Effects of pectin and guar gum on creaming stability, microstructure and rheology of egg yolk plasma-stabilized emulsions |
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Authors: | Emine Alben Erçelebi Esra Ibano?lu |
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Affiliation: | (1) Department of Food Engineering, Gaziantep University, 27310 Gaziantep, Turkey |
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Abstract: | 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. At the end of 10 h, 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
\mathop g. \mathop \gamma \limits^{.} = 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 behaviour with flow behaviour
index, n, of 0.9–1.0. All emulsions exhibited a liquid-like behaviour 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. 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. |
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