The combination of atomic force microscopy and sugar analysis to evaluate alkali-soluble Canna edulis Ker pectin

Alkali-soluble pectin, which has been extracted from Canna edulis Ker, was characterized by single sugar determination and atomic force microscopy (AFM). The results indicated that the amounts of four predominant sugars including arabinose (Ara), glucose (Glc), galactose (Gal) and galacturonic acid (GalA) significantly decreased during the process of mild acid hydrolysis. The decreasing rates of these four sugars followed a sequential order of Ara > Gal > Glc > GalA. The homogalacturonan (HG) chain present in pectin, and the quantity of branched material is greater than the sample containing the main neutral sugars. The results indicated that the neutral sugar and HG side chains are attached to pectin as part of the rhamnogalacturonan I (RGI) complex. Moreover, hydrolysis leads to the reduction of mean lengths of backbone and branch, as well as the number/weight-average molecular weight. Meanwhile, the amount of short chain fractions increased during hydrolysis. Furthermore, the decrease of the polymerization degree of alkali-soluble C. edulis pectin as a function of the hydrolysis time could be described by a first-order exponential decay function.