Fabrication of composite hydrogels by sonication-assisted assembly of okara cellulose nanofibers and guar gum: unraveling structure, properties, and tofu quality enhancement

This study focused on the fabrication of composite hydrogels using okara cellulose nanofibers (CNFs) and guar gum (GG)and then evaluating their potential application in modifying the properties of tofu. Okara CNFs were extracted and oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), and then various hydrogels were prepared and added to tofu. The results indicated that the hydrogen bonds between okara CNFs and GG (FTIR: O-H peak red shift) and the strong electrostatic repulsion among okara CNFs (ζ-potential of CNFs: −32.9 mV) contributed to the formation of the hydrogel. The crystal structure (crystallinity:76.3 %) and thermal (thermal degradation:729.7 °C) of the composite hydrogels (TG-US) were better than those of individual GG hydrogels. Rheology indicated that sonication treatment significantly improved the storage modulus (G′) of the composite hydrogel. In tofu, adding oxidized and/or sonicated hydrogels improved textural properties. Overall, this research reveals the potential of utilizing composite hydrogels made from okara in plant-derived food applications, aiming to turn soybean processing waste materials into valuable functional materials and food additives, thereby enhancing economic returns and environmental sustainability. • Composite hydrogel was mixed okara cellulose nanofibers (CNFs) with guar gum (GG). • CNF and guar gum form hydrogels by hydrogen bonding and electrostatic interactions. • CNF was extracted from okara using TEMPO oxidation. • Hydrogel-modified tofu shows high water/oil-holding and swelling capacity.