Kinetic behavior of the network structure changes in funoran gelation studied by rheological and NMR measurements

Funoran is a promising food polysaccharide with unique gelling properties but understanding its gelation behaviors remains inadequate. This study aimed to investigate the influence of cooling and heating rates on funoran gelation properties and study its gelation mechanism by dynamic rheology and NMR studies. With constant heating rates, the melting point was unaffected by changing cooling rates, whereas higher cooling and heating rates enhance the gel strength and thermal hysteresis. The gelation kinetics mechanism of the funoran solution was elucidated at different quenching temperatures. The rheological measurement results indicated that the funoran solution quenched to lower temperatures resulted in higher G` in the gel state, and faster gelation rate compared with the solution quenched at higher temperatures. 1H NMR results revealed a slow decay in funoran signal intensity at higher temperatures (20 °C) and a fast signal decay at 2 °C. A theoretical model involving second and first-order reactions was proposed to describe the gelation kinetic process of funoran at different quenching temperatures. It was shown longer helix lengths were required for stable intermolecular association and gel formation at higher temperatures than at lower temperatures. These results offer valuable insights for optimizing the funoran gelation properties for various food applications.