Transcript: Chef Secrets The Science Of Cooking

TITLE: Chef Secrets: The Science of Cooking (2021) | Full Documentary CHANNEL: PBS America DATE: 2026-02-25 ---TRANSCRIPT--- Narrator: If science teaches us anything, it’s that experiments often fail. And cooking is one giant kitchen experiment. (alarm beeping) Understanding how cooking transforms food can help us make our dishes delicious. So, we’re turning to some of the world’s top culinary experts… I am an ice cream scientist. I have a PhD in mashed potatoes. Narrator: To find out why science is the secret recipe…

Buzz it up.
(whirring) Narrator: To becoming a better home chef. Having a better understanding of the science that you use in cooking makes you cook smarter. Narrator: On the menu? Appetizers, entrees, sides and dessert… Mmm. Narrator: As these master chefs reveal inside tips… See that? Narrator: To help us sharpen our kitchen skills… With sizzling chemistry… Male chef: Molecular orgy. (laughing) Narrator: Mouth-watering microbes… The yeast is, like, whoo-ee. Narrator: The power of heat… That is one red hot chili pepper. Narrator: And frozen perfection. I have the coolest job in the world. Narrator: Preheat your ovens as we cook up some scrumptious science. Deep in the English countryside, Vanessa Kimbell is in the midst of a lifelong love affair. Vanessa: I did fall head over heels in love with bread in southwest France when I was a little girl. I was clambering out the window at about 2:00 in the morning to go and help the local baker. It’s so, so nice to do this. Narrator: For the past few decades, she’s been in an exclusive relationship… …with sourdough. It’s about connecting your hands, your heart, your mind. Treat your sourdough like a lover. Narrator: Vanessa is so passionate, she’s pursuing a doctorate in nutritional science. She’s been teaching her sourdough secrets for more than a decade, and now, this ancient bread is experiencing a renaissance. Vanessa: It was very telling during the pandemic that everybody went sourdough-mad. When we were asked to stay quietly at home, we all wanted to connect to our most basic food. Narrator: Basic, but any way you slice it, this is no run-of-the-mill, mass-produced loaf. Sourdough is the tangy result of one of nature’s original cooking techniques, fermentation. Vanessa: The bacteria that do the work to ferment the bread, they’re on your hands, they’re in the air around you, and they’re on the grain that you make your bread with. Narrator: If you give them a warm, comfy home, teeny organisms like lactic acid bacteria and wild yeast can transform raw ingredients into a whole new food. Vanessa: What you need is flour, salt, water, microbes, time, and confidence in something that’s utterly invisible. (laughing) Man: What you’re doing is essentially letting microbes have their way with whatever the ingredients are. When that goes badly, it’s spoilage. When it goes well, it’s fermentation. Narrator: Harold McGee is the author of On Food and Cooking, the science-based bible for everyone from master chefs to home cooks. Harold: The fascinating thing to me about fermentation is what an amazing transformation it is. When you take something like flour and water and just let it sit around for a few days and it does it by itself, that’s magical. That’s like alchemy. Narrator: The magic begins right from the start. To make sourdough bread, you need a starter. So, how do you capture those wild yeast and lactic acid bacteria? Well, you start with a sterilized jar, because you do not want to be cultivating pathogenic bacteria. And you simply need some organic flour… And warm water. And it’s as simple as that. Narrator: It may seem simple, but starters need a lot of attention. In fact, some people get so attached to their starters, they name them after family. If your starter isn’t optimally nurtured, you’re going to make terrible bread. (laughing) Narrator: That’s because fermented food, whether it’s sauerkraut or sourdough, is alive, and like any living, breathing community, it needs to be fed. Over the next two or three days, you’ll empty half of it out and replenish it with more water and more flour. Narrator: To freshen up your starter, you have to get rid of some of it first. Seems a bit cruel, doesn’t it? But it’s the only way to activate the bacteria and yeast. Vanessa: Wild yeast is any yeast that is not cultivated by an industrialized system. Narrator: These tiny fungi produce carbon dioxide, which is what makes dough rise. But first, how do you know if your starter is ready? If your sourdough starter is ready, it’s going to float. And there we are. Narrator: When a starter fails the float test, the goop goes straight to the bottom. That’s a sign that the yeast isn’t producing enough CO2. You can modify the way that you treat your starter through the kind of flour that you’re giving it. We’ve got, um, the stone-ground diversity blend here. It smells just like a meadow. Narrator: Vanessa’s starter may be ready for the next step, making dough, but the microbes’ work has just begun. And importantly, I’m going to use my water. It’s nice and warm. If I put all of the water into this at once, I’d basically be making a sourdough soup. This is where the party starts. You’ll find recognizable patterns of wild yeast and lactic acid bacteria gathering together and clustering, and they kind of work together. Right about now, they’re absolutely having a party and reproducing. They’re doubling every 20 minutes. Narrator: That party is a bubbling brew of activity. Bacteria produce