The Cookbook Podcast

The Science of Cooking
Every Question Answered to Perfect Your Cooking

By Dr. Stuart Farrimond

Suzy Chase: Welcome to the Cookery by the Book podcast, with me, Suzy Chase.

Dr. Farrimond: Hi, my name is Dr. Stuart Farrimond, and my book is the Science of Cooking: Every Question Answered to Give You the Edge. I'm a science writer, a cook, and a food scientist and a former medical doctor.

Suzy Chase: You are a science and medical writer, presenter, and educator. Plus, if that's not enough, you're a doctor and teacher. Thank you for coming on my podcast to dispel food myths.

Dr. Farrimond: An absolute pleasure, Suzy. Yes, I do like that glowing introduction. It makes me sound very clever.

Suzy Chase: Let's start off with tasting.

Dr. Farrimond: Yes.

Suzy Chase: I always thought-

Dr. Farrimond: The most important bit.

Suzy Chase: I always thought that different parts of your tongue detected different tastes.

Dr. Farrimond: I know. We kind of taught this at school. Well, I always thought this at school. I'd always remember just up on the wall, there were kind of these pictures stuck up of your tongue, and you've got the sweet at the front, and then the ... I think it's the sour at the back, and the salty on the side. I always thought that was true, but it's not true, and if you've ever tried it yourself ... I don't know if you've got something salty. Say like a salty peanut or something. If you put it in your mouth, it doesn't particularly taste exceptionally salty at any particular point. It just tastes salty.

And that's because this whole tongue map thing is a complete myth. It started from ... it was kind of a case of Chinese whispers, where something gets lost in translation. There was a German scientist in 1901 who was interested in the tongue and how different parts of the tongue were sensitive. And in 1901, he published his paper, and on his paper, we did lots of graphs and lots of diagrams. And he showed that different parts of the tongue, in the group of people that he tested, were slightly different in their sensitivity. And he found that, say, the tip of the tongue was slightly sweeter and salty around the edges.

But what he was describing ... these were just subtle differences, very, very subtle differences, that ... He wasn't saying that you can only taste sweet at the tip of your tongue. But unfortunately, an American textbook writer many years later came over his research, mistranslated it, and thought that these were just kind of carefully drawn lines of where your tastes actually are. And so since then, we've thought or believed this lie that this tongue map thing is real.

Suzy Chase: That's crazy, because I do remember seeing the map in school.

Dr. Farrimond: Yes. Well, that-

Suzy Chase: The map of your tongue.

Dr. Farrimond: It's a load of rubbish. I mean, you know this intuitively, if you taste ... if you have a candy, put it in your mouth, it tastes sweet everywhere. There you go. Now you know.

Suzy Chase: Okay. In terms of taste buds, what's the best temperature to taste food?

Dr. Farrimond: Okay. I'll bust you with another myth now, because taste buds ... when you look in your mouth and you feel the little bumps on your mouth, now, you and I normally ... you think, "They're my taste buds," those little bumps on your mouth.

Suzy Chase: Yep.

Dr. Farrimond: But they're not actually taste buds. They're called papillae, which means ... I think it's medical speak. I'm not sure if it's Greek or Latin. Probably Latin, for ... meaning little nipples. And so these are little dimples, if you like, on your tongue. And the taste buds themselves are minute, and they're around ... if you can imagine, around the edges of these little nipples. And they're minute little bundles of cells whose job it is to detect different things that we put in our mouth.

And these cells, these taste receptors or taste buds ... the taste buds are essentially just clusters of these cells. They work best around body temperature, much like everything else in our body is designed to work at about 37 and a half degrees C or 98-99 degrees Fahrenheit. In just the same way, taste works best at body temperature. If you have something that's very hot, you don't taste it as well, and if something's very cold, you don't taste it very well. But when it's kind of warm-ish, that's when you get the most taste from the food, the most flavor.

It's another reason why ice cream has to be super, super sweet. If you ever let ice cream melt, it tastes really, really sweet. And that's because they have to put extra sugar in it and extra sweetener in it, because you wouldn't taste it otherwise when it's frozen cold.

Suzy Chase: Huh. Now, what about with hot peppers?

