Gel characteristics and microstructure of fish myofibrillar protein/cassava starch composites

- Composites were prepared by mixing fish myofibrillar protein and cassava starch.
- Gel characteristics were determined by the protein or starch domination.
- Strongest synergistic effect occurred at starch fractions of 0.5 and 0.6.
- Synergistic effect resulted from semi-interpenetrating network of protein and starch.
- Starch fraction had no obvious influence on protein secondary structure.

The changes in fish myofibrillar protein/cassava starch composites in the starch fraction range from 0 to 1, with their total content maintained at 60 mg/mL, were investigated in terms of textural properties, rheological behaviours, morphology, spatial distribution and protein molecular structure. The results revealed that the starch fraction of 0.5 was a critical point for the conversion of the protein matrix to starch matrix and conversion of the gel from elastic to weak. Moreover, the protein-starch synergistic effect on the storage modulus was strongest at fractions of 0.5 and 0.6, due to the formation of a semi-interpenetrating network, with more amylose from the melted starch granules interpenetrated with the protein molecules, and the absorption of water by the starch granules to concentrate the protein matrix. Additionally, no covalent interaction between the protein and starch occurred with increasing starch fraction, thus having no significant influence on the protein secondary structure.