High viscosity of hydrocolloid from leaves of Corchorus olitorius L.

Viscous hydrocolloid from leaves of Corchorus olitorius L. was fractionated with ammonium sulfate solution (50%, w/v) followed by the stepwise extraction with distilled water. The yield of the hydrocolloid was 4.5% (w/w) based on dry material. Ash, protein, moisture and total sugars were 3.4, 5.3, 12.3 and 83.8% based on dry-material, respectively. The hydrocolloid consisted of mainly uronic acid and the weight ratio was approximately 90% of total sugars. When the molecular weight distribution was checked by size-exclusion chromatography, the hydrocolloid showed a wide uronic acid peak with a molecular weight of 940 kDa. The viscoelastic properties of the hydrocolloid were examined by low-amplitude oscillatory measurements and the hydrocolloid exhibited gel-like character at the concentration higher than 0.5% (w/w). Viscosity of the hydrocolloid surpassed other food hydrocolloids such as guar gum and locust bean gum at the same condition (0.25∼1.0% [w/w], 25 °C). When the hydrocolloid was heated over 60 °C (∼100 °C), an irreversible increase in viscosity was observed, suggesting the conformational change of the polysaccharide molecule.