![]() ![]() ![]() The ethanol-OH moiety was responsible for Kirkwood-Buff theory through exclusion effects and direct binding with IC. Ethanol facilitated IC gel formation with predictable increasing gelling temperature (52.6-62.6☌) and critical gelling points (50.8-61.3☌). In summary, a scheme was proposed to demonstrate how sucrose addition promoted the gelation of k-carrageenan by facilitating the formation of denser and thicker fibril helical junctions.Ī R T I C L E I N F O Keywords: Polysaccharide Fourier transform infrared (FTIR) Rheology Gel Microstructure A B S T R A C T The gelation of iota carrageenan (IC) with different ethanol concentrations (0-40 mL/100 mL) was investigated in terms of rheology, chemical structure, and microstructure. Moreover, upon 30 wt% sucrose, the average cross-sectional radius of gyration R c of the carrageenan chains increased from 1.17 to 1.47 nm. SAXS and FESEM results supported the rheology findings and revealed that denser and thicker carrageenan fibril structures formed when addition of sucrose increased. The shift of FTIR band of G4S in k-carrageenan and loss of the vibration band of free hydroxyl group in sucrose indicated the interactions between sucrose and k-carrageenan molecules. More specifically, with an increased addition of sucrose, n decreased while both S g and normalised S g increased. The critical relaxation exponent n, critical gel strength S g and normalised S g obtained from Winter-Chambon equation varied as the concentration of sucrose increased. Incorporation of 30 wt% sucrose shifted both the gelation temperature (from 36.8 C to 52.8 C) and melting temperature (from 51.2 C to 67.3 C) to a higher level and made gel network stronger. The structures of these k-carrageenan/sucrose gels were characterised by Fourier transform infrared (FTIR) spectroscopy, small angle X-ray scattering (SAXS) and field emission scanning electron microscopy (FESEM). ![]() The thermoreversible gelation behaviour of aqueous k-carrageenan solution with addition of sucrose (up to 30 wt%) was investigated via small and large deformation oscillatory rheology. A schematic representation was provided to show how sucrose could affect the structure and gelation of iota carrageenan (differs from kappa carrageenan) and the potential bonds related to the effect. Excess sucrose may form sucrose-sucrose hydrogen bonds that loosen the iota carrageenan network. The zeta potential (−0.92 mV) and confocal laser scanning microscopy images also showed the most abundant aggregates at 5% sucrose. s n) at 5% (w/v) sucrose concentration, indicating the highest density and critical strength.The Winter-Chambon equation provided the fractal dimension d f (2.22) and critical gel strength S g (12.52 Pa The gel was the strongest (251.71 Pa) at 5% (w/v) sucrose however, too much sucrose decreased the gel strength. Fourier transform infrared spectroscopy further confirmed the bindings by detecting band shifts (from 845 to 835 cm −1). Application of the Kirkwood-Buff theory demonstrated that exclusion effects of water and direct binding between sucrose and iota carrageenan are the possible mechanisms for the stabilisation, which act by providing significantly greater ΔG u2 than ΔG u1 from all samples using Clausius-Clapeyron equation (ΔG u1 and ΔG u2 are calculated KB parameters representing the contribution of the rearrangement of water and co-solvent around the solute to the thermodynamics of sol-gel transition). Easier gelation with a higher gelling temperature (51.4-57.4☌) could be achieved by sucrose addition, and the trend could be predicted using mathematical models. In the present study, the rheological behaviours of sucrose-supplemented iota car-rageenan at different concentrations (0-20%, w/v) were determined. Sucrose addition contributes to the rheology of carrageenan, which improves the quality of food that includes carrageenan as an additive. ![]()
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