Exploring the relationship between cooking and scientific discovery
Penn physicist Arnold Mathijssen and colleagues have authored a review article discussing the history of food innovations and the current scientific breakthroughs that are changing the way we eat.
Laser tomography of champagne glasses: (left and right) counter-rotating convection cells self-organize at the air-champagne interface, and (center) stabilized eddies in a surface-treated glass.
(Image: Fabien Beaumont, Gérard Liger-Belair, and Guillaume Polidori)
Preparing a great meal can be a process that necessitates considerable patience, skill, and a profound understanding of each ingredient and the steps needed to bring out the best in all of them.
Akin to an orchestra, ingredients can play in unison and generate taste and olfactory-based harmonies, and throughout human evolution, like the composers and conductors of these symphonies, chefs have had to come up with creative new ways to better the final product and solve problems like making certain foods safe to eat.
Some of these adaptations have led to profoundly innovative scientific discoveries.
In a recent review article, a curated summary of research within a given discipline or topic, published in the journal Reviews of Modern PhysicsArnold Mathijssen, an assistant professor of physics in the School of Arts & Sciences, and colleagues describe the rich history of science and food and how many of the solutions to cooking constraints resulted in innovations that paved the way for the culinary arts.
“Just like how one hand washes the other before one prepares a meal, food has taught us so much about science and the breakthroughs throughout the sciences continue to change the way people eat,” Mathijssen says.
He and his colleagues began this review article during the pandemic when many researchers found themselves unable to work in the laboratory and began experimenting in their homes, particularly the kitchen.
“It started mostly with the intent to make an educational tool, seeing as kitchens offer a low barrier of entry to doing science—all you need are some pots, pans, and a few ingredients to get a few reactions going—but quickly grew into a more scientific reflection of the history of food once we realized how interwoven the fields are,” Mathijssen says.
The researchers explored the world of food science through the lens of fluid mechanics, unearthing an intricate fusion of physics, gastronomy, and the dynamics of the kitchen. This review reveals the science of everyday cooking, seamlessly marrying the culinary arts with engineering principles.
To make the information more digestible, the team chose to structure their review as a metaphorical dining experience beginning with “kitchen sink fundamentals,” an exploration of the basics of fluid mechanics as they relate to food preparation and presentation. Like a carefully prepared meal, the review guides readers through various scientific concepts, using the familiar stages of dining as thematic anchors.
“Once you enter the kitchen and open the tap, a wealth of fluid mechanics concepts pour out,” says Vivek Prakash, coauthor of the paper and an assistant professor of physics at the University of Miami.
“As you increase the flow rate, the water jet turns from what is known as a ‘smooth laminar flow’ into an ‘unsteady turbulent jet’ with a hissing sound. Then, when the water jet impacts the sink’s surface, you can see the appearance of a circular ring that represents a hydraulic jump, another phenomenon that is a still an active research topic.”
Next, the researchers explore the “pre-dinner drinks” as they focus on the hydrodynamic instabilities in cocktails, referring to the unpredictable behavior of different fluids interacting like alcohol and mixers. This state is the result of multiphase flows, where two or more phases, liquids, solids, and gases, coexist and influence one another.
A fundamental instability induced by evaporation. The colors indicate the alcohol concentration, from blue (low) to red (high), measured with device that gauges phase shifts by using beams of light.
(Image: Sam Dehaeck)
“Think of a bottle of champagne; there’s a lot of physics going on before and after it’s uncorked,” Mathijssen says. “You have these tiny CO2 gas bubbles that want to separate from the ethanol, a process that takes a lot of energy, affects the taste, and leads to the characteristic pop.”
Referring to the main course, the researchers elucidate the role of heat and its influence on food textures, aromas, and flavors, touching upon the Leidenfrost effect, where a liquid on a very hot surface forms an insulating vapor layer, preventing rapid boiling. This can be seen when water droplets skitter on a hot pan instead of instantly evaporating.
“The subtle squiggly structures that you see near the surface of a heated pan of water are actually plume structures,” Prakash says. “These plumes are hot parcels of fluid and transport heat towards the surface.”
Besides shedding light on culinary practices, the researchers demonstrate the utility of fluid mechanics in developing advanced food technologies, highlight the applicability of these technologies in areas like food safety and quality control, and emphasize the importance of making scientific knowledge more inclusive and accessible.
They point to principles of fluid mechanics used to improve food processing machinery. These microfluidic techniques, extensively used for creating edible foams and emulsions, could, they say, be pivotal in developing novel food microstructures or in extracting bioactive compounds.
In addition, the researchers argue that by using principles of fluid dynamics, the scientific community can contribute significantly to public health by deploying devices that can detect foodborne pathogens or toxins. And they address the need for science-based policy related to environmental sustainability and food safety, referencing the announced EU ban on PFAS nonstick coatings by 2030.
In emphasizing the importance of making scientific knowledge more inclusive and accessible, the researchers encourage contributions from diverse backgrounds as a way to spark curiosity-driven research and education and facilitate a broader societal engagement with science. The authors cite Agnes Pockels' pioneering work in surface science that was inspired by her observations of soap films while washing dishes.
“Hers is a story that speaks to the inequality of science as she was a woman in late 19th century Germany, so she wasn’t allowed to attend university for formal training, which made it difficult for her to submit her research to journals,” Mathijssen says. “But she was undeterred and would use the kitchen as her lab, and she started making devices to measure surface tension in soapy water, findings that greatly contributed to our understanding of surface and liquid interactions.”
By dissecting the science behind everyday phenomena like cooking a meal or brewing a cup of coffee, the researchers say they hope to hold a mirror to the omnipresence of fluid mechanics in human lives.
“The way forward is filled with opportunities to unravel new insights and apply them for a sustainable and inclusive future, turning the act of dining into a scientific adventure. It’s an exciting time to be at the intersection of food and science, where a simple meal can unfold into a captivating exploration of physics, engineering, and human ingenuity,” Mathijssen says.
Arnold Mathijssen is an assistant professor in the Department of Physics & Astronomy in the School of Arts & Sciences at the University of Pennsylvania.
Vivek N. Prakash is an assistant professor in the Department of Physics at the University of Miami
Other authors include Maciej Lisicki of the University of Warsaw and Endre J. L. Mossige of the University of Oslo.
This research was supported by the United States Department of Agriculture (USDA-NIFA AFRI 2020-67017-30776 and 2020-67015-32330).
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