the acid that gives sourdough its delicious tangy taste, and they use enzymes in the flour to break down starches into sugar, as a sweet treat for the yeast. And the enzymes, they’re so busy right now. They’re like Edward Scissorhands, and they’re chop-chop-chopping everything up. So, the yeast is, like, “Woo-ee! I’ve got sugar.” And the more yeast there are, the more carbon dioxide they make; the more carbon dioxide they make, the bouncier and more open your crumb structure, and the more likes you get on Instagram for your bread. Vanessa’s breads are gorgeous, delicious, and according to the latest research, could be easier to digest. She wishes she’d known that in her 20s, when she became seriously ill and her life changed overnight. I had an operation. I was given some antibiotics, and within 24 hours, I couldn’t eat bread. So I had to give up being a baker, give up everything I loved. Narrator: Until a few years later, when she visited the village baker in France. And he pushed this warm sourdough into my hands. And before anyone could stop me, I had literally devoured half of it and I braced myself to be really ill. And then slowly but surely, I was, like, “Oh, I’m okay! I can eat bread!” Two, three. And I wanted to understand why the bread that was long, slow-fermented in the village bakery in France was so different to the fast-yeasted bread in the UK. What you’re going to see is that while I’ve walked away from it, it’s become shiny and the gluten has really started to form. Narrator: Gluten? Isn’t that a dirty word these days? The protein found in wheat that gives some of us a stomach ache? So, there’s a lot of gluten-bashing that goes on. But without the gluten, you simply cannot capture these incredible holes that you get in this bread. Narrator: Gluten traps the gas bubbles and binds the dough. But in sourdough, acids actually break down the gluten, making it easier for some of us to swallow. Vanessa: The degradation of that gluten is actually one of the things that makes the bread more digestible for people who have non-celiac gluten sensitivity. Narrator: Bakers can strengthen the dough by giving it a little stretch. What you can do is a maneuver called a stretch and fold. No, that’s not a yoga maneuver. I’m going to lift the dough over and fold it four times. There we go. And you can actually see, just from that, the dough has now become recognizably bread dough. Narrator: But for the bacteria and yeast, the party isn’t over yet. Vanessa: A Dutch oven for the domestic baker is essential. You want to generate a lot of steam around, and what steam does is it keeps the dough soft. That fermentation continues in the oven, and the CO2 and the warmth kind of lifts it open. Narrator: It takes a while for sourdough to rise to the occasion. In the meantime, let’s move on to a popular starter, a simple green salad. All you need to do is dress it up with a little oil and vinegar. But why won’t this salad dressing behave? I’m going to start by adding some vinegar to this bowl. Narrator: If anyone can get to the bottom of it, it’s Nik Sharma. He’s a molecular biologist, and he writes bestselling cookbooks based on science. Now, it’s important to remember that both vinegar and olive oil are the worst enemies in the world. They’ll do their best to stay apart. Narrator: Vinegar is basically acid and water, and we all know oil and water don’t mix. Nik: They hate each other. They’re foes and they’ll move away from each other. Narrator: It’s all about the laws of attraction. Water molecules are made up of hydrogen and oxygen, polar opposites. Hydrogen atoms have a positive charge, and oxygen, negative. They can’t wait to bond together. But a fatty substance like oil has non-polar molecules that will stick to themselves and repel water. Using your own energy, you can play matchmaker and force these two stubborn liquids into a marriage, but it won’t last long. What’s happening when you whisk is that the olive oil and the water are being broken into small droplets, and the olive oil gets surrounded by droplets of the water. But if I leave it to stand for a couple of minutes, it’s going to come back to its two separate phases. Now, we’re going to make this vinaigrette again, but we’re going to add one new ingredient. We’re going to add mustard. Narrator: Adding mustard changes everything. It’s an emulsifier, a substance that coaxes two ingredients to get along. Nik: Whole-grain mustard has an extra advantage because of the whole seeds. They carry a substance called mucilage, which is a carbohydrate. And that acts as the molecule that holds the vinegar and the oil phases of the vinaigrette together. Narrator: The mucilage has one part that loves fat and another that loves water, ultimately coating the droplets and keeping the mixture together. Nik: You could use egg yolks, and you can also use honey. And it’s going to form a thick, creamy emulsion. Harold: So, oil is oily. Water is watery. But if you make an emulsion of the two, then you end up with something that’s creamy. Narrator: Now that the oil and vinegar are back together, it’s time to check in on the sourdough. Vanessa: So, this is the exciting bit. I’m going to take the lid off and see what happened. And there we have it. A beautiful sourdough loaf. Narrator: Mmm. Freshly baked bread goes quite nicely with a sizzling entree. So, we’re heading to Texas. Houston chef Nick Wong has quite the culinary cred. He’s worked at top New York restaurants like Momofuku and Gramercy Tavern, and has a degree in nutritional science.
