More Science Talk
Jeff Potter, author of Cooking for Geeks: Real Science, Great Hacks and Good Food, talks with daily podcast correspondent Cynthia Graber, and podcast host Steve Mirsky (pictured) tests your knowledge of some recent science in the news. Web sites related to content of this podcast include www.cookingforgeeks.com
Steve: Welcome to Science Talk, the weekly podcast of Scientific American, posted on September 3rd, 2010. I'm Steve Mirsky. This week on the podcast…
Potter: Cooking is all about physical and chemical changes in the things that you're heating and those changes occur at particular temperature points.
Steve: That's Jeff Potter, author of Cooking for Geeks: Real Science, Great Hacks and Good Food. We'll hear from him, plus we'll test your knowledge of some recent science in the news. Jeff Potter is a software engineer and science-oriented cook. Cynthia Graber, who does many of our daily podcasts, sat down with Potter last week in his apartment in Cambridge, Massachusetts.
Graber: So I want to start first with, kind of, the purpose behind the book. It's a great, clear explanation of what happens in the kitchen, got lots of recipes, interviews with really interesting chefs and scientists. It's different from other food-and-science books like the kinda massive tome I have in my own kitchen—On Food and Cooking by Harold McGee—which is more of, kind of, a massive reference book. What were you trying to do with this book?
Potter: I was actually writing it for myself. This is the book that I wanted 10 years ago, when I first started to learn how to cook and for me, as somebody who likes to experiment with things and play with things, most cookbooks just don't work. Because cookbooks generally are collections of exact instructions. [There is something] you execute, like a software engineer might execute code, but they're not so much the science behind that. They don't give you the big picture of cooking that helps you understand how to go into the kitchen and put new things together in new ways. So, for me the book really is a story about food science with recipes illustrating and explaining how that food science looks in the kitchen.
Graber: Your title is Cooking for Geeks. Who do you see as geeks?
Potter: To me a geek is anybody who is curious about the details. So, it might not be a technology geek, although admittedly my background being software engineering, I am a technology geek.
Graber: And there are few references at the beginning of the book to technology geeks.
Potter: Yeah absolutely, you know, it's part of my history and it's part of who I am. But the book really is for anybody who wants to understand how stuff works, who is curious about those details, regardless of what kind of geek they are. I think we need to take the word geek back to be as a positive word for anybody, you know, who likes to understand how things work and is willing to go in and chase down the details and be curious and ask themselves, "Hey, I wonder what's going on here, let me go find out." You know, this book really is for that kind of person, for their exploration and journey in the kitchen.
Graber: So I have lots of questions about that and about the science that you illustrate in the book, but I want to start with a little bit, I have a few more questions about your background. How did you get interested in cooking?
Potter: Well, my parents always took time with me as a kid, growing up to actually cook. I remember my dad actually showing me how to make pancakes. It was probably like second or third grade. And I consider myself very lucky to have growing up with parents that took time to show me how to cook. So many people who are the same age as me though, didn't have that experience growing up, and so for them when I talk to them about cooking, well they're very frustrated, they don't understand why stuff doesn't work. And to me it's just it's been part of my background. And when I went to college, I discovered much to my chagrin that I didn't really know how to cook dinner. I made things like, you know, pancakes, breakfast, I'd [made], desserts—you know, what kid doesn't have a sweet tooth? But somehow I just hadn't actually figured out or been exposed to making dinner. So, I went through this period of a couple of years, where I'd try to do all these things, you know, making spaghetti with salmon, which just really doesn't work; I mean, it can work but it's really difficult. So, there was a lot of trial and error for me learning how to cook, but if I had known a lot more of the food science stuff, if I had understood what I was doing and why I was doing it, then I would have gotten through that trial-and-error phase a lot faster.
Graber: So when did you start bringing science into the kitchen?
Potter: You know, I remember actually for my 16th birthday, my family took me to a restaurant in San Francisco that is well known for making soufflés; and I remember trying to figure out how to make soufflés, because there's this myth around soufflés, there's a whole mythology that they're very difficult and very finicky and prone to fail. So, I started actually doing experiments, where I would make it, and then right after making it and seeing how it came out, I would do it again, and just change one thing. Like, "Oh gee, it seems too wet" or something, so you know, maybe make it with less base in it; or "Wow, you know, the top got really brown, but the middle still wasn't cooked; you know, maybe my oven is too hot." So there was this period of time where I would try making something and then see what I thought needed to be done differently and then do it again, and actually that process, that's the kernel, that's the core idea for me about how to go into a kitchen and learn how to cook better. And that's what the book really aims to do is help somebody understand how to ask that question for themselves, so that when they go into the kitchen, that trial and error becomes informed trial and error.
