Modified starch on quality of low moisture extruded soybean protein-wheat gluten

The impact of cassava starch (CS), carboxymethyl starch (CMS), and hydroxypropyl starch (HS) on the protein structure and physicochemical properties of extruded products was investigated with soybean protein-wheat gluten as the primary raw material. The quality improvement effect of starch addition on the extruded products was elucidated.

The quality of extruded products was controlled by the type and content of starch. It was shown that the secondary structure of the protein changed to the ordered β-sheet structure, which was conducive to the increase of the hardness and chewiness of the extruded products by adding 2-6% starch, by Fourier-transform infrared spectroscopy analysis. However, protein aggregation and crosslinking were destroyed by adding 10% starch, and the internal cavity of extruded products became larger, resulting in poor formability and quality of extruded products, with the increase of starch content. The extruded products showed the largest energy storage modulus and could form more hydrogen bonds to maintain protein structure stability with 6% CMS. The addition of 6% HS led to an enhancement of hydrophobic interaction and an increase in energy storage modulus. This promoted protein molecule aggregation, significantly improving the extruded product's quality.

Modified starch (CMS and HS) was appropriately added at 2-6%, and the extruded products were formed into a uniform laminar flow. The quality of the extruded products was significantly improved compared with the addition of CS. This study has provided useful information for improving the quality of extrusion products by adding natural starch and modified starch. © 2025 Society of Chemical Industry.