It's what's on the inside that counts. (Marangoni)

Tell me to picture something “awe-inspringly beautiful,” and my mind will probably wander to an infinite pile of baked goods, a cheese store with endless free samples, or any other stockpile of rich, buttery milk fat. It turns out that many scientists would agree with me.

Fats themselves don't look all that gorgeous at face value. To the human eye, they look like smooth white pastes or thick yellow liquids. But their appearance, taste and nutritional value all depend on microscopic building blocks — the individual fat molecules themselves. Scientists led by Alejandro Marangoni at the University of Guelph are using X-rays and electron microscopes to tell the gorgeous inside story of those milk fats. They published their most recent results in the journal Food Chemistry earlier this month.


A high-contrast microscope image of a milk fat spherulite – the "bookcases" in the library. (Marangoni)

Think of a fat like a delicious library. At the smallest scales are the pages — rows of individual triglyceride molecules. These molecules stack to form the books, or crystalline nanoplatelets — rectangular sheets of fat molecules about a hundred times smaller than the width of a human hair. Each book is aligned neatly in a bookcase; the nanoplatelets, too, arrange themselves neatly in a crystal structure. Finally, each of these bookcases together forms the whole library (or the big cheese).

Milk fat nanoplatelets – the "books". (Marangoni) Milk fat nanoplatelets – the "books." (Marangoni)

As is the case in any library, every small unit can tell you something about the bigger picture. A page can tell you what kind of book you’re reading, a book can tell you what sorts of books are in the case you pulled it from, and the bookcase itself can tell you which section of the library you’re standing in, assuming you still remember how the Dewey Decimal System works.

Scientists are reading individual pages to understand what the fat library looks like.

“What we're planning to do is study how the arrangement of the nanocrystals [is] affected by the different processing conditions we apply to food,” said Pere Ramel, a graduate student working on the study.

The scientists started with a liquid mixture of melted milk fats from a Kraft foods plant, cooled it slowly to form crystals, put the crystals under an electron microscope in Guelph and bounced X-rays off them at the Advanced Photon Source at Argonne National Lab in Illinois to analyze their structure. Cooling the fats at different speeds made different sized crystals, which in turn changed the fats’ melting points. This gave them the varying textures of different dairy products.

The research has obvious applications in the food industry. “There's a lot of issues with milk fat regarding nutrition and sustainability,” said Ramel. “Understanding what milk fat does in food can help you look for or develop alternatives for it.” For example, if a food producer wants to replace trans fat with a healthier alternative — without changing the taste of the food — they’d look to scientists like Ramel to find the best alternatives. Tinkering with foods at the molecular level could make the difference between "I can't believe it's not butter," and "well I don't know what that is but it's certainly not butter, buddy."

Even if health isn’t a big concern, picking and manipulating milk fat based on these structures can help make tasty food even tastier. “If you have a chocolate bar, you want one that tastes and behaves well. The fat actually needs to melt on your tongue to have a good taste,” said Jan Ilavsky, the scientist who runs the USAXS facility at Argonne that measured the fats with X-rays.


A fat crystal shown in polarized light. (Marangoni)

Several of the researchers also noted that the crystalline structure of the fats can be quite beautiful, although I would argue that chocolate bars are beautiful even without extreme magnification.

Putting fats into an electron microscope has its challenges. In Guelph, Ramel’s lab was in a different building than the microscope, so he had to run between buildings with a cooler full of ice blocks and milk fat crystals (yes, run, he says) in order to look at the samples before they melted. And yes, the scientists see the humor in putting milk fat into hundred-million-dollar experiments.

“I love it,” said Ilavsky. “On one of the beamlines we looked at plutonium and chocolate in the same week.”

Ryan Mandelbaum is serious about science, pizza, Guy Fieri and not much else. He enjoys writing about the environment, physics and the macabre. You can spot him wearing a CERN basketball jersey halfway through the movie "Particle Fever."

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