Dan Pashman:  Hey everyone, Dan here with another Sporkful Reheat for you, and this one we're bringing to you in memory of the acclaimed chef Charles Phan, who recently died at the age of 62. I was so sorry to hear that he passed away. I was so glad that I got the chance to meet him and interview him in person. He really popularized modern Vietnamese cuisine in America. He was instrumental with his restaurant, The Slanted Door, which has locations in San Ramon, Napa, and in France, and I just remember him as being a guy who was super knowledgeable, super passionate, but also just no BS. Like if I said something that was wrong or made no sense, he would just shoot me down. He's also the guy who taught me that in Vietnam at a pho shop, you could ask for extra beef fat, like a beef fat floater on top. I still want to go to Vietnam just to do that. I really enjoyed getting to meet Charles in person. He was generous and genuine and I really will miss him.

Dan Pashman: This episode also includes some pretty hardcore nerding out on the science of slurping noodles. It's a good one. This is an episode that I think back on all the time.  Now remember, if there's a Sporkful you'd like us to pull out of the deep freezer and reheat, please let us know. Send us an email or voice memo to hello@sporkful.com. Include your first name, location, which episode you'd like us to reheat, and why. Thanks so much, and enjoy.  

Charles Phan: Taste the broth, see if you like it. You can always add more stuff to it. Never put hoisin in there. Most white people, they pour the hoisin right in and kill my broth. So I like to slurp it down…

Dan Pashman: This is Chef Charles Phan, he’s probably the most famous Vietnamese-American chef in the country. His restaurant in San Francisco is called The Slanted Door. And I’m sitting in front of a steaming hot bowl of pho that Charles made just for me. Pho is a Vietnamese soup with rice noodles, and this thinly, thinly sliced meat, and this rich, delicate broth. 

Charles Phan:  I have to say, only broth that tastes like this is broth when I am in Vietnam. This is what I remember. You walk in, you smell beef, you smell butter, like a butcher shop, you know?

Dan Pashman: A bowl of pho also comes with all these sides that you can add as you eat – there's Thai basil, bean sprouts, lime. I love it, I love pho. It has all these flavors coming together, so many different bites you can compose. But as I told Charles, pho also stresses me out.

Dan Pashman:  One of the things that I think is kind of fun about pho, but also a little intimidating to maybe white folks and people who haven't eaten it that much is the sort of interactive element of it.

Charles Phan: Uh huh. 

Dan Pashman: Because I think there's sort of the fear that like, what if I do it wrong?  

Charles Phan: Well, you're not gonna die, first of all.

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Dan Pashman: Yeah, you’re not gonna die. But you can definitely screw it up.

Dan Pashman:  Can you just take... Is this sriracha?

Charles Phan: Yeah.

Dan Pashman: Take the sriracha and put it right in the broth?

Charles Phan: No, a lot of people do that. I hate that. 

Dan Pashman: Tell me how you do it. 

Charles Phan: The sriracha and all that is really meant for you to dip the meat, take the meat, dip the sriracha.  But the minute you put that sriracha into the broth, you kind of ruin the broth. If someone’s already perfected the broth, why are you messing with it? 

Dan Pashman: This was not reducing my pho anxiety. Then, it got worse.

Dan Pashman: Oh, have I been using my chopsticks backwards all this time? This is embarrassing. [LAUGHS] I totally was using my chopsticks backwards. 

Charles Phan: That's another show.

Dan Pashman: Today on The Sporkful, Chef Charles Phan sets me straight on pho. Then later in the show, we take a deep dive into the science of soup slurping, with a researcher who knows all about the minutiae of eating:

David Hu:  I have a student studying animal tongues. She's known as Tongue Girl over in our lab. 

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David Hu: I mean, food is a very mechanical process, and I just wrote a grant today about how much saliva you produce when you eat. 

Dan Pashman: That’s coming up, stick around.

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Dan Pashman: This is The Sporkful, it’s not for foodies, it’s for eaters, I’m Dan Pashman. Each week on our show we obsess over the details of eating to uncover truths about food — and people.

