Extraction, characterization and spontaneous gel-forming property of pectin from creeping fig (Ficus pumila Linn.) seeds

Creeping fig (Ficus pumila Linn.) seeds can be manually rubbed and squeezed to produce a water extract (WE) that can gel at room temperature without any additives. Its gelling material, extraction behavior, and mechanism of spontaneous gel-formation were investigated. Gelling material was extracted from seeds using water, ammonium oxalate and hydrochloric acid, respectively. Results showed the main component of three extracts is low methoxyl pectin. The pectin locates in a transparent layer on the surface of seeds, as revealed by an inverted microscope. Hence, explained the feasibility of the squeezing and rubbing method in traditional handcraft. Comparing with the other methods, water-extracted pectin has high galacturonic acid content, viscosity-average molecular weight and intrinsic viscosity but low degree of methoxylation. This pectin forms the major component of WE, together with the high amount of calcium ions present in WE, it suggests the spontaneous gelation may be based on the ‘egg-box’ formation.