Science Friday - Spoiler Alert, Glyphosate, Unisexual Salamanders. May 31, 2019, Part 1

Episode Date: May 31, 2019

How many times has this happened to you? You’re standing in front of an open freezer, wondering what type of mystery meat has been left in there, when you purchased it, and if it’s still safe to eat? If you’re puzzled by sell-by dates, freezer burn, and just how long food can remain edible, you’re not alone. Studies show that more than 80 percent of Americans misinterpret date labels and throw food away prematurely to protect their families’ health. That adds up to $218 billion worth of food each year. Janell Goodwin, with the USDA’s Food Safety and Inspection Service, and Francisco Diez-Gonzales, professor and director of the Center for Food Safety at the University of Georgia, join Ira for a master class in food microbiology and safety. Then, Roni Neff of Johns Hopkins University Bloomberg School of Public Health explains how confusion over date labeling is worsening food waste and climate change. Plus: A population of mole salamanders in the Midwest is throwing a curveball at our understanding of sex and reproduction. Some populations of this salamander are unisexual—they’re females that can reproduce without males. Katie Greenwald, an associate professor of biology at Eastern Michigan University, joins Ira to explain what advantages living a single-sex life may have for the mole salamander. The herbicide glyphosate, found in products such as Roundup, has become a crucial tool on midwestern farms—but weeds are becoming resistant. What's next? Chris Walljasper, a reporter from the Midwest Center for Investigative Reporting, tells Ira more on the State Of Science. And The Atlantic's Sarah Zhang tells us what's whipping up 2019's active tornado season in this week's News Roundup. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Flato. Coming up later in the hour, we'll be unpacking the myths of spoiled food. How long can mayonnaise stay out before it goes bad? What do those dates on meat packaging really mean? And we'll be answering your question. So give us a call. 844-724-8255. What would you like to talk about? You make the call, but you have to make the call. 844-724-8255. But first, if it feels like you, you'd like to talk about, you make the call, you make the call. 844-724-8255. But first, if it feels like you've been hearing about an unusual number of tornadoes recently, you are not wrong. There have been reports of at least 1,000 tornadoes in the U.S. this year, 200 just in the past two weeks. The unusually high number has to do with the current shape of the jet stream, and yes, there is a link to climate change. Here to tell us more about that story, as well as other short subjects and Science is Sarah Zang, staff writer at the Atlantic. Sarah, welcome to Science Friday. Hi, great to be here. So what's this extreme tornado season? There was a tornado warning here in New Jersey, I mean, New York, just this past week. What's going on?

Yeah, I live in Washington, D.C., and we also had a couple of tornado warnings this past week. So the reason that we've been having in these tornadoes has to do with this unusual pattern of the jet stream across the United States. So the jet stream is this river of air. It's really high up in the atmosphere. It's kind of far above our heads, and it usually blows west to east, and it circulates the globe. Sometimes its path can get a little bit curved, and in the past couple of weeks, it's just been kind of extremely curved. It's basically formed a U across the United States. And inside this U, you have this blob of cold air.

It's kind of for California, the northwest, in the southwest, and that's been unusually cold for the past couple of weeks. And outside of this U of the jet stream, you have warm air coming in from the Gulf of Mexico, and the rest of the country is actually been having a heat wave. And the basic recipe for tornado is cold air meets hot air. Then you have the winds of this jet stream. And that's basically what you're seeing in the middle of the country. We're seeing all these hundreds of tornadoes all of a sudden. So why is the jet stream acting so weirdly out of place? Yeah, there are a couple of possible explanations.

One is just kind of the normal oscillations in the Earth's weather. So there's something called the Mad and Julian oscillation. And it's kind of like El Niño, except it plays out in the span of a few weeks rather than years. And basically what it means is it's created this batch of thunderstorms over the Indian Ocean. And this has actually had ripple effects that has affected the path of the jet stream over North America. So, like, everything is connected. And the other, of course, is, you know, what is the role of climate change, right? So it's been also really warm in Alaska this year.

And there's this bubble of warm air that seems maybe have pushed the cold air that is in the U of the jet stream down. And as the Arctic gets warmer, it's possibly you might be seeing more of that. Obviously, it's always really hard to say, like, this particular event happened because of climate change. But as things happen in the future, we'll see, might see more of that coal there coming down, and we can see how it's going to affect tornadoes in the future. Yeah, well, just the new normal. Next up, there was an amazing picture of a fossil I saw this week. It was like a whole school of fish fossilized it once.

