373: Flavor Science 101 with Dr. Arielle Johnson

0:28This episode is brought to you by Resi and American Express. Understanding how things work, and in this case, food on a molecular level, is really like a form of x-ray vision or like being able to service your own car. So it just adds a layer of understanding why you're doing things and being able to then know what you should do next. This is Taste. I'm your host, Eliza Barbanel.

0:59Dr. Ariel Johnson is a flavor scientist who advises some of the top restaurants and chefs in the world on how to turbocharge their cooking with chemistry. She's currently the science director of Noma Projects and sharing all of her wisdom in a new book, Flavorama. It's a delight having Dr. Ariel on the show to answer all of our questions about the science behind our food, and truly a must-listen episode for anyone interested in cooking.

1:32Dr. Arielle Johnson, this is Taste. Thank you for coming on the podcast. Thank you so much for having me. It's so much fun. I feel like this is every food person's dream, which is just to ask a flavor scientist all of the questions that people want to know about cooking. And I guess to start, I'm wondering if you could tell me, how does one become a flavor scientist in the first place? That's an excellent question. I'm sure there are other people. Well, I know that there are other people that do it, but I can tell you how I did it. Short version. Always been really into food. Also interested in science.

2:05I got to college where I was doing a chemistry degree and not really sure what I wanted to do with it, then figured out via El Bui and Ferran Adria, who were on like the cover of the New York Times magazine and Harold McGee and his book on food and cooking that you could use chemistry to do very cool things with food. So at that point, I decided this is what I need to do and I've got to figure out how to do it. And there wasn't really like a established pathway to get there. So I ended up going to grad school. I applied and got into the agricultural and environmental chemistry graduate program at UC Davis, which is applied analytical chemistry, essentially.

2:48So, you know, chemistry, love chemistry, am a chemist and ended up in the wine department, viticulture and oenology. And there's some really great analytical chemists and sensory scientists looking at wine. so I sort of found out on the job that flavor was a thing that was sensation and it was also chemistry and also psychology and also ecology and evolution and I hate doing just one thing. I like things that let me do combine multiple things at once so it was sort of the perfect topic and you know ultimately I think the one that people who want to know something about science or the science of their food really want to know.

3:33Yeah, that makes a lot of sense. And I feel like it's funny because obviously we think of like the Maillard reaction is like that's probably the only like food chemistry thing I could name drop on a podcast with you right now. I'm curious if there was a reaction or a discovery or something that like you found particularly illuminating or exciting to you when you were kind of going down this food science path. Yeah, I mean, a lot, a lot, a lot. One of the very first ones was that flavor is technically not objectively measurable. We can measure sensation, but in terms of putting a food sample into some sort of chemistry device and getting an answer out about exactly what it would taste like, that doesn't exist.

4:21And you have to do lots of tricky things to work around it. So that's trippy. Is that at all? Like, I feel like there's the stoner thought of like, is my blue even your blue man? It's like that vibe. Yeah, it's like that times, you know, 10 billion or so for all the different flavors. That's so interesting. And then after you got your degree, I know that you kind of found your way to Noma, which I imagine is like any listeners kind of peak idea of what it would mean to be a food scientist somewhere. How did you find your way there and what kinds of work were you doing? Well, so, you know, while I was in grad school becoming a scientist, I kept my very strong interest in using what I was learning with chefs and restaurants up.

5:07There was some I'd worked with here in New York while I was at NYU. And, you know, at that time, long before Twitter became the dumpster fire that it is now, a lot of people who were interested in the science of food and creative cooking were on there just posting about it. So just by kind of hanging out in that space, I got to know quite a few people doing interesting stuff with food and with science. Noma had a project at that point called the Nordic Food Lab, which was their sort of lab to understand ingredients and techniques. It was housed in a houseboat, actually anchored right outside the restaurant in Copenhagen Harbor.

