Rheological, functional, thermal and physicochemical properties of mucilage extracted from gelatinous pulp of Dillenia indica.L (elephant apple).

Dillenia indica L., commonly known as elephant apple and belongs to Dilleniaceae family, contains mucilagenous substances. This study investigates the rheological, functional, thermal, and physicochemical properties of mucilage derived from the gelatinous pulp of Dillenia indica as a novel hydrocolloid. The yield of freeze-dried mucilage powder obtained from gelatinous pulp was 4.20 %. The proximate composition analysis revealed contents of moisture (9.96 %), ash (7.84 %), protein (5.84 %), fat (0.08 %) and carbohydrate (36.64 %). Sugar composition analysis identified the presence of xylose (34.1 %), fucose (6 %), glucose (4.76 %), and cellobiose (3.45 %). FTIR spectra displayed characteristic peaks of polysaccharide in the extracted mucilage. The mucilage exhibited notable functional properties in terms of emulsion capacity (80.291 %) and stability (98.295 %), foaming capacity (17.863 %) and stability (61.79 %), water (16.005 g of water/g of sample) and oil holding capacity (1.543 g of oil/g of sample). Steady shear measurements at different concentrations (1, 2 and 3 % w/v) exhibited shear thinning behaviour. Frequency sweep experiments indicated the dominance of storage modulus(G') than loss modulus (G″) at mucilage concentrations (2 % and 3 %), suggesting weak gel formation capability. SEM and XRD pattern confirmed the amorphous nature of mucilage, while DSC and TGA analysis revealed high thermal stability up to 170 °C. These findings suggest that the remarkable properties of Dillenia indica mucilage make it a potential ingredient for food industry applications as a thickner, emulisifier, binder, and gelling agent.