How does that happen? Yeah, it's almost like a photograph, right? It's like it's 259 tiny little fish. They're kind of all swimming in the same direction. And you can see their little eyes and their little spines and little fins. And the scientists who saw this in the museum, he was actually an interesting animal behavior. And he thought that, oh, maybe they all died at once. So maybe it's a sand dune collapsed on them.

And that explains why they look like this. I spoke to some other paleontologists. They're a little skeptical of the idea. They thought that maybe this fish did die all at once. Maybe it was like a volcanic eruption or it hit like a bubble of water with no oxygen. But then they sank down to Lake Bed, and maybe there was a current that was kind of like moving along the fish and kind of lime all at once. Whatever it is, they did die all at once, and that's really unusual. Yeah, a lot of maybes there.

All right, you've been following a group of scientists who are testing the DNA of books. Books have DNA in them? Yeah, well, at least old books do. So if you remember before we had paper, we had parchment, and parchment is made of animal skin. usually cows or sheep or goats and skin obviously has DNA in them. So I've been talking to a scientist named Matthew Collins. He's actually a bio-archologist. And he got into this because he was originally digging up bones

and trying to figure out how sheep were domesticated in Europe. The problem with bones is that if you're lucky, you might find like a couple dozen of them. And he was just in an archive one day and just had this epiphany. He was like, wow, I'm surrounded by so many books made a parchment. Like literally like hundreds of sheep and goats are on these shelves. And so he decided to do DNA analysis of the paper or the parchment, as you say. Yeah, the parchment, exactly.

So he could actually take, you don't actually even need to cut up the parchment, which is important for people who, you know, are conservatives of old books. You can actually just take an eraser like you might buy in the store and lightly rub it over the parchment. And this is actually something conservators do to clean manuscripts. You can just take those eraser crumbs and you can get the DNA from animals from those crumbs. That is cool. So you could have different pages. You could tell which animal the different pages.

of the parchment came from. Yeah, exactly. You can go down to level individual animals. You could say, like, you know, this page, the sheep on page 10, how is it related to the sheep on page 25? And you could ask, you know, what kinds of breeds of animals were being used back in the Middle Ages?

And what that says tell us about trade in Europe back in the time. That is cool. Finally, some discouraging news for the scientists who thought they'd discovered an exo moon? Yeah, or maybe not in exome. So last fall, if you remember, an exo moon is basically a moon that orbits around the planet and another solar system.

And last fall, scientists thought they discovered the first one. But recently there have been a couple of groups who looked at some of the same telescope data. And they were like, we're not sure if we see a moon. Maybe it's an artifact in the data or maybe it's a planet? Question mark, question mark. I think this kind of shows just shows us how hard it is to find exo moons because they're so distant. We can't actually see them.

Where we're actually looking at is as they pass in front of a star, that star gets just a little bit dimmer. And that's just really hard to analyze. But in those little tiny blips in the data, astronomers are trying to find, you know, planets and moons. Yeah, well, still looking for planet nine, so. Yeah, exactly. All right, Sarah Zang, thank you for taking time to be with us today.

Thank you. Sarah Zang, staff writer at the Atlantic. And now it's time to check in on the state of science. This is KERNNO. St. Louis Public Radio News. Iowa Public Radio News. Local science stories of national significance. When the chemical glyphosate was introduced in the 1970s under the brand name Roundup,

it quickly became popular with farmers, and that popularity grew rapidly. The introduction of seeds genetically modified to be resistant to glyphosate, the so-called Roundup-ready crops, boosted the chemicals use on farms even more. From 1992 to 2016, use of glyphosate-indexam. increased by some 40 times. But now, weeds have learned to resist Roundup 2. And international health officials are also questioning its safety. Joining me now to talk about what all this means is Chris Waljasper, investigative reporter with the Midwest Center for Investigative Reporting, a nonprofit journalism group based in Champaign, Illinois. Welcome to Science Friday.

Yeah, thanks for having me. You're welcome. Give us an idea of just how widespread this herbicide is. Yeah, well, it is really the most used chemical herbicide in agriculture, more than three times as much as the next chemical. And really, the reason why is because it's so easy to use. Before Roundup, farmers would have to use certain chemicals to treat different weeds, so they'd be mixing these chemicals, and they could be dangerous to touch or to handle. So Roundup was really a game changer because it was so easy and so effective. And it just, it allowed for a lot of, you know, a lot of innovations in farming. And I understand that you grew up on a family farm.

