A Flavor Scientist Explains Cooking

Summary

Episode Summary: "A Flavor Scientist Explains Cooking"

All Of It, hosted by Alison Stewart on WNYC, delves into the intricate relationship between science and culinary arts in its December 27, 2024 episode. Featuring renowned flavor scientist Dr. Arielle Johnson, the episode explores the chemistry and biology behind flavor perception, the science of fermentation, and the profound connection between taste, smell, and memory.

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1. Host's Welcome and Introduction

At the outset, Alison Stewart expresses her gratitude to listeners for their support and shares a personal update about her recent brain surgery, which temporarily paused her hosting duties. She introduces guest host Kusha Navadar, who takes over the conversation in her absence.

Alison Stewart [00:13]:

"Earlier this year, after brain surgery made it impossible for me to speak... I'm grateful to be back here with you listeners."

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2. Exploring the Science of Flavor with Dr. Arielle Johnson

Kusha Navadar introduces Dr. Arielle Johnson, a flavor scientist with a PhD in flavor chemistry from UC Davis, who has authored the book Flavorama: A Guide to Unlocking the Art and Science of Flavor. The discussion delves into Johnson's journey, the fundamentals of flavor science, and practical applications in cooking.

a. Dr. Johnson's Path to Flavor Science

Dr. Arielle Johnson [02:06]:

"Always very interested in both food and science... specializing in flavor chemistry."

Johnson recounts her fascination with food and science from a young age, leading her to pursue advanced studies and ultimately co-found Noma's Fermentation Lab. Her work focuses on the chemistry behind flavors, sensory analysis, and collaboration with restaurants for flavor development.

b. The Fundamentals of Flavor: Taste vs. Smell

The conversation highlights the often-overlooked role of smell in flavor perception. Johnson explains retronasal olfaction—how we perceive smells through our mouth as we chew—and its significance in experiencing complex flavors beyond the basic tastes.

Dr. Johnson [04:32]:

"Smell is actually a very big part of that... responsible for pretty much everything about flavor beyond sweet, sour, salty, bitter, and umami."

She clarifies that while taste buds detect the basic tastes on the tongue, the nuanced flavors we experience are largely due to our sense of smell.

c. The Connection Between Flavor and Memory

Drawing parallels to Marcel Proust's famous madeleine episode, Johnson discusses the neurological underpinnings that link specific flavors and smells to vivid memories and emotions.

Dr. Johnson [06:13]:

"You'll often have an emotional connection or, like, a memory of a flavor before you can even recognize what it is."

She emphasizes that the olfactory signals are processed in the limbic system, the brain's center for emotions and memories, explaining why certain foods can evoke strong recollections.

d. Listener Question: The Science Behind Fermentation

Listener Stephanie from Greenpoint inquires about the tanginess in fermented foods and the biochemical processes involved. Johnson responds by elucidating how lactic acid bacteria ferment sugars into lactic acid, enhancing both flavor and food safety by inhibiting mold and spoilage organisms.

Dr. Johnson [07:08]:

"Lactic acid bacteria... convert that into lactic acid, which is both deliciously tangy and conveniently... improved food safety."

e. Debunking Myths About Taste Buds

Addressing common misconceptions, Johnson debunks the outdated "tongue map" myth that suggests specific areas of the tongue are responsible for different tastes. She clarifies that all taste buds are distributed across the tongue, allowing for a more integrated flavor experience.

Dr. Johnson [09:49]:

"We actually have all kinds of taste buds all over our tongue. They're basically just mixed together."

f. The Transformative Nature of Flavor Molecules

Johnson explains how culinary techniques transform flavor molecules, making them detectable by our taste receptors. Processes like browning bread or fermenting grains break down large molecules into smaller, flavor-active compounds.

Dr. Johnson [11:01]:

"Flavor is molecules... you can change molecules, you can break them down, you can make smaller pieces."

g. Bridging Art and Science in Cooking

Concluding the interview, Johnson advocates for a harmonious relationship between scientific understanding and culinary creativity. She encourages cooks to use scientific principles as a foundation to enhance their artistic expression in the kitchen.

Dr. Johnson [12:00]:

"I think it's much more rewarding and exciting and fun to let my science instincts help out my cooking instincts."

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3. Episode Conclusion and Teaser

Alison Stewart wraps up the episode by summarizing the insightful discussion with Dr. Arielle Johnson and teases the next segment, which will explore the sonic ecosystem of the marine world in the episode titled Sing Like a How Sound Rules Life Underwater.

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This episode of All Of It offers a comprehensive exploration of flavor science, blending scientific explanation with practical culinary applications. Dr. Arielle Johnson's expertise provides listeners with a deeper appreciation of how our senses collaborate to create the rich tapestry of flavors we experience in everyday life.

Transcript

[Arielle Johnson]

Listener support WNYC Studios.

