A new mathematical model describes the swelling, elasticity and adhesion of pasta during cooking

In new research, a team of researchers from the University of Illinois at Urbana-Champaign have documented how pasta – made up of starch granules – swells and softens depending on cooking time, cooking temperature, water and adding salt. They combined measurements of different dough parameters to solve a variety of equations to form a theoretical model for the swelling dynamics of starch materials.

Hwang et al. studied the coalescence induced by capillarity of swelling pastes; they observed that as the pasta is cooked (therefore puffed up and softened), capillary action deforms the noodle more easily, and two pasta noodles can fuse together with the shorter stick length: (a) image of spaghetti aglio e olio; capillary adhesion between noodles is induced by olive oil seasoned with garlic and pepper; (b) radial and axial growth of pasta over time at 100 degrees Celsius cooking due to hygroscopic swelling; the radial deformation increases to 70% of its original deformation and axial to 40% of its original deformation after 30 min of baking (at 100 degrees Celsius); cross section of pasta shows color gradation before it is sufficiently cooked. Image credit: Hwang et al., doi: 10.1063/5.0083696.

“Exploring the properties of noodles was a direct pivot to the lab’s core work of studying the fluid-structure interaction of highly flexible and deformable fibers, hairs, and elastic structures,” said Dr. Sameh Tawfick, a researcher at the Department of Mechanical Sciences and Engineering and the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign.

“For the past few years, we’ve joked about how noodle pasta stickiness is very much related to our work.”

“We then realized that specifically, the mechanical texture of noodles changes with cooking, and our analysis can demonstrate a relationship between adhesion, mechanical texture and cooking.”

In the study, Dr. Tawfick and his colleagues observed how noodles come together when lifted from a plate by a fork.

This allowed them to understand how water-induced hygroscopic swelling affects pasta texture.

As the pasta cooked, the relative rate of increase in circumference of the noodle exceeded the rate of elongation by a ratio of 3.5 to 1 until it reached the firm texture of ‘al dente, before becoming uniformly soft and overcooked.

When the noodles are pulled from the liquid, the surface energy of the liquid creates a meniscus that sticks the noodles together, balancing the elastic resistance of the noodles bending and aided by the adhesion energy of the surface tension of the liquid.

The degree of doneness of a noodle was directly related to the length of the portion that adhered to its neighbors.

“What surprised us the most was that adding salt to boiling water completely changed the cooking time,” Dr. Tawfick said.

“So depending on how much salt is added to the boiling water, the time to reach al dente can be very different.”

The teams results appear this month in the newspaper Fluid Physics.

_____

Jonghyun Hwang et al. 2022. Swelling, softening and elastocapillary adhesion of featured baked pasta. Fluid Physics 34:042105; doi: 10.1063/5.0083696