Neutron scattering explains why gluten-free pasta falls apart (2025)

Using small angle neutron and X-ray scattering, researchers from the European Spallation Source and RWTH Aachen University have compared the nanostructure of gluten-free and normal spaghetti, finding that the kind with gluten is much more forgiving to varied cooking conditions.

Andrea Scotti from RWTH Aachen University, Judith Houston from the European Spallation Source (ESS) have worked with Nathan Cowieson from Diamond's B21 beamline and Greg Smith from ISIS as well as collaborators from the Institut Laue Langevin to study the nanostructure of spaghetti. More specifically, they were looking at the different structures created by gluten-free spaghetti, in comparison to gluten-containing spaghetti. The study is published in the journal Food Hydrocolloids.

Normal pasta is made up mostly of starch and gluten. Starch forms ball-like structures that expand when the pasta is boiled. Gluten, however, is more of a stringy mesh. It tangles around the balls of starch, preventing them from falling to pieces upon expansion. Gluten-free options need to overcome this problem through other means. Currently, these tend to leave the pasta with a strange chewy texture, for a generally less appealing experience in comparison to gluten-containing options.

Aiming to improve this mouthfeel, these researchers used small angle scattering to investigate the nanostructure of spaghetti. Their X-ray experiments involved comparing spaghetti when it was raw, boiled for a variety of cooking times, and boiled with salt.

They also saw that salt not only affects the taste, but also the structural integrity. Adding salt preserved the structure of the spaghetti, but only when used at the right concentration, and if the pasta was cooked for the right length of time.

For their neutron experiments, the researchers cooked the spaghetti in D₂O in one of the ISIS labs, slicing the spaghetti into tiny pieces before it was loaded into the sample chamber. By using different mixtures of H₂O and D₂O, they could make samples that each highlighted a different component of interest, with others appearing invisible to the neutron beam. This meant they could separate the effect of cooking on the starches and the gluten.

They found that the starch granules swell upon cooking and tend to disperse, whereas the gluten proteins become insoluble and coagulate into a network. This has the effect of trapping the starch and retaining the structure of the pasta.

In the gluten-free spaghetti, this network is missing, which means the starch granules can over-swell. This is why gluten-free pasta can fall apart or become sticky during cooking, especially if cooked for longer than the manufacturer's instructions.

The researchers plan to continue their work, using small angle neutron and X-ray experiments to study pasta varieties of different shapes and manufacturing conditions, as well as replicating what happens to the pasta once it's inside the stomach and seeing what effect that has on the structure.