Effects of oil-modified crosslinked/acetylated starches on silver carp surimi gel: Texture properties, water mobility, microstructure, and related mechanisms

• Oil-modified starches increased the texture properties of surimi gel. • Oil-modified starches decreased the water mobility of surimi gel. • Surimi/oil-starches formed a homogeneous and compact gel network with tiny pores. • Oil starches promoted the protein conformational transition from α-helix to β-sheet. • Oil-modified starches increased hydrophobic interactions of surimi gel. This study investigated the texture properties, water mobility and microstructure of surimi gel added with crosslinked tapioca starch (CTS) and acetylated tapioca starch (ATS), and their counterparts modified with oil (Oil-CTS and Oil-ATS, respectively). Both Oil-CTS and Oil-ATS could improve the breaking force, deformation and elasticity of surimi gel, especially Oil-CTS. Additionally, oil-modified starches could increase the water-holding capacity of surimi gels and prompt the transformation of free water to bound water, resulting in the decrease of water mobility. The difference between oil-modified starches and their counterparts in gel-enhancing effect is due to the swelling ability and different microstructure of surimi/starch gels. Namely, oil-modified starches prompted the formation of a more homogeneous and compact gel network, endowing the surimi/Oil-CTS gel with tiny pores due to its restricted swelling property, while others were opposite. Raman spectral results further unveiled that the addition of oil-modified starches promoted the protein conformational transition from α-helix to β-sheet and β-turn, as well as a decrease of ionic bonds and an increase of hydrogen bonds and hydrophobic interactions of surimi gel, which were beneficial to form firm and compact gel structure. The overall results indicated the new oil-modified starches (especially Oil-CTS) have great potential to improve the quality of surimi-based products.