Why food sticks to nonstick frying pans

WASHINGTON, February 2, 2021 — Inspite of the use of nonstick frying pans, foodstuff will at times get caught to a heated area, even if oil is made use of. The effects can be extremely messy and unappetizing.

Experts at the Czech Academy of Sciences began an investigation of the fluid houses of oil on a flat surface area, such as a frying pan. Their work, documented in Physics of Fluids, by AIP Publishing, displays convection might be to blame for our stuck-on food.

The experimental investigation applied a nonstick pan with a floor comprised of ceramic particles. A movie camera was placed earlier mentioned the pan as it was heated and used to evaluate the speed at which a dry spot shaped and grew. Additional experiments with a Teflon-coated pan confirmed the identical.

“We experimentally spelled out why foodstuff sticks to the centre of the frying pan,” reported creator Alexander Fedorchenko. “This is triggered by the formation of a dry place in the slim sunflower oil movie as a result of thermocapillary convection.”

When the pan is heated from down below, a temperature gradient is established in the oil movie. For popular liquids, these kinds of as the sunflower oil employed in the experiment, the surface stress decreases when temperature raises. A surface pressure gradient is recognized, directed away from the center exactly where the temperature is greater and toward the pan’s periphery.

This gradient sets up a kind of convection recognised as thermocapillary convection, which moves oil outward. When the oil film in the middle gets thinner than a essential worth, the movie ruptures.

The scientists established the disorders that guide to dry spots for the two stationary and flowing films. These circumstances contain a lower in the community film thickness down below a crucial measurement as perfectly as the sizing of the deformed location falling underneath a selection regarded as the capillary size.

“To steer clear of undesirable dry places, the pursuing set of actions really should be used: expanding the oil film thickness, reasonable heating, wholly wetting the surface area of the pan with oil, employing a pan with a thick base, or stirring foods consistently during cooking,” Fedorchenko stated.

The phenomenon also occurs in other scenarios, these as the slim liquid films utilised in fluid distillation columns or other devices that may well have electronic parts.

“Dry place formation or film rupture performs a detrimental job, resulting in sharp overheating of the electronic factors,” claimed Fedorchenko. “The benefits of this study could, as a result, have wider application.”

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The write-up “On development of dry spots in heated liquid movies” is authored by Alexander Fedorchenko and Jan Hruby. The write-up will appear in Physics of Fluids on Feb. 2, 2021 (DOI: 10.1063/5.0035547). Following that date, it can be accessed at https://aip.scitation.org/doi/10.1063/5.0035547.

ABOUT THE JOURNAL

Physics of Fluids is devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and sophisticated fluids. See https://aip.scitation.org/journal/phf.

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