Comparative Studies of Combined Influence of Variables on the Esterification Degree of Pectin Extracted by Sulfuric Acid and Citric Acid

Abstract

The influence of extraction variables on degree of esterification (DE) of pectin was studied due to the significant effects of DE on the properties of the pectin-based functional biomaterials. The extracting agents (sulfuric acid and citric acid), pH value of extraction solution, extraction time, and temperature were selected to study the hydrolysis reaction of carboxylic acid ester by response surface methodology (RSM). The hydrolysis reaction occurred more violently in the weak organic acid solution than that in the strong inorganic acid solution. The DE was significantly influenced by pH of extraction solution, extraction time, and temperature through the analysis of variance. In addition, the values of DE reduced with the increasing of extraction temperature, lapse of time, and decreasing of pH value. What is more, the effects of extraction conditions on the yield, monosaccharide composition, content of protein, and ferulic acid were also studied. It is evident that the lower pH value contributed to higher extraction yield. The content of Total CH and GalA of pectin extracted by sulfuric acid were higher than that of pectin extracted by citric acid, and the content of monosaccharide showed an opposite trend.