IRA FLATOW: This is Science Friday. I’m Ira Flatow. If you’re like me, you’ve had enough rich foods for the holidays, and your attention has turned back to one of our most beloved foods, pizza. After all, who doesn’t love pizza? That magical combination of sauce, cheese, crust, maybe a topping or two.

And depending on where you eat it, the ratio of sauce and cheese and topping changes, also. There’s Neapolitan, New York style, Chicago deep dish, and nearly every country in the world has some type of variation on the classic. The way they bake it, too– coal, wood, gas-fired ovens, all impart their signature flavors.

You know how I know this? Because Nathan Myhrvold visited over 250 pizzerias all over the world to appreciate the differences, and then made over 12,000 pizzas, tweaking each one slightly, relying on the physics and chemistry of cooking. And then he and his team wanted to stretch the limits of pizza, and they wrote all about it in a three-volume, 35-pound set of beautifully illustrated, painstakingly researched books.

Nathan Myhrvold is the former CTO at Microsoft. Founder of Intellectual Ventures and Modernist Cuisine, he co-authored this most recent book, Modernist Pizza, with Chef Francisco Migoya. He joins us now from Bellevue, Washington. Nice to have you back.

NATHAN MYRHVOLD: Well, nice to be back.

IRA FLATOW: I’m just wondering how many antacid tablets it takes to go through 12,000 pizzas.

NATHAN MYRHVOLD: [LAUGHS]

IRA FLATOW: Well, a lot of the book is devoted to busting pizza myths. And one of the biggest ones is that the type of water used to make the dough makes a huge difference. How did you go about testing and possibly disproving that hypothesis?

NATHAN MYRHVOLD: The most delicate part of the crust that people usually point to is the yeast. So we made bread and we made yeast concoctions from every kind of city water, from bottled water to distilled water and finally water from a swimming pool.

IRA FLATOW: Really?

NATHAN MYRHVOLD: And it turns out the yeast doesn’t care. The yeast really doesn’t care. Even the swimming pool water, it puffed up beautifully. Now, I don’t recommend swimming pool water. It has a taste to it. And you should never use water to make dough that has a bad taste.

IRA FLATOW: And in order to test out your recipes, you used something called the triangle test. You try three slices of pizza at a time. Two of them are the same, and one is different. Why does this method work so well?

NATHAN MYRHVOLD: Well, it’s very easy to fool yourself, OK? This is the same reason that we do double-blind studies when they look at drug efficacy. So the first question is, can you tell which one is different? Now, if it was a gross difference in cooking time or something, it might be kind of obvious. So it doesn’t work as well then, but when you’re making small changes, what we discover is lots of times people can’t tell which one is different. And if you can’t tell which one is different, I really don’t care which one you think is best, OK?

IRA FLATOW: Yeah. I get it. You were talking about the water. And let’s get into the chemistry of this a bit, because even though the type of water might not make a huge difference, the amount of water in the recipe does, doesn’t it?

NATHAN MYRHVOLD: Yeah, the amount of water is what a baker will call the hydration percentage. They talk about the percentage of water mass relative to flour mass. So if you make a pizza as low as 50% hydration, that means you’ve got one part water to two parts flour. You get a really dry, hard, and kind of unappealing pizza. Meanwhile, as you raise the amount of water, that changes the texture of the dough. You get large bubbles. You get just a very different feel to the crust.

IRA FLATOW: Interesting. How does the sauce keep the center of the pizza from rising? You spend quite a bit of time talking about that.

NATHAN MYRHVOLD: This sort of shows our approach. You know, I was looking at a pizza that had just been served to me, and it had a nice, puffy rim. It was probably an inch, inch and a half high. And in the center of the pizza, the crust was super thin. Now, I’d watched that pizza being made, and the dough was dead flat. So how could that be?

So we talked to pizzaiolos– that’s the Italian term for a pizza chef– and the dominant theory we heard was, well, it must be the weight of the source. We tested that by weighing our sauce and then putting the equal amount of sand on a pizza in place of the sauce. And it puffed right up.

What we eventually realized is that it’s because sauce is wet. Now, we all know water boils at 212 degrees. And water soaks up a huge, huge amount of heat when it boils. That’s why steam engines work.

So when you put your pizza into an oven, which is typically 600 degrees Fahrenheit, 800 degrees Fahrenheit, extremely hot, you might say, oh, well, that’s the temperature of the oven. But guess what? All that area covered by sauce, as long as that sauce has got a drop of water in it, that area is going to be only 212 degrees.

IRA FLATOW: Ah-ha. You know, that might explain something else, that when you try to separate the slices, sometimes the toppings come off. And below is this white, may I say mushy, dough. Is that the reason? You say that’s called the gel layer.

NATHAN MYRHVOLD: If you have a thin crust pizza, usually that gel layer is not objectionable. However, in a lot of thicker crust pizzas, you get a problem. New York City, if you order what’s called a Sicilian or a square pizza, and the trouble is that then you get a very large layer of this goo in there, which is uncooked dough.