[Alison Stewart]

This is all of it on wnyc. I'm Alison Stewart. Thank you for spending part of your day with us. I'm grateful you're listening, and I really mean that. Earlier this year, after brain surgery made it impossible for me to speak, there was a time when I wasn't sure I'd be able to host all of it again. So as I said at the top of the show, I'm grateful to be back here with you listeners, and I'm grateful for my medical team and my team at all of it, including guest host Kusha Navadar. So today we're revisiting some conversations Koosha had in my absence. Later this hour, we'll hear about the chemistry and biology of flavor. And then as we prepare to commence the new year, we'll talk about commencement speeches and the art of writing to inspire. But first, let's learn a little kitchen science before we dive in. Just a reminder that this is an all of it encore presentation. So you might hear some people who called in previously, but we won't be able to take your calls today. All right, now let's get into some flavorama.

[Kusha Navadar]

Think about the last time you ate something that just blew your mind. Was there a certain flavor that was surprising or intense or satisfying? It turns out there's a lot of science behind flavor and how we experience taste and scent. A new book from Arielle Johnson is all about how our senses create the experience of food, from our taste buds to the complex neuroscience of smell that create the more subtle hints of flavor. Johnson actually has a PhD in flavor science, and she joined me recently to talk about her book. It's called flavorama, A Guide to Unlocking the Art and Science of Flavor. I started by asking Ariel how she ended up on the path to become a flavor scientist.

[Arielle Johnson]

Well, so the short version, always very interested in both food and science, eventually figured out that there was a lot of science behind not only industrial food, but also cuisine and gastronomy. And you could use chemistry to learn a lot about those things. So ended up going to UC Davis in Davis, California, in the wine department, specializing in flavor chemistry. So doing a lot of chemistry, sensory analysis, modeling of things. And since then, you know, I do a lot of work with restaurants on research and development and experimentation. So making a lot of flavors with fermentation and other stuff. And at this point, there's so many bits of science that I work on that I just say flavor scientist.

Do you remember the first food in your life where you thought that flavor. Flavor will stick with me forever. Wow. I want to learn more about that flavor.

It was definitely the smell of coffee, specifically. Specifically coffee beans. When I was about three years old, I would start taking the coffee beans out of the shopping bag on the way home from the grocery store and like, smelling it really deeply. I was disappointed that brewed coffee didn't taste exactly like that smell, but it definitely piqued my interest in coffee, which I still I'm interested in.

And now you have written a book, and there are recipes in the book. It looks and feels like a cookbook, but it's not really a cookbook. How do you advise people to use this book?

I would say it can be used as a cookbook. It can be used as a reference book. If you're interested in understanding sort of the generals of how flavor works and how knowing about the science of flavor can apply to cooking at all. Just flip through it, and there's a lot of sort of shorter pieces of information that'll like, hook you in even if you're not a cook. If you are a cook, I would recommend thinking about flavors, tastes, smells that you like. And there's a whole section that's almost a field guide to all of those flavors. So that's a good place to start to understand, like, what is sourness? What is an acid? Where can I find sourness?

Well, you know, it's funny because those questions kind of lie at the very science of how taste and flavor work. So help us understand the sense of taste and the sense of smell. How do they combine together to create our sense of flavor?

So when we say flavor is taste and smell, usually to the, you know, if you're taking a bite of an apple, what you feel as flavor feels like it's just taste. Smell is actually a very big part of that, and that's not actually sniffing the apple before you bite it, although that is, you know, a little bit. You can actually smell food in your mouth as you're chewing it. We call that retronasal olfaction. And it is responsible for pretty much everything about flavor beyond sweet, sour, salty, bitter, and umami. So fruitiness, roastiness, floral flavors, that all comes from smell. So taste comes from taste buds on your tongue. That gets routed into the brain. Smell gets routed a slightly different route into the brain. And eventually they come together in the orbitofrontal cortex, where we can recognize them not just as tastes and smells, but as, like, unified flavors and then come up with descriptions and names for them.

You mentioned that they get routed Differently. Is there a special reason behind that, why that routing is different?

It's just a. It's a physical question, actually. Most of our senses pass through the brain stem and through sort of like the quote unquote, lower parts of the brain before they get to emotions and thoughts. Smell is actually sensed directly with brain cells. That one side is anchored in your brain. One side passes into your nasal cavity. Your. No, the inside. And that, rather than going through the brainstem, goes right into the emotional centers of our limbic system, especially our amygdala. So you know the Proustian story of dipping a madeleine in tea?

You stole my next question. It's okay.

It's okay. Go ahead. Yeah. It is biologically and neurologically true and valid. That is exactly what happens. In fact, you'll often have an emotional connection or, like, a memory of a flavor before you can even recognize what it is.

We have Stephanie in Greenpoint with a question. Hi, Stephanie. Welcome to the show.

[Stephanie]

Hi. I like to make fermented loaf without using much wheat. And I would like to know, for one thing, why things get tangy when you culture them. And also what does it really do to the grains or to the chickpea flour or barley or whatever when you fermented? And then any other thoughts about, you know, fermented foods and how your body senses them would be interesting.

[Arielle Johnson]

Thank you, Stephanie.

