Structure formation in high moisture extrudates produced from soy protein fractions varying in 7S/11S globulin ratio.

Abstract

Soy proteins mainly comprise 7S and 11S globulins, which have distinct structural and physical properties. To investigate the impact of soy protein composition on structure formation during high moisture extrusion (HME), fractions enriched in 7S or 11S globulins were prepared and blended in different ratios for lab-scale HME processing. Extrudates prepared from the 11S globulin-enriched fraction were inhomogeneous, as opposed to all other extrudates. Differences in extrudate structure and texture by varying the raw material protein composition were limited. However, 11S globulin-enriched fraction based extrudate was mainly stabilized by disulfide bonds, while with increasing raw material 7S globulin content the importance of non-covalent interactions increased. Even after disrupting all (non-)covalent bonds, high MW aggregates were detected in all extrudates. Thus, the protein composition of soy protein ingredients clearly impacts the type of protein-protein interactions and bonds formed during HME processing. This may hold relevance for the occurrence of specific phenomena during HME, such as syneresis, or the digestibility of the obtained products, although this requires further investigation. Overall, the findings of this study have implications for the use of protein-rich ingredients, which may vary in protein composition as the result of biological variability or prior processing, in high moisture extrusion.