Dr. Farrimond: Ah, hot peppers. Now, hot peppers ... they are tricking your taste buds into feeling hot pain. There are particular nerve endings, nerve receptors, that are responsible for detecting when you put something scorchingly hot in your mouth, that's kind of hot enough to ... so sort of 50 degrees C hot, or that's actually in danger of scalding your mouth. These nerves, they're responsible for detecting that. But the substances in chili, chili peppers called capsaicin ... and there are other, similar chemicals called capsaicinoids.

They're like a toxin. They go into your tongue, and they latch onto these pain recepting nerves, and they make them fire. And so it feels just ... and it's exactly the same as if you've had something that's really hot in your mouth. If you are serving at a hot temperature, the hot temperature of the food combined with this illusion of scaldingly hot pain will make it taste even worse, or hot. Or if you like chili hot, then that's good for you.

Suzy Chase: Unless we're vegetarian, we're all buying chicken and beef. What should we look for in white meat and red meat at the butcher or grocery store?

Dr. Farrimond: Sometimes, the things that we're taught to look for, especially if you do supermarket shopping, aren't always completely right. We're told to look for very red, pinkish meat and very white fat, but that isn't necessarily good. That isn't necessarily the best thing that you should be looking for. If the fat is slightly yellow, that may well just be reflecting its diet. And likewise, if the meat is looking darker on the edges, starting to look a bit brown, then that may well be just because it's being aged.

Ideally, you need to use all your senses, so you need to kind of ... the same for the red meat and for chicken is to feel it, if you can, or get the butcher to handle it. And white meat, like chicken, will start to get a bit glue-y and kind of tacky. And it should be nice and firm and bouncy, but not kind of ... It doesn't have ... Do you know what I mean, when you get kind of that slickiness on it?

Suzy Chase: Yeah.

Dr. Farrimond: That means that there's bugs growing, basically, so that's a definite no-no, and yeah.

Suzy Chase: If we find beef with a yellow hue, what does that mean it's eating?

Dr. Farrimond: Yellow hue can suggest that it's grass fed meat. What you're seeing is ... there are substances in the grass, in the vegetable diet, that are coming out in the fat. If you've ever eaten too many carrots or you've seen a kid that's eaten too many carrots, they go a kind of orangy color. That's because of all the carotenoids in the vegetables that they're eating. It kind of shows through in the skin. And the same way if your cow is not just eating grain, but is eating a variety of vegetables, and ... not vegetables, lots of grass. Then, that will come out in their fat, and so you have this kind of yellowish hue to the fat.

Suzy Chase: In 2008, you were diagnosed with a malignant brain tumor and had successful surgery, thank goodness. Let's talk about brain food. Why is fish brain food?

Dr. Farrimond: Yes. I don't know exactly where this ... kind of this old wives' tale came from, as fish is brain food. I remember my mom always used to tell me to ... "Eat your fish. It's brain food." The earliest record I can find of it is from the novelist PG Wodehouse, so like 100 years ago or so, was writing ... it appeared in his novels. It's clearly quite an old kind of idea.

And I've been, I guess, very fortunate to have had ... not to have had a brain tumor, but to have survived a brain tumor thus far, because it's given me the opportunity to do completely different things, like leave medicine and embark upon this exciting career in food science and cooking and writing books and things like this.

And one of the reasons why fish are good for our brains is because of the fats that they have in them. And if you're a bit of a foodie or you read your healthy eating websites, you'll probably have heard of omega 3 fats, I presume. I presume omega 3 fats ... that's kind of a sort of a thing that you hear. It's kind of advertised everywhere, and these are particularly important for brain health. Within your brain, there's lots of nerve fibers. These nerve fibers, they're like electric cables, and each of the electric cables has, like, insulation around it, like your electric cable has a plastic coat going around it. The same thing.

And the coat that's around our nerve fibers, our brain cells, the things that do our thinking, are a fatty layer called myelin. And an important building block of this myelin is this fat that we find in oily fish that's called omega 3, and there are a variety of other fats, as well. That's one of the things that's important in fish, and particularly oily fish, because that's a nutrient that we need to help our brains regenerate themselves, or rather to keep this insulating layer really healthy.

And there's research that shows that these omega 3 fats that we get in fish are good for a whole variety of things. There is a bit of research to show that it's good for memory in old age. There's some evidence, although I mean, some of this isn't completely conclusive. But there's some evidence that it could delay Alzheimer's. There's definite evidence that if you've had a traumatic brain injury, then omega 3 can help that to repair and to recover your cognitive function. Oily fish are a fantastic food.