Dan Pashman: I went into my interview with Chef Charles Phan looking for guidance. Like I said, I love pho, but I always felt like I wasn’t quite eating it right. Like there was a flavor combination I wanted to unlock,  and I thought it was there, somewhere, in that bowl, but I just couldn't find the key. I thought Charles could help. 

Dan Pashman: A bit more about pho: It’s spelled P-H-O, but it’s not pronounced FO, it’s FUH. The beef is sliced really thin and they drop it in the soup raw. And then the hot broth cooks the meat in the bowl. And that broth,  whoa. I mean, Charles's takes six hours to cook. And that broth is fatty but it's light, a little salty, a little spicy. It’s really really good. And he knows it.

Charles Phan:  I just love the purity of the broth, and you should enjoy it, and you should never dump stuff in it, and I see it all the time, it drives me bonkers, I don't know where that started from. People in this country had this fascination towards sauce on everything like, we sell a steamed bun, they ask for sauce, but they don't do it, you know, you don't go to Subway and say, give me some sauce for my sandwich. But somehow they eat a steamed bun from a Chinese restaurant, and it's like, where's the sauce, where's the sriracha?

Dan Pashman: But in this sort of dumbed-down American adaptation of a lot of Asian food, so much of it is just about taking some meat or vegetables and dumping sauce on top. In the not-as-good versions of the food, I'm saying, that sort of has become very popular. 

Charles Phan: No, I don't know. I mean, there are a lot of bad people making a lot of bad food.  But it's just, I'm just talking about the act of eating.

Dan Pashman: One of the things that I struggle with when I eat pho is there's so many great flavors and components that are kind of all coming together. You have the jalapenos, you have these different herbs, you have the noodles, you have the meat, you have the broth. I feel compelled to try to get all of these things together into one amazing, mind-altering bite. 

Charles Phan: This is not a hamburger. You don't have to shove the whole thing into your face. So you ought to do one thing at a time. You know, like, I would drink and enjoy the basil with that and take a bite of the noodle separately. And if you're ready for the bean sprout, you know, in fact, you don't want to dump all the stuff at once. What happens is you're cooling the soup down, right? And then I think soup temperature is very important. Once it gets cold, it doesn't, you know... That's why we heat up the bowl. And this is like... No, no, I'm sticking your chopsticks straight up.

Dan Pashman: Oh, sorry. 

Charles Phan: Yeah, like, you gotta put it down. It's like some bad juju omen stuff. 

Dan Pashman: Oh, no. 

Charles Phan: But just don't stick it up like you stick a fork in a haystack. 

Dan Pashman: Okay, you can't have the eating end of the chopsticks sitting in the soup. 

Charles Phan: The food's sticking up. I don't know why, but... 

Dan Pashman: You just can't. 

Charles Phan: But they tell you these things as an Asian kid. Like, if you leave a lot of rice in the bowl, you're gonna marry an ugly woman. Because  you don't finish your food. 

Dan Pashman: How's your love life? 

Charles Phan: No, I got a beautiful wife, so I eat all my food. What are you talking about?

Dan Pashman: But isn't it funny that now, even as an adult, when I would drop my chopsticks into the pho and they're sticking up that way, even now you had like a visceral reaction.

Charles Phan: Yeah, my uncle used to hit me across the table. Like with his chopsticks. You know smack me. 

Dan Pashman: I want to get back to the idea of the perfect bite of pho. I’m not talking about shoving. It's not about quantity. I'm just saying that when I see this many different ingredients together in one dish, my instinct is that there must be a way to combine them all in, in, in some sort of perfect nirvana bite that's going to, like...

Charles Phan: Yeah, but that's your, I mean, like, first of all, there's no way you're gonna get the jalapeno, the basil. They're all different distinct things, the beansprouts, so they're meant to eat, like, individual bite with the broth. So you're saying that you want to have the basil, the Thai chili, the jalapeno, the bean sprout, and the beef, and they're all in one bite and swallowing it. 