Graber: You also, sort of, allow, people to, sort of, skip many of those steps because you've already done it, you've tried, you know, baking things a bunch of different ways; so you then tell your readers, "Well this is what happens when you do it this way."
Potter: Sure, that's definitely true, but getting the idea that you should use science and that methodology of experimental approach in the kitchen, that's the really important bit; and so seeing in some cases, like looking at certain recipes or say, looking at egg whites and whipping them in copper bowls versus, you know, a glass bowl or something like that; just the idea that "Hey, if I'm not sure which way to do this, I can do it both ways and see which comes out better", that's the real goal.
Graber: You mentioned the egg whites and the copper bowl versus the glass bowl and how they're better in the copper bowl—why?
Potter: This is, of course, the limit of experimental observation. With experimental observation, you can't necessarily precisely say why something occurs. You can just say, "We observe it". Looking at On Food and Cooking, Harold McGee talks about the copper actually donating some copper ions to that egg white mixture and actually providing stabilization to it. It's a similar reason why we add a crème of tarter as a buffer when whipping egg whites. Not being a food scientist myself, I can't say for sure, but I can say that there's this question, does it help or does it not, and my approach is to say, "Well go and test it." The quickest way to understand something is to simply observe it if you can.
Graber: It's true and at the same time, one of things that I found most useful from the book is the explanation of why things happen; because I've been cooking for years, and I don't really know why, you know, why certain things turn brown and then they don't in this situation; and, you know, it was really useful for me as a long-term cook to hear more about the actual science behind why things happen in a certain way. Because that also informs how I'm going to cook.
Potter: Yeah, absolutely. It's really difficult to come up with a hypothesis without some understanding of the bits behind that. And it turns out with cooking, at least for a basic level, I'm not talking about, you know, very, very high-end restaurants, but for [a] basic level of cooking, anybody doing home cooking, having a little bit of food science gets you a very, very long ways towards being able to correct many of these things. You'd mentioned browning reactions and cooking. It turns out with food that there are really only handful of really important temperatures and once you understand those, suddenly you can look at what you're doing in the kitchen with a pair of informed eyes and suddenly begin to be able to make lots of guesses, informed guesses about which way to do something.
Graber: Maybe this is a good time to talk about some of those temperatures—what are some of those temperatures and what happens at different times and how does that matter for when you're cooking?
Potter: There's a couple of really important temperature points, Maillard reaction is probably one of the most well known one, and of course, caramelization—sugar breaking down—is a second important one.
Graber: Can you explain what the Maillard reaction is?
Potter: Absolutely. A Maillard reaction is basically proteins and simple sugars breaking down and forming hundreds of new compounds, and we just happen to prefer and enjoy those flavors that those new compounds, that that reaction generates. So that's why we often will roast and sear meats, is to get that nice brown outer crust; and that brown crust that's the Maillard reaction essentially occurring.
Graber: So, it's the crust on meat or, kind of, a toasted piece of bread.
Potter: Yeah, that's true. Maillard reactions are again between proteins and simple sugars and there are of course proteins in flours. Maillard reactions begin to occur starting at around 310 degrees Fahrenheit. For me actually, some of the best moments for me working on the book were when I came up with the hypothesis and said, "Well I'm going to go test this." One of those moments was actually taking a[n] infrared thermometer and metering the exterior temperature of a loaf of bread as I was baking it, and it started to turn brown right around 310 degrees. I was like, "Yes, you know, reality aligns up with science again. Wow!!!" So with bread. that 310 degree rough temperature—I mean, it is a time-at-temperature variable; I mean, it's not just strictly a single point in time where its setting and it starts to turn brown; it will occur— the reaction will occur faster and faster as the temperature goes up. So, understanding that Maillard reaction[s] start to occur around 310 mean[s] that when you go to, say, roast a piece of meat, if you want that brown exterior, you'll need to put it into an environment that is at least that hot, otherwise that reaction won't occur. This is why when you, say, steam a piece of chicken, or not that you'd normally steam a piece of steak, but if you did, you won't get that reaction on that outside, and hence that's why foods that are cooked in moist environments, like steaming or boiling, don't have that same set of rich flavors.
