Somewhere on University College London's campus there is a lab occupied by a number of engineers making breakfast. The only thing on the menu in this lab is pancakes, and many of the chefs have terminal degrees in fluid mechanics. Everyone in the lab is possessed with a singular purpose: creating the perfect flapjack. Few would disagree that this is an admirable goal, but the engineers' maniacal pursuit of pancake perfection has less to do with ensuring a delicious breakfast than figuring out what the physics of pancakes can teach us about restoring eyesight.
As the UCL team details in the current issue of Mathematics TODAY, figuring out the physics involved in cooking pancakes could help improve surgical methods for treating glaucoma, a group of eye diseases that can lead to total or partial loss of vision.
By looking at pancake recipes from around the world, ranging from Canadian ploye to Dutch poffertjes to Malaysian lempeng kelapa, the team sought to study how the texture and appearance of the pancakes varied by recipe. According to the UCL team's research, the appearance of pancakes largely depends on how water escapes from the batter during cooking, a factor which is itself influenced by the thickness of the batter.
To arrive at this conclusion, the team analyzed two parameters of each of the 14 pancake recipes. First they looked at the cake's aspect ratio (the pancake's diameter raised by a power of three in relation to the volume of its batter), and then the "baker's percentage" (the ratio of liquid to flour in the batter, which determines the batter's thickness).
What the team found was that small, thick pancakes like Dutch poffertjes had the lowest aspect ratios (3) whereas large, thin pancakes like French crêpes had the largest aspect ratios (300). The baker's percentages didn't have such wild variations, staying in a range of 100 (thick batters with an equal amount of liquid and flour) to 225 (runny mixtures with significantly more liquid than flour).
By maintaining a fixed amount of egg and flour in different batter recipes, the UCL team experimented with different amounts of milk to see how the baker's percentages would affect the appearance of the flapjacks. They found that thicker batters with a baker's ratio of around 100 led to pancakes with irregular craters on the bottom surface because water vapors were trapped in the cooking process and would unevenly raise the pancake from the pan. The thinnest batters with baker's ratios of 225 were found to have even color surfaces pockmarked with darker spots and a distinctive dark outer ring around the edge of the pancake where the batter was thinnest. Water vapor escapes smoothly across the bottom of the pancake, leaving a uniform color and small channels where the water vapor escaped.
"We found that the physics of pancake cooking is complex, but generally follows one of two trends," Yann Bouremel, a co-author of the study at the UCL Institute of Ophthalmology, said in a press release. "If the batter spreads easily in the pan, the pancake ends up with a smooth surface pattern and less burning as the vapor flow buffers the heat of the pan. We found a thin pancake can only be created by physically spreading the batter across the pan and in this case, the vapor tends to escape through channels or diffusion."
According to the team, the observations provide valuable insight into how flexible sheets, like those found in the human eye, interact with flowing vapor and liquid. This is of particular use in figuring out new ways to treat glaucoma, a group of diseases which is characterized by the buildup of liquid around the eye. This liquid is unable to escape and puts pressure on the optic nerve, and overtime this pressure causes damage that can lead to partial or total blindness. Thus, figuring out a way to allow this liquid to escape (say, by studying the way liquid escapes pancake batter) could save people's eyesight.
"To treat [glaucoma], surgeons create an escape route for the fluid by carefully cutting the flexible sheets of the sclera,"Professor Sir Peng Khaw, co-author and Director of the NIHR Biomedical Research Centre at Moorfields Eye Hospital and UCL Institute of Ophthalmology, said . "We are improving this technique by working with engineers and mathematicians. [The pancakes study] is a wonderful example of how the science of everyday activities can help us with the medical treatments of the future."