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Food Science

Limoncello observations and more thesis treats

by Laura Howes
April 28, 2019 | APPEARED IN VOLUME 97, ISSUE 17

 

Looking into limoncello

09717-newscripts-limoncello.jpg
Credit: Laura Howes/C&EN
Mellow yellow: Limoncello, best served chilled, cloudy, and with an appreciation of the nanoscale structure within.

Running fun experiments in a scientist’s spare time has a long and illustrious history, but not all researchers have access to a neutron beam source. Someone who does is chemist Leonardo Chiappisi, a Sicilian and lover of limoncello who works at the Institut Laue-Langevin, in Grenoble, France. What, he wondered, could neutron scattering tell him about his beloved aperitif?

The results, he says, “turned out to be much more interesting and relevant than we thought.”

Limoncello, for those who haven’t enjoyed an ice-cold glass of the drink after a meal, is a bright-yellow and intensely lemony spirit. It is made by macerating lemon zest in high-strength ethanol for several weeks and then diluting the fragrant extract with a sugar syrup. And while each family’s recipe is different, the resulting liqueur displays an effect common among similarly flavored spirits: when the aqueous sugar solution is added to the ethanol-lemon oil mix, the drink becomes cloudy.

This phenomenon suggests that an emulsion forms spontaneously with just a little shaking and no additional emulsifiers. And Chiappisi says he won’t drink a limoncello that isn’t cloudy.

With lemons he bought when back in Sicily, Chiappisi used his normal recipe to make limoncello but with deuterated ethanol and heavy water. The result, he says, is the same “except the limoncello is a bit more expensive.” It also means the neutrons interact with the nanostructures in the drink.

Chiappisi found that the oil droplets in limoncello have a radius of around 100 nm (ACS Omega 2018, DOI: 10.1021/acsomega.8b01858). It’s this small size, he suggests, that makes limoncello so stable. “You can buy a bottle of limoncello and it can stay cloudy in the fridge for years,” he says. In contrast, his French coworker Isabelle Grillo says that if you forget a glass of pastis, a French drink that displays a similar effect, you can come back to find that it has become transparent again.

While Chiappisi and Grillo hope that their findings can eventually be applied to industrial applications, the Newscripts gang will enjoy the next glass of limoncello with more appreciation for what’s going on inside.

 

Doctoral indulgences

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Credit: Douglas B. Seba
Something fishy: It seems artistic inspiration can strike many a thesis-writing chemist.

In January, the Newscripts gang shared its appreciation of treats slipped into PhD theses. One author added a flip book to the corner of his thesis, and several other scientists added treats to their academic work. We asked for more to be sent in, and our readers did not disappoint.

Andrew Lees dedicated his thesis to the rabbits, both lab and magic, and Douglas B. Seba added an image of a tarpon (shown) to the front page of his thesis on the effects of a pesticide on the teleost class of fish. “I thought this image perfectly conveyed the essence of my studies and the nature of this fish,” Seba says. However, he recalls that the University of Miami felt that the image of a game fish striking a dieldrin molecule detracted from the scholarly nature of the work.

Harry K. Garber added selected quotations to the start of every chapter of his thesis and points out that these sorts of additions have also been used by eminent scientists such as Max Born, who added flip-book images, or as Born called them, “films,” into the corner of The Restless Universe. And Michael Bayler recalls a curious citation appearing in the third edition of Advanced Inorganic Chemistry by F. Albert Cotton and Geoffrey Wilkinson. “According to a story I heard, the authors had their students proof check the many literature references,” Bayler explains. To confirm that “thallous solutions are exceedingly poisonous and in traces cause loss of hair,” one proofreader inserted a reference to an Agatha Christie mystery tale in which a character is poisoned by thallium.

Thanks also to Brian Love, who shared both his poetic acknowledgments and the phrase his colleagues used to describe flourishes to theses, the slightly unedifying term “thecal matter.”

Laura Howes wrote this week’s column. Please send comments and suggestions to newscripts@acs.org.

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