Pectins amidated with different amino acids via MMTM activation: Structural characteristics and emulsifying properties

For many applications as a food additive, the emulsifying properties of commercial pectin are usually need to be upgraded to obtain better stabilization properties, to extend the shelf-life of food products. In this study, a novel method was developed in which pectin was activated by 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholin-4-ium chloride (MMTM) to obtain pectins amidated with different amino acids and then the structural characteristics, emulsifying properties, and structure-property relationships of the resulting modified pectins were systematically explored. MMTM efficiently activated the amidation of pectin with different amino acids. Pectin amidated with alkaline amino acids had the highest degree of amidation (DA), ranging from 13.5% to 24.8%, followed by amidation with neutral (6-11.9%) and acidic (4.5-6.4%) amino acids. The high DA and larger number of hydrophobic groups of pectins amidated with lysine, arginine, histidine, methionine, or phenylalanine resulted in emulsions with a smaller particle size (610.1-907.0 nm) and greater stability than obtained with the original pectin. The thicker adsorption layer resulting from the high-molecular-weight cysteine-amidated pectin accounted for the high stability of the emulsion. These results provide the basis for the development of novel methods for modifying pectin, based on amidation with amino acids, to significantly improve emulsification.