Effect of kelp powder on gel properties and microstructure of shrimp (Litopenaeus vannamei) surimi

This study systematically investigated the effects of kelp powder (KP) (0%, 1%, 3%, 6%, 9%) on the gelation behavior, physicochemical properties, and protein structural changes in shrimp ( Litopenaeus vannamei ) surimi gel (SSG). Notably, it enhanced gel strength by 156% and increased hardness from 80.05 N to 231.87 N, while appropriately reducing springiness to form a firmer texture. KP addition also improved water retention by facilitating the conversion of free water into immobilized and bound water, leading to a water holding capacity of 86.6% and a cooking loss as low as 1.6%. Rheological analysis revealed that KP fortification increased the storage modulus (G’) and viscosity, indicating enhanced gel network elasticity. At the molecular level, Fourier-transform infrared spectroscopy revealed that KP promoted the transition of protein secondary structures from random coils and α-helices to β-sheets. This structural rearrangement was accompanied by strengthened hydrophobic interactions and disulfide bonding, as confirmed by chemical interaction analysis. Scanning electron microscopy further validated that KP facilitated the formation of a denser and more homogeneous gel microstructure. Collectively, KP acts as an effective functional modifier to enhance SSG quality, providing a theoretical basis for the development of high-quality shrimp surimi-based products with natural additives. • Kelp powder (KP) significantly improved the gel strength and textural properties of shrimp surimi gel (SSG). • The structure of SSG became more homogeneous, and the bound water of SSG increased after KP addition. • Disulfide bonds in SSG was enhanced and KP effectively promoted the cross-linking of SSG proteins. • KP notably improved the water-holding capacity (WHC) and viscoelasticity of SSG. • A compact and integral gel matrix was observed in the SSG with KP addition.