5:46But they were doing really, really amazing, fascinating stuff that combined, you know, a chef's perspective with a scientist. And it was pretty obvious to me that that's what I needed to be doing. So I introduced myself, got to talking and ended up going over for a summer in the middle of my in the middle of grad school. So I sort of snuck away from California and ended up in Copenhagen and completely fell in love with everything about it. Yeah, I would imagine like when you talk about working with chefs to be kind of helping solve these problems, like I imagine you being like a pinch hitter or like a mercenary, like coming in in some way, because these are chefs who I imagine already understand a lot about food and technique just through their own work.

6:30So what kinds of questions would chefs be coming to you to solve? Yeah, when I started when I started working with chefs, especially at Noma, I noticed that they knew in some ways far more about food than I did along many dimensions, just from, as you say, becoming like really, really, really skilled cooks at the top of their game with very good powers of observation. There were other things that I knew a lot about that they didn't know so much about, but all of our knowledge was like complementary. So it was kind of just a matter of figuring out how to talk about the same thing using like two different languages.

7:04So one question I worked on early on was everyone was very interested in eating insects. I think people are still interested in eating insects, but it was just becoming sort of part of the mainstream conversation at that point. and they had been tasting these ants and the ants had really interesting, you know, sort of citrusy herbal flavors and they wanted to know why. One of the chefs ended up finding a paper about the chemical communication. So like pheromones, ways that ants talk to each other with molecules and was kind of trying to figure out if there was anything useful from it and asked me to take a look.

7:43And I was like, well, those are all flavor molecules. So, you know, that ant is going to taste like lavender. That ant is going to taste like cilantro because it has the same molecule, the same flavor molecule that's in those ingredients. So sometimes it's, yeah. You're like blowing my mind. And I often find myself doing something like that where, well, a lot of people are shocked to find out that many questions in the science of food are answerable, but have not been studied just because there's not funding for it, really. So there are some things that there isn't an objective data-based answer to directly, just because no one's looked at it.

8:21But if you can figure out how to rephrase the question to see if some other discipline has looked at something similar, you can often find a useful paper in, for example, like an entomology journal or archaeology, protein biology, all kinds of crazy areas of science you wouldn't necessarily think of when you think of food. That's so interesting. And I don't mean to sound like unscientific, but why does it, from a chef's perspective, why does it matter knowing why ants taste certain ways when you can just taste them and know how they taste? Yeah. So obviously there's a huge amount that can really only be learned by practice and experience.

8:57And this is how you become a great chef. But then, you know, ultimately there are unfamiliar ingredients or unfamiliar situations or new techniques you want to try out. And in all of those cases, understanding a little bit about chemistry and about molecules is like the secret sauce that lets you do things that you haven't been able to do before. Yeah, that does make a lot of sense. I'm curious if you have any white whales kind of problems that you've been asked to solve that you don't have the data or the answers to quite yet. I recently got asked if it was possible to preserve an artichoke heart or many artichoke hearts without making it taste cooked or too cooked, too soft, too sour, too salty, anything fermented.

9:45And my first answer was, no, that's not possible if you want to store it for any length of time. Sure, that sounds like magic. That would be nice. And then after some pausing and thinking, I dug together a couple of different things. One paper about bacterial counts and pasteurization in sort of bagged carrots, and another one about enzymes that cross-link the pectin glue that holds the cells inside of a plant together, and it kind of makes it firmer and chewier. So by kind of combining this one paper about enzymes, another one about calcium, which also helps glue together pectin, and pasteurization, we managed to at least construct a trial to see how artichokes would behave under those conditions.

10:36We haven't tasted them yet, but I really have high hopes for how it's going to look. Okay, well, I want to know about the results of that because I feel like that's a question I would never have even come up with. And the answer sounds like it would be very intriguing. And to anyone listening who's like, oh, I wish I could understand more about these scientific concepts. The great thing is that you have written a book, Flavorama, where you're kind of digging into all of this. How did you like decide to approach these scientific concepts in an approachable way? Did you come up with any like parameters?

11:07Well, it all happened actually very organically. I didn't necessarily have a plan to write a book at all. I'd just been working at NOMA and, you know, in restaurants for a few years at that point and found that I kept getting asked either the same or very similar questions. And so I was answering a lot of things over and over again and also trying to figure out how to phrase them, what language to use, how to help people understand that, you know, hadn't had, certainly don't have a PhD in chemistry, but, you know, some very great, very smart chefs dropped out of high school to become chefs and English isn't their first language, especially if you're in a foreign country.

