The Mystery of Taste: Beyond Sweet, Sour, Salty & Bitter | Christopher Kimball’s Milk Street

JOIN! 12 Weeks for $1

Episode 707
March 23, 2023

The Mystery of Taste: Beyond Sweet, Sour, Salty & Bitter

The Mystery of Taste: Beyond Sweet, Sour, Salty & Bitter

Are humans the only species that loves sour? Does everyone taste bitter the same way? And could there be flavors we can’t even comprehend yet? Emily Kwong and Aaron Scott from NPR’s “Short Wave” join us to explore the amazing science of taste, from the mysteries of salt to why dolphins can’t taste sweet. Plus, chef Khanh-Ly Huynh shares Vietnamese street food from Paris; Adam Gopnik investigates what it takes to become a culinary maestro; and we go to Bangkok for Thai Cashew Chicken.

Questions in this episode:

"Is there a method to selecting certain wines for cooking?"

"What’s the best way to judge heat level on a gas burning stove top?"

"Is it possible to make a chocolate Italian meringue?"

Short Wave Hosts01 2022

Christopher Kimball: This is Milk Street Radio from PRX. I'm your host Christopher Kimball. And today we're experimenting.

Aaron Scott: Let's try the dill pickles.

CK: Okay dill pickle,

Emily Kwong: Here we go, dill pickle.

CK: Oh, it's weird. It's like you're riding a bicycle, and somebody jumps on the back unexpectedly. So, you get sweet. At the same time the sour still working in the background

EK: That's like listening to a song that's been over produced electronically. And they did weird things to the guitar.

AS: You guys are both such purists.

CK: What can make a dill pickle tastes so strange. Well, Emily Kwang and Aaron Scott from NPR Shortwave are here to share the amazing science of how taste works and how it can be tricked.

EK: I love hijacking my body's natural responses.

CK: We'll hear more from them later on the show. First, it's my interview with Vietnamese French chef Khanh-LyHuynh, when she's the co-founder of two restaurants in Paris, The Hood, which serves Southeast Asian street food, and Nonette which specializes in banh hi and donuts. Khanh Ly, welcome to Milk Street.

Khanh Ly Huynh: Hello, Christopher. Thank you for having me.

CK: You and I met in Paris not too long ago. And what really struck me was that you have so many different interests in your life goes way beyond restaurants. You told me you studied law, then you traded luxury watches for a while. So how did you end up coming to work in the world of food.

KLH: So, when I left the city, I grew up in Avignon. When I was 20, I went to Paris to do a diploma for international business. And I interned for a luxury watch company on Place Moderne. So, I worked there for about three years. And I got very bored at the end of my contract. And I decided to reconvert into cooking because a lot of friends advised me to do that, because I was apparently very good at it. And I I did a big jump because i i got to have to say I kind of dated for the TV show Master Chef in 2015. So, I got casted and then I want the same year. So, things really moved fast. Because I went from Oh, I love cooking to oh, I want this TV show now. So, it's basically it's, it's, it's a time for you to prove yourself and, and make cooking your life.

CK: Well, we should just point out that when you won Master Chef France in 2015. I don't think at that point, you'd had any formal training. In fact, you got a culinary degree after winning Master Chef France so

KLH: Because I'm a double culture child, it was really hard for me to find my style in cooking, because I was trying really hard to be French and to be accepted as French, as much as I was struggling to find my own Vietnamese roots altogether. So, when I did the show, my food was really really, really complicated. Now, of course, it's about my newsletter, and my style has evolved a lot. So really, it made me more it made me mature very fast into the style of cooking that I was going into, and also as as me as a human being.

CK: So, let's talk about your two restaurants, Nonette and The Hood. Nonette has these amazing doughnuts and Banh mi sandwiches. And then The Hood has this really. It's a really specific feel their musical instruments lying around, people are hanging out there drinking juices. So so what's your idea there your idea is more than just a place to serves food. It's more of a community center. What what is it?

KLH: So when we founded The Hood, back in 2016, it started off as a coffee shop therefore all the instruments, the guitars, the piano, but when we wanted to bring the food I wanted to showcase what I actually grew up with and what Purlin my business partner we grew up with is authentic and genuine Asian food as we would have as a kid. The thing is, in France people have so much stigma of how Asian restaurant should look like. It should have red velvet chairs and aquarium you know, some unpleasant uncle's serving the plates in front of you, you know, and it's it's, it's of course one of the different possibilities and what a different looks that an Asian restaurant can look like. But it's not most of it. It's not necessarily supposed to be looking like and the thing is that as a business owner, you can make your restaurant look the way that you want it to look, it's yours.

CK: Let's talk about banh mi you know this is one of the things that should be easily translatable for home cooks. So, if you want to give people a one-minute course and banh mi for them to make it at home, what would you tell them.

