm sure you, too, know that satisfying popping sound as your jars cool.

But sometimes, things don't go as planned. You don't hear the pop. Or your jar breaks. Your lid buckles. Or worst of all, you're growing enough deadly bacteria to kill the whole city.

It all adds up to another food failure. And my next guest runs a call center for Jarden Home Brands. They are the maker of Ball canning products. You've got some of that stuff around your home if you do canning. And she gets around 400 calls a day, another 100 emails from canners who just didn't get it right. There's a lot of chemistry and science involved. Your recipe has to take into account pH, temperature, density, and to make sure your cans will keep.

Here she is to share a few tips. Jessica Piper is a home canning expert, also the lead representative of consumer affairs at Jarden Home Brands in Daleville, Indiana - not far down the road from the original Ball Glassworks in the Muncie.


JESSICA PIPER: Well, welcome to you. I'm so excited to be here.

FLATOW: Well, it's nice to have you.


FLATOW: Thank you. Well, you know, we like to talk about science. There's a lot of science and chemistry in canning, is there not?

PIPER: There actually is. It's super simple. But at the same time, there's a lot of science that goes behind it, and that's what people forget sometimes and why they experience those food failures.

FLATOW: All right. Let's talk about the science they forget. Give us the number one failure that - the cause of a failure.


PIPER: Number one is not following a tested and approved recipe. When you do that, you take a lot of risks. You could have the incorrect head space, which can affect your seal. If you under-process you are creating a wonderful breeding ground for bacteria to grow in your food, and no one wants to deal with food poisoning. That's not fun - or spoiled food, after you put all that time and effort into trying to preserve it.

FLATOW: Mm-hmm. Let's talk about the need to have the correct water temperature when you're doing canning. Talk about that.

PIPER: Well, actually, what we probably want to start with is which method you want to do.


PIPER: So we have two different methods. For your high-acid foods, you can water by can. And for your low-acid foods, you need to use a steam pressure canner.

FLATOW: Stopped there for a minute.

PIPER: Yeah.

FLATOW: Tell me the - what's the pH, the acidity have to do with choosing either one?

PIPER: Great question. So your high acid foods are going to have a lower pH. So your lemons, pickles, you know, you think fruits, veggies - excuse me - fruits, jams, jellies, pickles are all going to be your higher - lower pH foods, which make them high acid. And so those require a temperature of 212 to kill any molds and yeast and bacteria that may be present in those foods.

FLATOW: Mm-hmm.

PIPER: And then with your low-acid foods - think your vegetables, soups, stews, meats - they're going to have the higher pH, and they're going to require a temperature of about 240 to kill any bacteria that would be present in those food types. So you can actually get to that temperature when you're cooking with steam and under pressure in a pressure canner.

FLATOW: Yeah. 1-800 is our number, if you're a home canner, you'd like some advice. I'm sure that Jessica doesn't get enough email and phone calls.


PIPER: We're so busy right now. It's the height of canning season, so we're very busy. But we love it. This is what we look forward to every year.

FLATOW: 1-800-989-8255. You can also tweet us at scifri, S-C-I-F-R-I.

This is the peak canning season, you say?

PIPER: Yeah.


PIPER: Yeah. Definitely. So right now, we're getting a lot of calls about tomatoes and salsas. We still have some pickle calls coming in. Your veggies are what we're really dealing with a lot right now.

FLATOW: Huh. OK, let's go to the number two problem that people have when they're canning.

PIPER: Number two would be lids not sealing. That would probably be the number, definitely the number two. So what can happen there is if folks adjust their bands too tightly, then what's going to happen is that lid - it's a two-piece cap, for those of you who don't know. And that lid needs to be able to kind of hover to allow venting to occur, because as the gases are trying to get out of the jar, they're building a lot of pressure. They need to be able to escape, and that's what creates that vacuum seal. So if your band's are on there too tightly, that's, you know, it's not going to be able to do that, and the lid's designed to buckle when too much pressure is built up inside of the jar.