How did the introduction of glyphosate changed things on your farm? Yeah, well, you know, yeah, I grew up in southeast Iowa, and I can remember, you know, I was helping out with farming in the 90s, and I'm a little younger. but I can remember going out with a machete and hacking at weeds in the early 90s. But you didn't have to do that anymore. With the advent of Roundup Ready crops, they could spray roundup right over the top of the growing crop. So you didn't have to go out with a field cultivator, you know, dig up the weeds between the rows of crops. And so with that, farmers went from spraying, you know, once or twice a year, maybe before the crop went in and after it came out,

to spring three, four or more times throughout the season to catch weeds that they might have missed. And as they did that, the weeds started developing resistance. They found a way to survive this herbicide. And that's where we got into some trouble in the 2000s. Because that's what they'll do, you know. Weeds are any animal. They get enough of them.

They'll be mutations and they'll find a way around it. Yeah, exactly. It is restricted, though. Its use is restricted in the European Union, right? But not here. Yeah, yeah. Vietnam banned the use of it. So around the world, there has been some pushback. And some farming advocate organizations are worried about that

because, you know, in places in developing countries, they see use of things like glyphosate as a real quality of life changer. You know, if you're, if, you know, a farmer in Africa, you're able to go from, you know, a lot of manual labor to prepare your crops and keep your crops, you know, free of weeds. If you can start using glyphosate, you can, it gives you time back in your day, time that could be spent, you know, sending your kids to school instead of, instead of attending the farm. So there is some, there's some concern internationally as well. So, yeah, no regulations here. Yeah, so what's up next? Do we know what the future of this will be?

That's the big question, right? So farmers have been using increasing amounts of glyphosate. It's becoming less effective. So there is a little bit of, there's a new chemical or an old formulation of an old chemical called dikamba that's being introduced. So that treats weeds a different way. But that too is growing resistance. It just came out in 2016 and weeds are already adapting to that.

farmers are exploring non-chemical ways of fighting weeds but with all of the attention glyphosate and Roundup is getting with these lawsuits and health concerns, a lot of agriculture experts are worried that we might start to see restrictions and regulations on glyphosate and if that happens, that's going to be a big challenge for farmers. This is the primary way they're using to deal with weeds and if they lose it, that's going to mean more,

having to go back to more expensive, more labor-intensive ways of treating weeds. And that's, we're in an agricultural recession right now. Times are tough for farmers financially and taken away glyphosate could really hurt them, could put some folks out of business. Okay, Chris, thank you for filling us in on that. Chris Wall, Jasper, is an investigative reporter

with the Midwest Center for Investigative Reporting, a nonprofit journalism group based in Champaign, Illinois. When we come back, the items in your freezer stay good forever. Now that you're grilling, you know, look in the freezer for some old, you know, steaks, you know, hot dogs, whatever. We've got food spoilage experts here to answer your questions. Give us a call our number 844-724-8255-8-4-Sight-Talk or tweet us at SciFri. This is Science Friday. I'm Ira Flato.

AJ, can you come here and look through what's in the freezer with me, please? We need to figure out what we're going to grow. How many of you were like Katie and AJ last weekend, rummaging through the freezer to see what's good to grill, only to come across packages of long-forgotten frozen food and wondering, is this stuff still good to eat? I don't remember this at all. What are they? Their steaks. What is it say?

September 5th, 2018. Would you eat those? We defrosted them? Probably not. Why not? Because they're pretty old, and I don't know how long they were in the fridge. I think there's some hamburger. Oh, this is from the last time we had hamburgers.

Two leftover hamburger patties. Oh, okay. Would you eat those? So that's like a month or two ago. Yeah, that's fine. Would you eat those? Probably not because I have a little freezer burn on them. They don't look great.

We definitely unpack them and then put them in this plastic bag. so they don't look like they would come out looking really great. But that's more based on taste, not on the fact that I think that these would kill you. Kill me. Yeah. Well, I don't, I think they probably just would have made me puke, but yeah. Okay, I guess we'll put new hamburgers on the grocery list for today's barbecue. Man, that's you.

That's not me. I just think that they looked a little freezer burned. But maybe we'll check out these steaks. No, you know what? No, I'm not going to. No, no, no, now that you've got to. actually tried to give me to eat them. No.

Why? What about them? Their sell-by date was last September. Also, I don't remember buying them or what they were for. I forgot them at Whole Foods. When would we have gone to Whole Foods for that? I mean, I don't know. Yeah. Expensive.

Really losing. $17. Yeah. Wow. Not only I mean, like is it food waste, but it's also money. Sound a little familiar, huh? If you're puzzled by sales-by-dates, freezer burn, and just how long frozen food can remain edible, you are not alone.