11:53So figuring out the communication piece was big. But then once I did, I kept thinking, oh, if only I should make a cheat sheet for all this stuff so I can just, you know, hand it to people when they come and ask. Or like, I wish there was a book I could give you. And eventually I figured out that that is the universe telling you that you need to write a book. So I talk about the laws of flavor in this, in my book. And they are that flavor is molecules. Flavor is taste and smell. Flavor follows predictable patterns. Flavor can be concentrated, infused and extracted and flavor can be created and transformed.

12:31So that's basically just describing that flavor. Flavor is chemistry in those ways and there are ways to use it creatively. So I tried to keep stuff all within what I had already explained to, you know, some professional chef or cook and any other extra information that was super useful to know. So at first it was just almost making your life easier, but now it's going to make a lot of other people's lives easier in the process. It did. Yeah, that's my hope. Yeah. I hope so. And I like the principles or the basic laws of flavor that you write about. I think when I was reading it, I had this very silly moment when I was like, oh, it's like I'm reading my high school chemistry book.

13:10And it's because it is a chemistry book, but it's also a cookbook and all of these other things. How did you think about including recipes? Do you think of them as like the scaffolding of the book? Are they more of like proving the concepts? In some cases, they're the like scaffolding or impetus for framing a certain section a certain way. So something like the section on infusing oils. I really started with the smoked tea infused smoke oil and then kind of built it out from there. A lot of other ones are knowing that a concept is important, but also that people should have a practical application for it.

13:46Definitely. So I want to read you something from your intro to have you unpack it a little bit further. So in your intro, you write flavor isn't just ineffable vibes or an abstract quality that imbues lemon with lemoniness. Absolutely everything required to set off the wonderful perceptual experience of flavor in your brain is contained within the food you are eating in the form of molecules. So can you unpack why it's important to remember that flavor and food comes down to molecules and chemistry in the first place? Like I said earlier, with why chefs would want to know stuff like this, understanding how things work, and in this case, food on a molecular level, is really like a form of x-ray vision or like being able to service your own car.

14:31So it just adds a layer of understanding why you're doing things and being able to then really know what you should do next rather than relying on someone else to tell you. So, yeah, when you when you look at an ingredient like a lemon, you can think of it as an object that tastes like lemon. But, you know, the different parts of it taste like lemon in different ways because it's not, you know, a homogenous object. It has complexity to it. So, you know, if you know that in the outer layer, there are a lot of deposits of very flavorful aromatic oil and that the layer underneath that is mostly bitter and spongy and full of pectin and that the layer underneath that, the fruit itself is like little balloons of water held in place by membranes and cell walls.

15:21And, you know, within that tiny, tiny amounts, like a few percent of sugars and acids and even smaller amounts of aroma molecules are dissolved in it. Then just the way that you approach working with that is different than just thinking of it as like one thing you can do one thing with. Yeah, I think it's kind of obvious that everything is made out of molecules. But I don't think most people are used to thinking about things in like a chemistry kind of way. and just kind of refocusing your brain even is just kind of a fun exercise. I think for me as a home cook, when I was reading this book, I was just like thinking about the things that I inherently knew to do and why that would make sense from a science perspective.

16:00And that's my like biggest hope for the book is that people recognize, yeah, this isn't a completely new thing that I have to learn now or something that's telling me what to do. It complements what I already have developed intuitively as a cook. Definitely. I had a recent experience that I was quite proud of where I had something that I was making that was too salty. I was braising greens in a braising liquid. And I don't know what happened, but when I tasted the braising liquid, it was just so salty. And I started spinning out trying to think about how I was going to fix the greens. And then I realized that I was just trying to eat the greens and not the liquid and that the greens themselves hadn't been fully like, they hadn't absorbed all the saltiness yet.