FLATOW: Hmm. So don't screw the lid down too - how do you know how tightly to screw it?

PIPER: So we say fingertip tight, but that's kind of, you know, my idea of fingertip tight could be totally different than yours. But I would say just kind of like a snug. We actually have a tool that will get the proper amount of torque and make it perfect every time. But for those of you who don't have our Sure Tight Band Tools, then you just want to kind of get it just a little snug.

FLATOW: Now, let's talk about - you said that - something very important that you - to use a recipe that's been tested out. Don't go off on your own too much.

PIPER: Right. Absolutely. And so what's important there is if you're creating your own recipe, then you don't know what the combined pHs of that entire recipe. And so every recipe that we have, whether its on our website, freshpreserving.com or any of our publications are all - they've all been tested and approved. And there's also the - USDA has a website with a ton of recipes on there too.

And they've done all the testing to make sure proper heat penetration 'cause what you're actually doing during canning is you have the coldest spot in the jar needs to process first in a duration of time to kill that bacteria or microorganisms or whatever. And they've did all the testing.

FLATOW: Right.

PIPER: We don't have that capability at home to see where the coldest spot is in our canner and figure out how long to process to make sure that we process it correctly. So the only way that you can always have 100 percent certainty in the food that you can is to always follow a USDA-tested and approved recipe. And there are so - we have plenty of consumers who call in who have a recipe that's maybe with their great grandmother's. But things change over time and recommendations change over time because bacteria and microorganisms evolve over time. So things change.

FLATOW: Right.

PIPER: And sometimes people just don't realize, again, the science behind it and why it's so important to stay up to date with current guidelines.

FLATOW: And if you are boiling it or if you're pressure cooking it...

PIPER: Mm-hmm.

FLATOW: ...you have to allow for the heat to get through all the food, right?

PIPER: Exactly. So what you're doing is you have to, you know, if we were in a big manufacturing company where they were producing a lot of this, they have a huge retort, and they can actually see where the coldest spot is and make sure that gets processed correctly. But at home, the only sure way to do it is to follow a tested recipe. And they're all going to vary by recipe, so it's all, you know, jams and jellies are usually around, you know, 10 minutes, pickles maybe like 20, 25. They all vary.

So it's really important to always stick with the recipe 'cause they're always easy. It's not a difficult thing to follow, but sometimes people just get a little maybe too excited or see a fun recipe online and want to give it a shot. But then you take a risk of possibly getting sick and then also to your food spoiling and then you've wasted all that time trying to prepare food.

FLATOW: They get so excited they want to eat it.

PIPER: Exactly.


PIPER: Exactly. And with pickles, you have to wait, like, four to six weeks to allow the flavors to really set in. So that's another thing too. Someone will call them and be like, it doesn't taste great yet. Well, give it some time. Let all the flavors settle in.

FLATOW: Yeah. You're in this for the long haul.

PIPER: Right.

FLATOW: You're learning how to do this stuff.


FLATOW: OK. Let's go to the phones. Let's go to Jennifer in Missoula, Montana. Hi, Jennifer.


FLATOW: Hi there. Go ahead.

JENNIFER: Hi. Thanks for taking my call. I recently purchased a steam canner. This is not a pressure canner. It's like a water bath. And I'm about to use it to make a bunch of jams and preserved fruits and everything, but I'm wondering if the processing time is going to be equivalent to the water bath I'm used to using. Are you familiar with this?

PIPER: I am familiar. We get this question a lot. And unfortunately, right now the USDA only has two methods of home canning that they deem safe, and that would be your water bath where the jars are completely submerged in water for proper heat penetration and the other is the pressure canner. And so with that steam canner that you have, there are no guidelines for that appliance for the USDA.


FLATOW: Hmm. You got to think it over...

PIPER: So a little more risky.



FLATOW: What's food poisoning worth to you, Jennifer?


JENNIFER: Boy, not much. I'm not willing to pay much.