Dan Pashman: Well, maybe I'm wrong. Maybe that's not what it's for. It sounds like what you're saying is that pho is more like…

Charles Phan: It's not like a fancy pairing. I mean, they're meant to eat their kind of own thing, you know?  So, it's a very individual preference. I mean, you know, you're talking to a guy who'd like to eat their sandwiches in layers, so I'm a little biased, you know. I don't shove the whole thing in my mouth. I like to eat and enjoy each item's flavor. 

Dan Pashman: Now, typically pho comes with the chopsticks and the spoon.

Charles Phan: Right.  

Dan Pashman: Is there anything you use the spoon for other than the broth? 

Charles Phan: If you want to be really elegant in front of a lady, then you put the noodle in your spoon. If you don't care like me, I just slurp it.  

Dan Pashman: Oh, slurping. Well, let's get to slurping. Tell me about your slurping technique. 

Charles Phan: I slurp if there's no pretty people in front of me. [LAUGHING] Nobody's watching, I slurp. If you're a little bit more, uh, serious business conversation, then, then you wouldn't do that. And you would take your spoon and slowly bring that up. But I never like to do that, because I lose all the heat. So I like to slurp it down with the bowl in my face. But if I'm in a serious meeting, chances are I'm gonna sacrifice my noodle soup and let it die, and more focus, and hopefully I can close the deal. 

Dan Pashman: That's how you've gotten so far. Sometimes the focus is not on the food, is what you're telling me. 

Charles Phan: Yeah. 

Dan Pashman: One of the things that I think is interesting is that I asked you about, you know, getting the different components of the dish together into one bite. To me, a soup would be a dish where you have these different components, but they're, in theory, they're, you know, greater than the sum of its parts. They all come together into one bite, one dish. But it's clear from talking to you that that's not what this is, right? Separately from that, you're also talking about how Americans are always asking for sauce. And you're like, what the hell? We don't need any sauce. This is delicious as it is. In essence, with pho, it's not a soup. Really what it is is a dish in which the broth is like the sauce. 

Charles Phan: Mmhmm.  

Dan Pashman: So you don't need more sauce because the broth is the sauce. 

Charles Phan: That's the vehicle already. Yes.

Dan Pashman: So that's what it is. That's what people need to understand. 

Charles Phan: Now, if you're in the pho shop, you would ask for extra fat. Some of the shops...

Dan Pashman: You can ask for that?

Charles Phan: Yeah.

Dan Pashman: Oh snap! [LAUGHS]

Charles Phan: So because in Vietnam and some of the better shops, if you get there before eight o'clock, you get there by seven, there's marrow that flows to the top. That's another extra price that you can ask for. You want marrow and fat. So you literally get the bone marrow and fat, and you wolf that down with a piece of donut. It's not good for you, but it's really good. 

[LAUGHTER]

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Dan Pashman: That’s Chef Charles Phan, his restaurant in San Francisco is called The Slanted Door. He’s also the author of a cookbook called The Slanted Door: Modern Vietnamese Food.

Dan Pashman: And after talking to him, I feel a lot better about my pho game. What I learned is that I was, I was just approaching it all wrong. To put it in Sporkful terms, I was trying to find one amazing all-encompassing bite that I could perfect and then repeat over and over again – I was looking for bite consistency. But that's not what you're supposed to be looking for when you eat pho. You're supposed to look for bite variety. So now when I eat pho, I think of it more like a buffet in a bowl. 

Dan Pashman: Coming up, we’ll dig into one of the topics I touched on with Charles: slurping. Is there a right and wrong way to slurp? What are the mechanics at play when we slurp soup and noodles? Is there a way to slurp noodles without splattering sauce and broth all over myself? These are the questions that keep me up at night. Stick around, we’ll get the answers.

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Dan Pashman:  Welcome back to another Sporkful Reheat. I'm Dan Pashman. Do you ever go to our show page in your podcasting app, and you’re scrolling back and you're like, Oh, that, that seems like a good episode, how did I miss that? Well, you missed it because you're probably not following our show in your podcasting app. And it's really important that you do. So please do this right now. Go to our show page in your podcasting app of choice. If it's Apple Podcasts or Spotify, you click follow. Other apps, maybe it's a plus sign or a heart or a favorite, or the word subscribe. Whatever it is in your app, it's really important that you click it. That way, you won't miss great episodes, super quick and easy. You can do it right now. Thank you so much. 

