Effects of alkali on protein polymerization and textural characteristics of textured wheat protein

- Gluten was extruded by a twin-screw extruder with a fiber structure.
- Alkali added in textural wheat protein decreases SDS extractability.
- Alkali in textural wheat protein improves hardness, elasticity and chewiness.
- Gluten polymerization correlated with textural wheat protein quality.
- Microstructure of textural wheat protein was compact under proper alkaline pH.

The impact of alkali addition on the degree of gluten polymerization and textural characteristics of textured wheat protein was investigated. Results showed that the extrusion process increased the average molecular weight of gluten as evidenced by SDS-PAGE and SDS extractable protein. The addition of alkali not only promoted the degree of gluten polymerization, but also induced dehydroalanine-derived cross-linking. Alkali addition decreased the content of cystine and increased the contents of dehydroalanine and lanthionine. The obvious decrease of free SH showed that dehydroalanine-derived cross-linking was quantitatively less crucial than disulfide cross-linking. Furthermore, the protein cross-linking induced by alkali improved the texture properties of gluten extrudates. SEM analysis showed extrusion under alkaline condition conferred a more fibrous microstructure as a consequence of a compact gluten network.