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YouTue / Wired
YouTue / Wired

What's in Your Cup of Coffee?

YouTue / Wired
YouTue / Wired

Have you ever wondered what gives coffee its distinctive odor? How about those chemicals in coffee that aren't caffeine -- what are they, and what do they do? In this super-short video from Wired, we get a breakdown of what's in a typical cup of coffee...and why good things sometimes come in small doses.

If you like your data in old-fashioned "written" form, check out this Wired page, which conveys roughly the same info. For instance:

Putrescine
Ever wonder what makes spoiled meat so poisonous? Here you go. Ptomaines like putrescine are produced when E. coli bacteria in the meat break down amino acids. Naturally present in coffee beans, it smells, as you might guess from the name, like Satan's outhouse.

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Researchers Pore Over the Physics Behind the Layered Latte
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The layered latte isn't the most widely known espresso drink on coffee-shop menus, but it is a scientific curiosity. Instead of a traditional latte, where steamed milk is poured into a shot (or several) of espresso, the layered latte is made by pouring the espresso into a glass of hot milk. The result is an Instagram-friendly drink that features a gradient of milky coffee colors from pure white on the bottom to dark brown on the top. The effect is odd enough that Princeton University researchers decided to explore the fluid dynamics that make it happen, as The New York Times reports.

In a new study in Nature Communications, Princeton engineering professor Howard Stone and his team explore just what creates the distinct horizontal layers pattern of layered latte. To find out, they injected warm, dyed water into a tank filled with warm salt water, mimicking the process of pouring low-density espresso into higher-density steamed milk.

Four different images of a latte forming layers over time
Xue et al., Nature Communications (2017)

According to the study, the layered look of the latte forms over the course of minutes, and can last for "tens of minutes, or even several hours" if the drink isn't stirred. When the espresso-like dyed water was injected into the salt brine, the downward jet of the dyed water floated up to the top of the tank, because the buoyant force of the low-density liquid encountering the higher-density brine forced it upward. The layers become more visible when the hot drink cools down.

The New York Times explains it succinctly:

When the liquids try to mix, layered patterns form as gradients in temperature cause a portion of the liquid to heat up, become lighter and rise, while another, denser portion sinks. This gives rise to convection cells that trap mixtures of similar densities within layers.

This structure can withstand gentle movement, such as a light stirring or sipping, and can stay stable for as long as a day or more. The layers don't disappear until the liquids cool down to room temperature.

But before you go trying to experiment with layering your own lattes, know that it can be trickier than the study—which refers to the process as "haphazardly pouring espresso into a glass of warm milk"—makes it sound. You may need to experiment several times with the speed and height of your pour and the ratio of espresso to milk before you get the look just right.

[h/t The New York Times]

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11 Behind-the-Counter Secrets of Baristas
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Andrew Burton/Getty Images

Being a barista is no easy task, and it’s not just the early hours and the don’t-talk-to-me-unless-I’ve-had-my-coffee customers. While people often think working at a cafe is a part-time, temporary gig, it takes extensive training to learn your way around an espresso machine, and most baristas are in it for the love of coffee, not just to pay the bills. Mental Floss spoke to a few baristas working at the New York Coffee Festival to learn what exactly goes on behind the counter, and why you should never, ever dump your extra coffee in the trash.

1. THEY REALLY LOVE COFFEE.

One of the biggest misconceptions about the profession, says New York City-based barista Kayla Bird, is “that it's not a real job.” But especially in specialty cafes, many baristas are in it for the long haul. Coffee is their career.

“It's a chosen field,” as barista Virgil San Miguel puts it. “It's not like you work in a coffee shop because it's a glamorous job,” he explains. “It's more like a passion.”

2. THEY GO THROUGH A LOT OF TRAINING.

“Being a really good barista takes a lot of studying,” explains Jake Griffin, a wholesale representative for Irving Farm Coffee Roasters who has worked in the coffee industry for almost a decade. “It can take a few years. You have to start to understand origins, production methods, where your coffee came from.” You have to go through an intensive education before you start pulling espresso shots for customers, so it's possible that the person taking your order and fetching your pastry isn't even allowed to make you a drink yet. “They have to be what we call 'bar certified' before they're even allowed on the machine,” he says. “Usually people start off in our cafes in various support roles, then start to go to classes and go through the training program.”

3. THEY’RE PROBABLY PRETTY WIRED.

Sure, baristas take full advantage of all that free coffee. And if they work in their company’s training programs, their whole job is to drink coffee. But it has its downsides. “I taste—at minimum—ten shots of espresso a day,” John Hrabe, who trains baristas at Birch Coffee in New York City, says. On his busier days, it might be as many as 20. You get used to all the caffeine, he claims—at least until you take a few days off. “Then when you go on vacation and you're not working ... everyone's like, 'Why's John so tired?’”

Other baristas who have worked in the field for a long time say the same. “I’ve been doing this for 15 years, and I used to have five or six coffees a day,” Michael Sadler, who helped develop the barista education program at Toby’s Coffee, says. “Now I do two,” he says, both because of the caffeine-induced anxiety and the withdrawal headaches he would get on his days off.

4. OR THEY’RE DRINKING … SOMETHING ELSE.

Like any job, there are things that go on in coffee shops that the boss would definitely not approve of. According to one barista who has worked at both a corporate coffee chain and specialty cafes in Delaware and New York, coffee shops can get pretty rowdy behind-the-scenes. “If you see a barista with a lidded cup behind the bar, there's probably a 50/50 chance: It's either coffee or beer,” he says. “You never know.” And it’s not just the booze, either. “I’ve been a part of secret menus that have cannabis-infused coconut milk,” he explains. “I had a pretty good cappuccino.”

