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YouTube / The Royal Institution
YouTube / The Royal Institution

Science for Kids: Making Butter and Whipped Cream

YouTube / The Royal Institution
YouTube / The Royal Institution

Here's a delightful science/cooking project for kids: turning cream into butter and whipped cream! The only equipment you need is a whisk and a jar (no churn required; though that might be more efficient.) In the video below, a group of Brownies do a bit of science and play, learning how and why cream transforms into these alternate forms. This is adorable, and you can actually learn something from it. Enjoy:

You can also download the info-sheet (PDF) for more on the activity and the science behind it.

If you're more into industrial butter production, check out this How It's Made video:

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Kirill Ignatyev, Flickr // CC BY-NC 2.0
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Why Some Cold Cuts Make Iridescent Meat Rainbows—and Why They're Still OK to Eat
Kirill Ignatyev, Flickr // CC BY-NC 2.0
Kirill Ignatyev, Flickr // CC BY-NC 2.0

We eat with our eyes first, and sometimes what we see on our plate turns us off a meal altogether. Take so-called “meat rainbows”: They happen when a slice of deli meat takes on an iridescent shimmer reminiscent of an oil puddle in a parking lot—a.k.a. not something you want on your sandwich. Despite giving a whole new meaning to the phrase "mystery meat," the odd discoloration is perfectly safe to eat, as physicist Dave McCowan at the University of Chicago explained for The Takeout.

The colorful sheen on a slice of roast beef or pastrami isn’t a sign of spoilage or chemical additives—it’s actually a result of the way the meat is cut. Slicing meat “against the grain” means cutting through, rather than parallel to, the bundles of fibers composing the meat’s musculature. This makes for a more tender bite, and it also leaves a grid of evenly-spaced meat fibers. In the right light, this surface lends itself to something called “diffraction.”

Diffraction occurs when light hits a repeating pattern of nooks and crannies. As the white light bounces off the grooves in the meat, it separates into a spectrum of distinct colors. Some of these colors are amplified, creating a mother-of-pearl appearance when viewed together. This is the same effect we see on the backs of CDs and DVDs.

Another possible culprit behind your rainbow meat is thin-film interference. This is sometimes present in meat with a thin layer of oily fat on the surface. The film affects the light passing through it in such a way that only some of the colors in the spectrum come through, hence the rainbow. This phenomenon produces a sheen closer to that of bubbles or oil slicks than laser discs.

Why do meat rainbows only seem to show up in deli slices, not raw cuts? The answer lies in the curing process. A cured ham is likely greasier than a raw pork cutlet, which makes thin-film interference more likely. The muscle fibers in cured and cooked meats are also more tightly packed together, producing the rigid grid necessary for diffraction.

Color also plays a role. Iridescent shimmers are easier to spot on darker meats like beef and some pork—so if you’re eating a slice of turkey from the deli, it could be covered in meat rainbows you don’t notice. We’ll let you decide if that’s a positive thing.

[h/t The Takeout]

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This Holiday Season, Think Twice Before Tasting the Cookie Dough
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Making festive cookies—and licking the bowl—is a time-honored holiday tradition. But while you likely know that raw eggs carry a potential Salmonella risk, it isn't safe to sneak bites of batter even if you opt to use another binding agent. As The New York Times reports, uncooked flour can make at-home chefs ill, according to a new study published in The New England Journal of Medicine.

Authors investigated an E. coli outbreak in late 2015 and 2016 that caused 63 cases of illness in 24 states, and ultimately led to the recall of more than 10 million pounds of General Mills flour and dozens of products that contained the ingredient. They concluded that strains of E. coli bacteria can live in raw flour (in addition to moist food like hamburger meat and produce), and might be more of a widespread health hazard than researchers had previously realized.

"Linking this outbreak to flour was challenging," the report says, according to CNN. "Consumption of raw or undercooked flour is not included on most routine state and national foodborne disease questionnaires, so epidemiologists were not initially able to assess whether case patients had consumed raw flour."

Public health officials ended up having to conduct in-depth interviews with 10 afflicted individuals to identify flour as the culprit ingredient, according to Science News. Sure enough, two of them recalled eating raw cookie dough right before falling ill. Two bags of flour used to make the treats were traced back to the same production plant, and a subsequent analysis located strains of E. coli.

E. coli can stay dormant in flour for months, but re-activates when it's added to eggs, oil, and water. Bakers can avoid infection by heat-treating raw flour, washing their hands with hot water and soap after handling it, or (sorry) by simply not giving into temptation and sneaking a bite of batter mid-baking session.

[h/t The New York Times]

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