June 9/Gaziantep, Turkey/Journal of Technology & Science -- "The influence of pectin and guar gum on the creaming stability, microstructure and rheological properties of 1.0% (w/v) egg yolk plasma (EYP)-stabilized 25.0% (v/v) soybean oil-in-water emulsions was studied at pH 7.0. Addition of pectin/guar gum decreased creaming percentage, and no creaming was detected in the presence of 0.5% (w/v) pectin/guar gum as a result of increasing viscosity," scientists writing in the journal European Food Research and Technology report.
"At the end of 10 hours, creaming percentage decreased from 61% to 57% with the addition of 0.05% (w/v) guar gum and to 39% with the addition of 0.2% (w/v) guar gum. Microscopic observations represented the droplet aggregation arising from the presence of nonabsorbing biopolymers. At (gamma) over dot = 10 s(-1), a tenfold increase in viscosity was observed in the presence of 0.5% (w/v) guar gum compared to the presence of 0.1% guar gum due to the thickening effect of polysaccharide. Increasing gum concentrations enhanced the viscosity and hence the consistency index. All emulsions, except for those containing 0.5% (w/v) guar gum, reflect the near-Newtonian behavior with flow behavior index, n, of 0.9-1.0. All emulsions exhibited a liquid-like behavior at low frequencies (<7.0 Hz) where G '' values were higher than G'. Both G' and G '' showed a frequency dependency and these two moduli crossed each other at higher frequencies (>7.0 Hz), G' became greater than G '' and the system behaved like an elastic solid," wrote E.A. Ercelebi and colleagues, Gaziantep University.
The researchers concluded, "Addition of pectin at all levels cause no significant change in G' and G '' values, whereas addition of guar gum, especially at a concentration of 0.5% (w/v), significantly improved these values."
Ercelebi and colleagues published their study in European Food Research and Technology ("Effects of Pectin and Guar Gum on Creaming Stability, Microstructure and Rheology of Egg Yolk Plasma-stabilized Emulsions." European Food Research and Technology, 2010;231(2):297-302).
Additional information can be obtained by contacting E.A. Ercelebi, Gaziantep University, Dept. of Food Engineering, TR-27310 Gaziantep, Turkey.
From the June 21, 2010, Prepared Foods E-dition