Protein pH is key for improving texture in meat alternatives

Consumption of meat, especially of red meat, represents a significant share of the global greenhouse emissions, in particular CO₂, methane and nitrous oxide. Per kilo, beef generates 99.48 kilograms of carbon dioxide equivalent emissions, according to a Science publication from the University of Oxford.

Consequently, a plant-based diet is starting to take a prominent place in western countries. However, trying to mimic the desired textural properties typical of the hierarchical structure of fibers in animal meat has proven to be a challenge.

Today, manufacturers use high-moisture extrusion (HME) to recreate the right texture from plant proteins, such as soy or pea. During HME, proteins go under hydration, heat and shear, and this causes molecular changes that lead to anisotropic (directionally aligned) structures.

Recently, scientists have focused on alkalinization and acidification of water used during extrusion to control protein structure and texture, a process called protein pH-shifting.

Now a team led by the Wageningen University and in collaboration with food manufacturing company Unilever, TU Delft, the ESRF and ISIS, has investigated how pH-shifting during the HME of a soy protein concentrate affects the material’s structure across different scales, from nanometers to millimeters.

They used a multidisciplinary approach, which included Small Angle X-ray Scattering, carried out at the ESRF, and Small Angle Neutron Scattering at ISIS, to look into the nanoscale properties and magnetic resonance imaging and diffuse reflectance for the macroscale structure. “The multiscale nature of meat alternatives makes it necessary to use different methods, SAXS being one of the critical methods here”, explains John van Duynhoven, professor at Wageningen University,   senior scientist at Unilever and co-corresponding author of the publication.

At the ESRF’s ID02, they analysed how protein nano-aggregates change in size and structure depending on pH conditions during extrusion. They found that depending on pH levels, the aggregates further organize in particulate or fibrillar networks.

The researchers believe that the combination of SAXS and SANS is the winning formula in this research: their publication six months ago on the techniques’ “love story” provides details as to how combining both approaches can provide a full picture of the structure (see “SANS and SAXS: A Love Story to unravel structural evolution of soy proteins and polysaccharide fibres during high moisture extrusion for meat alternatives”)

Camilla Terenzi, professor at Wageningen University and corresponding author, explains how the findings could be applied to manufacturing processes: “We found that pH shifting is very promising to enhance the functionality of soy proteins.  In our paper, we explain some practical considerations to consider when implementing pH-shifting at extruders that differ in scale”. 

Reference:

Kuijpers, S.A. et al, Food Hydrocolloids, December 2025. https://doi.org/10.1016/j.foodhyd.2025.111456

Garina E. D., et al, Food Hydrocolloids, October 2024. https://doi.org/10.1016/j.foodhyd.2024.110121

Text by Montserrat Capellas Espuny

Top image: A meat alternative dish. Copyright: The vegetarian butcher