Suzy Chase: You have a super informative chapter called kitchen essentials, with guides to knives, pots, pans, and utensils. Give us some information on the good old serrated knife.

Dr. Farrimond: Your serrated knife ... unlike other knives, they cut at a slightly different way. If you look at the side of your serrated knife, you'll see there are kind of like these scalloped edges, and it goes down to individual points. When you put your knife in, they're brilliant for kind of cutting into smooth foods like your tomatoes or ... I don't know. Let's say you've got a piece of fruit that you're going to cut into, or your piece of bread that you're cutting into, because the surface of a piece of bread is quite smooth.

When you cut in, those little points, they put in ... they pierce the food. All the pressure that you're pushing down with your knife goes into a very small area, and you pierce the food in those tiny little points. And then, as you pull towards you and push against, the scalloped edges of those blades ... they're very sharp, just like any other blade. And so you're actually slicing into the food from these tiny, tiny little points that you first make. And so the more points that you have, the less pressure you're able to put down into the food. Does that all make sense?

Suzy Chase: Totally.

Dr. Farrimond: Okay. Cool.

Suzy Chase: Why is it safe to eat rare beef but not rare chicken or rare pork?

Dr. Farrimond: It's how the meat is handled. Beef is relatively expensive, and it's a big animal, and it tends to be handled quite well, the meat. Whereas if you look at chicken, you can go onto YouTube and be horrified by how many meat handling and slaughterhouses process their animals and their meat. It's all quite horrifying, if you look at that stuff. But because the chickens are small and they're often not handled well, is the pathogens ... the bugs, the nasty bugs that make us unwell can spread all over the meat.

And a lot of these tend to come from the poop of the animal, and so if you've got all these chickens ... you're not handling them very well. You're throwing them around. Then, essentially, the bacteria-infested poop can spread all over the meat, and potentially any ... just a tiny fragment, just a handful of bugs to be left on there after it's been butchered and washed and all the rest of it, to cause a nasty, nasty food poisoning infection.

Whereas a cow, you don't have that problem. As I say, you look after them better, and the same with pigs. You don't have that same problem. And because the cuts are bigger ... so your steak, for example. It's a bigger cut. Everything on the inside of the flesh ... there won't be any bugs there at all, because it's only the surface that you've got to be worried about. Your steak, for example. Your beef. You would sear it, cook it all over before you eat it. And so if there are any bugs on there, you've killed them all when you've been cooking it.

But with chicken, because it's handled so poorly ... and if you've got a chicken breast, maybe, and the way kind of the meat folds over, there's a possibility that you won't completely cook the entirety of the surface. You only need a tiny bit for it not to be cooked, for a bit of contamination there to make you very, very sick. That's one of the reasons.

Pork has historically harbored a worm that lives within the muscle itself. Whereas most meats are safe if you sear them on the outside, pork, if it's infected with this nasty worm ... which, if you eat it, it will actually infect you from inside your intestines. It wriggles in through the walls of your intestines and will infect you and go into your muscles. Because it's actually in the muscle of the pig, it doesn't matter how much you cook the outside. Unless it's cooked all the way through, there's chances that those worms and their worm eggs could be alive inside. Quite nasty.

Suzy Chase: Ugh.

Dr. Farrimond: And so for that reason, we've always said, "Cook it until it's cooked all the way through." And my mom used to always cook pork to within an inch of its life, so you know, pork chops when they're just kind of leather.

Suzy Chase: Yes.

Dr. Farrimond: That was what I was brought up on, and so I've always hated pork until, as an adult, I've realized that you don't have to cook pork that way. And in fact, now, you don't have to worry too much about cooking pork. If you look, and it's a little bit on the inside, because essentially, unless you're importing your pig meat from the developing world, the worm infections are eradicated in America and in Europe.

Suzy Chase: I will name six vegetables, and you'll tell us if they're better raw or better cooked, and why.

Dr. Farrimond: Excellent. Okay.

Suzy Chase: Let's kick it off-

Dr. Farrimond: It's like the quiz.

Suzy Chase: Right.

Dr. Farrimond: It's like my own personal quiz.