Graber: That can be related to a piece of meat, say, if you throw chunks of meat into a stew before browning them first, then you don't have those same umami-rich flavors that we like that come from that reaction because they don't get hot enough in the liquid, right?
Potter: Right absolutely. And this is why, if you are making a beef stew, you should sear your beef chunks before actually tossing them into your stew pot, because without that moment before they're in the stew of having that Maillard reaction, these flavors aren't going to have a chance to ever really develop.
Graber: So you mentioned your infrared thermometer; I think that would be fun to play with right now. Can you show me?
Potter: Ah, yeah. It's actually right here.
Graber: Lovely. That's very convenient.
Potter: Yeah, I have it in my drawer. I use this all the time and I basically think this is the best geek toy ever. I mean really run out and grab an infrared thermometer because you can take [it] and point at your hand and go. "Oh! Wow! You know, my hand right now is about 92 degrees Fahrenheit." You can point it at the top of your tongue and (points at tongue) my tongue right now is about 93 degrees Fahrenheit. There's all sorts of fun things you can do. The thing is, what's important about understanding temperature and why I mentioned those two is that chocolate begins to melt around 92, 93, 94 degrees, which is why it won't melt in your hand but does melt in your mouth.
Potter: M&Ms actually started out from the Spanish war, I believe it was, where, I think, there was an American soldier—I think it was Mars, Jr.; I'd have to look this up to be completely sure—but he saw [the] Spanish troops eating chocolate that had been coated in candy to prevent it from melting in the hot environment of the heat. Of course, M&Ms are coated in sugar which means they're not going to melt in your hand, no matter what temperature your hand is; but for dark chocolate, this certainly seems to be the case, you know, it doesn't melt in your hand, but does melt in your mouth. That's kind of a silly example of temperature. There are much more important ones. So if I dropped a piece of toast in the toaster, and pops it up I and meter it, it'll say around 310 degrees.
Graber: So while we're talking about heat though, and temperature, there's a story I'm sure you have had to tell a million times, but it's a great story. It's a great tale of you blowing out the door of your oven in the name, of course, of research for your book and making pizza. So, can you tell that?
Potter: Sure. So, by clipping the lock off of your oven door, you can open your door while it's on cleaning cycle, which means you can bake a pizza at 900 degrees.
Graber: Because—I just want to interrupt—usually, you know, an oven will lock, so you can't get in when it's at that super-high heat for cleaning.
Potter: Right. Obviously of course because our ovens aren't designed to be open. And the glass in my oven actually went through thermal shocks and broke after doing this. Now why would you want to cook a pizza at 900 degrees? Well it turns out that if you have a pizza that's cooked over a wood fire, in a wood-fired oven, that the temperature actually gets up to the 800-900 degree range. I've taken my infrared thermometer and actually checked this with one of the local pizza places that does wood-fired pizza, and sure enough it gets that hot. So, the great thing about doing pizza this way is that you can cook it in like 45 seconds, and it comes out amazingly good; it's really thin, crispy crust with your toppings on top melted and bubbling and just delicious.
Graber: And they cook in that 45 seconds—everything cooks?
Potter: Yeah. I mean at 900 degrees, the heat is getting transferred into that pizza really quickly. Cooking is all about physical and chemical changes in the things that you're heating, and those changes occur at a particular temperature points. So, Maillard reactions begin around 310; caramelization—well the browning of sugar—begins around 356. So, as soon as you start crossing these temperature thresholds, those reactions begin to occur. And, of course, as you get hotter and hotter the reaction picks up.
Graber: Your oven's okay now? Everything's fine?
Potter: I have replaced the piece of glass with something called pyroceram 3, it's quartz crystal. It's what the U.S. military used for missile nose cones in the 1950s. It's amazing what you can buy on the Internet these days.
Graber: So, you have an experiment here prepared for us to talk about the role of collagen in meat. And so let's talk about what collagen is, and where it is and the, kind of, the role it plays in the meat we might buy at the store.
Potter: Yeah, collagen is basically a protein that provides structure to muscle, and different parts of an animal will have different levels of collagen. Collagen, of course, since it provides structure, is also very tough, and this is why some pieces of meat, when you don't cook them for long periods of time, have this really tough quality to them. Since collagen itself is a really long, complicated molecule, it takes a long time for it to actually denature and hydrolyze.
