Short Wave - TASTE BUDDIES: Science of Sour

Episode Date: March 9, 2022

Pucker up, duderinos! Short Wave's kicking off a series on taste we're calling, "Taste Buddies." In today's episode, we meet Atlantic science writer Katherine Wu and together, we take a tour through the mysteries of sourness — complete with a fun taste test. Along the way, Katie serves up some hypotheses for the evolution of sour taste because, as Katie explains in her article, "The Paradox of Sour," researchers still have a lot to learn about this weird taste.Baffled by another mundane aspect of our existence? Email the show at [e-mail] and who knows — it might turn into a whole series!See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

Kevin, do you like sour candy? He says, eh. You have to have two, because I put two in my mouth. Sure. Yay. What is it? Toxic waste sour candy. You're listening to Shortwave from NPR.

So we're grabbing two scroes. Bonapitie, Shortwave. Co-host Aaron Scott here. I'm grabbing some white wine vinegar from the pantry. Together with science writer, Katie Wu, we are getting culinary, shortwave style. I've got this lovely Amazon package full of very sour candy. We're kicking off a new series we're calling Taste Buddies.

We're often taught that there are five basic tastes, sweet, salty, sour, bitter, and umami. So in the coming weeks, we're going to delve into the science behind some of those. Plus, some other tastes that don't normally make the cut. I mean, taste is both super simple and super complicated. It is one of our five sort of classic senses. And when we taste things, we are basically perceiving the chemicals in our food. Those are picked up by little cells in our mouths, and they signal to our brain, and our brain says, hey, I just tasted something. Kitty's a staff writer at The Atlantic, and she wrote an article that inspired this whole series called The Paradox of Sour.

Subtitle, it's a weird sense to need. What got you on the kick then of pursuing these questions? Why quest after sour? So there is kind of the boring answer and maybe the more interesting answer. I mean, I have always really been into food and tasting things. I am personally a sour nut. You know, when I feel a yen for sour, I will literally suck on a lemon. And that is like an idiom for punishment, but I think it's awesome. Either that or I'm some kind of masochist. I love that. And particularly the sucking on a lemon bit because we have a little activity for you. And we sent you a mystery package and we asked you to gather a couple of items.

Yes. So my smorgas board of sour, I have two cut halves of a very cold lemon, a tub of plain non-fat yogurt. So this is not sweetened. It feels important to specify. I have some white wine vinegar and some toxic waste. hazardously sour candy. Now, it's a little early to give the whole taste test away, but let's just say it involves knocking back some vinegar. Cheers.

Cheers. Yeah, that's tart. Yeah. I'm starting to get the sour face. That is definitely pickling my tongue a little bit. Kitty's our perfect partner for this, dive into taste, because much like us over at Shortwave, she's not just fun in games.

She's also about the science. Honestly, part of this was just inspired by a paper I stumbled across. I think the title was, you know, the evolution of sour taste. And I saw that and I thought, wait a second, if this paper is only just coming out, that means we didn't have a good answer to this before. How could that possibly be? So today on the show, we explore the mystery of sour. Where did it come from? why do we have it?

And really, what's the point of it? I'm Aaron Scott, and this is Shortwave, the Daily Science Sourcast from NPR. So, Katie, I mostly think of all the tastes as just going hand in hand. You know, everybody has all of them, every creature, but they don't actually. Can you kind of take us through this evolutionary story of taste that first got you interested in this?

Oh, my gosh. So who can taste what is? one of those things that absolutely blows my mind. You know, humans have, oh, I guess you could say five classical tastes, the ones you named at the top of the episode. But actually, that's kind of a misnomer that we have five tastes. You know, arguably, like, we have maybe more than a dozen. Some researchers say it's important to talk about the fact that we can taste like calcium or, you know, what foods are hardy or even, you know, metallic. There's just so many ways to taste. food that go way beyond the top five. But even within the top five, I think it's so cool that

not all animal species have those five in their taste holster. Some of my favorite examples is some carnivores. They've lost the ability to taste sweet. Why do they need it? All they need to taste is, you know, nice, tasty flesh. There's not a ton of sugar in there for them to latch on to. Giant pandas that, you know, eat pretty much only bamboo. They can no longer taste umami or savouriness. And there are certain animals that can barely taste anything, which I don't know. I don't think I would want to live that life, man. Yeah, that sounds like a taste tragedy. But sour, it seems to have stuck around, right? And from what you write, it also seems to be the first taste that evolved. So I have to admit, it seems a little weird to me that it's everywhere,

and yet it also is the one that we know the least about. Right. Sour is just totally weird. Like the fact that it is in everyone would seem to indicate, okay, no one has lost this taste that we're aware of. It must serve some purpose. Like maybe it's like bitter and we really need to be tuned into let's definitely not eat sour food. Or maybe it's like sweet or rumami. Like we definitely need a ton of the stuff that's in sour food. It's going to keep us healthy. It's going to keep us alive.

But it's kind of neither. It's kind of both. You know, as one researcher put it to me, you know, no one really gets this. What is the point of this weirdly ubiquitous taste? Is it really just about tasting food in our mouths? Or is there some weird mystery that a ton of sour foods have in common that we haven't totally uncovered yet? A set of questions we tried to answer through an extremely scientific taste test.

So we're starting with yogurt. This is maybe the least sour of our sour delights. Yes. Okay, so I am opening the yogurt, and this is a fresh tub. I'm opening a fresh tub of yogurt for y'all. Oh, my God, I feel so special. Feels so special. Pretty tasty.

I mean, I feel like this is a good gateway sour for us to have started with. Gateway sour. I like that. So let's maybe wade a little into deeper sour waters. We're doing white wine vinegar next. Yeah, let's do the vinegar next. Do I like chug it or like I don't think I want to drink straight from the bottle. I feel like that's too much.

