Surface and emulsification properties of a new gum extracted from Portulaca oleracea L.

Hydrocolloids are water-soluble polysaccharides used mainly as food stabilizers. We are searching for a new surface active gums as an alternative to the gum Arabic. Efforts are being made to extract some new water-soluble polysaccharides from selected plants, preferably free of proteineous matter and exhibiting low viscosity and to examine their surface, interfacial and emulsification properties. The present study explores the properties of a new gum extracted from the leaves of an edible herb of the Portulaca family. The biopolymer is relatively small molecular weight polysaccharide and exhibits significant charge density at pH > 2. The extracted gum has surface and interfacial properties derived from its chemical composition and structure. The Portulaca oleracea gum (POG) adsorbs onto the oil (n-tetradecane or soya) interfaces and stabilizes oil-in-water emulsions. Emulsions (5 wt% oil and 0.7 wt% gum) are stable to flocculation and coalescence at room temperature (for a year) but upon heating the gum desorbs and the emulsion coalesces. Mechanistic considerations regarding its adsorption isotherms, the role of the residual proteineous matter contaminating the polysaccharide and the charge are discussed. FOG is a good example of a new gum that can be considered as a food emulsifier. (C) 1999 Elsevier Science Ltd. All rights reserved.