(sizzling)
That’s a good sound. (laughing) Narrator: But maybe it all comes down to this. I’m a fat kid that likes to eat. (sizzling) I started cooking from a very early age. Narrator: Lesa Tran Lu teams up with star chefs like Nick to teach the chemistry of cooking at Rice University. Girl: Can I have a cookie? I know. Look at that. Narrator: She’s a scientist, not a chef, but she grew up in the kitchen. Lesa: Culturally, food is, you know, a central part of our family. When my parents came as Vietnamese refugees, they worked really hard. You know, I barely saw them as a child. That forced me to learn how to cook myself, at a very young age, and feed my brothers and me. What really kept us together was the food. I almost dropped that on him. We are making some Vietnamese-style short-rib fajitas. Narrator: Tex-Mex dishes are a staple in Houston, but Vietnamese fajitas? Nick wanted to create a recipe that honors Houston’s vibrant cultural melting pot. It is a mouth-watering example of the Maillard reaction. (sizzling) The Maillard reaction is arguably the most interesting and the most amazing, I think, of all reactions in chemistry and in cooking, because it really does create all of those nutty, roast-y, umami flavors that we love so much. (sizzling) It really starts ripping at around 300 degrees Fahrenheit, about 150 degrees Celsius. (sizzling) And that’s the sound of the Maillard reaction happening. Yeah. Narrator: This sizzling science is named after a French chemist who first described it a century ago. It’s the reason why browning food at high temperatures becomes a taste sensation, and it’s a reaction that pops up everywhere, from toast to roasted marshmallows, coffee, even beer. It’s like a chemical explosion of flavor. (sizzling) Right as you actually sear the meat, you’ll start activating protein, sugar and the heat, all reacting together, that will then decompose and re-react and decompose again, to yield you hundreds of different types of flavor, aroma and color molecules. So, we can kind of start to see around the edges. Lesa: Yeah, yeah. Nice and brown there. Nick: Brown. Narrator: Whoa! All those molecules moving around, mingling, bonding, breaking up, and then doing it all over again? No wonder one chef calls it a molecular orgy.
