Exploring the water mobility in gelatin based soft candies by means of Fast Field Cycling (FFC) Nuclear Magnetic Resonance relaxometry

Abstract 1H spin-lattice relaxation experiments for gelatin-based candies prepared by different amounts of d -allulose have been performed in the frequency range of 4 kHz–40 MHz. In addition, physical properties such as moisture content and hardness were also measured. Analysis of NMR dispersion profiles showed the presence of two fractions of water: confined and free-water. The relaxation data have been associated with parameters characterizing translation diffusion and rotation of the confined-water molecules and dynamics of the free-water fraction. The translation dynamics has turned out to be about three orders of magnitude slower compared to bulk water; the time scale of the rotational dynamics is similar to that of translation diffusion. Moreover, quantitative analysis of the relaxation data has provided a unique parameter, the number of water molecules undergoing translation dynamics within the confined-water fraction per unit volume. On this basis, the influence of d -allulose on the mechanisms of water motion has been discussed.