Graber: Explain that. So what happens to it, denaturing and hydrolyzing?
Potter: Sure. Collagen will go through two different processes as you heat it up. The first one is denaturation and this just refers to the actual molecular structure of that protein changing. It gets, basically, knocked out of its native, normal state; and then the second thing that happens eventually is that that collagen will hydrolyze, and this, basically, is the actual structure starts to fall apart. This is no longer just in [a] different shape but, it's actually getting chopped up into little pieces, essentially. So, keep this in mind if you're actually cooking something that's got a fair amount of collagen in it; you need to cook it either quickly or long enough that the collagen has time to completely break down.
Graber: How would that relate to, say, pieces of beef that you might pick up in the store?
Potter: Well, depending upon what cut of beef it is from the animal, some cuts will have more collagen and some will have less collagen. Since collagen is responsible for, well essentially, providing structure, those bits of the animal that actually are responsible for bearing the weight of the animal have more collagen. So this is why, you know, parts of the leg or the rump will have, that's why we make beef stew with those things, because to break the collagen down, you need to cook it for a long period of time.
Graber: What happens to the collagen when it hydrolyzes, when it breaks down?
Potter: It essentially turns into gelatin. You just get something that's very, I think the technical term is like "lubricious" from a mouth feel point of view. [It gives you something that's] got this really nice kind of texture, but doesn't have any of the rubbery quality.
Graber: And you have an experiment to show this?
Potter: Yeah, I do actually. There is a really easy way to try this, which is to take a couple of pieces of beef stew and cook one piece for well, say, six to eight hours; put it into a slow cooker, give it enough time, so that the collagen actually breaks down, hydrolyzes and becomes really tender. Then, take a second piece, and drop it in that slow cooker, but only let it sit there for an hour or so, enough time that it's definitely come up to temperature, but not so long that the collagen has had a chance to actually break down.
Graber: So do you have that to show us?
Potter: I do. Here I'll go grab it. So, here's my handy-dandy slow cooker. I dropped a few pieces in earlier today and then, you know …
(sounds of utensils)
Graber: So it's just beef in clear liquid.
Potter: Yep, in this case, I just used water; because what we're really looking at is the actual meat itself. So I'm not going to tell you which is which. I know based on where I put them in the container, and you don't even have to taste this to actually be able to tell. So I'll give you the fork.
Potter: And you can try going through and actually taking a guess at which one you think has been in there for 6 to 8 hours, and which one's only been there for an hour.
Graber: Okay, let's see. Ooh! I don't, (laughs) you're right. I don't even have to taste it. This one the one that's been, I imagine only there for an hour, I can't even pull it apart, it's totally rubbery; and the one that has been in there for six hours is falling apart, just like my mom's brisket.
Potter: And that's the secret to a good brisket. It's not about the temperature that you're cooking it at, it's about the temperature and time that you cook it at.
Graber: I want to go back to some of the kind of the funky experiments that you did as you were putting this book together. I was really interested in the cooking the fish in the dishwasher one; you know, that's in the later chapter where you're talking about more advanced types of cooking such as severed ware where you might package say a piece of fish in plastic and submerge it in a moving bath of liquid that keeps it at a certain temperature to bring that fish up to that temperature—but a dishwasher?
Potter: Heat is heat. The fish has got no idea at that point that it's in a dishwasher versus in a water bath. If your dishwasher happens to run at 140 degrees, and you're going to cook the fish in a water bath of 140 degrees, they're essentially the same thing.
Graber: How do you know that your dishwasher ran at 140 degrees?
Potter: Infrared thermometer.
Graber: (laughs) Makes sense. So you just opened the dishwasher while it was running, aimed the infrared thermometer and see what happens?
Graber: Very convenient. So other than, of course, reading your book, do you have any advice for either science geeks who are not so comfortable in the kitchen or cooks who might not know as much about the science as they would like to when they're, kind of, exploring cooking?
Potter: Just get in there and try it; go do an experiment. You know, next time you're in the kitchen and something's not working, stop, think about what might be causing the problem; if you don't know, go and look up online. I mean, the Internet, some one has probably had the problem before, therefore it's probably on the internet. So go and search and see what you can find. If you're nervous about going into the kitchen, just go and try it. I mean, to me failure in the kitchen is not burning the dinner; failure in the kitchen is failing to go and try something. Sure, if you burn it, doesn't turn out so good, you know, it's unfortunate; it means you might be a little bit hungry for a while until the pizza delivery guy shows up; but if you learn something in the process, that's success. And if you learn not to do that the next time, then you've learned something, it's been a successful evening in the kitchen.
