Effect of low moisture extrusion on a pea protein isolate's expansion, solubility, molecular weight distribution and secondary structure as determined by Fourier Transform Infrared Spectroscopy (FTIR)

To investigate the effect of low moisture extrusion cooking on the structural changes of protein and expansion properties, a pea protein isolate was processed in a twin screw extruder at varying screw speed (400-700 min−1), moisture content (26-35%) and barrel temperature (130-170 °C). An expanded protein isolate matrix was achieved for a specific mechanical energy input above 180 kJ/kg and product temperatures above 130 °C. The expanded protein network was presumably stabilized by increased protein aggregation, which most likely was formed by α-helices, β-sheet, non-covalently bonded β-turn or anti-parallel β-sheet structures as identified by FTIR. SDS-PAGE suggested, that neither the vicilin nor the convicilin fraction of the protein were altered, whereas legumin was either proteolysed or aggregated. Processing reduced the protein's water solubility. This knowledge contributes to a deeper understanding of the structural changes in a pea protein isolate as caused by low moisture extrusion.