Effects of Combined Addition of Modified Starch and Non-Muscle Protein on Gel Properties and Protein Conformation of Squid Surimi Products

To improve the gel properties of squid surimi products, we optimized the addition of modified corn starch acetylated distarch phosphate (ADSP) and the non-muscle proteins egg white protein (EWP) and soy protein isolate (SPI), and we evaluated the effects of the addition of ADSP, EWP and SPI on the texture, intermolecular force, protein secondary structure and microstructure of squid surimi products. Furthermore, we explored the mechanism by which modified starch and non-muscle protein improve the gel quality of squid surimi products. The results showed that the gel properties of squid surimi products with 10% ADSP, 7% EWP and 6% SPI were the best. Compared with the control group, the addition of modified starch or non-muscle protein decrease the relative contents of random coil and α-helix in proteins, and increased the contents of β-sheet and β-turn. Their combined addition was beneficial for the retention of β-sheet and β-turn structures during the gelation process, and promoted the hydrophobic interaction between proteins, resulting in the formation of a denser gel network structure, which in turn improved the gel strength and water holding capacity of squid surimi products. Correlation analysis showed that the gel strength and water holding capacity, hydrophobic interaction, and relative contents of β-turn and immobilized water of squid surimi products were significantly positively correlated with each other (P < 0.01), and significantly negatively correlated with the contents of free water and random coil (P < 0.01). Therefore, the addition of 10% ADSP, 7% EWP and 6% SPI improved the gel quality of squid surimi products by affecting protein secondary structure and water distribution.