Easy to digest: neutrons reveal how the human body processes plant proteins

A newly published gives an important contribution to the understanding of physiological processing of plant-based foods. Their results can be used to optimise production, improving the digestibility of plant proteins and thus the nutritious value of vegetarian and vegan dishes.

Throughout the past decades, evidence of the numerous difficulties associated with an overconsumption of animal-derived products such as dairy and meat has been steadily increasing. As a result, more and more people are adopting plant-based diets. Soy, wheat and pea are popular protein sources for vegetarian and vegan dishes and products. In order to optimise their nutritious value, it is essential to understand how they are digested by the human body.

Schematic representation of the in-situ digestion scattering experiments (see text for further details)

A Swedish team of researchers had a very simple, yet complex idea: “We wanted to simulate a human stomach “on a laboratory bench” and to observe what happens to plant-based products during digestion in an acidic environment - which is exactly what our food encounters when we consume it”, says Davide Schirone, post-doctoral researcher at the University of Lund in Sweden and first author of the study.

Together with his colleagues, he succeeded: the scientists deposited a pea protein gel, obtained by heating a protein mixture, on a tiny microfluidic chip – a miniature platform made to manipulate and analyse small volumes of fluids – and flushed it with a liquid closely resembling gastric juice, thereby triggering an artificial digestive process. The compact nature of this experimental setup allowed them to perform their experiments at MAX IV in Lund and the ILL.

“Scattering techniques were key to our project because they allow for studying molecular processes in real time and on multiple length scales at once”, explains Felix Roosen-Runge, the principal investigator of the study. Using small angle neutron scattering (SANS) on ILL’s instrument D33, the team was able to discern molecular characteristics of their gels as they were digested. “Before starting the digestion process, X-ray and neutron scattering showed that our gels contained smaller structures - individual protein molecules - and larger ones, corresponding to assemblies of proteins”, says Schirone. The digestion process was observed to occur in two steps. First the gel reacts to the gastric environment, the clusters of proteins within the gel became more rigid and compact. Then, the breaking down of molecules (hydrolysis) begins.

The digestion of one particular pea protein named convicilin seems to have a particular role. It is fully hydrolysed within the first digestion step, marking the transition towards the second phase. After its disappearance the reaction proceeds faster. “Convicilin appears to have a major role in maintaining the gel structure. Once it is gone, the gel became much less dense, likely due to lacking a structural support matrix”, explains Schirone. Importantly, the team observed that convicilin was more easily digested when it was part of a gel than in solution. This has important implications for the processing of plant-based foods to increase their digestibility. The researchers were also able to draw conclusions on the behaviour of individual protein molecules. “The proteins became more compact before eventually undergoing digestion”, explains Felix Roosen-Runge. “We hope that future experiments can help us clarify these steps in more detail.”

The team’s experiment represents a valuable contribution to the production and to the understanding of physiological processing of plant-based foods. Importantly, their results can be used to optimise the digestibility of plant proteins, thereby ensuring an optimal utilisation of our valuable and limited crop resources. In view of the current challenges surrounding the need to provide sustainable and healthy nutrition to an ever-growing population, such knowledge is becoming increasingly important.

Reference: Schirone, D., Maischberger, A., Dessì, F., Merten, L., Rahdar, N., Herranz-Trillo, F., Matsarskaia, O., Jeffries, C.M., Del Giudice, R. and Roosen-Runge, F. (2025). Two-step digestion pathways of hydrogels from pea proteins. Journal of Colloid and Interface Science, p.139215.

https://doi.org/10.1016/j.jcis.2025.139215

ILL Instrument: D33