Effects of nanosized okara dietary fiber on gelation properties of silver carp surimi

Gelling properties of the silver carp surimi incorporated with nanosized okara insoluble dietary fiber (NIDF) were studied. Breaking force of surimi gel continuously increased (P < 0.05) with NIDF concentration up to 0.8 g/100 g surimi. As the concentration of NIDF increased, percentage of free water in surimi gel decreased (P < 0.05); and distribution of water molecule became more uniform. However, the percentage slightly fluctuated and the distribution became less uniform as the concentration was exceeded 0.2 g/100 g surimi. Light microscopy images indicated that NIDF particles were well embedded without disrupting the integrity of gel matrix. Fourier transform infrared spectra of the surimi gel samples incorporated with various concentrations of NIDF were not obviously different, implying the chemical structure of fish myofibrillar proteins from surimi gel was not affected by NIDF. Results suggested that NIDF improved surimi gel texture primarily by the physical functions of filling in gel matrix and absorbing water.