Extraction and characterization of pectin from sweet potato (Ipomoea batatas) peels using alkaline extraction method

Pectin is a polysaccharide consisting of galacturonic acid (GalA) that is found in the cell wall of plant. Sweet potato (Ipomoea batatas) peel contains pectin, which acts as thickening and gelling agents in food application. In Malaysia, sweet potato peels are mostly waste materials resulting from the sweet potato processing industry and are normally discarded. The aim of this study was to extract and characterize pectin from sweet potato peels using alkaline extraction. Pectin was extracted using 0.05, 0.10, 0.15, 0.20 and 0.25 M sodium hydroxide (NaOH) at temperature 90°C for 15 min. Pectin was characterized for its yield, GalA profile, degree of esterification (DE) and rheological properties. GalA and DE of the extracted pectin was characterized using Fourier Transfer Infrared Spectroscopy (FTIR). Rheological properties of pectin were analyzed using viscometer to investigate the viscosity changes due to shear rate. In this study, extraction using 0.25 M NaOH yields the highest percentage of pectin which is 16.78% while 0.05 M NaOH gives the lowest yield (10.98%). The results proved that the sweet potato pectin has low degree of methyl-esterification.