不同取代度羧甲基葫芦巴胶的制备、表征及功能特性OA

Fenugreek gum(FG),a natural galactomannan,has limited industrial applications because of its slow dissolution rate.Carboxymethylation can improve its water solubility and broaden its applications,with the degree of substitution(DS)being a key determinant of the modification effect.To systematically investigate the effects of different DS values,car-boxymethylated fenugreek gum(CMFG)was prepared using a wet method.The effects of various process parameters,including NaOH dosage,alkalization temperature and time,chloroacetic acid dosage,and etherification temperature and time,on the DS of FG were evaluated.CMFG samples with DS values of 0.18,0.52,and 0.87(CMFG0.18,CMFG0.52,and CMFG0.87,respectively)were subsequently prepared.The structural and physicochemical properties of FG and CMFG with different DS values were characterized,and the effects of carboxymethylation on the solubility,emulsifying properties,and foaming properties of FG were investigated.Size-exclusion chromatography showed that CMFG had a lower molecular weight than FG.Congo red assays indicated that neither FG nor CMFG possessed a triple-helical structure,and all samples exhibited a random-coil conformation.The appearance of new characteristic absorption bands at 1421,1322,and 1604 cm-1 in the infrared spectra confirmed the successful introduction of carboxymethyl groups into FG.X-ray diffraction and ther-mogravimetric analyses showed that carboxymethylation reduced both crystallinity and thermal stability.Rheological anal-ysis demonstrated that both FG and CMFG exhibited pseudoplastic behavior;however,increasing DS reduced solution vis-cosity,shear-thinning behavior,and both storage and loss moduli.Functional property analysis showed that carboxymethy-lation significantly accelerated the dissolution of FG in water.At a concentration of 10 mg/mL,CMFG0.52 with a moderate DS exhibited the highest emulsifying activity and foaming capacity,reaching 28.31±0.30 m2/g and 32.17%±0.38%,respec-tively,and outperforming FG,CMFG0.18,and CMFG0.87.In contrast,CMFG with a high DS showed significantly reduced emulsifying and foaming properties.These findings demonstrate that CMFG with a moderate DS provides the optimal func-tional properties and offer a theoretical basis for understanding the effects of carboxymethylation on the structural,physico-chemical,and functional properties of FG.