Studies show that more than 80% of Americans misinterpret date labels and throw food away prematurely in order to protect their family's health. That adds up to $218 billion worth of wasted food each year. And yes, it also contributes greatly to greenhouse gas emissions. We'll get into that a little bit later. But first we're going to unpack. See what I did there? Myths of Spoil Food, when it goes bad and why, but more importantly, when it doesn't.

Here to bring us a different kind of spoiler alert are my guests. Janelle Goodwin, technical information specialist with the USDA's Food Safety and Inspection Service, and Francisco Diaz Gonzalez, professor and director of the Center for Food Safety at the University of Georgia. Welcome to Science Friday. Hi, thank you for having us. Nice to have you. Hello. Hello, Frances. Happy to be here.

Nice to have you. Janelle, you work with the USDA, which inspects meat, poultry, and eggs. You heard our little intro there. Did that sound familiar? Oh, for sure. I mean, I talk to maybe hundreds of people a year, and that is by far one of the most common questions we get. So we've got to clear up this issue of food on your freezer. First, let's talk about it.

Does it ever go bad if it's in the freezer? So it doesn't. Frozen foods are actually safe indefinitely, and that's obviously given that they were safe when you put them in there. I mean, you don't want to freeze, molded food and come back and expect it to be perfectly fine once you thought. That's just not going to happen. Does it have to be in a deep freeze? Is there a prime temperature you want to hit? As long as your freezer is set to zero degrees Fahrenheit or below, it would keep your food safe indefinitely. Oh, that's 32 degrees below freezing. It's a Fahrenheit. Yeah. So we've got that, okay, Dr. Diaz, you're a food microbiologist.

So why is the food considered safe if it stays in the freezer? Because microorganisms are not going to be able to grow. They're not. Never. They're just going to stay dormant forever. Yes. Well, some of them may die during freezing, but the might. The majority of them will remain dormant and just sitting there.

And as long as it continues to be frozen, the microorganisms are not going to grow and nothing is going to happen to the food. As a microbiologist, tell me the difference between food spoilage and food safety. Well, that's a great question. I'm glad that you're addressing the issue because there is a big confusion between spoilage and safety. But the main difference is just to illustrate, you could have a perfectly edible food that has not been spoiled that could make you sick. So that's food safety. And on the other extreme, you could have a perfectly spoiled food that if you consume, you may not get sick at all. It will depend.

The kind of organisms that spoil food may be different from the kind of organisms that make people sick. Sometimes they're the same. I mean, in some rare occasions, you're going to have the same pathogenic organisms that actually spoil the food. But the majority of the cases, you could have completely different organisms. Why is it that if we defrost something that's frozen, we tell you not to refreeze it again? Well, I guess because of that possible risk, once you defrost the food item, then you will open up the possibility for microorganisms to grow. and if it depends on the handling of the food, by the time you freeze it, as Janelle mentioned,

they could have already grown and may get to a level that can make people sick. Especially they say if you've cooked it, don't ever re-freeze it, right? Janelle, what do you? Yes. So, yeah, I'll go ahead and chime in here. So basically, like he said, it has to do with the way that you handle the product,

while it's obviously thawed and while you cook it. If you handle it safely, you know, we recommend to use leftovers, which is any cooked product within three to four days or you can freeze it within three to four days. That would be perfectly safe. And again, that's if you're following, you know, the four steps to food safety, clean, separate cook chill, being very, you know, cognizant of how you're handling your food. That's very important.

and that's going to be the biggest factor in whether it would be safe or not. Our number 844-8255. Let's get the first question right at the top to Robert in Cleveland. Hi, welcome to Science Friday. Hello. Hi there. Go ahead. Yeah, I've got one for you on canned food. I've got several cases of canned turkey that's about seven years old.

What do you think of bird is on that? That's a good question. Janelle, how long do canned products, do they last indefinitely? So they do, and that's obviously with any food safety rule, as long as you're handling it safely. Now, with cans, you're like, how can I handle this safely? The best way is to control the environment that it's in. Here at the USDA, we say, yes, a can that is 10 or more years old, just being, you know, a bit. exaggerate here, but that is still good if it's in good condition. It's technically safe to eat. There are several factors that may limit the shelf life or quality of canned foods, and that's,

of course, extreme temperatures, corrosion, dense, rust, crushed cans, all of that impact, how long cans remain safe and at best quality. If your cans are bulging, rusted, leaking, or deeply dented, you don't want to use them, and they would not last indefinitely. As long as they look okay, they would be safe. You don't want to open up a bulging can. For sure. That has really bad stuff in it. Oh, yes.