Graber: Talking about experimenting and last year I was thinking about putting up food for the winter from what the farmers are growing in the summer, and I decided I wanted to try to freeze some vegetables, but I don't generally like frozen vegetables. And so I decided to learn a little more about it and how it works before I started freezing things. So, I opened up Harold McGee's On Food and Cooking, and he explained that in commercial freezers, you know, commercial industrial, the companies who freeze the food that you might buy in the supermarket, they can plunge it to such low temperatures so quickly that the ice crystals are tiny. But if I'm going to blanch something dry it off, stick it in the freezer, those ice crystals are much larger and so they puncture the cell walls. So, then I realized that that would make my food even mushier. So I decided to only freeze things that had fairly strong cell walls like kale and that was wonderful all winter. So it was just interesting what learning a little bit more about the science can do to inform your cooking.
Potter: Absolutely, and if you don't happen to have a blast freezer or liquid nitrogen around…
Graber: And it looks like—Do you have both? Is that the…
Potter: Well, no, I don't have a blast freezer, those are kind of large.
Graber: Is that the liquid nitrogen?
Potter: It is.
Graber: Ooh. Fun.
Potter: You know that'll definitely freeze water very quickly, meaning that those ice crystals won't be large enough to pierce through the cell walls. Yeah, absolutely, I love your example. Having a good understanding of, hey what's the mechanism that causes this to be mushy—you know, water content level, structure of the actual tissue—and then using that to approach the kitchen. It sounds like you had a successful experiment. Not only did you learn something, it worked.
Graber: It did. It was very tasty all winter long. Thank you very much; it was great speaking with you.
Potter: Thank you. My pleasure.
Graber: Jeff Potter is the author of Cooking for Geeks: Real Science, Great Hacks and Good Food.
Steve: Jeff Potter's Web site is, you guessed it, http://cookingforgeeks.com, and you can follow him on Twitter as, that's right, @cookingforgeeks, all one word.
Steve: Now it's time to play TOTALL……. Y BOGUS. Here are four science stories, but only three are true. See if you know which story is TOTALL……. Y BOGUS.
Story number 1: A study of over 8,000 people in England found that only 23 percent did not have some kind of personality disorder.
Story number 2: Experienced bartenders are very good at estimating just how drunk a patron is.
Story number 3: A smuggler in Thailand tried to get a real tiger cub past airport security by sedating it and putting into a bag with a bunch of stuffed tiger toys.
Story number 4: An oregano-based supplement given to cows cut their greenhouse gas emissions by 40 percent.
Time is up.
Story number 1 is true. The study of 8,391 Brits found that only 1,933 had no type of personality disorder. What's wrong with the ones nothing wrong with, you got to wonder? The research was published in the British Journal of Psychiatry.
Story number 3 is true. The smuggler, or attempted smuggler, did indeed put a real tiger cub in a bag of stuffed tigers and tried to get through security. He did not make it. Still, he is better than the guy caught in Mexico in July trying to smuggle a dozen and a half tiny monkeys under his clothes.
Story number 4 is true. In work at Penn State, the oregano supplement was found to cut cow's greenhouse gas emissions almost in half. Domesticated livestock are responsible for about a third of all methane production related to human activities. The cows also produced more milk than their non-"oreganted" peers.
All of which means that story number 2 about bartenders being very good at estimating the level of drunkenness of patrons is TOTALL……. Y BOGUS. Because a review of the literature finds that it's very difficult to tell just how drunk somebody is, if they're not clutching the carpet of course. The review in the Journal Behavioral Sciences and the Law discusses how slurred speech, red eyes, reciting the alphabet and touching the forefinger to the nose are all terribly flawed indicators of inebriation. It also cites a 1983 study that found that bartenders who watched subjects talk and climb stairs could only tell a quarter of the time if they were slightly, moderately or very drunk.
Steve: Well that's it for this episode. Get your science news at http://www.ScientificAmerican.com or you can check out the "Ask the Experts" feature on bedbugs, which are back all over the place. You can follow us on Twitter where you'll get a tweet every time a new article hits the Web site. Our Twitter name is @SciAm. For Science Talk, the podcast of Scientific American, I'm Steve Mirsky. Thanks for clicking on us.