Extraction and characterisation of pectin from sweet potato (ipomoea batatas) pulp

Sweet potato (Ipomoea batatas) pulp contains pectin, which acts as thickening and gelling agents in food application. This study investigates the yield and profile of the galacturonic acid (GalA) and rheological properties of the sweet potato pectin produced using acid extraction method. In this work, pectins were extracted using hydrochloric acid at different concentrations (0.05 M, 0.1 M, 0.15 M, 0.2 M, and 0.25 M) at pH 1.5 and temperature 90 °C for 1 hour. Hydrolysis of residual starch in the cell wall of sweet potato using heat stable a- amylase and amyloglucosidase was employed prior to pectin extraction to eliminate starch contamination. Pectins were characterised for yield, GalA profile, degree of esterification (DE) and its rheological properties. Profile of GalA and DE were determined by using Fourier Transfer Infrared Spectroscopy (FTIR). Rheological properties of pectin were performed by addition of calcium ions (Ca2+) to investigate the viscosity changes due to gelation of pectin. The yield of pectin obtained was in the range of 5.0 – 6.0% (w/w) and the DE was affected by the acid concentrations used during extraction. For its rheological properties, viscosity of pectin increases as Ca2+ was added into the pectin solution indicating the gelation of pectin by the cross-linking formation between calcium ion and non-esterified GalA in pectic polysaccharide