KLH: So, banh mi it has a lot of different ingredients but if you have the right one it will go perfectly. So, the base is of course a good bread. Second, the fat, it's really important to use fat as the first layer. So, you have different possibilities between butter mayo or chicken fat, which is small, it's a good layer just on the bottom because you don't need to put on both sides. It's just my personal taste. I don't think it's necessary. Second layer, it's the protein. Of course, the classic is with a pork meat because it's the biggest meat we found in Asia, it's the easiest and the cheapest. So either some marinated pork meat, pork shoulder, pork loin. And then the thicker we use the mix of daikon and carrots, you can do a fast pickling, just white vinegar, a bit of sugar, a bit of salt doesn't have to be boiled. And I'll always finish the Banh mi with a bit of wood a bit of white pepper powder really is up to you whatever you want to do your banh mi with. If you want to do it vegan, you can replace with some Phyto food at your marinated before you can replace with some eggplants that you fry. There’re so many different recipes, you can do whatever you want with it, as long as it's crunchy and herbal, that's good to go.

CK: You mentioned somewhere that when you make mayonnaise, you use tofu. So you want to just tell us about that.

KLH: So, for our vegan Banh mi we use a vegan mayo, it's basically the same start as a classic egg mayo, you just replace the egg and you triple it with the silken tofu quantity. And you just emulsified with the with the neutral oil as you would do classically.

CK: You once said when I go out to eat, I want to go somewhere where I know nobody. You're so sick of being in the restaurant business, you want to go incognito.

KLH: It's more that you know, when you have a restaurant, you are talking to so many people daily. And it's not that I don't love people, it's more that I get so drained. Because it just drives me so much. And it takes so much of my energy and brain space that whenever I want to eat, I want it to be and professionalized. I don't want to think about where I'm going to eat. Or if I'm meeting someone from the industry, I just want to go and eat. And oh, this is good and not even think about, oh, it's undercooked, it's overcooked or how they're heard the plating behind the bar. How many people is there? I don't want to be analytic about what I'm eating. And I want to just switch off my brain for a second. That's me,

CK: Khanh Ly, thank you so much. It was great meeting you in Paris and now talking to you and all the best with your restaurants.

KLH: Thank you so much. Thank you for having me. Thank you so much.

CK: That was Khanh Ly Huynh chef and co-founder of two restaurants in Paris, The Hood and Nonette. Now it's time to answer your cooking questions with my co-host, Sara Moulton. Sara is of course the star of Sara's Weeknight Meals on public television. Also, author of Home Cooking 101.

Sara Moulton: So, Chris, have you had any aha culinary moments this year? You personally. Has there been a moment when you're like wow!

CK: Wow, yes, this is my aha moment and it happened in Paris. I was doing oeuf mayo, which is a classic French dish as you know you hard cook the eggs, cut them in half lengthwise, and then make a mayonnaise with mustard and (stuffed eggs.) So, I'm sitting there, some ungodly hour in the morning with this chef and he cooked the eggs. Okay. So, you put them in boiling water. I usually start them in cold water. You put them boiling water. He cooked them eight minutes and 40 seconds exactly. And then he takes them out because he wants the yolk to be still moist, right? He puts it in this huge water bath with ice. Oh yeah, tons of ice and he lets it sit for three minutes. And then he starts peeling the eggs. Egg after egg after egg perfect. I mean the shells came right off. So, it turns out that the cooking method had nothing to do with the solution. The solution was cool down the eggs, shock them and use a huge water bath with lots of ice in it. So, the temperature comes down. The egg inside the shell starts to pull away from the shell and shrinks. And so, I brought this back as my big aha moment everyone laughed at me. So, we went to the kitchen we took a couple dozen eggs, every single egg peeled, like instantly.

SM: Did you do the eight minutes 40 seconds?

CK: Eight minutes and 40 seconds and the yolk is still moist and not fully cooked. You know it's perfect.

SM: The White is tender

CK: And the white is cooked and tender. But it was the shock of the cold that is what solves the problem of how to peel hard cooked eggs. And so, you know maybe could have been something more interesting. (No) like I finally figured out the mystery of beef Bourguignon (No) but that works.

SM: No, I feel so enlightened. Because I love hard boiled eggs. Wow. I'm going to have to try that.

CK: But big ice bath

SM: Got it. I will do that.

CK: That's my moment.

SM: All right. Welcome to milk Street who's calling?

Caller: Hi, John.

SM: Hi, John. Where are you calling from?

Caller: Carol Stream, Illinois.

SM: How can we help you today?

Caller: I liked Looking with mushrooms, I like cooking with wine. And I thought there might be a little trick to selecting the wines for each type of mushroom or for the type of beef. We just take any wine that we have and pour it into the food, and it seems to taste better. But I thought, it's time to learn a little something about wines and mushrooms.

SM: I love adding wine to recipes too. And, you know, in the old days, they used to say, don't ever cook with a wine that you wouldn't drink. And you know, mostly that's true. But a lot of the nuances of wine are lost when you cook with it because you reduce it down like crazy. So, I would say the two most important considerations are the acid and the sugar. So, you don't really want to use a sweet wine unless you're looking for a sweet sauce. But you know, in terms of the rest of it, it sort of all cooks down in the nuance, as I said, gets lost. So, I generally when I'm cooking with mushrooms, use a red wine. But if I don't have red wine handy, I've added a dry rose or a dry white and it's all worked really well. Chris, do you have any thoughts?

