Composition versus microstructure in the formation of legume expanded extrudates
Research collaboration to investigate how plant cell microstructure—not bulk composition—drives expansion behavior of legume extrudates during thermomechanical extrusion. The project uses model isolate mixtures and air-classified legume samples to optimize expanded food product development.
Overview
This research investigates why legumes from different botanical sources exhibit markedly different expansion properties during thermomechanical extrusion, despite having similar bulk composition. The central hypothesis is that the microstructural organization within legume cells—which encapsulates starch and protein components—persists even under extrusion shear conditions, resulting in non-homogeneous melt structures that directly affect extrudate expansion. Understanding this relationship will enable better control and optimization of legume-based expanded food products, supporting development of high-protein, plant-based ingredients.
Technical specifications
The research team will use a ThermoPrism twin-screw extruder (length-to-diameter ratio of 40:1) with two different screw configurations. Temperature, shear, and water content will serve as major processing variables. Four legume varieties—urid bean, pea, lentil, and chickpea—will be assessed both as high-protein air-classified samples and as starch/protein isolate mixtures.
Analytical methods include:
- Composition analysis and starch conversion measurement
- Protein solubility profiling
- Microscopy and stained confocal imaging
- Bubble structure characterization
- Glass transition temperature (Tg) analysis
- Thermorheological property assessment
- MicroCT scanning to track microstructural changes
Samples will be evaluated post-die and along the barrel to track protein and starch transformations throughout processing.
Technology readiness level
The research builds on extensive prior work at the University of Nottingham's research and pilot facilities, including demonstrated expertise in starch and protein extrusion. Previous investigations established the relevance of protein crosslinking to extrudate quality, and recent comparative studies of legumes confirmed that expansion does not correlate with chemical composition or physicochemical status alone. This project represents a foundational research stage aimed at generating new understanding to guide future development of additives, legume processing methods, and preconditioning strategies for optimized expansion.
About University of Nottingham
The University of Nottingham is a comprehensive public research university and Russell Group member based in Nottingham, with campuses in China and Malaysia, enabling international collaboration and talent pipelines. Industry partners engage through an on-campus research and technology park that co-locates companies with university groups, plus shared-use facilities and pilot spaces for scale-up. Integration with a major NHS hospital system supports clinical trials and translation, while placements and professional programs connect companies with student and graduate talent. Research is supported by competitive funding from UKRI research councils and Innovate UK, with added support through NHS partnerships and European programs. A dedicated technology transfer office manages IP, licensing, and spinout formation.
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