Great. Well, so when we're talking about culturing, for example, making sourdough or even yogurt or sauerkraut, we're talking about food that becomes sour. And the way that it gets sour is through the fermentation action of lactic acid bacteria. So these are bacteria that also live in our skin and all over different surfaces that will eat small amounts of sugars in whatever you're fermenting them in and convert that into lactic acid, which is both deliciously tangy and conveniently is fairly toxic to mold and spoilage organisms. So we get this, like, double bonus of delicious sourness as well as, like, improved food safety.

If you're just joining us, this is all of it. We are talking to Arielle Johnson, a food scientist and co founder of noma's Fermentation Lab. Just put out a new book, a Guide to Unlocking the Art and Science of Flavor. We have a text that I'd love to read. Any unexpected food combinations or tastes that pair well scientifically, but most people don't think of. And what about their chemistry makes them work? Great text. Thank you for it.

Yeah, I would say the number one weird Flavor pairing that makes chemical and scientific sense is salt on grapefruit or more generally, salty and bitter together. You know, generally if your coffee is too bitter, you might add more sugar to it or try to dilute it to kind of like cover up the taste. You wouldn't necessarily think to add salt, except salt will actually interfere with the bitter receptor on the surface of the tongue and make it less effective at sensing bitterness and sort the kind of effect of this. If you put salt on a piece of bitter grapefruit, the grapefruit will actually taste sweeter in addition to being saltier.

So we're talking about taste buds as well right now. There's a common misconception about how taste buds are laid out on our tongues. So where did this wrong belief come from that there is a sweet zone and a salty zone and a bitter zone on everyone's tongue? And what's the reality?

So, yeah, there's this common. The common graphic shows sort of areas of the tongue, like a map that I believe was published. I know it was a textbook. I think it may have been a nursing textbook. Just as an explanation of these are tastes, these are where they're on the tongue. And I think the kind of, you know, attractiveness of that very graphic image with colors and zones made it catch on. And so now there's this belief that, you know, we only have sour taste buds on one part of our tongue. We actually have all kinds of taste buds all over our tongue. They're basically just mixed together to, you know, best. Best sense as much as possible.

You mentioned memory before, and you mentioned Proust. For listeners who love French literature, you might be thinking about the French novelist Marcel Proust, who wrote about how the crumb of Madeleine cookie unlocked memories of his aunt. You had mentioned that before. This connection between what we eat and our memories feel so strong. Can you explain why that connection exists?

Yeah, that. That smell and emotions connection feels very strong because at a neurological level, it is very strong. The. The first place that we process smell signals in our brain, once they get written on a structure called the olfactory bulb, is the limbic system. So especially the amygdala. All of them are what we use for storing emotions, emotional memories, responses to things. Before you even perceive what a smell is or could put a name to it, you'll already be having any sort of emotional connotations and memories of the last times that you experienced that smell bubble up to the surface.

That reminds me of one of the last laws of flavor that you have in your book, which is that it can be created and transformed. How so?

Well, so flavor. Flavor is molecules. There are molecules that make flavor. What makes a molecule have a flavor is just if it fits in a receptor that we have, have either a olfactory receptor in our nose, taste receptor on our tongue. A lot of molecules are just way too big to do that. So, you know, we can taste a glucose molecule with our sweet receptor, something like starch, which is, you know, a thousand linked glucose molecules, way too big to fit in the receptor. So we just don't perceive it as having a flavor. But if you do some chemistry, which in the case of cooking might be browning a loaf of bread in the oven, you can change molecules, you can break them down, you can make smaller pieces. So once you're cooking, doing fermentation, anything like that, you'll be taking molecules that don't have a flavor and then chemically transforming them into new molecules that do have a flavor.

What's your advice for how folks can make the most out of the relationship with food where it's an art and a science?

Well, I think like a lot of people associate science from their, you know, experience in school of like, there is a right answer and if you are too creative with it or you don't get it right, then you're wrong. Which is a way that some people use science. But it's definitely not innate to science. For me, you know, I tried to keep the laws of flavor fairly, fairly broad and then give specific examples because, like, I don't necessarily want to or, you know, want to tell someone exactly how they should do things in their kitchen. I can give them suggestions, but to me, I think it's much more rewarding and exciting and fun to let my science instincts help out my cooking instincts. So, you know, both of them are ways of looking at the same thing but giving you different kinds of insight. So I in the book, there's a lot of ways, whether from my own cooking or from my time working in restaurants, that, you know, the science of flavor is very helpful and just very tasty, straightforward, not complicated or difficult.

[Alison Stewart]

That was Kusha Navadar's conversation with Dr. Arielle Johnson about her book A Guide to Unlocking the Art and Science of Flavor. Coming up, a book called Sing Like a How Sound Rules Life Underwater. It explores the sonic ecosystem of the marine world. Stick around.

[Arielle Johnson]

This.

[Alison Stewart]

This is all of it.

[Ira Flatow]

I'm Ira Flato, host of Science Friday. For over 30 years, our team has been reporting high quality news about science, technology and medicine. News you won't get anywhere else. And now that political news is 24 7, our audience is turning to us to know about the really important stuff in their lives. Cancer, climate change, genetic engineering, childhood diseases. Our sponsors know the value of science and health news. For more sponsorship information, visit sponsorship.wnyc.org.