CK: You know, I think the issue is less about which wine I mean, I think a medium bodied wine, you don't want anything with big tannins. As you said nothing too sweet. You want a decent wine. But I think the big rule, I believe this with all my heart is never add wine from the bottle to a pot. Always take the wine, put it at a very low simmer. If it's a whole, you know, 500 milliliter bottle, cook it down till it's just a few tablespoons, maybe a quarter cup. And then you've reduced it down in a way where you don't ruin the wine. And also, I find when you cook meat, like beef in wine, just leeches out a lot of the flavor from the meat and makes it kind of nasty. So, in most of the recipes I've seen from like Italian beef stews, the wine is reduced separately, and it's added in near the end, and I find then you get a wonderful flavor. And you don't ruin the meat. That would be my recommendation.

SM: I absolutely would recommend cooking the wine too. Because if you add it just straight out from the bottle, it gets sort of a raw wine taste. And so, you do need to reduce it. You know, my short ribs recipe, the secret to it is a whole bottle of wine reduced down to one cup, not to two tablespoons.

CK: And just don't buy a lousy wine.

SM: Yeah, I mean it is that remotely helpful there John?

Caller: Oh, absolutely. I've never even thought of that technique. And I have a question when you reduce it. Is it going to thicken like a glaze? Or is it just going to get richer in color? Or does this the liquidity?

CK: Yeah, if you reduce a whole bottle down to a cup or half a cup. Yes, it'll still be liquidly. It might be slightly thicker. If you reduced it down to a few tablespoons, then it will be like a demi gloss. It'll be very thick.

Caller: That sounds really exciting because that's going to concentrate this flavor.

CK: Yeah, you also don't lose all the aromatics, which you would normally Anyway, give that a shot.

Caller: Thank you.

SM: Thanks, John.

CK: Take care. Welcome to Milk Street who's calling?

Caller: Hi this is Glen ____

CK: How can we help you?

Caller: I have a question in regards to following recipes. I'm pretty good about the different techniques that are required. But one thing that eludes me though, is setting the temperature on a stovetop, medium, medium high. I was wondering if you guys had any rule of thumb, that might give me a hand with that.

CK: Well, I can answer this question if you tell me how many angels dance on the head of a pin, because it's about as obscure as that. There's basically no answer. Gas burners are all different. Some of them have 8000 BTUs output, some have 15,000, some of 20,000 it also depends on the burner itself. Some of them the pans sitting way above the heat source, some of them it's closer down, finally it depends on the pan with the cast iron pan or a stainless-steel pan with a aluminum sandwich inside that's thinner. A few things I can tell you. In general, it's better to heat a pan slowly so you get nice even heating. And that's also good for cast iron, it's good to start sort of medium low. So, it really gets a chance to evenly heat. (Okay), the last thing I can say is if you can put your hand like two inches above the surface for just two or three seconds, it's really hot. If you can let it sit there for five to seven seconds, it's kind of medium. And if you can leave it there forever, it's sort of low. The other thing to do is just put a little oil tablespoon or two at the bottom of the pan. And if you're going to sauté, you want it hot so when the oil starts to smoke and ripple, you know that the pans up to you know 420 450 degrees because that's when oil smokes. But if you want to sauté that's a good trick, Sara.

SM: Yeah, what Chris just said, I agree with that the oil starts to ripple before it smokes. And that's a good way to know that it's hot. But another thing is, if you heat the pan, you can heat them dry without the oil and then add the oil. Sometimes if I want to see if it's getting hot enough, I'll throw a little water into it before I add the oil. And if the water evaporates immediately, then I know it's really hot. And then I'll add the oil.

CK: I do have two other quick things. I found onions, I now put them in a cold pan. I don't preheat the pan. Someone taught me this trick, actually a chef here in Boston said, Listen, it's the noise. So, you can listen to the sizzle of something's cooking. And once you get a little experience, you know, when onions, for example, are cooking at the right rate. The other technique I think is really important is as you're cooking very often you need to start turning the heat down. Like if your sauteing, once you set it to a temperature don't leave it there, listen to what's going to pan, look at what's going to pan and then adjust the heat. You know, it's like driving, you don't want it on cruise control the whole time, because you'll end up with a disaster. So, you just have to constantly monitor it

SM: You know, based on what you just said, Chris to also I think an important thing to say, if you're cooking a steak or a piece of meat and you want to get some color on it and you put it in the pan and it's crickets there's no sound. It's way too low. You want to get the steak in there and hear hssst.

CK: Can you do that again? That was really good.

SM: That was a fun question I liked, that was a great question.

CK: Yes, that was a great question.

Caller: Oh this is wonderful.

SM: All right.

CK: Thanks for calling.

SM: All right. Take care.

Caller: Thank you so much. Bye bye.

CK: This is Milk Street Radio. Sara and I are here to answer any and all of your cooking questions. Give us a ring anytime. 855-426-9843 that's 855-426-9843 or simply email us at questions at Milk Street

SM: Welcome to Milk Street who's calling?

Caller: Hello, this is Katrina from Scottsdale, Arizona.

SM: How can we help you today?

Caller: So, I have a bit of a problem with chocolate Italian meringue mostly, I'm not sure if it's actually possible. So, I've made Italian meringue’s before, and I've made Italian ring icing before with chocolate flavoring. But I've never actually made just the meringue itself with chocolate and I was putting the cacao powder into the actual syrup mixture that you end up pouring into the egg whites once they're whipped. And for some reason, it just completely collapsed from soft peaks and I could not revive it. I don't know what happened.