(laughing)
Nick: Molecular orgy? Harold: And that’s actually a great description. I wish I’d come up with it. Energy is agitating the molecules. It’s exciting them. It’s making them crash into each other with greater and greater force. What that ends up doing is essentially messing up what’s inside, but in a good way. Narrator: As for these short ribs, they have to spend the night chilling out with a marinade. We have some honey, fish sauce. Lesa: Fish sauce is essentially fermented runoff from anchovies that we use in Vietnamese cuisine for that umami salty flavor. Nick: Basically, all we’re going to do is just kind of rough-chop everything, and then we’re just going to throw it in the blender and buzz it up. (whirring) Lesa: Marinating is really simple. It is the process of soaking your meat into a bath of all sorts of flavorings for a few hours. Salt and acid actually open up the proteins of the meat, kind of like a sponge, so that it actually absorbs some of that flavor molecule mix. Narrator: Since the marinade has a higher concentration of salt than the meat, the particles spontaneously move over to balance it out. That process is called diffusion. Lesa: Much like how we were able to smell the aroma of a perfume from across the room, when you cook off the meat, that hits our nose, and that’s what makes us start salivating at the very thought of what fajitas are like. Narrator: At the restaurant, Nick uses a fancy technique called sous vide, which essentially immerses the meat inside a vacuum-sealed bag. But for home cooks, you can just wrap it in plastic. Nick: So, the next step is we’re just going to marinate this overnight. Every molecular orgy deserves its own nice little massage, so… Lesa: Absolutely. (chuckling) Narrator: Another way to intensify flavor? Bringing out the sweetness of onions. (sizzling) Lesa: That’s smelling so good. Nick: So, anytime you see brown, you’re probably in a good place. Yeah. Golden-brown delicious is a thing. Oh, yeah. Look at that. Narrator: Caramelization isn’t exactly the same as the Maillard reaction. It’s more like a hot close cousin. Lesa: Both types of processes give us really yummy flavors, but caramelization is just really the sugar decomposing in the presence of heat with a little bit of water. And here’s a little bit of a pro tip. And I don’t know, Nick, whether you know this. Add just a smidgen of baking soda. It will cut down that cooking time, I would probably say, by threefold. Narrator: Baking soda adds alkalinity. By adjusting the Ph balance, the Maillard reaction will speed up, too. So, Lesa even adds a pinch of baking soda to turn a turkey crispy golden brown. Lesa: Having a better understanding of the science behind the food and the methods that you use in cooking makes you cook smarter. Again, this molecular orgy… Yeah. …is happening now at a higher rate. A lot of layers here. A lot of layers. Narrator: And things are about to heat up again for Nick’s marinated short ribs. After roasting in the oven for about an hour, it’s time for the test. Nick: And we’re going to check the texture of it. If you don’t have a cake tester and you want to get kind of fancy, a bent-out paper clip also works. So, all we’re doing is we’re going to insert it in and there should be no resistance.
Narrator: And then…
(sizzling) There’s that sound. …a final flash in the pan. We’re trying to really enhance that Maillard reaction. Narrator: But don’t turn it up too high, or you risk turning browning into burning. Nick: And then, that’s it. Harold: We have these senses of taste and smell to be stimulated. The more molecules there are for us to sense, I think the more pleasure we get out of it. Thank you. This is so good. (laughing) Narrator: That looks tempting. But many of us are trying to cut down on meat and eat more fish. Smoked salmon is a tasty option. But if you’re a novice, you might need some tips. And who better to ask than the experts who have been smoking fish for thousands of years? (woman singing in Indigenous language) Narrator: Wet’suwet’en territory, near Canada’s western coast. (singing continues) Narrator: It’s a traditional welcome for the Bear clan as they enter a feast. (drumming) Seems fitting for three generations of chefs. Man: I’d like to introduce Gulughan, the bear that sleeps all winter, my matriarch and our teacher, Rita George, and my mom, the best chef in the world. Right? (laughing) Narrator: Andrew George learned how to cook on a wood stove, and out in the bush. Now, you can see the oils bubbling away here. Those are really, really healthy for you. So, that’s the omega-3 oils. Narrator: As a professional chef, he’s made award-winning meals for everyone from Olympic athletes to US presidents. Andrew: I’ve been a Red Seal chef about 32 years. Getting old. (laughing) Narrator: But the training he treasures most is right here. Andrew: The way of life of the Wet’suwet’en is learning how to read the seasons, how to read the trees. This particular plant is known as wild celery or cow’s parsnip. In our language, it’s called “kos.” When the flowers first turn white, that’s when we know the fish are going into the rivers. Salmon plays a very integral role in our life, in our diets. It identifies who we are. We’ll see if we can catch your grandma