Let's talk about Diaz. What is the microorganism, the exact microorganism that spoils food? Is there one kind of organism? No, we have a wide, diverse kinds of organisms that can spoil food. You're talking about any kind of food. You could have bacteria, you could have mold, you could have yeast. Those are the three major organisms that can spoil food. Yep.

Let's go to phones. More questions. Sarah in Columbia, Missouri. Hi, Sarah. Hi. Hi. My question is about raw onions. A while back, I caught some clickbait article that said, once you cut into an onion, that you need to consume it quickly,

because it can even go so far as to make people sick if it's raw and been cut, which seems so weird to me, and I didn't believe it, but, like, every third time I cut into an onion, I wonder if that's true. Okay, onion question. Francisco? Yeah, sure, if you can. I'll be happy to take it. Yeah, onions actually are one, some of, among all the fresh vegetables, onions are the kind that is rarely associated with foodborne disease, fresh onions.

Now, what you're describing is whether you cut the onion, and if you let it sit, let's say, four hours or overnight at the countertop, probably may not be good idea to come back to it because there could be some organisms capable of growing. But for the most part, cutting the onion, if you can leave it out there for maybe less than three hours and nothing's going to happen, you can put it in the fridge. And yeah, onions, there have been some studies that actually onions have so many macrobials that explains why they may not actually be very often. But rarely to learn that there is any case of foodborne poisoning with onions. So onions, that's, I would say, is definitely.

they are fairly safe. Cut away on those onions. What about dried food products like flour and wheat and things like that that stay in a container all the time and don't seem to ever go bad? Is there any possibility they could go bad? For the most part, no. They can remain, as you know. You can have your flour and your cupboard for years. You could pick it up and you can use it fairly well.

So in terms of spoilage, dry foods are some of the most stable foods that there are. Of course, if you have high fat foods such as some nuts, they may go rancid, and it's not going to be much of a safety issue, but a quality issue. But, yeah, the low water protects all of the dry foods. But at the other hand, we've been learning recently there are cases of outbreaks with, for example, wheat flour, with some type of other dry foods. bacteria are capable of surviving for a very long time during storage. Wow, that's quite interesting.

Let's go to the phone to Kathy in Minneapolis. Hi, Kathy. Hi, thanks for my call. And our local public radio station, Minnesota Public Radio, did a topic of food spoilage about a week ago. And my question is, what is the best way to thaw food? Now it's in the summertime should, you know, and it does depend on the kind of food, you know, meat versus vegetables?

So in the fridge, on the counter, use the microwave. And then the other point I was going to make is I went to a wedding potluck wedding reception a number of years ago. And, you know, between the time that the people drove to the church, the ceremony at the church, drove to the park for the potluck, you know, our food was sitting in our hot cars in July for probably three or four hours. So my point is that remember the time from when it leaves your kitchen to the time you sit, down and eat. Whether you're at a wedding or a sports game, you know, it's going to be a long time and keep your food cold. But anyway, my question was about the thawing. So thank you for all this and on the air. Let me get Janelle who was booing or ooing at that one.

Yeah, I mean, that again sounds so familiar, especially in this hot weather as we're approaching the summer months. So to answer your first question, never, never, never thought meat, poultry, produce, whatever has been frozen, we absolutely do not recommend to thaw on the counter. That is just not a controlled environment. You run the risk of, you know, foodborne pathogens just growing and multiplying rapidly. The best way that we say is to thaw in the refrigerator, and that's always because if you decide that, you know, something comes up, you can't make an event, whatever the case may be, you can safely re-freeze those products.

So always thought in the refrigerator, if you have time, plan ahead. If you don't have time you're running tight, go ahead and put it in, you can absolutely cook from the frozen state. Let me say that. If you don't want

to do that, you can use the cold water method, which is where you submerge the product in cold water. You make sure that you change to water every 30 minutes. That's a very good, you know, quick wrap it to thaw products, or you can thaw in the microwave. I know a lot of folks don't like that just because of the quality that comes out

with thawing food in the microwave. You're actually beginning the cooking process. So that answers that question. Let me just jump in before you get to the second question and remind everybody that I'm Ira Plato, and this is Science Friday from WNYC Studios. You can finish you now. Well, thank you. Okay, so the second question kind of has to do with the first one as well.

Here at the USDA, we have this zone that is called the danger zone. You all have probably heard of it. It's the range of temperatures or the zone of temperatures between 40 degrees Fahrenheit and 140 degrees Fahrenheit where bacteria grow and multiply rapidly. You want to avoid this. You don't want to keep your food in this zone for, you know, more than two hours. And then like you mentioned, if it's a hot summer day where the outside temperature is more than 90 degrees Fahrenheit, that time reduces to just one hour. And you do want to account for the time of travel time, the prep time, all of that, you know, counts in that two-hour rule.