CK; So, you beat egg whites. And then you pour in a hot sugar syrup. I forgotten the temperature went to under 240 30 to 40 something. You drizzle that in while you're beating them and you continue being the whites for a few minutes, right, I think right afterwards.

Caller: until you get firm peaks,

CK: Right So you brought the sugar syrup up to temperature then added the cocoa powder to it or

Caller: I actually brought it up to temperature with the cocoa powder in the syrup. I used a really fine cocoa powder too. And I sifted it in to make sure there wouldn't be any big chunks.

CK: Well, cocoa powder doesn't have a lot of fat in it. Because the fats in the cocoa butter.

SM: I can't think of any occasion where you actually add some dry ingredient to whipped egg whites. No, it would always deflate it. Your goal is to make what kind of meringue?

Caller: I was just hoping to get a chocolate Italian meringue mostly because I wondered if it was possible.

SM: Do you mean a cookie? Do you mean a frosting? What do you mean?

Caller: I'm thinking of using it as a topping on a trifle. If I could get it to work

SM: and you don't want to go the whole buttercream route.

Caller: Right

CK: I would do it a butter cream and I would melt chocolate you know over double boiler or when a very low heat. I'd let it cool down. Then do it that way.

SM: and then add it to the buttercream

CK: that would work. Well. You've done something nobody's done before.

SM: Yeah,

CK: I’ve never heard of doing it

Caller: Something incredibly stupid that nobody’s ever done

CK: No, no, no, I know I hold the world record in credibly stupid things

SM: Some of the best things that have ever happened like champagne were a mistake. So ever not try.

CK: But the question we've not answered because we're so good at not answering questions is why by adding cocoa powder to sugar and water and creating a syrup and then pouring it into whipped egg whites did the egg whites immediately collapse that’s

Caller: I’m trying to understand the science behind why it's not possible to add in the solid until after the meringue itself is formed.

CK: You’ve made Italian meringue before obviously, right?

Caller: Yes. And Italian meringue buttercream which was chocolate flavored.

CK: You know what we're going to have to get back in touch with you because we had to go test this you stumped us.

Caller: I mean, if it helps, there's a chance that will never work because it wasn't even in the textbook, I tried modifying it from

CK: We’ll have to ask our science consultant and we'll get back to you

SM: Okay,

Caller: Thank you so much.

SM: Bye bye.

CK: This is Milk Street Radio coming up we answer the question is your bitter the same as my bitter? And are humans the only species that love sour? We'll uncover that and more right after the break.

Wes Martin: Hi, this is Wes Martin. I'm the director of culinary production at Milk Street between cooking for photoshoots recipe development and tastings. I get to make wonderful food from all over the world, which I make it home for myself all the time. Learn more about membership options at Milk Street

CK: This is Milk Street Radio I'm your host Christopher Kimball right now it's my conversation with Emily Kwong and Aaron Scott, hosts of NPR is daily science show shortwave. In their taste bud’s series, they cover everything from sweet and sour to what's beyond our classic idea of taste. Emily and Aaron, welcome to Milk Street.

EK: Thank you so much for having us. We're excited to be here.

AS: Yeah, it's a pleasure. Thank you.

CK: You know, taste is really one of my favorite topics of all time, because the science is really interesting. But you guys have a more in depth take on all of this. So why is taste important to human beings?

AS: I mean, on one level, it's about pleasure. So, it's important because it's a source of great joy in life. But it's also very much about biology. Taste is how our bodies know what to consume, how much of it we should eat, you know, salty is wonderful in certain quantities, but you eat too much of it, and it's repulsive. So, I mean, taste is really kind of like how our bodies biology meets the world.

CK: So, let's separate taste into two parts, right? There's the tongue, and then there's the palate where the tastebuds are. And then their nasal receptors, where you get a lot of information about taste from scent from aroma. So how much of what we consider tastes really comes from the nose versus the palate.

EK: Yeah, it's really difficult to pin down a hard number on how much of what we commonly think of as taste actually comes from smell. So, I like to think of it in terms of flavor flavors, a combination of so many things. And that includes smell. We did an episode with Kara Hoover, a biological anthropologist, she says there's actually two kinds of smelling. So, there's the kind that is that is air coming in through your nose. But the second kind is when you're chewing and air gets pushed up into the nose from your mouth, and then back down into the mouth. It's one of the reasons why a lot of professional wine tasters actually chew the wine. That's because they want to get that retro nasal olfaction, that cycle of air going from the mouth to the nose to the mouth and fully experience the flavor, which is again the blend of smell and taste together.

CK: So sweet, sour, salty, bitter. Those when I was a kid where the basic tastes. I guess umami has been added to that. But you've talked to scientists who think that there are a lot more taste than five or six, calcium is a taste metallic effervescence. So, does this list just go on and on and on or are the five main tastes are they essentially bedrock?

