image: This is an example of pancakes. view more
Credit: Rob Eagle, UCL
Understanding the textures and patterns of pancakes is helping UCL scientists improve surgical methods for treating glaucoma.
The appearance of pancakes depends on how water escapes the batter mix during the cooking process and this varies with the thickness of the batter, according to new UCL research. Understanding the physics of the process can help perfect pancake making and gives important insights into how flexible sheets, like those found in human eyes, interact with flowing vapour and liquids.
Co-author Professor Ian Eames, Professor of Fluid Mechanics at UCL Engineering, said: "Pancakes come in many shapes and sizes and everyone has their favourites - some prefer a small, thick pancake with a smooth surface whereas others enjoy a large, thin crêpe with 'craters' and crispy edges. We've discovered that the variations in texture and patterns result from differences in how water escapes the batter during cooking and that this is largely dependent on the thickness and spread of the batter."
The study, published in Mathematics TODAY, compared recipes for 14 different types of pancakes from across the world including the Canadian ploye and Malaysian lempeng kelapa. For each, the team analysed and plotted the aspect ratio, i.e. the pancake diameter to the power of three in relation to its volume of batter, and the baker's percentage which is the ratio of liquid to flour in the batter, i.e. the thickness of the batter.
They found thick, almost spherical pancakes such as Dutch poffertjes had the lowest aspect ratio at 3, whereas large, thin French crêpes had the biggest at 300. The baker's percentage didn't vary as dramatically, ranging from 100 for thick mixtures (i.e. equal measures of flour and liquid) to 175 for thinner mixtures containing more liquid.
To explore how these ratios influence the textures and patterns of pancakes, the scientists made batters with a fixed amount of flour and egg but different amounts of milk. Pancakes were made using the batters in the same pan, at the same heat and without fat. The scientists found that:
- Thick batters with a baker's percentage of 100-120 form pancakes with irregular craters on the bottom surface. Water vapours released during cooking get trapped, unevenly lifting the pancake from the pan. Islands form on top surface as the pancake isn't a uniform thickness (images available if not shown below).
- Thinner batters with baker's percentage of 175 form pancakes with an even colour on the bottom surface as water vapour is released smoothly from the base as it cooks. This effect is also seen in small pancakes irrespective of the thickness of the batter (images available if not shown below).
- The thinnest batters with a baker's percentage of 200-225 form pancakes with an even coloured bottom surface which is dotted with dark spots. Water vapours escape smoothly across the bottom surface and through channels in the batter. The top surface of the pancake is uniform in colour but is pitted with tiny channels where the vapour escaped. It also has a distinctive dark ring around the outer edge where the batter was thinnest (images available if not shown below).
Co-author Dr Yann Bouremel, UCL Institute of Ophthalmology, said: "We found that the physics of pancake cooking is complex but generally follows one of two trends. If the batter spreads easily in the pan, the pancake ends up with a smooth surface pattern and less burning as the vapour 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 vapour tends to escape through channels or diffusion."
Co-author Professor Sir Peng Khaw, Director of the NIHR Biomedical Research Centre at Moorfields Eye Hospital and UCL Institute of Ophthalmology, said: "We work on better surgical methods for treating glaucoma, which is a build-up of pressure in eyes caused by fluid. To treat this, surgeons create an escape route for the fluid by carefully cutting the flexible sheets of the sclera. We are improving this technique by working with engineers and mathematicians. It's a wonderful example of how the science of everyday activities can help us with the medical treatments of the future."
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The research was funded in part by the Helen Hamlyn Trust in memory of Paul Hamlyn, the UK National Institute for Health Research Biomedical Research Centre at Moorfields Eye Hospital and the UCL Institute of Ophthalmology and Moorfields Eye Charity.
Notes to Editors
For a copy of the paper or to speak to the researchers, please contact Dr Rebecca Caygill, UCL press office. T: +44 (0)20 3108 3846 / +44 (0)7733 307 596, E: r.caygill@ucl.ac.uk
Ian Eames, Peng T. Khaw and Yann Bouremel, 'How to make the perfect pancake' appears in the current issue of Mathematics TODAY, the membership publication of the Institute of Mathematics and its Applications (IMA).
Video available: https://www.youtube.com/watch?v=wsFjIJMTUiE
About UCL (University College London)
UCL was founded in 1826. We were the first English university established after Oxford and Cambridge, the first to open up university education to those previously excluded from it, and the first to provide systematic teaching of law, architecture and medicine. We are among the world's top universities, as reflected by performance in a range of international rankings and tables. UCL currently has over 35,000 students from 150 countries and over 11,000 staff. Our annual income is more than £1 billion. http://www.ucl.ac.uk | Follow us on Twitter @uclnews | Watch our YouTube channel YouTube.com/UCLTV
NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology is a partnership between Moorfields Eye Hospital NHS Foundation Trust and the UCL Institute of Ophthalmology. Established in April 2007, its purpose is to conduct 'translational research' that is designed to take advances in basic medical research from the laboratory to the clinic, enabling patients to benefit more quickly from new scientific breakthroughs. Our centre is currently one of 12 biomedical research centres that were awarded in 2007 to NHS/university partnerships with an outstanding international reputation for medical research and expertise, and experience of translating that research into the clinical setting. For further information, please visit http://www.brcophthalmolgy.org/
Moorfields Eye Hospital NHS Foundation Trust is one of the world's leading eye hospitals, providing expertise in clinical care, research and education. We have provided excellence in eye care for more than 200 years and we continue to be at the forefront of new breakthroughs and developments. We are an integral part of one of the UK's first academic health science centres, UCL Partners, and now one of the first academic health science networks, were one of the first organisations to become an NHS foundation trust in 2004. For further information, please visit http://www.moorfields.nhs.uk.
About the NIHR
The National Institute for Health Research (NIHR) is funded by the Department of Health to improve the health and wealth of the nation through research. Since its establishment in April 2006, the NIHR has transformed research in the NHS. It has increased the volume of applied health research for the benefit of patients and the public, driven faster translation of basic science discoveries into tangible benefits for patients and the economy, and developed and supported the people who conduct and contribute to applied health research. The NIHR plays a key role in the Government's strategy for economic growth, attracting investment by the life-sciences industries through its world-class infrastructure for health research. Together, the NIHR people, programmes, centres of excellence, and systems represent the most integrated health research system in the world. For further information, visit the NIHR website http://www.nihr.ac.uk