So you want to be very conscious of this, especially if you have traveling plans. Yeah, we got that. That's a very good point. Let's see if I get a question from Scott and McGregor, Iowa. Hi, Scott. Hi, how are you guys today? I had a question regarding high sugar foods that tend not to spoil, and I'm thinking of honey, sorghum, molasses, and I'm just really curious as to why their sugar content can be so high with such a liquid environment and not have serious bacterial growth.

Dr. Diaz? Yeah, well, sugars are chemical compounds that are capable of dissolves. in water at relatively high levels. This is what we call it in chemistry, saturation point. So, yeah, you could have perfectly a liquid with high content of sugar molasses, and, yeah, you got it right. Exactly the high level of sugars that those products have decrease what we food scientists call the water activity. The water content is still pretty high. You would think maybe 30 or 40 percent of water,

but because of the sugar, that water will not be, or microorganisms are not going to be able to use that water for growth. So they will be inhibited and they will remain fairly stable, things like honey. You still have plenty of water. if you have that kind of water in other kinds of foods, they may spoil. But in the case of honey, it won't spoil because the water is not available for the organisms to grow. Interesting. We're going to take a break and take more of your questions.

844-724-8255 is our number. We're talking with Janelle Goodwin and Francisco Diaz Gonzalez. And we're going to bring on another public health official to talk about food spoilage with us. And so all kinds of questions. also tweet us at SciFRI. We'll be right back after the break. This is Science Friday. I'm Ira Flato. This hour we are unpacking the myths of spoiled food with my guest, Janelle Goodwin, technical information specialist with the USDA's Food Safety and inspection service. Francisco Diaz Gonzalez, professor and director of the Center for Food Safety

University of Georgia. And I want to bring on another guest now who is looking at the connection between date labeling and food waste and how it's impacting climate change. Rodney F is Program Director for Food Systems, Sustainability, and Public Health at Johns Hopkins Bloomberg School of Public Health. Dr. Nath, welcome to Science Friday. Thank you. I'm pleased to be here. You're welcome. So what are consumers most confused by when it comes to date labeling?

So there are a lot of things that confuse people. I think previously we had found that the number one and number two, reasons why people are throwing away food is concern about food safety and food quality. And often they are perceiving the date label as an indicator of food safety. And up until recently, that had not been the case. But now there is a date label that does indicate safety. So that's a really important step forward. So let's talk about that. Are there certain groups of people more likely to misinterpret these labels? Yes. We, we, we, just recently completed a national survey. And overall, there are about 84% of the overall population

that are throwing out food based on labels. But the group that is age 18 to 34 may be most likely to rely on the date labels to discard food. So the labels don't really tell you about the quality of the food. What do they tell you about? Why are the labels there? Oh, they do. They tell you that's exactly what they're telling you is about the quality. I guess I meant to send safety of the food. Sorry if I spoke wrong. No, no. It's safe to eat them, but they may not taste as good.

And they may. So often the labels are set at a point, they're set at a point before that quality would start to decline. And so even after the date label, you know, maybe most people couldn't detect a difference, or it may be a very small difference. in quality. But let me tell you about the new system of date labels, because this is a really positive advance. Basically, they've set up so that a small number of foods that would be

most likely to become unsafe over time, based solely on the time factor, would get a label called Used By, and then all the other foods would get a label that says best if used by. And this is a new industry standard that's been put out since 2017, and it's on more and more foods. And what this means is that if you see a label that says best if used by, you can use your judgment about whether to eat that. You don't have to throw it out, and that's on most foods. Most foods are not going to become unsafe before they become quite unpalatable. That's interesting. How is this confusion contributing to food waste?

I mentioned how much food waste is out there. Yeah, and the amount of waste of food is just staggering, as you mentioned. And so we tested six different labels, and across all of them, the people who perceived them as having something to do with safety were much more likely to say that they were discarding food based on the labels. Wow, and is there a link to climate change here if you have all that wasted food? Yes, indeed. So globally speaking, the amount of waste of food is so great that if it was a country, it would be the number three greenhouse gas emitter.

