Ipomoea turpethum seeds:: a potential source of commercial gum

A non-ionic water-soluble galactomannan, having a galactose and mannose in 1:2 molar ratio was isolated from endosperm of the seeds. Seed gum has a branched structure consisting of a linear chain of beta (1 --> 4) linked mannopyranosyl units with D-galactose side chains attached through alpha (1 --> 6) linkage to the main chain, a fundamental structural pattern found in other seed galactomannans like guar, carob, locust bean, tara and dhaincha commercial gums. The gum was subjected to viscosity behavior study at different conditions of concentrations, temperature and pH. Gum solutions showed similar behavior to the guar and were found to be stable over a wide range of pH. With borate ions reversible cohesive gels resulted. Gel formation with transition metal ions is pH dependent and non-reversible. Thus, the seed gum from Ipomoea turpethum show similarity in structural pattern and properties to guar gum. Grafting of polyacrylamide on to the seed gum in aqueous medium, initiated by potassium persulphate/ascorbic acid redox system has been carried out at 35 +/- 0.2 degreesC in the presence of atmospheric oxygen and Ag+ ions. After grafting the viscosity of the gum solution was found to increase tremendously. L turpethum seed gum thus in natural form and, after modification by grafting may find use as a commercial gum. (C) 2003 Elsevier Science Ltd. All rights reserved.