a salmon here. Narrator: Andrew’s son Drew is a rookie cook in Vancouver. Andrew: Today, he’s an apprentice in the bush. Narrator: And today, he’s going to learn how to smoke and preserve fish, to preserve a way of life. Andrew: Our resources are disappearing. Our salmon are disappearing. So, transferring that knowledge to my son is very critical right now because it is a science. Ah, missed. The information I’m transferring to Drew here goes back seven generations. I like to say it is “culture on a plate.” Narrator: Culture, sustainability, and natural science. Andrew: So, this is poplar, which is quite light, so it’ll actually soak up the water. Narrator: The type of wood affects flavor and the temperature of the smoke. Andrew: Get it ready for the smokehouse. That keeps it at a nice cold smoke, and it’ll last for a long, long time. Narrator: But first, Rita has to prep the salmon, a skill passed down from her parents and grandparents. Rita: And then, you start cutting down against the bone. Andrew: If you look at our elders, they’re professors of the land. They didn’t go to school for that. They didn’t get a certificate. They were raised out here through oral history. Rita: What our ancestors taught us, we don’t throw away nothing. And make sure that, once we hang it in the smokehouse, we have a little tiny fire going. Smoke, so that the flies or nothing gets onto it. Narrator: Hanging the fish in strips helps it dry properly. Make sure they’re apart a little bit, so that the air can get through them. Not too close together. There. Andrew: So, you can see, Drew, the fire is not that big, eh? Drew: Wow. There’s no heat. Narrator: It may seem counterintuitive, avoiding heat in a smokehouse, but that’s exactly what they want. See that? It cools down once it gets up to here. Narrator: It’s called cold-smoking. By controlling the fire, they can slowly dry the fish while killing off harmful bacteria. Rita: If you put too much fire to it, all this will just get really soft and they’ll start falling because there’s nothing to hold them together. Andrew: You always got to monitor the heat, because the last thing you want to do is cook your fish. Narrator: These dried strips can last for months. Drew: This is the food that would sustain us through the hard winters, when we’re not able to catch fish. Yes. Drew: So, this is how we’d feed ourselves. Yes, exactly. And if you look at all the ventilation in this, it allows the air to come through here and that’s actually what dries this; it’s not the smoke. Narrator: Smoke is a signal of incomplete combustion, a fire that doesn’t have enough oxygen to burn off all the wood. And where there’s smoke, there’s flavor. As tiny unburned particles lift skyward, the chemicals break down into the compounds that make food smell and taste delicious. Rita: And this is the part, the backbone. You dry it really nicely. And some people, when it’s dry, they dip it in bear grease, and I love it with butter. Andrew: So, when you’re in a modern kitchen doing your stuff, this is called charcuterie. You can use this in a banquet. You can taste that. See the oil on that, Drew? See?
Thank you.
Oh. Andrew: This is heaven. Drew: Wow. My mom does not look 80 years old because of her diet. It’s the berries, the salmon and how it’s handled that keeps her young. That’s the importance of what we do. Well, Grandma, did he pass? Rita: He did. And I want to tell you, Drew, what you learned today, it’ll be with you the rest of your life. We can live in New York, but this is your home, to prepare this. You’ll never, ever get this in anywhere, except with the Aboriginal people. (drumming) (woman singing in Indigenous language) Drew: It’s my treat with my grandma. So, thank you, Grandma, for showing me this. (speaking Indigenous language) Rita: I love you very much. Well, thanks, Grandma. Andrew: Another generation taught. (drumming continues) Narrator: From the science of smoking… …to mastering the mash. I have a PhD in mashed potatoes. Narrator: As a culinary consultant, biochemist Ali Bouzari develops new dishes for some of the trendiest restaurants in California. Ali: Basically, I help those chefs figure out whatever crazy idea they have in their head. How do you actually make it into food? Coming from a half-Iranian, half-Texan family, it was this strange mix of authentic Persian food alongside just a lot of Happy Meals. Narrator: That love for food led him to become a culinary scientist. I think I went through 20,000 little Yukon gold potatoes over the course of four years of grad school. Basically, I wanted to map out how does the tissue of a potato shift and change during cooking, and how to make mashed potatoes with the best possible texture. Narrator: The ideal texture is in the mouth of the beholder. Some swear by fluffy. Ali craves creamy. Either way, transforming a potato into a spoonful of gooey goodness involves some heavy-duty chemistry. Zoom in to a potato and you’ll see what looks like a cobblestone wall. Each of the stones is a potato cell containing dozens of tiny, pebble-shaped starch granules. Ali: And they’re like a jack in the box, like, this coiled, tightly wound ball of starch. Narrator: Each one is cemented in place next to its neighbors with pectin, a compound found