Suzy Chase: I just need some theme music.

Dr. Farrimond: You can add that in later, I'm sure.

Suzy Chase: And a buzzer.

Dr. Farrimond: And oh, yes. Yes, you need a buzzer.

Suzy Chase: Let's kick it off with carrots.

Dr. Farrimond: Yes. Oh, yes, my answer. Carrots are better cooked. Carrots are better cooked, and that's because when you cook them, you release more of these health-giving substances called carotenoids. Yes, you should cook your carrots, although I do like raw carrots.

Suzy Chase: I do too.

Dr. Farrimond: Yeah. You can eat them. You can have them both, but if you're going to eat them one way or the other and you want to know which is nutritionally the best, then carrots are best cooked. You get more of the nutrition out of them cooked.

Suzy Chase: Okay, garlic.

Dr. Farrimond: Garlic is better raw, unfortunately, because raw garlic breath is particularly repulsive. But it is better for you raw, and the reason for that is that there's an enzyme in it called allicin, which is very good for you. Garlic's extremely good for your heart, but the more you heat it, the more you cook it, the less of this very beneficial enzyme there is in your garlic. It's better raw. Or if you're going to use it, don't cook it until it's brown and completely dead.

Suzy Chase: Wow, that's a tough one.

Dr. Farrimond: I know, and like garlic ... there's that garlic thing that lingers with you, isn't it?

Suzy Chase: Yeah, for days.

Dr. Farrimond: I had a couple ... Yes. Yes, that's right. Yes. And I could tell you why that is, but I won't bore you.

Suzy Chase: Okay.

Dr. Farrimond: It is, actually, used-

Suzy Chase: Broccoli.

Dr. Farrimond: Yeah, okay. Broccoli. Broccoli. There is an enzyme in broccoli that gets destroyed when you cook it called myrosinase ... called myrosinase that has anti-cancer properties. Broccoli, for that reason, is better raw, although I must say that if you're eating vegetables full stop, that's a good thing. You shouldn't say, "Oh, I can't eat that, because that broccoli has been cooked." It's just that there are benefits particularly with broccoli of having it raw.

Suzy Chase: Tomatoes.

Dr. Farrimond: Tomatoes? Cooked.

Suzy Chase: Tomatoes, sorry.

Dr. Farrimond: Cook, cook, cook. Oh, yeah. I'm sorry, yeah. That came out, didn't it? Tomatoes.

Suzy Chase: Tomatoes.

Dr. Farrimond: Yes, tomatoes. Tomatoes are ... how did that sound, tomatoes? It has an English-

Suzy Chase: It sounds-

Dr. Farrimond: An English person-

Suzy Chase: I like tomatoes better.

Dr. Farrimond: Tomatoes. An English person trying to say tomatoes like in American style. Tomatoes are better cooked or tinned or pureed. When something is canned, it's cooked, so that makes it sterile, which is why things last so long if you get it canned or tinned. And there's a substance in tomatoes called lycopene. It's an antioxidant, so it helps your body fight disease and fight cancer. And the levels of that lycopene go up hugely whenever you cook it or you process it in any kind of way. Tomatoes are better cooked, and if you want to get your lycopene dose, then just get some tinned tomatoes or put in a squirt of tomato puree into whatever you're cooking.

Suzy Chase: Onions.

Dr. Farrimond: Like garlic, better raw, although your partner probably won't like you for it. They contain antioxidants in them that contain sulfur. They're also ... when you chop onions, the reason why your eyes water is because you've got sulfur-containing substances that are going into the air and hitting the liquid on your eye and making you cry. But these substances, these sulfur-containing substances, are good for you. And so it's better if you have the onion raw.

Suzy Chase: Asparagus.

Dr. Farrimond: Asparagus is better cooked, and that's because when you're cooking, it makes a cancer-fighting substance called ferulic acid. It makes it easier for the body to absorb, so asparagus, better cooked.

Suzy Chase: The other night, I used your tips for roasting firm and crispy vegetables on page 156. First of all, I cracked up when you sent me the message asking if I preheated the oven, because I was like, "Does he know me?" Because I forgot to preheat the oven.

Dr. Farrimond: Oh, did you?

Suzy Chase: That made me laugh.

Dr. Farrimond: Oh.

Suzy Chase: No, but I pre-heated it and waited.