AS: It seems that there's definitely more than the five. I mean, I think when we were talking with Katie Wu, who is a staff writer at The Atlantic, she was estimating, you know, like maybe a dozen. We even know that there are receptors in the tongue that we don't know what they are receiving. I mean, it seems for the people who are really into like, what are the other tastes out there? The the search is to figure out what is that receptor and then kind of the, the baseline of Is it a taste is can we turn that receptor off and suddenly you don't taste that thing anymore? I mean, these receptors are actually throughout our bodies. I mean, we're talking about you know, there's taste receptors on your tongue, and in your nose, but there is bitter taste receptors in our respiratory system. There was, you know, a viral trend a while ago, based off of research that found that there are salty and umami taste receptors in testicles that led to, you know, all sorts of ridiculous online videos of people trying to figure out if testicles could taste soy sauce. But there's

EK: Oh, the internet, how I love thee.

CK: First of all, is that speculation or is that fact? And secondly, could someone explain to me if it is true, why it would be true.

AS: So, my understanding is it is fact however, the taste receptors are inside the testicles. So, it is not something that you could sense by doing what people online were doing of dipping their dumplings into soy sauce. I mean, basically, taste receptors are just, you know, sensing certain chemical compounds. And we assume because we’re, so you know, human and food focused that it's all about just tasting what tastes good or bad, but every compound has flavors to it. So, I think in the case of the testicles, it has to do with sperm production, like they knocked out those taste receptors, I believe in mice, and the mice stop producing sperm. And so, in the case of fish, they have sour taste receptors all over their body, which is monitoring how acidic the water is that they're swimming through.

CK: Sweet, sour, salty, etc. This is interesting. Not all animal species have those five senses in the taste holster. And you go on to say some carnivores, for example, have lost the ability to taste sweet.

AS Yeah. So, cats, otters, I think hyenas, they don't really consume carbohydrates, they mostly are consuming, you know, a protein meat-based diet. So, they've like, over time, lost the ability to taste sweet because they don't need it. Or the saddest one to me was dolphins whose mostly swallow their food whole, have less bitter, sweet, and salty. Of all the animals that have been studied, the only taste that seems to be universal is sour. That kind of signifies that it must be doing something important. Scientists still don't really know what that is.

EK: What I've realized about taste and just brain stuff in general, is we, we know a lot. And we know very little, you know, like, we know more than we've ever known in the history of humanity. And we also truly don't know how it works.

CK: That's why we love science. Yeah, answer questions. Back in the 70s. I remember I went to a science of food seminar. And there was a test given to us about whether you can taste bitter. And I guess some people can taste a lot more than other people. Why is that? Is that true? And if so, why?

EK: Ooh, good question.

AS: Yes. And I mean, if you would indulge us, we'd love to reenact this test. (Right). You probably took that in which is the PTC test papers strip.

CK: Yeah, I have one right here.

EK: Yeah, I have one too, that Aaron mailed me.

CK: So, it's a little white strip of paper looks like confetti?

AS: Yes, indeed. And it's soaked in this compound, phenol phyto carbamide. That has like a really neat backstory, and that it was, you know, a chemist in the 30s was working with it. And a puff of it went up in the air and he didn't really notice. And then his lab mate was like, what is that terrible, bitter thing that you're working with? And it was the first time that he was, you know, the realization of like, wait a minute, you taste something, but I don't taste it. And so then like he tried to poll people on if they could taste this or not. So yeah, if we all want to take the strip and put it in our tongues,

EK: Should we count down?

CK: All right, already on my tongue.

AS: Me too. Sorry.

EK: Fine, fine. Fine. Fine. All right. Ready?

AS: How is it?

EK: Unpleasant

AS: Yeah.

EK: Oh, it's horrible. Oh, that's really bad. Yeah, it tastes bitter but not like I'm out to dinner eating something bitter and complicated, but like I'm eating something bitter and poisonous.

CK: I unfortunately have a cold which may or may not affect this. I didn't love it. But you know, I've done this before and gotten a pretty strong maybe you just mail me plain strips just to fool me.

EK: Aaron you?

AS: I don't taste anything really tastes like I just put a piece of paper on my tongue. And one reason bitters, so neat is there's 25 different bitter receptors. So, there's a complexity to bitter that's not there for like sugar. And so basically, one of my 25 bitter receptors doesn't function, which I was really heartbroken to find out because I'm like, oh, I love bitter things. I love cruciferous vegetables. I love coffee. And then the scientist ____ that I was talking with was like, actually, the reason you love some of those things might be because you don't taste this aspect of bitterness that some people do taste.

CK: Okay, I've just made a discovery the samples I got, say control paper. So, I just got what I thought I got, which is a piece of paper. But this paper is inert and tasteless and should be used as the placebo and genetic taste testing. So okay, so you are our control. I knew someone was fooling with me, because I was going like this really is very bitter my because I have a cold. So, let's move on to a umami. I think most people know the origin story here. But you want to just describe it quickly how it was discovered.

EK: Sure, it was discovered 100 years ago in Japan. But there was this century long delay. And the paper that was published in 1909, wasn't translated in English until 2002, the Japanese chemist 100 years ago who was trying to isolate that taste, used this specific seaweed called kombu, which is native to Japanese cuisine. He distilled that seaweed and distilled and distilled until a single substance began to crystallize. And it's called glutamate. So that's what umami taste is. It's this amino acid called glutamate that sticks to the receptors in your tongue and in your brain and gives you that kind of brothy meaty feeling that isn't just a feeling of like, this is what it tastes like, but I think it kind of lasts and lingers.

