When you bite into a high quality chocolate bar, there’s a certain crack to it just before it melts in your mouth. Ensuring the chocolate doesn’t melt in one’s hand before you get to this sweet moment, is simply just physics.
This is just one of the many topics discussed in CAS PY 107 Physics of Food and Cooking, a course in BU’s College of Arts and Science, taught by materials physicist Karl Ludwig.
“We’re thinking about food as materials and bringing what we have learned in physics and other branches of science to bear an understanding of food as a material,” Ludwig said.
Rama Bansil, a biophysicist who loves cooking, developed the course inspired by a similar course at Harvard University. When Bansil retired two years ago Ludwig took over the course.
“I hope that [students] take this information and they take it with them as they eat food, they think about what they’re eating and why it is like it is,” Ludwig said. “As they make food, they can appreciate what they’re doing.”
In the class, students make ice cream using two different methods to compare their composition. The more traditional approach uses a salt water solution to cool the ice cream below freezing. Due to the solution not being too far below 0 degrees Celsius, larger ice crystals will form, giving the ice cream a coarser texture, Ludwig said.
In a second trial students use the significantly colder liquid nitrogen and the resulting ice crystals that form are much smaller— giving the ice cream a smoother texture. The experiment demonstrates phase transition between a liquid and frozen water, which Ludwig said is dependent on how far the liquid is cooled below the freezing point.
Students also explored the density of different ice creams, which led them to discover a notable difference in composition between Edy’s and Ben & Jerry’s.
Ben & Jerry’s vanilla ice cream is almost two times as dense as Edy’s slow-churned vanilla, Ludwig said. This is due to a larger amount of air in Edy’s ice cream.
Ludwig learned last year from a student in the School of Hospitality Administration that an ice cream like Edy’s is made to be light and has the minimum amount of cream to be considered ice cream.
At the end of each semester, students have the opportunity to make their own experiment. In the past, groups have looked at the elasticity of gummy bears, the diffusion of a good marinade through a chicken breast and how to make the perfect rice.
Manuela Victorelli, a sophomore in the College of Communication who has taken the class, wrote in an email that Ludwig makes the class a very inviting environment.
“[Ludwig] teaches in a way that is helpful for non-science majors, like me, who aren’t familiar with many of the terms and concepts of the class,” Victorelli wrote.
Ludwig said he has learned a tremendous amount from his students. Food culture in other parts of the world is very different than in the U.S., so Ludwig encourages students with different perspectives to share what they know.
“Like everyone else, I enjoy good food, but I do not have a background in cooking,” Ludwig said. “I’m going to be learning just as they are.”
Ludwig said many students come into the class hoping it’s a cooking course, but find out that it’s really a physics course.
“By the time they come out,” Ludwig said, “a lot of them see that physics can be a lot of fun when we apply it to things we care about.”
Daniela Zubillaga, a sophomore in COM, said she took the course for a BU Hub unit, but it ended up being one of her favorite classes. However, she was initially intimidated.
“I like to give something out of my comfort zone a try,” Zubillaga said. “If it sounds interesting to you but you think it might be hard, that’s not a reason not to [do it].”
Although the food students get to work with in class are often times delicious and fairly enticing, you shouldn’t sign up if your goal is to eat while you work.
“One thing I should also point out,” Ludwig wrote in a follow-up email, “[Is] the lab is not a certified food safe area, so students are not allowed to eat their lab work. Of course it’s difficult to always police the situation.”