Dr. Farrimond: Oh, you did?

Suzy Chase: But do many people forget to preheat the oven?

Dr. Farrimond: I would say most people do it. And it's a hard one-

Suzy Chase: Okay, good.

Dr. Farrimond: Yeah. And it's a hard one, because we're very energy-conscious now and we don't want to just leave things on unnecessarily. But if you want the best results out of, I mean, really, whatever it is you're putting into the oven, it's always a good idea to preheat it. And when I mean preheating, I mean you've got to let it get to temperature for about 15 minutes, 15 to 20 minutes, because what you're doing when you're preheating is you're not just heating the air. You're heating the metal walls in there.

When you turn it on, the thermostat clicks off as soon as the air temperature reaches whatever you've set your oven temperature to. But actually, the metal walls in there are still cold. When you open the door, the hot air rushes out, and because the oven walls are still cold, when you close it again, it takes it a long time to get back up to temperature. That's why it's a good idea to preheat it.

And the other thing is that those hot walls radiate a lot of heat inwards. If you've ever put your hand inside of the oven when you're trying to get anything out when it's really hot, it feels warm. But it's ... but your hand doesn't burn, and most of the heat that you're feeling there is from the heat that's being blasted in from those hot walls that's being radiated in like your heating radiator in your room. The same thing is happening.

If you don't preheat your oven, you're not getting that cooking intensity on the food that you're putting in there. If you want something to cook properly and cook in good time, you should preheat it, leave it for 15 to 20 minutes until it gets up to temperature. Or your oven might have some recommendations based on the particular model.

Suzy Chase: In addition to preheating the oven, you have four steps to roast perfect and crispy vegetables. And the first is to cut the vegetables evenly. Two, arrange them loosely on the roasting pan. And step three, which I think is the key, was to briefly cover to trap the steam. And then, the last step is to uncover to crisp.

Dr. Farrimond: The key part of it is the covering. The 15 minutes of covering, because what you're doing there ... you're essentially steaming the vegetable pieces in ... when it's covered in the foil. If you have it open, you're dehydrating your food, which is why it's so easy to let food go dry when we're roasting it. We're trying to activate, in the vegetable pieces, a protective enzyme. It's an enzyme called PME. And when you heat a vegetable between 45 and 65 degrees C ... or that's 110 to 150 degrees Fahrenheit, this enzyme gets switched on permanently. And it goes to work strengthening the internal structure of the vegetable cells.

There's a pectin glue that holds the vegetable cells together, and it strengthens those, so that if you can cook your vegetables briefly at a fairly low-ish temperature to turn on that enzyme, when you roast it, they don't go limp and floppy and horrible and get slimy.

Suzy Chase: Well, my veggies turned out lovely. They were so good, and you can see them on Cookery By the Book Instagram, the Facebook page, and my Twitter.

Dr. Farrimond: It's important. That's what social media is for.

Suzy Chase: Right, to show my-

Dr. Farrimond: For food photos.

Suzy Chase: My perfectly roasted vegetables.

Dr. Farrimond: Excellent, yes.

Suzy Chase: Now, where can we find you on the web?

Dr. Farrimond: On Twitter or Instagram or any of those things like that. My handle, my nickname is Real Doctor Stu, so it's R-E-A-L, Doctor, spelled D-O-C-T-O-R, and then Stu, S-T-U. And if you go to realdoctorstu.com, I've got a blog there, or you can just Google my name and you'll probably find me. There'll be something about me doing some silly food science research.

Suzy Chase: If you want answers to over 160 of the most common culinary questions, The Science of Cooking will be your go-to book in the kitchen. Thanks, Dr. Stu, for coming on Cookery By the Book podcast.

Dr. Farrimond: An absolute pleasure, Suzy.

Suzy Chase: Do you want to chat about Cookery By the Book shows, cookbooks, recipes, and authors, or post a photo of what you've made out of a Cookery By the Book cookbook? Well, now you can. Join the Cookery By the Book community on Facebook. Search for Cookery By the Book, or send me an email at suzy@cookerybythebook.com, and I will add you to our cookbook community.

You can also leave me a review on iTunes, say hi on Twitter. My handle is IAmSuzyChase. And connect on Instagram at Cookery By the Book. Thanks for listening to Cookery By the Book podcast.