Swelling, softening, and elastocapillary adhesion of cooked pasta

The diverse chemical and physical reactions encountered during cooking connect us to science every day. Here, we theoretically and experimentally investigate the swelling and softening of pasta due to liquid imbibition as well as the elastic deformation and adhesion of pasta due to capillary force. As water diffuses into the pasta during cooking, it softens gradually from the outside inward as starch swells and relaxes. The softening follows three sequential regimes: regime I, the hard-glassy region, shows a slow decrease in modulus with cooking time; regime II, the glassy to rubbery transition region, or leathery region, is characterized by a very fast, several orders of magnitude drop in elastic modulus and regime III, the rubbery region, has an asymptotic modulus about four orders of magnitude lower than the raw pasta. We present experiments and theory to capture these regimes and relate them to the heterogeneous microstructure changes associated with swelling. Interestingly, we observe a modulus drop of two orders of magnitude within the range of al dente cooking duration, and we find the modulus to be extremely sensitive to the amount of salt added to the boiling water. While most chefs can gauge the pasta by tasting its texture, our proposed experiment, which only requires a measurement with a ruler, can precisely provide an optimal cooking time finely tuned for various kinds of pasta shapes. Published under an exclusive license by AIP Publishing.

Automated summary

The chemical and physical reactions that occur during cooking connect us to science on a daily basis. In this study, the swelling and softening of pasta due to liquid imbibition, as well as the elastic deformation and adhesion of pasta due to capillary force, were investigated both theoretically and experimentally. The softening of pasta during cooking follows three sequential regimes, and is associated with changes in microstructure. Notably, the study found that the cooking time and the amount of salt added to the boiling water have a significant impact on the texture and elasticity of the pasta.