FLATOW: Ok. A word to the wise here this time may be sufficient, I don't know. Thanks for calling, Jennifer.

JENNIFER: Thank you.

FLATOW: Good luck to you. 1-800-989-8255 is our number. Let's go to - a lot of people want to talk. Elizabeth in Sister Bay, Wisconsin. Hi, Elizabeth.

ELIZABETH: Hi there.

FLATOW: Hi there.

ELIZABETH: I have a two-acre organic garden, which means I put up hundreds and hundreds of quarts of everything you can think of. And I try to coax people to join me, and people are always terrified of botulism. And I've never had a problem, and I'm really precise. My understanding - and I'm just trying to wrap my brain around exactly what the problems are with botulism. My understanding is that it's actually really - it's kind of a weak critter and that the problem is that when you process and you don't quite do it long enough, it's the last man standing, and that's when it's dangerous.

And so if you don't quite do it as long as they're supposed to, when your pressure canning, tomatoes is what I'm thinking of, that the - when it it's dangerous is when everything else is destroyed and all you've got left is botulism 'cause you just didn't quite make it, didn't quite meet that temperature and didn't watch your clock. Is that what's happening? Is that when botulism is a problem?

PIPER: So at least what I understand of the - of botulism is that it needs to be killed at a temperature of 240. So if you notice that maybe your pressure canner loses pressure of not keeping it at pressure or maybe you've lost track of time and you happen to under process, you have two hours to reprocess that food after you remove it from your canner if you feel like you need to - something may have gone wrong with your process.

But I don't know anything about its actual strength. But there are ways if you - like I said, if you think that maybe you under processed or if it wasn't holding the right pressure for this entire duration, you can reprocess this food to kill that.

FLATOW: And botulism is nothing to fool around with.

PIPER: No. No, no, no.

FLATOW: It's probably the biggest poison on Earth, as far as I've heard before, the most powerful. You don't want to - in the old days, people used to, you know, they find a can in a store and they would - it'd have an expansion it, and they'd open it up and they would taste it to see if it was bad, and they were gone, you know, 'cause it was botulism that got them. So, Elizabeth, thanks for that call 'cause it will warn a lot of us about it.

ELIZABETH: Yeah. Thank you.

FLATOW: Thanks a lot. Do you get botulism calls a lot?

PIPER: No, actually do not. What we typically get the most of, consumers will call us because they're like, oh, the lids came unsealed. Your lids are, you know, they came unsealed. Well, one of the questions we'll ask is, how long after you removed them from the canner did they come unsealed? And they're like, oh, a week, three months or, you know, it varies.

And that's - I mean, that's a pretty clear sign right there that there was a miss in the process, and they've made a beautiful buffet of food for these microorganisms, bacteria to grow on. And they create gases as they're eating away, and that's what's going to pop the lid off. So we do a lot of educating in our call center every day.

FLATOW: Well, educate us about the foods that are just off limits, you don't can them.

PIPER: Well, we have a nice list of foods that you don't can. So dairy, we get a lot of calls wanting to can dairy products and - or eggs, noodles. So if you have like a chicken noodle soup, you'll want to actually keep the noodles out and do your broth and your chicken breast. But then add the noodles when you go to prepare it.

FLATOW: I see.

PIPER: So those foods. And it really boils down to a density issue and not being to actually penetrate through all of those products. The USDA just doesn't have any guidelines to safely do that at home. We get a lot of - and the big one right now we're into the fall is pumpkin butter. Pumpkin butter is a no, no, no. We get a lot of that this time of year. But it's just so dense that you can't, you know, there's just no way to ensure that you're going to get to that coldest spot during that processing time. Now, the USDA does have guidelines to cube your pumpkin and can it that way. But a puree, way too dense.

FLATOW: Yeah. All right. This is SCIENCE FRIDAY from NPR. Talking with Jessica Piper, home canning expert for Jarden Home Brands in Daleville, Indiana. Just as a point of reference, how do they put the chicken noodle soup in the cans you buy in the store, if you can't can it yourself?

