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Senior Sigrid Kiledal researched coffee at Hillsdale College this summer (photo: Madeleine Jepsen / Collegian).
Senior Sigrid Kiledal researched coffee at Hillsdale College this
summer (photo: Madeleine Jepsen / Col­legian).

Since the 10th century, coffee con­nois­seurs have sought after and crafted the best brews. This summer, senior chem­istry major Sigrid Kiledal looked at the “perfect” cup of coffee through the lens of science.

Kiledal’s research project com­bined two of her interests: chem­istry and coffee. She orig­i­nally learned about the coffee-making process from her father, who roasts his own coffee.

“It’s always been some­thing I’ve been inter­ested in because my dad has been roasting coffee for a long time, just for fun,” she said.

For this project, Kiledal set out to analyze the amounts of caf­feine and chloro­genic acid present in an ideal brew. Chloro­genic acids con­tribute to coffee’s acidity, which can corrode teeth and cause indi­gestion. Based on the data she col­lected, Kiledal would be able to find which coffee roasts had minimal acidity and high caf­feine content while still falling within optimal brewing stan­dards.

“Being able to look at what the instrument tells you and see how much is there, that’s really inter­esting,” Kiledal said. “A lot of coffees will say, ‘If you make it like this, you’ll have this much caf­feine,’ but you don’t really know if that’s accurate or not.”

Kiledal is con­tinuing to look at her data in-depth, but the trends show Kenyan coffee beans to be most acidic, with dark roasts gen­erally con­taining more caf­feine and less chloro­genic acid than light and medium roasts.

“It really looks like a darker roast actually yields more caf­feine,” Kiledal said. “You would think that the caf­feine would break down during the roasting process, but that does not seem to be the case.”

For her project, Kiledal fol­lowed inter­na­tional stan­dards for the ideal cup of coffee, which differ from region to region.

“There’s some­thing called a brewing ratio for what the ideal coffee is, and it depends on what country you’re in,” Pro­fessor of Chem­istry Lee Baron said. “What you’re trying to do is get a coffee that fits in the ideal range.”

Orga­ni­za­tions such as the Spe­cialty Coffee Asso­ci­ation of America, Spe­cialty Coffee Asso­ci­ation of Europe, and the Nor­wegian Coffee Asso­ci­ation all offer stan­dards for roasting and brewing coffee beans for an optimal cup of coffee.

Using these stan­dards, Kiledal focused her research on coffee beans from Guatemala, Kenya, Maui, and Papua New Guinea.

But brewing the coffee was hardly the beginning. Before she could determine the levels of chloro­genic acid and caf­feine, she first had to roast the green coffee beans, and then grind as well as brew the coffee in a con­sistent manner so the sub­se­quent analysis would yield mean­ingful results. In the process, she had to develop a new method to analyze both com­po­nents simul­ta­ne­ously.

“She was trying to look at a very com­pli­cated thing,” Baron said. “Coffee is hugely com­pli­cated, and that’s the issue. There are so many com­po­nents, and you have to figure out a way to pick out just the ones you want to look at.”

Kiledal used a liquid chro­matog­raphy instrument to sep­arate the com­po­nents of the coffee samples, and a mass spec­trometer, which sorts out and mea­sures the com­po­nents according to mol­e­cular weight, to determine the levels of caf­feine and chloro­genic acid present in each coffee brew.

“After it goes through the chro­matog­raphy column, then those indi­vidual por­tions go into the mass spec­trometer,” Pro­fessor of Chem­istry Mark Nussbaum said. “Then you’re looking specif­i­cally for a given mass. The mass spec­trometer gives you the ability to detect and quantify what’s there at one par­ticular mass, but it also allows you to scan a range of masses so you can get a full mass spectrum.”

She then com­pared the readings from the coffee samples to stan­dards of pure caf­feine and chloro­genic acid pre­pared at known con­cen­tra­tions.

“That’s what they do in crime labs, that’s what they do in hos­pital labs,” Baron said. “They only know how much of some­thing is in a sample if they have stan­dards [to compare it to].”

Baron said Kiledal’s detailed prepa­ration of the coffee and the extra work she put into ensuring her results were repro­ducible made her project stand out.

“People have looked at coffee and caf­feine for forever, but the way she went about it and chose her vari­ables was unique,” Baron said.