Fabrication of agarose/fish gelatin double-network hydrogels with high strength and toughness for the development of artificial beef tendons

Agarose/fish gelatin (AR/FGA) double-network hydrogels (DNs) were fabricated via a one-step heating-cooling method. The structure, mechanical and textural properties, water-holding capacity, swelling behavior and sensory characteristics of the DNs were analyzed and compared with the corresponding single-network hydrogels (SNs) and beef tendons. An increase in FGA concentration (10-40 wt%) significantly enhanced the mechanical strength and toughness of DNs, while a moderate increase in AR concentration (0.5-1.5 wt%) only improved their mechanical strength. The 1.5 wt% AR/40 wt% FGA DNs attained excellent fracture stress and strain compared with the single AR and single FGA gels. This can be attributed to the energy dissipation effect, intermolecular hydrogen bond interactions and higher entanglement density of molecule chains. Furthermore, AR/FGA DNs attained a higher hardness, water holding capacity and lower swelling rate compared with SNs. The principal component analysis and correlation analysis showed that the 1.5 wt% AR/30 wt% FGA DNs displayed the most comparable correlation with beef tendons, which was consistent with the results of the sensory evaluation, showing great potential as artificial beef tendons. Our findings provide guidance for the modulation of gel properties and development of artificial foods.