in fruits and vegetables known as nature’s glue. Pectin is sort of like grout. It’s keeping the tiles, keeping the bricks all in place. Narrator: Until the potato gets cooking. Ali: Water starts to weasel its way into all the little cracks and crevices, which causes things to start to dissolve. Heat starts coming in, causing things to get loosey-goosey. Narrator: As the wall starts to crumble, the starch granules make their escape, expanding like a balloon and releasing the molecules that determine consistency. Mashed potatoes, like most cooking, is all about demolition. And the way that you demolish that wall will dictate what kind of experience you’re going to have with the mashed potato. Narrator: The more starch that escapes, the heavier and creamier the potatoes. Here’s where it gets sticky and tricky. Ali: Those starch granules can also explode, like just a confetti cannon of starch and just spray starch all over the place. When that happens a little bit, the confetti of starch that’s sprayed out kind of just dissolves in the background, and you get this really nice creamy smoothness. If you have too much of it, they create this webby network that feels gummy and sticky. Narrator: So, to keep some of the starch cells intact, Ali uses whole, unpeeled potatoes. Cutting and peeling them liberates more starch. Ali: I found that boiling potatoes with the skin on, the small controlled amount of water that’s able to pass through the skin is the perfect amount. So, you have your fully cooked, lovely mashed potato in waiting. I think most mashed potatoes go wrong at this stage in the game. Narrator: Pummeling your potatoes with a hand masher is a no-no, at least for Ali. Ali: Using a tamis or a food mill with a little crank, it allows you to kind of sift all of those cells apart, so that in the pot, you end up with a mixture of intact whole cells, some starch that has trickled into the corners and made things creamy. But otherwise, things are pretty organized and pretty delicately demolished. If you have a pasta strainer that’s just fine mesh, that will work just as well. At this point, the ultimate best friend in your quest for making mashed potatoes as smooth as possible is a rubber spatula. It’s like a supportive lover. It’s there to push you where you need to go, but never cause too much friction. And we’re going to start adding a comical amount of butter. Every scrap of starch that’s in this pot is pulling its weight in binding up all this butter. So, that’s usually what I’m looking for, is you can just kind of see ripples. It’s almost like really under-whipped whipped cream. So, it should kind of just disappear in your mouth. Uh-huh. We did it. Mashed potatoes. Narrator: Now that we’ve got the secret to silky spuds, we can move on to a more ambitious side dish and add a little spice. These are really hot. They’re tiny, but really hot. Narrator: Nik Sharma creates world-renowned recipes… This is a guava tree. …rooted in new flavors and old favorites. And guava is a soft, creamy, you know, really good tropical fruit. I grew up eating them in India, which is why I have them here. It’s important for me to reflect my heritage in cooking because in many ways, food is an expression of who I am. Today, I’m going to make a roasted eggplant dish and use heat to bring out all these flavors in the dish. I like to cut the eggplant in large chunks because you get much more of a meatier texture. Vegetables aren’t really bland. It’s how we transform them. Just toss it together. Narrator: And he’s about to transform this eggplant by playing with fire. I actually didn’t grow up appreciating hot food a lot. In fact, I still can’t handle a lot of heat in my cooking. My dad, on the other hand, he takes fresh green chilies and he’ll pop them into his mouth and eat them directly, kind of like a side dish with every meal. Narrator: So, to spice things up just a bit, Nik makes his own special sauce, combining cool yogurt and hot peppers. Nik: To start off, we’re going to use Greek yogurt. One of the reasons why we’re making this sauce is because it’s a fantastic way to not only play with flavor but also with a sensation called chemesthesis. Narrator: It’s a fascinating phenomenon, based on how our bodies and our brains respond to fiery foods. Nik: When you eat food, the receptors that cover the surface of our mouth and even our nose get aggravated in response to chemicals that are present in ingredients like chilies, in ingredients like garlic, onions and even ginger. They all contain certain molecules that provide a sensation of heat. The next ingredient that goes in here is a green chili. I’m using a hot green chili. You can use something that’s milder if you prefer less heat. Narrator: Have you ever tried eating a chili pepper? It’s painful. Your eyes water. Your throat burns. It’s an edible inferno. Nik: What makes chilies spicy, or rather fiery, is this special molecule called capsaicin, which has the ability to aggravate our pain and thermal receptors. Woo! Narrator: That’s one red hot chili pepper. Harold: The receptors respond to touch and to temperature and to pain. And so, put all those three things together and put them in overdrive, which is what capsaicin does, and that’s what gives us the sensation of hot