IRA FLATOW, HOST:
Flora Lichtman is here with our Video Pick of the Week. And it is more coffee.
FLORA LICHTMAN, BYLINE: Our fabulous coffee series by the great Jenny Woodward continues on SCIENCE FRIDAY. Drink up, everybody. This week we're diving into a tiny glass of espresso.
FLATOW: Ooh. Ooh. So small dive.
LICHTMAN: You need to be very careful. Keep your limbs in.
FLATOW: And why - what's so fascinating about espresso?
LICHTMAN: Well, one of things that espresso drinkers will know probably is that when you have an espresso straight, not a latte, not a cappuccino, just a straight little mug of espresso, when it comes out to you, it has this frothy, foamy thing on top. It's a little thin layer of tiny bubbles. It's a little lighter in color, and it's called the crema.
FLATOW: Right. I love that stuff. Yeah.
LICHTMAN: Yes. I always try to get it with a spoon. It's delicious.
FLATOW: Yeah. All right. Back to the video.
LICHTMAN: Back to the science. OK.
LICHTMAN: So there's a story behind this, we learned, from Harold McGee, who's a food science writer. And it comes down to how the espresso is prepared. So the difference when you're preparing espresso, you know, you put it in this little metal thing, right? And you pound it down...
LICHTMAN: ...if you've seen people making it.
LICHTMAN: And then you put it in a machine that pumps hot water through it. But it pumps water through at great pressure, like eight bars.
FLATOW: Mm hmm. Yeah.
LICHTMAN: And what that does is that it pushes out these little oils that are in the coffee beans into the liquid. And those oils and a few other things like plant carbohydrates, which are also - also come out in this process, stabilize these tiny bubbles and give you that long-lasting foam, or the crema. And it turns out that the crema is actually like a cream. You know, like cream has fat.
FLATOW: Right. Yeah. Little globules in there.
LICHTMAN: This is the oil version and it comes from the coffee itself.
FLATOW: Who would've known, you know, when we started this coffee series a while back, and it's so much...
LICHTMAN: So many revelations.
FLATOW: Let me just remind everybody that this is SCIENCE FRIDAY from NPR. I'm Ira Flatow here with Flora Lichtman, and talking about the coffee series. Who would've known, you know? We always used to talk about chocolate having so many things going in it.
LICHTMAN: Yes. But coffee, definitely. And the people who prepare it, these baristas who we talk to...
LICHTMAN: So you can go to sciencefriday.com/coffee, and you'll see the latest video and our older one too. They're like technicians.
LICHTMAN: I mean, they're doing a lot of experiments to get the coffee tasting just right and using the right equipment for the job. It was very educational.
FLATOW: Yeah. It is. It's true. There's a lot of chemistry and a lot of physics. Now, we've got the physics part with the steam that goes through the giant pressure. You hear those things pumping away.
LICHTMAN: That's right.
FLATOW: I never knew why that was. You know why? You get something different than just putting the coffee in a cone with boiling water.
LICHTMAN: Right, right, right. Yeah, what's your favorite preparation?
FLATOW: I like - I - well, I used to have a vacuum maker, an old coffee...
LICHTMAN: Describe it.
FLATOW: It's hard to describe. It was a big - it came in the '40s, the 1940s. It's a big glass bowl and it has a bowl on top. It's like a double boiler bowl and it has a funnel that goes down into the middle and you put water in the bottom. And once you start heating that water, the hot air or the steam inside - the bottom part pushes the water up the glass into the top where the coffee grounds are. It's the most fun one.
LICHTMAN: The pressure differential, right?
FLATOW: Yes. And then once you take it off the heat, it loses the pressure at the bottom and it comes back down through. I was just fascinated with that one.
LICHTMAN: Very cool. I learned - one of my favorite ahas from the series is how maligned the French press is.
LICHTMAN: As a French press drinker for so long, I'm now embarrassed of my French press.
FLATOW: You don't want to tell anybody.
LICHTMAN: No. Oh, no. Yes. French press disgusting. But apparently, it's very hard, again, you know, because coffee making really can become a science with the right temperature and the right amount of time steeping...
LICHTMAN: ...the French press is hard to nail because there's...
LICHTMAN: ...so many variables that are outside of your control.
FLATOW: Right. Right. And it's our Video Pick of the Week up there on our website, and it's beautiful animation.
FLATOW: A lot of gorgeous...
LICHTMAN: And they did a nice a job.
FLATOW: ...they did great animation in this. And I can't imagine having the patience to move these little dots around.
LICHTMAN: No. It's a...
FLATOW: It's coffee granules, I think.
LICHTMAN: ...a great visualization. And I should say that we have another video that done in the same animation style. It's part of the series. It's an experiment people can do at home. So...
FLATOW: Yeah. Oh, yeah.
LICHTMAN: ...this is a good one, and it's very simple. If you have a cone - a cone and a filter that you can just...
LICHTMAN: ...pour hot water over your grounds into. So you have a set of five glasses. You have this cone. You put grounds in it. And then you pour a little bit of - you put the water in and then move the cone from glass to glass over time and you can see the different flavors that come out at different times during your burning process. And the color changes as you go through. It's fun. It's a fun, you know, Saturday morning experiment.
FLATOW: Yes. It's something - it's fun - it's something that you can try at home. And also the other part of the series, and you mentioned this just a bit, is actually evaluating the different ways to - the different coffeemakers...
FLATOW: ..and which one works best for what reason.
LICHTMAN: We've all seen, you know if you've gone to one of these snooty coffee shops - I say that lovingly because I go to them.
LICHTMAN: But, you know, there are all these machines, and you wonder, well, why do you really have to use this one for this?
LICHTMAN: And this video decodes that.
LICHTMAN: It's the gear for your grinds video.
FLATOW: The coffee decoder series.
LICHTMAN: And with some very surprising results. Thank you, Flora.
FLATOW: Flora Lichtman here talking about - it's up there on our website. The whole coffee series, very - quite fascinating, up there on our website at sciencefriday.com. And if you like to watch the way I do, I download them on our app on my iPad app and watch the series all together. It's kind of an interesting way to do it. Transcript provided by NPR, Copyright NPR.