Dan Pashman: Now, back to this week's Reheat. 

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Dan Pashman: Alright, let’s get to slurping. I’ve always been fascinated by the science and mechanics of slurping. Does it actually cool down hot liquids? What are the physics at play? Are there ways to do it that make your food more or less delicious? Fortunately I found the perfect guy to answer these questions. David Hu is a professor of mechanical engineering at Georgia Tech, and he’s a kindred spirit. He’s obsessed with the tiniest details of eating. From how our tongues work, to the role of saliva in eating, to yes, slurping. 

David Hu: Slurping, it's an interesting thing because it brings two things into the mouth: the soup and the air above the soup, which is where a lot of the flavor is. 

Dan Pashman: And are you actually cooling the temperature of the soup when you slurp? 

David Hu: Well, I actually kind of like getting my mouth burned, but that's kind of a masochistic thing. 

Dan Pashman: That'll be for another episode. [LAUGHS] 

David Hu: Yeah, I don't think it tastes good unless I come back with an injury. 

Dan Pashman: Full contact soup consumption.  

David Hu: So. I mean, you notice when it's really, really hot, like, when it's almost still boiling, you still want to take a little, and you can still drink it. Like, if I have a boiling, a soup that's still boiling in front of me, I can actually take tiny little sips. And what I'll do is just change the ratio of the air to the liquid. The thing is, our lungs are really powerful. We can bring a lot more air than soup, so you can imagine, you know, when you exhale, your lungs, you have this whole liter full of air that comes out. You can really use all that air, and basically the heat from the soup will get absorbed into the air, and the soup will go down in temperature, not so that it's cold, but just so that you don't get burnt, which is this threshold at which the cells in your mouth just don't like it anymore. Slurping soup is kind of like beginner level slurping. Slurping noodles can be highly dangerous. So, it really is more for the advanced, advanced learners.  

Dan Pashman: So, really I guess the issue is that you're slurping in a noodle and depending on a variety of factors, that noodle can more or less fishtail. The end of the noodle will wiggle around. 

David Hu: That’s right.

Dan Pashman: And that can spray whatever is on the noodle all over you and everyone you're eating with if you're not careful. 

David Hu: You could create a, basically, mealtime disaster. 

Dan Pashman: That's right. 

David Hu: Especially with little kids, right? 

Dan Pashman: I was just going there. Totally. Do your kids slurp their noodles?

David Hu: They really like slurping noodles. So we're Chinese, so our noodles don't have that much sauce. If they were Italian, I mean, it could be, it could be really dangerous. 

Dan Pashman: Why? What's the difference between an Italian-style noodle and a Chinese-style noodle that makes the Italian one more dangerous? 

David Hu: It's not so much the noodle, it's with the weaponry that covers the noodle.

Dan Pashman: The sauces.

David Hu: Yeah, because it basically goes ballistic. [LAUGHTER] So, things are fine if you do it slowly. But, let's say you are in a rush, and you do it at high speed. So your lungs, when you sneeze, you can actually generate air flows that are like 25, 50 miles an hour. You can generate really high speeds. It's a powerful weapon, your lungs. And you're applying all this force onto this tiny little piece of flexible spaghetti. So if you were bringing in sort of a stiff rod, it wouldn't be a big deal. It's the flexibility of the spaghetti that makes it a weapon. So you bring this in, and you imagine your slurp, this noodle, is like a foot long, and it starts slowly because you want to start carefully, and your mouth is lubricated so it actually has very little friction. It comes in at pretty high speed, but it also accelerates. It gets faster and faster. And moreover, the remaining part of the noodle that's outside your mouth gets shorter and shorter. And so, as a result, that smaller and smaller part gets higher on higher acceleration, and it starts really getting fast. And when you have high speeds applied to really flexible objects, they start generating what we call instabilities, whipping around. So it might be flapping just a little bit as it comes in, but by the time it gets to halfway its length, it flaps at a higher frequency and a higher amplitude, and the last three inches, it's just going all over the place. It's like, you might even hit your own face with it.  