CK: We all know salt is like a glutamate, right? It just enhances flavor. How does it actually work? Do we know how it enhances flavor of what's going on chemically?

AS: One of the researchers we spoke with Dr. Danielle Reed, she mentioned to me that salt is kind of the next big chase, because we don't actually understand a lot about why it tastes good, or what the exact receptors are for it. So, like even though we know salts, flavor really well, we don't know much about how salt taste works.

CK: But it's become public enemy number one in the last, you know, 30-40 years, which I think is it's been mislabeled sugar however you talk about leading to an inflammatory process in the brain, etc. So, what's the chemistry of sugar in terms of what it does to the body?

AS: Our bodies need sugar like sugar is pure energy, we've evolved to really love it. And then that is now sabotaging us because we're no longer in the environment that we evolved in where you know, we'd get sugar from berries on bushes, like now we walk in the store, and we can buy a big gulp or a giant soda or something. So even though it is a divine wonderful tasting thing that our bodies need, on a large kind of societal level, it is the one that is most impacting our health. So is there a way we could trick our body into thinking something is sweet that is not full of sugar, like in the case of miracle berries as they've been dubbed, which is a fruit from Western Africa that you can now buy in kind of a little pressed tablet form.

CK: I have them right here.

AS: Perfect. We are going to do a fun little flavor experiment. Just take one of the tablets and let it dissolve slowly and kind of move it around your mouth so that it's coating your mouth.

CK: It looks just like an antihistamine or something. Okay.

AS: Yeah, okay

EK: oh, it actually tastes kind of nice.

AS: Yeah, it's not a super sweet berry. I mean, it's kind of a very mild berry. But it contains a protein called miraclean which is basically binding to our sweet taste receptors as we roll this around in our mouth. And it's shifting them so that they're going to be activated by sour things.

EK: I love hijacking my body's natural responses.

AS: And so, let's maybe start with something that it just straight sourness. Let's maybe do a slice of a lemon. Yeah.

EK: Okay.

AS: If you have a slice of a lemon in front of you.

CK: I do.

EK: Oh!

CK: That's amazing.

EK: That’s so strange.

CK: I don't think I'd like it very much. But boy, it's like a penny candy. But it's still has sour there but the first wave of taste. Is this kind of unpleasant sweetness.

AS: Yeah, it doesn't pucker at all. No, like have absolutely no puckering. Let's maybe try the cream cheese next.

CK: Mm hmm.

EK: You know when you go to the bagel shops and you can get regular cream cheese but then you could also get strawberry cream cheese, which is objectively inferior and no one should eat it. That's what this tastes like. It tastes like candy cream cheese.

AS: Otherwise known as cheesecake. It tastes like cheesecake to me.

EK: It does taste like cheesecake.

CK: Yeah, it does

EK: Now that you framed it that way, I kind of like it

CK: I think in the lemon, it was brutally clear that something strange was going on. This is this is more subtle.

AS: Okay, next, let's try the dill pickles.

CK: Okay, dill pickle.

EK: Ready. Here we go dill pickle,

CK: Oh, oh, wow. It's weird.

EK: It almost tastes artificial.

CK: What it does is it pushes down the sourness with this intense heavy layer of sweet. The sourness isn't gone. It's like you're riding a bicycle, and somebody jumps on the back unexpectedly. It's like, you know, you got two people when they really should be one. (Yeah) so you get sweet, an artificial sweet. And at the same time you also the sound is still working in the background.

EK: That's so true. That's like listening to a song that's been over produced electronically. And they did weird things to the guitar. (Right) That's what this pickle tastes like. It tastes like an overproduced dance house song.

AS: You guys are both such purists.

CK: So, could you just concisely explain what's going on in my mouth right now.

AS: So basically, this miraclean has bonded to your sweet receptors. And like, the more sour the substance is, the more it's now going to register as sweetness, which is I think why you know, the lemon, like the sweet is so overpowering. Whereas in the cream cheese, which is less acidic It's it's a much subtler thing.

CK: So as we expand our understanding the palate, how do you think we'll see the science of taste be applied, let's say a couple of decades from now?

AS: I mean, I think you know, there are a couple of things that researchers are really trying to do with this, like the search for a sugar replacement that still tastes sweet and wonderful is that it's a race. So, in the case of like these miracle berries, you know, there's work being done of like, could we combine this in a soft drink with a little bit of something sour, that will then taste sweet, but still be calorie free.

EK: And then Chris, there's also the aspect of using food science creatively for other kinds of research. It makes me think of someone like David Julius, who won the Nobel Prize a few years ago for figuring out how pain works in the body. And the way he did that was by cloning, the gene receptors that we use to taste capsaicin, the heat in chili peppers. And by basically harnessing the capsaicin response, he really expanded our understanding of our nervous systems, pain signaling apparatus, our bodies actually have pain receptors all over the place. And again, these are different from taste receptors. But that's why when you eat spicy food, you sometimes feel it out the other side, because your pain receptors on the other side of your digestive system are experiencing that spice all over again. Pretty cool.

CK: Well, I have to say this discussion has covered pain receptors and taste receptors that were totally unexpected.

EK: You're welcome,

CK: Emily and Aaron, thank you so much. Some images I would prefer to forget, but lots of good information. Thank you.

EK: Thanks for having us on the show.

AS: Thank you.

