Abstract:

A review with 49 refs. is presented, demonstrating that certain hydrophilic (anionic or non-ionic) polysaccharides purified to a level of being almost protein-free can exhibit surface and emulsification properties, in spite of their rigid and hydrophilic nature. The adsorption isotherms of the surface-active biopolymers are similar to other macromol. amphiphiles. The main gums discussed are those of the galactomannan family, i.e, locust bean gum, guar gum, and fenugreek. Other gums from less known sources, i.e., Portulaca Oleracea and Opuntia Ficus, also exhibit surface properties. Statements previously made by several authors, claiming that hydrocolloids cannot be considered as emulsifiers, were inaccurate. The requirements for built-in hydrophobic moieties on the hydrocolloids' backbone internal structure are not obligatory for active adsorption. Adsorption can be induced by a salting-out effect, resulting in semi-solid interfacial layers. Hydrocolloids can form thick birefringent gel-like mech. barriers at the oil-water interface of emulsion oil droplets. This new category of naturally occurring hydrocolloid emulsifiers should be reconsidered by food technologists and by other emulsion technologists for other industrial applications. [on SciFinder(R)]