Development of New Alkylated Carrageenan Derivatives: Physicochemical, Rheological, and Emulsification Properties Assessment

Abstract

In this research, amphiphilic derivatives of kappa carrageenan (KC) were synthesized by hydrophobic modification with an alkyl halide (1-Octyl chloride). Three hydrophobic polymers with different degrees of substitution (DS) were obtained by the Williamson etherification reaction in an alkaline medium. The effect of the molar ratio (R = reagent/polymer) on the DS was investigated at different ratios (1, 2, and 3). The KC derivatives (KCRs) were characterized by different techniques such as FT-IR, 1H-NMR, X-ray Diffraction, Scanning electron microscopy, and a rheological assessment. The FT-IR and 1HNMR analyses confirmed the binding of the hydrophobic groups onto the KC molecule. The degrees of substitution calculated by 1H-NMR demonstrated that the derivative KCR3 (0.68) presented a higher degree of substitution compared to KCR1(0.45) and KCR2 (0.53). The XRD and SEM analyses revealed that the alkaline etherification conditions did not alter the morphological and crystallographic properties, as well as the rheological behavior of the obtained derivatives. The amphiphilic character of the KCRs was investigated using a conductivity method which revealed that the molecular aggregation occurred above the critical aggregation concentration (CAC). Decreasing CAC values of 0.15% (KCR1), 0.11% (KCR2) and 0.08% (KCR3)with the degree of substitution (DS) were found. Furthermore, KCR’s derivatives greatly improved the stability of oil/water emulsions as the droplet size decreased with increasing DS. The derivative (KCR3) with higher DS, showed a greater amphiphilic character, and improved emulsifying power.

Chemically modified seaweed polysaccharides: Improved functional and biological properties and prospective in food applications

“…Rheological analysis disclosed that apparent viscosity of the acid-modified sodium alginate was significantly lower than that of original sodium alginate, and it was deduced that both M/G ratio and Mw of sodium alginate affected its viscosity (Jiao et al, 2019). Octylation of κ-CG was also found to decrease the viscosity due to the lower Mw of the modified κ-CG (Toumi et al, 2023). Oxidation of sodium alginate with NaIO 4 decreased its viscosity with increasing oxidation degree, and the oxidized sodium alginate hydrogel exhibited apparent shear-thinning behavior because cleavage of C2-C3 bonds in M and G units destructed the intramolecular hydrogen bonds (Wang, Chen et al, 2022).…”

“…Phosphorylation of low-molecularweight (LMw) κ-CG can be achieved by the treatment with POCl 3 in formamide using pyridine as a cosolvent (Praphakar et al, 2017) (Figure 4b; Yuan et al, 2005). Three octylated κ-CGs were prepared by the reaction with 1-octyl chloride with different 1-octyl chloride/κ-CG ratios (1, 2, and 3) under alkaline conditions at 60 • C, with DS values of 0.45, 0.53, and 0.68, respectively (Toumi et al, 2023) (Figure 4d). Their Mw was lower than that of κ-CG due to the slight degradation of the κ-CG (Toumi et al, 2023).…”

“…Three octylated κ-CGs were prepared by the reaction with 1-octyl chloride with different 1-octyl chloride/κ-CG ratios (1, 2, and 3) under alkaline conditions at 60 • C, with DS values of 0.45, 0.53, and 0.68, respectively (Toumi et al, 2023) (Figure 4d). Their Mw was lower than that of κ-CG due to the slight degradation of the κ-CG (Toumi et al, 2023). Toumi et al ( 2021) also compared O-octylation of κ-CG with octyl chloride using microwave and conventional heating methods and found that the DS was 0.77 and 0.45, respectively.…”

Effects of Alkaline Solvent Type and pH on Solid Physical Properties of Carrageenan from Eucheuma cottonii

“…Carrageenan, with low molecular weight, produces tensile strength, gel strength, and resistance to dynamic mechanical and thermal analysis [16]. The physicochemical characteristics of carrageenan determine its function as an excipient in pharmaceutical preparations, e.g., as a gelling agent, suspending agent, emulsifier, tablet matrix, binder, and disintegrating tablets or granules [17][18][19][20][21][22]. Carrageenan has the characteristics of being able to form gels, increase viscosity, absorb water, and expand [23][24][25][26][27].…”