PIPER: Well, I kind of mentioned this before. So these are these big, you know, big manufacturing facilities where they're going to have these huge retorts. And that's one method of doing it. That's like essentially a huge canner with tons of shelves. They can be really huge. But they have, you know, the technology to be able to look inside their can. And they've got those computers. They can see where the coldest spot is, and they can make sure that the foods are processed to that coldest spot regardless of where it is in their retort is processed for the full duration of time.

FLATOW: So there really is different temperatures inside your cans.

PIPER: Well, yeah.


PIPER: I mean, it just depends on where they're placing the canner and at what point did you put them in. There's - I mean, they're just sitting in hot water, so it's just a matter of how dense the food is in your jar and just getting to that spot. So when, you know, we get a lot of calls, like I said, about, oh, I can buy this at the store. Well, they have, you know, if you want to go and make the investment to have thermometers and cameras and - to check, you know, heat penetration, go ahead. But...

FLATOW: Add the noodles later, right?

PIPER: Yeah, exactly. And there's a lot of things, too, that, you know, if someone wants to add, you know, maybe like corn to their salsa, well, you know, we don't have a recipe maybe with that in there. So anything we don't have a recipe, just add it when you go to prepare it.

FLATOW: There you go. Let's go to Matt in Fairbanks. Hi, Matt.

MATT: Hey. How's it going?

FLATOW: Hey there.

MATT: Yes. I just had question. I recently got into canning middle of the last year and looking into canning some chili. I found recipes online for chili without meat, but what I'm looking to do is do chili with canned meat. And I browsed the Internet, the Ball home page on processing and stuff like that. All I'm looking for is a processing time for chili with meat in it, like ground meat. And I've look on the Internet, like I said before, for processing tomes and it says to process the chili for whatever needs to process the longest. Will I process my chili for the time and pressure that it says for meat?

PIPER: Yes. So whichever item that was going into your recipe, you would have to find it and then process for that duration, like whatever it says, whatever its processing time is for the one that has the longest processing time. Now, I'm looking - we have our Ball Blue Book. I don't know if you're familiar with it but it's been in publication. It's been around, you know, 125 years. Clearly, it's been updated since then...


FLATOW: I was going to say that's an old copy you have.

PIPER: Clearly, it's been updated. But we do have a chili recipe in here, and it calls for beef. It's beef, onions, garlic, canned tomatoes, chili powder, salt, peppers and cumin seed, and it has a processing time of pints for one hour and 15 minutes in a pressure canner at 10 pounds of pressure and the quarts are one hour and 30 minutes at 10 pounds of pressure. Obviously, if your altitude is higher than 1,000 feet, then you need to adjust the processing time.

FLATOW: All right, Matt. Thanks for calling. Before we go, tell us where your resources are where we can find all this information at if we want.

PIPER: Yeah. So we have a website, freshpreserving.com, where we have all of our different tools and our jars. You can learn all about them. We have a great getting started section. So anyone who's new to canning who hasn't tried it, it really is easy, super easy. We have great resources on there. We have recipes available. And then on freshpreservingstore.com, you can actually purchase any of these items and have them delivered right to your home. And that Ball Blue Book that I was just talking about, great resource, and it's available on there as well.

FLATOW: One quick question for you. How many people use your ball jars to drink beer out of?

PIPER: You know what, we probably have a ton. They are quite popular. For sure right now, you see all over Pinterest. People are drinking out of them and using them to - actually I've seen a couple of ideas which people are actually premixing drinks and having them in the jars with the lids and bands sitting in ice. People can just grab one depending on...

FLATOW: A whole new business right there for you.

PIPER: You know, right?


FLATOW: All right. Jessica, thank you very much. Have a happy weekend.

PIPER: You too. Thank you so much, Ira.

FLATOW: You're welcome. Jessica Piper, home canning expert. She's the lead representative of consumer affairs at Jarden Home Brands in Daleville Indiana. Transcript provided by NPR, Copyright NPR.