Dan Pashman: [LAUGHS] So, how exactly does the thickness of the sauce determine how much splatter you're going to get? Why does thickness matter? 

David Hu: So the thickness — engineers call it the viscosity. And like, honey has a really high viscosity. Water has low viscosity. And it tells you how much it clings to stuff. If you're eating really thin sauce, when you pick a noodle up out of the bowl, it doesn't have that much on it. But. If you, I don't know, want to eat something with thick sauce, you could have more, sort of, debris on the noodle as you're sucking it in. You could have enough, you know, sauce on a noodle that could fill a whole spoon. It's like taking a spoon, holding it back, and just flicking it at the table. And that's the danger of thick sauce. 

Dan Pashman: Is there another, like you talked about how the noodle, as you slurp it in, and it becomes shorter and shorter because less and less of it is outside your mouth, it will increase in speed. You have more velocity, which increases instability. 

David Hu: Right. Yeah.

Dan Pashman: So is there something I can do with the speed at which I slurp to reduce that sort of fishtailing effect that you get with the very end of the noodle? 

David Hu: The easiest one is you could just eat shorter noodles. Now, when you have a longer noodle, you're just pulling it in and it just gets faster and faster. So if you had basically noodles that were half the length, I mean, this is not that much fun, right? It's only fun when you can actually endanger yourself. But you can imagine…  

Dan Pashman:  Do you tell your kids that? 

David Hu: No, no, they're not old enough. If I told them that, it would be havoc. It's only because we're professionals.

Dan Pashman: Right, no, naturally, no. 

David Hu: You can also imagine having pasta that's long and skinny on one end and then really heavy on the other end. If you basically slurped in the skinny end, it wouldn't flap around because it would basically, you know, while this spaghetti's trying to break the speed limit, it gets heavier and heavier. Your sort of kinetic energy, the energy that you're putting in to whip this thing around, can't compensate for the fact this thing is getting sort of thicker and heavier. So that, I don't think, would also be so dangerous because then, while you're accelerating it, it just doesn't, it can't lift off your own plate and go airborne. 

Dan Pashman: I feel that when I slurp, I often end up with air going into my stomach. And then that fills up my stomach with a lot of air over many slurps, and I get a similar phenomenon that I get if I drink soda, which is that you sort of feel full and bloated, and then you may burp and release that air, and then suddenly realize that you're more hungry again, and that you could have eaten more. You could have had more soup, and then you didn't. That's something that I call slurper's remorse. Is there any science to back up this condition that I've identified?

David Hu: So, our lab, we've been studying the digestive system. So, the process of peristalsis probably, it will not allow air to go down. It really is pretty good at getting, getting just the food. The epiglottis is also good for only getting air down the lungs and not, not food. So, it's a pretty finely tuned process. I mean, I can imagine if you eat very fast, you could start to get confused. And I think that's what happens when you get this... What was the technical term you said? 

Dan Pashman: Slurper's remorse.

David Hu: I mean, you also notice you can only eat so fast because these muscles have a maximum speed. They can only really contract so quickly. 

Dan Pashman: Okay, so, so if I feel like I'm getting slurper’s remorse, it's not the slurping that's at fault, it's my own just eating too fast. And maybe if I slow down, then the systems will work better.

David Hu: That's right. 

Dan Pashman: Alright, well, Dr. David Hu, enjoy that next bowl of soup. Don't burn your mouth too badly. 

David Hu: Thanks, it was great being on the show.

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Dan Pashman: That’s Professor David Hu from Georgia Tech. So is there a right and wrong way to slurp? There’s a recent study about how you breathe when you eat, and how it affects taste. Here’s the bottom line. If you breathe at a slow, steady pace while you eat, aroma from the food in your mouth will naturally waft up to your nose, and you’ll smell it, and your taste sensation will be heightened. But, if you eat too fast and you start gasping or gulping air, you’ll suck those aromas down into your stomach before you have a chance to smell them. On the other hand, if you take super slow and shallow breaths, there won’t be enough air flow to bring the aromas up to your nose. So the key in breathing and slurping is the same – moderation.