peppers. Nik: It sends a signal from these receptors through the nerve endings, directly to our brain. The brain then decides what’s happening, and it tells you, “Ooh,” you know, “it’s hot,” and it’s causing you pain. Woo! Your mouth is on fire. Or is it? Nik: It’s all an illusion. The capsaicin comes into contact with these receptors, and this tricks the brain into sending a signal that tells us our food is hot, even though it’s not actually a rise in temperature. (whirring) That’s good. Narrator: Nature designed it that way. It’s a plant survival tactic. Harold: The thing about vegetables is that they’re stuck in the ground. They can’t move. So, they can’t run away if an animal saunters over and decides to take a bite. So, they generate lots and lots of chemicals and use them essentially as weapons in chemical warfare, to discourage animals from taking bites out of them. Narrator: Birds, which disperse the seeds, can handle capsaicin. They lack sensitive nerve endings, so they don’t feel the burn like we mammals do. Nik: Now for the final touches for this dish. Narrator: Luckily for us humans, nature also has a solution. Be generous with the sauce, because this is what carries all the flavor. Narrator: Dairy. Yogurt is an integral part of spicy Indian dishes, and it’s not just because it’s so tasty. Milk contains a protein called casein that surrounds capsaicin molecules and washes them away. Nik: It’s kind of like soap and dirt. When you wash things together, they bind and they move away. Oh. Narrator: But what if you still can’t stand the heat? Do you have to get out of the kitchen? If you want to train yourself to eat hotter foods, you can do a couple of different things. Mmm. First, start off with less. Cut the chili along its length. When you do that, discard the seeds and the midrib. Those are the places where capsaicin is the most concentrated. You’ll cut back on some of that heat. The other thing that you can do is start to slowly eat more chili every day. This is absolutely delicious. Over time, you’ll start to notice your body adapting to how much you can handle. Narrator: Chemesthesis is also the reason why fresh mint seems cool, cinnamon makes you feel warm, and fresh lemon makes your tongue tingle. and onions launch an all-out attack. Harold: It’s a bomb. It’s going to go off the moment you begin to cut into it. Cooking happily defangs them, but the raw, wounded, angry onion is another story. Narrator: Harold McGee has spent decades peeling away the mysterious layers of this vicious veggie. Harold: Onions are the grizzly bears of the vegetable world, you know? They’re fierce defenders of themselves and especially of their offspring, and so they generate very potent chemical weapons, potent enough that the fumes can make you cry. Lots and lots of sulfur compounds are coming out from the cutting board up into the air, up into the nose, up into my eyes. Narrator: When those molecules land in your eye, they dissolve into sulfuric acid. Wow. And now it is really getting obnoxious. The more cuts that you make, the more cells you damage and the more cells you damage, the more these potent volatile molecules are going to come out of the tissues. Narrator: Cooking shouldn’t be such a battle. So, how can we build up our defenses? I actually find it a kind of cathartic experience, so I don’t mind it at all. But you can wear goggles. The other thing you can do is just chill the onions down before you chop them. So, when you do that, you kind of slow the metabolism of the onion more than if the onion was at room temperature. Narrator: Remember, when it comes to cooking, you are in control of the outcome. It’s all about trial and error, just like science. We’ve got one single egg. Ooh! That did not go well. With any lesson in life, you learn so much about yourself and about the process through the mistakes that you make. Narrator: Chemist Lesa Tran Lu loves to bake. There’s only one recipe that’s off-limits. Lesa: My parents owned the only fortune cookie factory in the Houston area. I was known as the fortune cookie girl when I was growing up. So, to this day still, I am just sick of fortune cookies. Narrator: So, in Lesa’s family, the go-to cookie is chocolate chip. For me personally, the perfect chocolate chip cookie is chewy and gooey and a little bit cakey and only crispy on the outside, not throughout. Narrator: The challenge? Finding the right formula for chewy and gooey. Lesa: My number one tip to the home baker is to really take the time to think like a scientist. And what I mean by that is that I want you to think critically about how a recipe can be changed up. Narrator: So, Lesa experiments with a single ingredient at a time. Lesa: Change one thing about it. Make some observations and make a conclusion and incorporate that into the next iteration of that recipe. Narrator: Take flour, for example. What happens if she substitutes some of the all-purpose flour with bread flour or cake flour? Lesa: The primary thing that you’re changing throughout those different types of flours is the protein content. Narrator: The more protein, the more gluten, which helps create taller cookies. So, look at that. They’re nice and puffy. Narrator: Then there’s sugar. While most recipes call for white and