Science Al dente: Elastocapillarity and Swelling of Cooked Pasta*

Food cooking involves diverse chemical and physical reactions, along with an opportunity to connect us to science on a daily basis. Examples include the boiling of eggs, caramelization of the sugar, softening and hardening of bread as function moisture, and cooking and adhesion of noodle strands. Here, we theoretically and experimentally investigate the elastic deformation of pasta noodles as a function of cooking duration and temperature. We submerge two pasta noodles fixed at the top into a hot water tank, then pull them out. The two noodles elastically deform and adhere together due to capillary action. We observe that the stick length of pasta noodles – the distance between the fixed end of pasta and the liquid meniscus between the noodles – decreases as cooking time increases. The duration of cooking affects the swelling of the pasta and its modulus. Liquid migration into the material by diffusion causes radial growth due to hygroscopic swelling and several orders of magnitude drop in Young’s modulus (softening). This, in turn, softens the outer layers of this slender structure, making it more susceptible to deformation by capillary forces. Considering the diffusion dynamics within the pasta, we developed the theoretical model that treats the pasta as a hard core-soft shell structure to predict the stick length at various cooking times, which is corroborated with experimental results. We anticipate that the current work can provide an optimal cooking time finely tuned based on predictive models for various kinds of pasta shapes.