5. THEY GET ANNOYED WHEN YOU SKIP THE PLEASANTRIES.

You don’t want to hold up the line telling a barista your life story at 7 a.m., but even if you’re in a hurry, don’t forget to say hi before you jump into demanding that large coffee. “Walking up to somebody and saying 'Almond latte,' when they just said 'How are you today?' is probably the biggest thing you can do to get on a barista's bad side,” Toby's Coffee's Sadler says. “It's like, exchange pleasantries, then get to business.”

6. IF YOU’RE NOT NICE TO THEM, THEY WON’T BE NICE TO YOU.

Not everyone is super perky in the morning, but if you can’t be civil, you’re better off making your own coffee at home. At some places, if you get snippy with the employees, you’re going to get worse than furtive eye rolls between baristas (though you’ll get that, too).

“Be nice to your baristas, or you get decaf,” warns one barista. While it varies from cafe to cafe, multiple baristas told Mental Floss that it happens. Rude customers might get three letters written on their cup: “They call it DTB—‘decaf that bitch.’”

There’s a less potent way a barista can get back at you, too. If the hole in your coffee lid lines up with the seam of your paper cup, you’re going to get dripped on. And sometimes, it’s not an accident. “When a barista puts the mouth on the seam, they want it to leak on you,” a New York City-based barista explains.

Others are a little more forgiving of rude patrons. “I like making them the best drink that they've ever had, just to kill them with kindness,” one coffee shop employee says. “I don't want them to be like, ‘She’s a bad barista.’” Just to be safe, though, it's better to be nice.

7. THEY PROBABLY KNOW WHAT YOU WANT BEFORE YOU DO.

“The longer you work in coffee, the more when someone walks in the door you read their personality type and say, I know exactly what you're going to drink,” Jared Hamilton, a self-described “espresso wizard” at the Brooklyn-based chain Cafe Grumpy, says. When I ask him to predict my drink, he proves his skills. “What you're going to drink is like, an alternative milk, flat white or cappuccino. So maybe soy, probably almond. Nonstandard. You don't want a lot of milk, just enough.” He’s not too far off—my go-to is, in fact, a non-standard, some-milk-but-not-too-much drink, a decaf cappuccino, though I drink regular milk in it. He points to another festival visitor who is dressed in business attire. "That guy right there, he drinks espresso all day," he guesses.

Depending on the coffee shop, the barista might know what customers want more than they do. Dominique Richards, who started her first barista job in Brooklyn three months ago, says she has to order for her customers around a third of the time. “Usually if someone's looking at the menu for more than 30 seconds, I jump in and say, ‘Hey, what would you like?’” She then asks them a few questions, like whether they want hot or cold coffee, and goes from there, often recommending lattes for people who are just getting into specialty coffee. “It's kind of a learning experience for the majority” of her customers, she says.

8. CUSTOMERS CAN BE REALLY PARTICULAR.

“People treat cafes like they're [their own] kitchen,” according to Cafe Grumpy’s Hamilton. “My favorite thing people do is when they walk in and they rearrange the condiment bar. Then they order, then they go use the condiments.” Apparently, some people are really particular about the location of their sugar packets. And if you throw off their routine, watch out. One of his colleagues describes a customer who threw a fit because the shop didn’t have a cinnamon shaker, demanding a refund for both her coffee and her pastry. (They eventually found some cinnamon for her.)

9. YOU SHOULD NEVER, EVER DUMP EXTRA COFFEE STRAIGHT INTO THE TRASH.

Even if you ask for room for milk in your drip coffee, the cup is still sometimes just a bit too full. It’s tempting to just pour a little into the trash can, but whoever has to take out that garbage is going to pay for it. “Please don't pour it in the garbage,” Bluestone Lane barista Marina Velazquez pleads. “Because at the end of the night, it ends up on our feet.” If the shop doesn’t have a dedicated container for you to pour out your excess coffee, take it back to the counter and ask them to dump a bit in the sink. Your baristas will thank you.

10. MAKING ESPRESSO DRINKS ISN’T A ROTE SKILL.

When you’re waiting in line, it may look like baristas are doing the same thing over and over for dozens of drinks. But in fact, every order presents its own challenges.

“There's probably not an appreciation for how much a coffee can vary,” explains Katie Duris, a former barista of 10 years who now works as a wholesale manager at Joe Coffee. High-quality coffee is “really dynamic as an ingredient,” she says. Baristas “have to make micro adjustments all day long. You have to change the grind based on the humidity in the room or a draft or how much coffee is in your hopper—if it's an espresso machine—so they're tweaking all day long … good baristas are making adjustments all the time.”

11. IT’S PHYSICALLY TAXING.

Making espresso drinks all day long can wear you out, and not just because you’re on your feet all day. There are also repetitive stress injuries to consider. “There's physical wear and tear on your joints when you're a barista,” Birch's Hrabe says. He’s worked in coffee for 11 years, and says that tamping espresso shots (compressing the grounds before brewing) day after day has given him tennis elbow. “It's totally common for baristas,” he says.

In short, baristas are probably doing more work behind the bar than you give them credit for, whether it’s dealing with customers or actually making coffee. “Being a barista is fun, but it's hard work,” Bluestone Lane's Velazquez says. “Everybody should be a barista at least once. I think it teaches humility.”

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