Microstructure and mechanical behavior of curdlan hydrogels: The role of thermal pre-treatment temperature

Curdlan, a bacterial polysaccharide, forms thermo-irreversible gels through temperature alone; however, the high strength of these gels limits their versatility in food applications. This study unveils thermal pre-treatment as a breakthrough to customize curdlan gels. Preheating suspensions (40-80 °C) before 90 °C gelation revealed that 48-58 °C - the gel transition range - dramatically weakens the network. Gels softened, with reduced hardness and viscoelasticity compared to untreated CU-90. Cryo-scanning electron microscopy revealed that thermal pre-treatment altered the gel microstructure, increasing pore size and reducing network density. Furthermore, Fourier-transform infrared spectroscopy and X-ray diffraction analyses suggested that preheating disrupted intermolecular hydrogen bonding, influencing triple-helix formation, and subsequently impacting the mechanical properties of the gel. Based on these findings, we propose that thermal pre-treatment at 50 °C influences curdlan gelation by initially promoting network formation, subsequently limiting chain mobility, and ultimately modulating triple helix formation, thereby controlling the final network structure and mechanical properties. Ultimately, the 4 % CU-50-90 formulation exhibited textural properties comparable to cooked porcine adipose tissue, highlighting its potential as a fat replacer in food formulations. These results introduce a novel, environmentally benign, and additive-free strategy for modulating curdlan gel properties, thus expanding its potential within the industry.