And I think most people don’t even realize it. But once you do realize it, you say, god, that’s kind of unpleasant. Isn’t there a way you can cook the damn dough?

IRA FLATOW: And how can you prevent that? If you still want your deep dish, what do you do?

NATHAN MYRHVOLD: You parbake it, which means you bake the crust most of the way, then you take it out and you can put all your fillings in and bake it the rest of the way. And it’s funny because in Chicago, the idea that you would parbake a pizza crust is viewed as negative. And places will proudly tell you, or at least they told me, we never parbake. And I’d say, what the hell?

IRA FLATOW: Get out of here. Get out of my pizzeria.

NATHAN MYRHVOLD: You serve underbaked dough.

IRA FLATOW: Now, I know you’ve developed several what you call Frankencheeses, hybrids of mozzarella, other cheeses like blue cheese, Parmesan, goat cheese. How did you make them melt better? Because they don’t like to melt that much.

NATHAN MYRHVOLD: Well, this started when I was in a store that sold cheese curds. Sometimes you can buy the curds of cheese, which is a stage early in the cheese-making process that’s not totally finished. And the ones that I saw for sale were cheddar curds.

And I’d learned how to make mozzarella, and part of mozzarella, you make curds, also. So well, what if I just substitute the cheddar curds? Will it work? The answer was, with some modification of the recipe, it would. With other cheeses like blue cheese, you have to use cheese after the curd process, because blue cheese is infected by mold, and that happens later in the process. And there, the problem is blue cheese, although it can taste good– some people say it’s an acquired taste, but it’s one I’ve acquired–

IRA FLATOW: Yeah, me too.

NATHAN MYRHVOLD: –it doesn’t melt well.

IRA FLATOW: No.

NATHAN MYRHVOLD: So then you have to mix it in with another melting cheese, and it helps to add a little bit of something called an emulsification salt. Sodium citrate is one of those. And it’s a perfectly natural ingredient. Well, it turns out that adding this emulsification salt does wonders for it.

IRA FLATOW: Let’s talk about the difference in baking pizzas in different kinds of ovens, because sometimes you will see that they advertise outside the building, we have a coal-fired or a wood-fired oven, not just the gas-fired. Do they all bake up the same way, or are there advantages to one over the other?

NATHAN MYRHVOLD: I like to use the analogy that a gas pizza oven is like a bicycle, and a wood-burning oven is like a unicycle. A unicycle will get you where you want to go, like a bicycle will, but it requires a lot more skill. Now, in the US, if you see wood-burning oven for pizza, a lot of folks think, oh, well, they’re using something hard, they must really care, and they must be really good at it. And if they are good at it, it makes a great pizza.

But a wood-burning oven, even with an expert, doesn’t make a better pizza than a gas oven. And if the person is not an expert, well, then you’re much better off with gas or an electric pizza oven. And this is total heresy, of course, to the people in Naples, but they’re experts.

IRA FLATOW: Well, what about we folks at home who want to optimize our ovens to make a better pizza? What are your suggestions there?

NATHAN MYRHVOLD: It helps a lot if you have something that’ll hold the heat and really cook the bottom of the crust. The traditional thing is something called a pizza stone that you put into your oven. The trouble is stone doesn’t release heat very quickly, and that’s counterproductive in this. So we prefer something called a pizza steel, which is like a 1/4-inch piece of aluminum or steel plate, or a big cast iron skillet will work great.

IRA FLATOW: Oh, that’s a good idea. Yeah

NATHAN MYRHVOLD: Get those hot, and then you put the dough down on it. And it gives a very reasonable facsimile.

IRA FLATOW: Nathan, I have to ask you a question that’s like asking which child do you prefer, you know? When you finished all your samplings and creating pizzas, did this change your preference for the type of pizza you like or thought you liked? Or do you have one that has stayed through all the way?

NATHAN MYRHVOLD: Well, I grew up in the United States, and my first pizza was a chain pizza from Shakey’s in LA. And chain pizzas, particularly in that era, were really based on a New York style. And so that’s the pizza I grew up on. And a lot of people in this world never move beyond the pizza they grew up on.

Now me, I say, hey, you should be adventuresome, and you should try other pizzas, because I did not grow up on sushi, but it turns out I like it. And so if I only focus on what I grew up on, it’s kind of limiting. I have a much greater appreciation for styles of pizza, some I didn’t even know existed.

IRA FLATOW: We could go on talking all day. We’ve run out of time, Nathan. I want to thank you for taking time to be with us today.

NATHAN MYRHVOLD: Well, thank you. It’s been a pleasure. And everybody, go out and enjoy some great pizza.

IRA FLATOW: Absolutely. Nathan Myhrvold, former CTO at Microsoft. He co-authored his most recent book, Modernist Pizza, with Chef Francisco Migoya. And if you’re one of those who can’t say no to an extra slice, you can hear more of my interview with Nathan Myhrvold. It’s in our podcast.

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