CK: That was Emily Kwong and Aaron Scott hosts of Shortwave on NPR. You may have heard thAT humans use just 10% of their brain. Well, that's actually a misquote of a doctor who once said that we only understand 10% of brain function. Now the really fascinating part is that the region of the brain that processes flavor inputs, also handles memory and emotion and sweet foods create the most powerful memories. We just can't explain how and why. So, the good news is that a birthday cake is a powerful time machine. Take a bite and repeat after me. There's no place like home. This is MilK Street Radio coming up Adam Gopnik investigates what it means to be a culinary Maestro. That's right up after the break.

I'm Christopher Kimball, you're listening to Milk Street Radio. Now it's time to chat with JM HIrsh about this week's recipe Thai cashew chicken. JM how are you?

JM Hirsch: I'm doing great.

CK: Thai cashew chicken as a takeout item in this country tends to be a little on the greasy or gloppy side. It's not a bright fiber dish. You just got back from Bangkok. And you you say otherwise you say it's a great dish.

JMH: At risk of being cliched. I'm going to tell you it was one of the best things I've ever eaten. It was bright. It was spicy. It was sweet. It was savory. There were so many layers of texture, crunchy cashews, tender chicken with a crispness to it itself. I mean, it was just unbelievably good. It's nothing like the cashew chicken we get here, which tends to be an American Chinese dish. And the version I had in Bangkok by this home cook, she was drawing on both Thai and Chinese traditions. And for that she made it a little bit sweeter than the Chinese versions, but not American Chinese versions, and a little bit spicier, and a little bit drier.

CK: So Thai chili paste is part of this. Is that really critical here because I would assume what they're using there is quite different than what we have here or not.

JMH: Actually, we can get a decent approximation of it here in most grocery stores, you know, the toasted Thai chili paste, which is sweet and rich, and very savory, and a little bit kind of tangy and sour. It's got a lot going on. It is an important ingredient. But we didn't have any trouble finding it at just any grocery store here.

CK: Just take me through the basic stir fry steps for this.

JMH: Sure. So one of the really nice steps that sets this dish apart is she created a slurry of soy sauce all-purpose flour, salt, pepper water, and then she took chicken thighs that she had cut up and she tossed in that slurry and I’ve got to tell you, I thought that was going to make a mess when she fried it in the wok, but it didn't it actually crisped up perfectly. And then the sauce is you know, the Thai chili paste plus sugar and oyster sauce and a little bit more soy sauce, toasted cashews that go into into the wok and get toasted briefly dried chilies get toasted briefly in the woks. Each of these occurs on its own, and then everything comes back into the wok all at once to finish the dish with the sauce. And she also adds mushrooms and onions which isn't very conventional, but we really liked it. It's delicious. And then you finish it with those crisped chilies and some scallions. And of course, the ice-cold beer it was really, really was quite unbelievably good.

CK: And what about the wok hei, the flavor of the walk the sort of smokiness of the wok, get into the dish.

JMH: You know, she was a home cook. Now wok hei is much easier to accomplish in the megawatt burners that you see in Asian restaurants and home cooks, even in Asia don't have that. But like a lot of home cooks I've met in Asia, what she did was pour the sauce down the sides of the wok because those sides of the wok get very hot. And what happens is as the sauce goes down those sides the sugars in caramelize and reduces because of evaporation. And that intensifies the flavor is that wok hei no, not really. But this is a way of kind of approximating that.

CK: So Thai cashew chicken done in Bangkok the right way a cold beer or two, and even a little shortcut to wok hei by pouring that sauce down the sides of the wok to get that caramelization in that smokiness JM I don't know why I didn't go on this trip. But I'm just dying to have this recipe. Thank you.

JMH: Thank you. You can get the recipe for Thai cashew chicken at Milk Street

CK: You're listening to Milk Street Radio. Now let's hear what Adam Gopnik is thinking about this week. Adam, how are you?

Adam Gopnik: I am well, and I have been meditating at length. Lately, Christopher on the difference between soft kitchen skills and showy kitchen skills. I wonder if you would like to hear some of this meditation.

CK: I'm on the edge of my chair. I can't wait.

AG: It all began this reflection having dinner with our friends. Peter and Susan Hoffman wonderful food friends ran a great restaurant in New York for many years now. And in the way of couples who've known each other for a long time we were all reminiscing about the most moment we fell in love. And Peter was saying of Susan, that he fell in love with her watching her chop shallots, in the kitchen of the restaurant where they were working together as very young chefs. And I said, well, how can you fall in love with someone chopping shallots. And he said, it was the quiet authority that she did it with. And it was such a lovely image of her skill and his fascination with it got me thinking about knife skills and what they mean and more broadly about all of the soft skills of the kitchen by soft skills I think of things exactly like chopping shallots. I don't know if I ever told you I once got a lesson in chopping shallots from Andre Soltner himself really was one of the great cardinals of French cooking in New York ran through tests for me.

CK: I went there and met him all very long time ago.

