Alkylated pectin: Synthesis, characterization, viscosity and emulsifying properties

• Pectin with different degree of substitution (DS) and alkyl chain length was prepared.
• Modified pectin has increased apparent viscosity but decreased intrinsic viscosity.
• The decrease of intrinsic viscosity may be due to more compact conformation.
• The modified pectins showed better emulsifying properties (EP).
• EP of modified pectin increased with the DS and alkyl chain length.

Recently there has been an increased interest in modification of pectins. Pectins were alkylated with alkyl chain of various lengths (hexyl, dodecyl or octadecyl) at different degrees of substitution (0.69, 2.43 or 3.60) by reaction of TBA-pectin with alkyl bromide in this study. Their structures were characterized by GC, FTIR and 1H NMR, which confirmed the formation of ester linkages between hydrophobic alkyl segment and carboxyl group of galacturonic acid. Alkylated pectins produced interesting rheology properties. They showed higher apparent viscosities but lower intrinsic viscosities than the original one. The higher apparent viscosities may be due to intermolecular association of hydrophobic segments in the molecule. The lower intrinsic viscosities would be ascribed to more compact conformation. In addition, the modified pectins showed an enhancement of emulsifying properties. These properties were significantly influenced by the degree of substitution and alkyl chain length. Such amphiphilic derivatives open new perspectives for improving or altering viscosity and emulsifying properties of pectin.

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