It's vast. And in the United States, the amount of greenhouse gas emissions coming out of food that is discarded could be said to be equivalent to about 37 million passenger vehicles worth of greenhouse gas emissions. Wow. So why is the labeling system so inconsistent from state to state? So, well, it evolved kind of as a free-for-all, and so manufacturers could put any label that they wanted onto those food products. But over time, there's been a real recognition of how problematic that has been and how it's kind of undermined the basic purpose of these labels,

which is to provide information to consumers. If the labels are misleading us, and we're thinking they're telling us to throw out food when we don't need to, then that's a real problem. There's also a problem in the other direction, I should say, which is that if you trust that label to keep you safe and you disregard other evidence like, oh, yeah, but that sat out on the counter for, you know, overnight,

that could also put you at risk. So recognizing how problematic this was, there's been more and more of a push, and there have been several federal policies put out that didn't yet pass to do this at the federal level. So when industry came together and said, we're going to put this forward as an industry standard, that's a really, you know, that's great. Just this week, the FDA endorsed the best if used by label as well. They didn't go so far as to talk about the used by label for the foods where it's a safety risk, but at least they're on board. with that all the same language. So once we know what that language means,

we can use it as a guide. So it's moving along is what you're saying. So what do you recommend that people do to check if their food is spoiled? So the standard things like look at it, smell it, use your senses basically, and use your knowledge of how it was stored, was it stored properly?

And one of the things I'd say is that what I mentioned that younger consumers may be more likely to misunderstand the date labels, I think it's even broader than that, that that kind of basic food safety education hasn't been given out as much in more recent years. You know, home economics classes no longer exist for the most part. And so there's a need also for a kind of cultural shift and more education and more communication and more communication and more thinking about kind of the benefits of eating food that maybe pass that label, if it's a best if used by label, save money, set a good example for the kids, and improve the environment, and have that food. Have the food.

Speaking of food, we have a lot of tweets coming in about stuff we haven't covered yet, so let me get to those patty tweets. How about yogurt? Always wondered about those dates on the container. As long as it looks okay, is it okay? Who wants to tackle that one? Janelle? So I can.

It has to do with the type of organisms and pathogens that are in yogurt. If this was a call that came into the meat and poultry hotline, you know, we get them so often, I would say for yogurt, if you are a part of an at-risk population, I would not use it past the best if used by date. And that's for just things such as Listeria that can survive and refuse. temperature temperatures that can make you very sick, especially if you're a pregnant woman or a young child. So yogurt, you have to be very cautious with things like dairy. You definitely want to be cautious with, but if it looks okay and smells okay, typically if you're a perfectly normal, healthy being, it would be safe. Let's go to the phones. 844-724-8255. Moshe and Newton Mass.

Hi, Moshe. Hi, thank you for returning my call. I plan to install a system of few containers in my kitchen and to drain the container of air, and in one case to fill the container with nitrogen, and another case just to keep the container in vacuum. And I would like to know if a food pathogen would reproduce in such an environment. Okay, last question.

What about his efforts there? All right. Let me take this one. Go ahead. Yes, well, I'm not sure. So let me see if I understand what you're trying to design. So you're trying to have some sort of container that will create what we would call an anaerobic environment. You would store food there, is that?

Yes, yes. So, okay, yeah, aneroic environments, we have pathogens that we are. concern. There are a number of organisms that actually are actually favored by low oxygen environment, like eliminating completely air. We have a glistrium botulinum, another organism close to street and per fringes. It would depend on the kind of food that you're going to be putting there, but those are going to be your two major concerns. And one of the reasons why, for example, canned foods are very safe is because the environment. is so tightly anaerobic, but at the same time, they have treated at the temperatures to kill Custodian botulinum,

because otherwise in the old days, it'll kill everybody. Stuff, yeah. We've run out of time. I want to thank my guests, Francisco Diaz Gonzalez, professor and director of the Center for Food Safety, University of Georgia, Janelle Goodwin, technical information specialist with the USDA, and a Rani NAF program, director for food systems, sustainability, and public health at Johns Hopkins. Thank you all for taking time to be with us today. Thank you.

Have a great one. In the Midwest, the population of mole salamanders is changing up our understanding of sex and reproduction. Some of these salamanders are unisexual. They're females that can reproduce without males, but they're not just cloning themselves. They make use of sperm from other species in their reproductive process. Katie Greenwald is Associate Professor of Biology at Eastern Michigan University in Ipsilanta, Michigan. She's one of the subjects of our latest macroscope video up on our website at Science Friday.com. Welcome to Science Friday.

Thanks so much for having me. So set the scene for us. What are these salamanders? Where do they live? Go ahead. Tell us all about them. Sure. So these salamanders, we generally call them unisexual salamanders because they are all female.