AG: Yes, he's an Alsatian actually. In France, it's very significant that you're Alsatian, because you sort of belong on the liminal land between France and Germany. In any case, he was shocked by my shallow chopping technique, not because it was sloppy, particularly because it was so dangerous, because he said, you are about to cut off your knuckles. And you have to move your hand back as you chop as though you are under assault by a foreign army and in retreat, a rather French metaphor I suppose you could say yes (for Napoleon I guess) Other things that I think, come under the heading of the soft skills of the kitchen, beating egg whites is one that I've always thought was extremely effective. I know that my own wife, she finds something enormously appealing about the sound of metal-on-metal wooshing through those egg whites and something hugely beautiful about the way that this clump of yellow membrane suddenly becomes this beautiful white cumulus cloud, in the bright shining copper bowl. My key memory of feeling the power of the soft skills of the kitchen, was seeing my mother unroll strudel dough when I was a very small boy, that's my first memory of mastery of somebody who in any realm, but particularly in the kitchen realm, could do something that looked impossible and do it well. And for the rest of my life, whenever I see someone doing that, I once saw a Greek baker making balaclavas that same way, I've my whole body shakes up because it recalls to me the the sheer power in the meaning of mastery. But it seems to me that those soft skills of the kitchen are very different from what we might call the showy skills of the kitchen, which we more often celebrate on television, for instance, nobody wants to watch on Food TV, someone's simply chopping shallots. Instead, we replace them sort of with the power skills, the the strong, showy skills of the kitchen. Obvious one of all is

flambeeing right? That's the showiest strong skill of the kitchen carving is a strong skill in the kitchen or a showy skill.

CK: Or maybe Jacque Pepin boning a chicken speaking of amazing kitchen skills.

AG: Exactly. And another variety of knife skills, from the skill you need to chop shallots or chop onions for that matter. And I got to thinking about why those soft kitchen skills are so seductive that they could begin a romance or in Peter and Susan's case, a marriage that has now lasted almost 40 years. And it seems to me it's in part because they suggest the kind of quiet understated mastery that we seek in a partner for life. We want someone who isn't showy, but who is subtly effective. But also, when I think about it more deeply when I take a second dive it's also don’t you think Christopher, because they suggest beginnings. And those are all things you do at the start of a meal, flambeeing, carving the chicken, those things tend to come later. And they're designed for the diners who are already in place. You know, they're not immediately when you're beating egg whites, it's translation into a delicious thing to eat, isn't self-evident, it's instead sort of self-contained.

CK: Well, I have to stop you for a second. (Please) I don't think it's so much it's the beginning. I think that the quiet certitude of somebody who knows a skill, it shows that they are self-confident and know themselves. Because I don't, I don't think you can do that well, unless you are very sure of yourself and who you are. That's what it shows about the person, I think.

AG: That's beautiful, Chris, and I think you're right it is it is isn't it? It's it's the interiority of that action, right, it's the the quiet, understated confidence. You have to as you said exactly in those classic words, know oneself, you have to know thyself in order to do a task like that well. It's not knowing your audience is the way we always talk. You got to know your audience, to please them. You have to know thyself in order to chop shallots. But let me ask you a question that I've been brooding on as I pass these thoughts on soft and strong. What's the one kitchen skill you most wish you had and honestly don't. Mine is a particular variant of knife skill and that is not chopping, which I think I do adequately, if not safely, according to the great Andreas Soltner, but slicing is something I always feel I do inadequately. I admire anyone who can take an avocado, strip it bare and slice it into beautiful portions that are neither too thick nor too thin, I admire the same kind of person can do that with a breast of turkey slicing is a skill unto itself. And one I must confess I don't really possess,

CK: I think the hardest thing to do you mentioned which is baklava, or any very thin pastry that's translucent almost. And people who can just take a big rolling pen and do that by hand, you know, without any device to help them. I think that's the number one skill I would like to have.

AG: Well, I buy that, and you know, what makes it so intense it was the first skill I ever saw an operation and the person I saw activating that skill was my own mother.

CK: Well, you and I should start a cooking school and the name of it will be Know Thyself, because that's the first, the first step to any skill in the kitchen is to know thyself. Adam, this has been a watershed moment for us.

AG: It truly has been, but you know, Socrates said that the key to realize life is to know thyself. So, I think we're moving in an ever more Socratic direction.

CK: Well, we always engage in Socratic dialogues. Adam, thank you so much.

AG: A pleasure talking to you, Chris.

CK; That was Adam Gopnik, staff writer at The New Yorker. His latest book is The Real Work on the Mystery of Mastery. That's it for today. You can find all of our episodes of Mik Street or wherever you get your podcasts. If you want to learn more about Milk Street, go to 177 Milk there you can become a member and get full access to all of our recipes or cooking classes, and free standard shipping from the Milk Street store. You can also find us on Facebook at Christopher Kimball's Milk Street on Instagram and Twitter at 177 Milk Street. We'll be back next week with more food stories and kitchen questions, and thanks as always for listening.

Christopher Kimball’s Milk Street Radio is produced by Milk Street in association with GBH co-founder Melissa Baldino, Executive Producer, Annie Sensabaugh, senior editor Melissa Allison, producer Sarah Clapp, Associate Producer Caroline Davis and production help from Debby Paddock, additional editing by Sidney Lewis audio mixing by Jay Allison and Atlantic Public Media in Woods Hole Massachusetts. The music by Toubab Krewe additional music by George Brandl Egloff. Christopher Kimball's Milk Street radio is distributed by PRX.