Effect of hydrocolloids on gel properties and protein secondary structure of silver carp surimi

Hydrocolloids are the most commonly used additive in the processing of surimi products. However, the effect of hydrocolloids on surimi protein conformation has not been reported, and the level of hydrocolloids may be a key factor influencing the quality of surimi. Therefore, this study investigated the effect of curdlan, xanthan gum, κ-carrageenan, and gelatin at various levels on gel properties and protein conformation of surimi from silver carp.

Addition of curdlan, κ-carrageenan, or gelatin at lower level could significantly promote gel strength, textural profiles, and water holding capacity (WHC) of the surimi gels. However, gel strength and WHC gradually decreased with increasing amount of xanthan gum added. The addition of curdlan or κ-carrageenan remarkably increased the whiteness of surimi gel, but the whiteness decreased when the concentration of κ-carrageenan reached 5 g kg^-1 . Along with the increase of curdlan, κ-carrageenan, or gelatin concentration, the index of hydrophobic interaction and hydrogen bonds first increased and then decreased, whereas index of ionic bonds first decreased and then increased. According to Raman spectroscopy data, a small content of curdlan or κ-carrageenan promoted the conformational transition of surimi protein from α-helix to β-sheet, leading to the changes in gel properties of surimi gels. Scanning electron microscopy photographs showed surimi gels added with 4 g kg^-1 curdlan or 2 g kg^-1 κ-carrageenan had a finer and denser network structure.

Curdlan or κ-carrageenan at an appropriate concentration is a potential modifier to effectively improve the quality of surimi products. © 2020 Society of Chemical Industry.