16:39So I just drained them and then tossed them in like orange juice and a little bit of sesame oil. So it's kind of like a vibe of flavor. And I was so proud of myself for just stopping to think that like the liquid was infusing into something, but that it wasn't when I needed, which to you might seem very obvious. No, I'm so happy that you that like, I'm like, yes, exactly how you should be thinking about it. Yeah, really, really proud and excited. Oh, thank you. A plus for me. A plus plus. So can you tell me a little bit about how flavor and smell are combining to make eating like this emotional thing?

17:14So, yeah, this is this is one of the biggest hurdles or, you know, unbelievable moments that people tend to have when they're first learning about flavor. It's that smell, smell as well as taste, but especially smell is one of the most important parts of flavor. And people don't generally know this one because we don't talk about it, but two, because it doesn't feel like smell while we're doing it. um so most people you say smell or olfaction and they think sniffing so putting putting something in front of your face and sucking its smells into your nose holes and perceiving them there um that's what we're doing when we smell that is what and now you will never be able to think of anything else when when you smell something smelling you're welcome basically those those smell molecules can get in from the front but they can also come in the back way uh sort of like up up your throat and into your nose because it's all one airway.

18:07So when you have a piece of food in your mouth, you're actually releasing aroma molecules that sort of float up the back of your throat and into your nasal cavity where you perceive them. And frustratingly, for explaining this anyway, the smell that you experience while you're eating, the smell that's part of flavor, feels like taste. It feels like it's happening inside your mouth. Your brain plays a trick on you. But it is actually happening in your nose. And, you know, anyone who's come down with COVID and lost their sense of smell, but kept their sense of taste can attest to how much more intense and enjoyable and, you know, bright and exciting the flavors are when they have smells involved.

18:45You actually have an activity in the book where you tell people to, I can't remember what it is to eat, but to eat something and to pinch your nose while you're eating it and then undo that and tell the difference. I'll often use a jelly bean for a demo like that. So if you pop a watermelon flavored jelly belly in your mouth and hold your nose and chew it, it's going to taste sweet and sour. And that's pretty much it. Then when you let go of your nose, you'll, you know, let these vapors kind of do their thing. And then all of a sudden, watermelon pops into focus. So yeah, it's a really magical feeling demo.

19:16I even feel surprised every time that it happens, even though I know it's going to happen. But yeah, it's a really great way to understand how smell is a part of flavor. And why the jelly belly? Is it just because it's concentrated flavor in a small package. Yeah, exactly. And they're, you know, they're nice and they're like a little bit tangier than most other jelly beans. So there's a little bit more kind of going on flavor wise. And I also I like the pear ones a lot. The pear ones. What color are they? They are light green with dark green speckles. Can we talk about color for a little bit also?

19:48Like with a jelly bean, for example, like do you think people would taste the watermelon as much if it was purple? That's an excellent question. No, they would not. So we use cues from all of our senses when we're perceiving flavor, because flavor is fundamentally about figuring out how to feed yourself well and not something that will hurt you. So, you know, you'll use every type of information you can get to make that decision. So there are studies in psychology, you know, sensory science where if they add green dye to orange juice, a significant number of people will taste it and call it limeade instead of orange juice.

20:31So, you know, they taste sweet, they taste sour, they sense some citrusiness, but then the thing that clenches it as lime and not orange is the green color. I think that's so funny. And it makes me think about the way that a lot of flavors are subjective and specifically wine, for example. I think a lot of people, myself included, feel kind of at a loss when it comes to describing the flavors that are within something like what oaky actually tastes like, for example. And I know that you've trained people to become analytical taste testers for research before. And I'm curious if you can say a little bit about what that process is like or what home cooks could take from that to become better tasters themselves.

21:13You know, because flavor doesn't really exist until you put food in someone's mouth and they have the sensory experience. In flavor and flavor chemistry research, we do a lot of sensory analysis, and that's essentially training people to be very precise about describing what they taste and estimating the intensity of what they taste. So this sounds like the kind of thing where maybe one in a million people could do it because it's like an esoteric brotherhood that you get inducted into. Definitely not. Pretty much anyone can get really good at tasting. I like to say that a good palate is 95 % paying attention and practice.