brown sugar, Lesa goes one step further. What’s unique about the recipe that I developed for myself is that I’m actually going to add not only light brown sugar but also dark brown sugar. The main difference is just how much molasses is in each type of sugar. Processed, refined white sugar doesn’t have any molasses added into it. And then the darker you go with the brown sugars, the more molasses you have. There’s plenty of flavor compounds and color compounds. And so by adding these types of sugars, you’re going to make your cookies even tastier but also softer, since molasses attracts water very well, which will ensure that your cookies are nice and chewy and moist. Narrator: Thinking like a scientist is about more than just ingredients. Lesa: I allowed my cookie dough to rest in the refrigerator for a couple of hours, to make sure that the flavors really mingle with each other. And then it really does allow for the cookie dough to be cold when it goes right into the oven, to make sure that your cookie stays tall, which again will give that chewy, almost cakey texture to it that I love so much. Narrator: According to a consumer survey, there’s only one dessert more popular than chocolate chip cookies. The treat called chemistry in a cone. Maya: I have the coolest job in the world. I am an ice cream scientist. Narrator: Maya Warren has done a lot of cool things, from earning a PhD in food chemistry to winning a top reality show. Maya: I was on The Amazing Race with my former lab mate, who’s a candy scientist, and we were deemed the Sweet Scientists. Narrator: Now, she’s on another adventure, testing and developing flavors for SMiZE Cream, a new ice cream company. Maya: Ice cream is literally my life. When I was a little girl, I remember getting an ice cream maker that was like an Easy-Bake oven and ripping open the package and mixing it all up. Bright-eyed, bushy-tailed, six-year-old little girl, just so incredibly elated that I made my own ice cream. And I’m here to tell you, it was not very good. I’ve definitely learned a lot along the way. Narrator: One of the key lessons? Every spoonful requires a serious topping of science. Maya: When we eat it, we just think about how good it makes us feel, but the science that goes into it is so complex because it’s actually a solid, a liquid and a gas. Narrator: A solid, a liquid and a gas all in one little bowl? That’s called three states of matter, but it’s also a miracle of physics and a bit of a mystery. How does a frozen food end up so soft and creamy? We’re going to make a special treat called no-churn ice cream. You do not even have to have an ice cream machine to make it. It takes really simple ingredients. Narrator: So, here’s the scoop. To make it, you have to understand how temperature transforms a slushy goo into partly frozen perfection. So, I’m adding 1-1/4 cups of sweetened condensed milk. Sugar is one of the most important ingredients in ice cream, because we do not want ice cream to freeze at the temperature at which water freezes into ice. Having sugar in ice cream is very similar to putting salt on the roads in the wintertime. Narrator: Water freezes at 32 Fahrenheit, 0 Celsius. But sugar freezes at a lower temperature, so it slows down the freezing process. Maya: And this sweetened condensed milk makes it so that it’s scoop-able and it’s not hard as a rock. Narrator: Sweet. But you need to add another ingredient to whip it into shape. Maya: Milk fat in ice cream is key. I have two cups of very cold heavy whipping cream. And we’re trapping in air when we’re whipping. Narrator: Whipping the cream causes bits of fat to bang together, forming long strands that resemble a pearl necklace. Those fat beads, called globules, wrap around air bubbles and prevent them from escaping. Air is such a critical ingredient in ice cream. Narrator: Critical because adding air adds volume as the cream turns to foam. That will help create a stable structure that won’t collapse. And what you want with your whipped cream is beautiful stiff peaks, just like we have here. When you have air, it actually helps the ice cream become more fluffy and easier to scoop at frozen temperatures. You do not want to over-whip it because if you do, you will create butter. So, I like to fold it in as gently as possible in order to keep some of that air trapped in. Ice cream allows me to be not only a scientist, but an artist. It is truly a blank canvas. Whether you want cookies and cream ice cream or if you want ketchup ice cream, the sky is the limit. Maya: Honestly, anything with chocolate sandwich cookies pretty much rocks my world. So, we’ve made our final layer with our no-churn ice cream, and we’re simply just going to put a lid on top of it and stick it in the freezer. Narrator: The gas in ice cream and the fats help create a solid structure, but the liquid only becomes partially frozen, in the form of ice crystals. Maya: You do not want them to be too large, because ice can be very coarse. You want your ice cream to be really smooth and creamy. Whether it’s the ice crystals, the air cells or the fat globules, it’s all a balance to make sure that we are getting to the right texture as well as the right flavor, so that when we eat the ice cream, we fall in love. Cheers. Mmm.