&Bullet; physics 14, p26

An X-ray scattering technique shows how protein gels on different length and time scales.

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When the protein of an egg boils, the protein molecules it contains unfold and combine to form a network that turns the viscous mass into a solidified gel. Nafisa Begam from the University of Tübingen and colleagues have now experimentally constructed a detailed picture of how the proteins form this structure [1] . Understanding how a protein transforms in the presence of heat is of interest to the food industry – because of the multiple uses the food has in cooking and baking – as well as to researchers studying the behavior of colloidal gels and proteins.

Researchers have studied protein gelation at the molecular level to see how individual proteins unfold and bond with their neighbors. However, to fully understand the gelation process, the substance must be observed on larger micrometer scales – something that was not possible with previous methods. In their experiments, Begam and colleagues extracted the protein from a store-bought chicken egg and then heated it on a laboratory heating platform. They examined the whites using X-ray photon correlation spectroscopy along with ultra-small angle X-ray scattering techniques that allowed them to observe gelation in the micrometer range of the resulting mesh size of the network.

The team found that the network formed in the white within minutes of the application of heat; after that, no further structure developed. Meanwhile, the dynamics of the gel showed two clear regimes: The relaxation time – the time that parts of the network need to reach a “relaxed” state after stress during network formation – first grew exponentially and then stabilized at a nearly constant value. The team says the X-ray scattering techniques they used can be applied to reveal the dynamics of other soft systems over a range of length scales.

–Erika K. Carlson

Erika K. Carlson is Corresponding Editor for physics based in New York City.

References

  1. N. Begam et al., “Kinetics of network formation and heterogeneous dynamics of a protein gel, which was demonstrated by coherent X-ray scattering”, Phys. Rev. Lett.126, 098001 (2021).

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