Impacts of zein-fucoidan nanoparticles with and without curcumin on gel properties of golden threadfin bream ( Nemipterus virgatus) surimi

Zein-fucoidan nanoparticles (ZFNPs) as an excellent colloidal delivery system for bioactive compounds, such as curcumin (CUR), show a great application potential in the food industry. Herein, various amount of ZFNPs, ZFNPs loaded with CUR (CZFNPs) and free CUR were added into golden threadfin bream ( Nemipterus virgatus) surimi to explore their impacts on the gel properties. Dynamic rheological tests showed that storage modulus (G') and loss modulus (G") of surimi gels with the additive amount of ZFNPs and CZFNPs under 0.8 % significantly increased and their loss tangent (tan delta) slightly reduced during thermal gelation, indicating stronger networks and better structural configuration. Puncture test and textural profile analysis confirmed the improvements in breaking force, hardness, chewiness and gumminess of surimi gels. Furthermore, 0.8 % of ZFNPs and CZFNPs induced conformational changes of surimi proteins from alpha-helix to beta-sheet and random coil, and then facilitating the cross-link between proteins. Low-field nuclear magnetic resonance revealed that ZFNPs and CZFNPs promoted the redistribution of water in surimi gel networks, converting more free water to tightly bounded water, and thus increasing the water holding capacity. However, the addition of equivalent amount of CUR caused detrimental to surimi gel properties. In conclusion, ZFNPs and CZFNPs conferred better gel properties and nutritional characteristics to surimi gels, and this study provided a theoretical basis for the development of high- quality surimi products.