21:50So there is hope for everybody, I believe. Yeah. So we have to train people. And so there's a line from one of my textbooks that I think about a lot, which is, humans are extraordinarily good at distinguishing flavors from each other. Humans are extraordinarily bad at describing those differences. So we already have the hardware and the sensitivity and the ability to tell that two things are different. So that's actually a huge start because once you can tell things are different, you just have to figure out how to describe how they are different. Yeah, most of training people to be a sensory panelist is getting them to smell things and talk about them, talk about what they smell a lot, bring in physical references for what they say.

22:37So in a wine sensory panel, if someone says they smell raspberry, you might bring like fresh raspberries, frozen raspberries and raspberry jam, because each is a kind of different interpretation of raspberry. So, you know, is your blue my blue? Is your raspberry my raspberry? This is a way to make sure that everyone's raspberry is the same raspberry. We'll often sometimes vote on what the closest reference is. And then, you know, by the end of training, having made people smell things over and over again, we'll have basically a set of black wine glasses with things like grass clippings for grassy and raspberry jam for raspberry and actual dirt for earthy.

23:19The actual things that we are talking about when we say those flavors to line everyone up with the same concepts. So, you know, you as a home cook don't have to then go through the process of tasting a set of samples in triplicate and painstakingly going through every single possible flavor and reading how intense it is. But the things you can take away from it that are actually useful, it's really just about experience and practice. You can start today. It's helpful to smell different versions, smell and taste different versions of the same thing and try to notice what the differences are and talk about them.

23:55And yeah, just make a habit of paying attention and, you know, work in some of these opportunities to learn how to describe things and learn how things are different. Yeah, I like that as like an additional part of the cooking process. I imagine especially I could romanticize in the summer when I get the produce that I've been waiting for all year to take the second to like smell the tomatoes before I cook with them and kind of describe it in that way would be fun. Yeah, no, I think it's super fun. And, you know, then you can notice how the flavor changed by cooking it or by what you paired it with.

24:26And then then you have a better understanding of how, you know, those flavor processes work. Definitely. And I appreciate you saying that you think that there's hope for everyone. I can't help but think that like some people just have very different palates based on like cultural experiences or like allergies or all kinds of different things. Like, you know, some people love the smell of gasoline. Yes. And other people don't. Like, how do you accommodate for those differences? So smell out of all the senses is the most closely tied to emotion and memory. You know, a lot of people know the Marcel Proust cliche of tasting a madeleine and being transported back to childhood.

25:02Or like the Ratatouille. Exactly. One of my favorite food movies, actually. Me too. Yeah. Yeah, there is this cliche, but it's completely true. Once smell signals bind to our olfactory receptors and get transmitted into the brain, the bits of the brain that it goes to are snuggled uptight to the limbic system, which is our primary center for emotion and memory. The amygdala in particular is very close and connected to the olfactory hardware. So often the signals from what you smell especially will get sent through these emotional centers and you will remember how you felt the last time you smelled or tasted that thing and what it was like before you consciously perceive what it smells or tastes like.

25:55So yeah, it's kind of inescapable. It's going to happen every time that you taste. And so sometimes it is a very dramatic emotion like being a symbol of your childhood. Sometimes it's, oh, I've smelled this before and I didn't really like it, so I'm not going to like it this time either, probably. One great example of that, when a lot of Europeans will come to America and try root beer and they hate it, they think it's disgusting. It turns out that a lot of the primary flavors in root beer are used in toilet cleaner in a lot of countries in Europe. So they have no food reference for what this flavor is.

26:35But the thing that their brain recognizes is like, oh, this is what a bathroom smells like. That's so interesting. And it makes me think about, I think, maybe an American version of this is when mint flavors get too toothpaste-y and it makes you think about being at the dentist. Exactly. Exactly. In terms of getting past differences, there are differences in obviously people's experiences. You know, we have about 25 different types of taste receptor and about 400 smell receptors. And, you know, any of those people can have variation in how sensitive they are or how well they bind to things. So there is variation in subjectivity, but, you know, no one's going to smell a glass of wine and say that it smells like a hamburger.