There are no males. And they are pretty broadly distributed kind of throughout the Great Lakes region, out into New York. in New England and then up into southern Canada. So they're actually generally quite abundant and populous salamanders in that part of the world. So if they're unisexual, how do they reproduce? Well, they reproduce in a way that as far as we know is actually globally unique. So there's nothing else that we know that does this. And what they do is they breed in ponds.

They're part of a genus of pond breeding salamanders. And the typical pond breeders have both males and females. and the males produce these little sperm packets called spermatophores in the ponds, and the females then pick those up, and there's internal fertilization, and they lay their eggs. So the unisexuals are actually in these same ponds with these other species, and they will grab those spermatophores produced by the males of the other species. And as far as we know, can we find a specific mutation or something that allows them to do this? I mean.

That's a great question. So what's really interesting about them is despite the fact that they are stealing genomes from up to five other species, they are actually all a single evolutionary lineage that's probably about five million years old. So it looks like something that just kind of cropped up one time, evolutionarily speaking, in this lineage, and then it's just allowed them to be really remarkably successful. Amira Flato, this is Science Friday from WNYC Studio. talking with Dr. Katie Greenwald. So how many genomes do they have in them if they're mating, so to speak,

with all these other salamanders? We find them with anywhere from two to five. Two to five. Yes. So what we call diploid, it's two sets all the way up through pentafloid. That is five sets. And those five sets, or those multiple sets, can come from any one of five other species. Interestingly, actually, the most common ones that we find have three sets of chromosomes, which is pretty unusual for animals.

So what is the evolutionary advantage of this way of life? This is really neat because one big question in evolutionary biology is why so many organisms reproduce sexually. The big question comes down to kind of a numbers game. So a unisexual or an asexual lineage that's all female. can grow twice as fast as the sexually reproducing lineage. This is actually known as the cost of producing males. So if you have a lineage that's all female, every female can reproduce on her own. You don't have to create males.

You don't have to have males taking up resources that could be used for females. You've got costs associated with finding mates and so on. So sexual reproduction is actually quite costly. Yeah. And so there have to be some big advantages, right, to outweigh those costs. and those are thought to be the additional genetic variation that you get from sexual reproduction, as well as being able to get rid of bad mutations. So if all these females are living in the pond, aren't we going to lose the males because you're not making any more of them?

That is also a very good question. What it looks like may be happening at least at a number of my sites where we have 90% of the salamanders in the pond are these unisexuals, is that I think if we had very long-term data, we might see that, in fact, they do kind of compete themselves out of existence, at least temporarily, until the sexual species are able to build up their numbers again, and then that might allow the unisexuals to then come back on the scene. So you may have a crash on the population that then stabilizes and rebuild itself? Exactly.

What do you want to know most about this? Oh, I have a lot of questions about this. So the most interesting question as far as the mode of reproduction in my mind is that sometimes the females include the male's genes and sometimes they don't. So they will actually produce clutches of eggs where they've picked up that spermatophore but then not used it. They've just basically cloned themselves. Sometimes though they do add the male's genome and sometimes they actually swap it in so they drop one of their own and add his. And sometimes the egg masses include multiple modes of reproduction. so they may have more than one of those things happening.

And that, I think, is a really fascinating system, and would allow us to kind of get at this question of when sexual reproduction is adaptive versus when it's not. That is quite mysterious, and I wish you luck and come back when you find out, okay, Katie? Thank you. Thank you. I'll do my best. Katie Greenwald, Associate Professor of Biology at Eastern Michigan University. That's in Ipsolanti, Michigan. And she's one of the subjects of our latest macroscope video.

website at ScienceFriady.com. It's a great video. You'll see Salamanders, terrific stuff up there on our website at Science Friday.com. Thank you for joining me today. Thank you. One last thing before we go, our degrees of change series about how we're adapting to climate change continues in a few weeks with a new chapter all about urban heat islands, the phenomenon of cities being significantly warmer than surrounding areas. The heat island effect is projected to get worse under climate change, but communities all over the U.S. and the world are working to keep citizens cool. Heat reflecting pavements

in Los Angeles, green roofs in New York City, heat disaster planning in Phoenix. But we want to hear from you. How is your community combating the threat of extreme heat? Go to science friday.com slash degrees of change to share your story. ScienceFriety.

com slash degrees of change. Charles Berkwurst, our director, senior producer Christopher and Talietta. Our producers are Alexa Lim, Christy Taylor, and Katie Feather with a cameo appearance by her husband, AJ, there in the freezer. We have technical and injuring help from Rich Kim, Sarah Fishman, and Kevin Wolfe. We're active all week on social media. You can also ask your speaker to play Science Friday whenever you'd like to.

I'm Ira Flato in New York.