I'm going to just sip. I'm going to sip it, take it right from the bottle. Okay, well, I got, I brought the big spoon for the vinegar. Okay. Cheers. Cheers. Ooh, yeah, that's tart. Yeah, and it lingers.

True. So should we do lemon next and then? I think that's right. Yeah. Okay, lemon next. Yep. All right. three, two, one.

This is somehow better for me than the vinegar. Yeah. It's interesting. Actually, I'm still having, like, my throat now is burning a little bit. So, like, I can feel it kind of tickling my tonsils. Okay. So this last one is the wild card that we shift to you. I like how this is shaped like a toxic waste drum.

Oh, man. And there's even, like, a little scale on here that tells you, how much of a sour wuss you are, depending on the amount of time that you can keep this in your mouth. All right. Okay. Ready? Oh, wow.

That is a salivary response. I'm pretty impressed by the sourness on this. Like, maybe it's just because it's lingering in our mouth, but that is sour. Yep. Also, lots of saliva on this end. I don't know. Having two of these bad boys in my mouth is an interesting experience. Like jostling for space.

I have to spit that out. I'm trying to like distribute them equally so that it's not just one part of my mouth salivating constantly. Yeah, that's one of the other things that seems to happen with sour. It causes the mouth to salivate, right? Yeah, and I mean, this is very cool. I mean, imagine what sour is, right? Like sour foods taste sour because they've got some kind of acid in them. You know, that's what's going to really trip those sour-sensitive cells.

in the mouth. Saliva kind of floods your mouth when you taste sour because it's trying to sort of neutralize or buffer all the acid that is hitting your taste buds all at once. Right. And that's the weird thing, right? Because too much acid is bad. I mean, I can feel my throat burning and only guess what it's going to do to our stomachs. You think in terms of its evolutionary purpose, like sour should taste bad to us. It should be gross, like too much bitter or something, and yet you and I, we love it. Why does scientists think that it's? Yeah. So, Bradley speaking, like, there are definitely people out there, right, who don't love sour in the way that you and I do, and I think their lives are very sad, but also no judgment,

like you do you. But this is actually true of a lot of primate species that are closely related to us. We think sour is awesome. And there could be a really interesting reason for this. So about 60 to 70 million years back in our family tree, we lost the ability to produce vitamin C ourselves, whereas most other mammals can do this. They don't need to get it in their diet. They're totally fine. The nice thing is, a lot of sour foods happen to have vitamin C, and that's one idea. Maybe we love sour food to keep ourselves flush with vitamin C. So I want to step a little bit further back in the evolutionary timeline here, because if sour is maybe the taste that was the first one to evolve, and its scientists think it at least has been around

as long as vertebrates have been around, it manifests completely differently in fish. Would you talk a little bit about the weirdness and the kind of majesty that is how fish taste sour, or I should say where fish taste sour, and what that does for their happy little fish lives? Oh man, the fish story is so weird. And I, you know, I think I should definitely qualify at this point. The further back in time we go, I think the shakier things get, you know, think of how many fish are out there, how many species, we have definitely not sampled them all. We have definitely not been able to ask all of them, hey, do you like sour food? They usually don't answer, and that makes things way more complicated. And also, fish are just so different. Like, they live in this watery world. They're surrounded

by chemicals all the time, just brushing up against them in ways that we don't quite experience living in the fluid that is air generally. But that also goes hand-in-hand with the bizarre way that they taste. And this almost gets to this weird question of like, what is taste? Is sensing any chemical in your environment kind of taste? Fish kind of make an ideal case for this or even a case against it because they don't just have taste buds in their mouths. They have taste buds all over their bodies, like even on their fins and stuff, they are like giant tongues with scales all over them. And this is just mind-blowing to me. I can't imagine what it would be like to be a fish and swim through gross water. I would not enjoy that. When you put it that way, yes, it sounds really

disgusting. I mean, you talk in the article about how it allows them to sense kind of the CO2 levels and maybe avoid water that's too acidic. But the thought hadn't occurred to me that that means you're also constantly tasting things all across your body. Right. You pointed out the potential benefit here. Like having those chemical receptors means that they can respond really quickly to what's in their environment, swim away from it, swim toward it. And this is possibly maybe, maybe where sour might have started to come from, because maybe it makes sense that the ability to just sense acid stuck around in the body. And it just happened to be present in the mouth as well, maybe especially because that's kind of near the gills, that's what's helping the fish

breathe and just regulate other aspects of their body. And maybe that just stuck around when animals moved onto land and then just started being repurposed for other things, even after we lost the taste buds all over our bodies. So in thinking of this taste that we totally take for granted, there's something so amazing about considering how important a role that actually might be playing in helping us navigate this complex world we live in. Has pursuing this research and really diving into this taste, has it shifted the way you eat every day? Is it shifted the way you think about food? Yeah, totally. I think this happens every single time I write some sort of food-related story.

And honestly, this is one of the best parts of being a science journalist, you know, like taking something mundane and every day and just kind of blowing it wide. open with science. I suddenly walk past something I would have walked past any other day and not even noticed. And I end up thinking about it for minutes, hours, days. Katie Wu, it has been a total pleasure talking with you and chasing this taste. Same to you. I am always delighted to talk about anything that brings us into the realm of sour food. Katie Wu is a staff writer at the Atlantic. Today's episode was produced by Rebecca Ramirez, edited by Stephanie and O'Neill and fact-checked by Catherine Seifer.

Josh Newell was the audio engineer. Giselle Grayson is our senior supervising editor. Neil Carruth is our senior director of on-demand news programming, and Anya Grunman is our senior vice president of programming. I'm Aaron Scott. Thank you for listening to Shortwave,

the Daily Science Podcasts from MPR.