Biomedical Engineering Reference
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fenugreek protein content was reduced to levels below 0.5 wt% but surface activity
was retained. Furthermore, they demonstrated that unlike gum arabic the protein-
rich fractions had very limited surface activity.
Oils emulsified with the pure galactomannans (at concentrations below 0.7 wt%)
produced stable, unflocculated emulsions. The oil droplets exhibited strong birefrin-
gence (under polarized light) indicating formation of a “liquid crystalline” type of
organization around the droplets, possibly with “limellar structure”. The gums were
found to bind “weakly” to the oil droplets but with good coverage and significant
thickness. This was the first study to show that water-soluble, rigid hydrophilic
polysaccharides have significant emulsification capacity. The authors noted that
while gum arabic efficiency is very low (20 wt% is required for 5 wt% oil-in-water
emulsions), the optimum levels for guar and fenugreek did not exceed 0.5 to 0.7 wt%
under similar oil concentrations.
Xanthan gum is also widely used in formulations such as salad cream, low
calorie dressings, mayonnaise sandwich spreads, etc. Gordon 201 reported that xanthan
gum is used in some salad dressings not as a stabilizer but as an improver of the
yield value. The yield value is referred to as the shear stress applied to the solution
in order for flow to occur. It is this property that allows the dressing to cling to the
salad and to appear to have body and not a thin appearance. The greater the yield
value, the greater the suspending powers. These unique properties have been attrib-
uted to some interfacial properties that the gum exhibits in the presence of oils.
These properties can be related to the ability of a gum to adsorb onto oil droplets.
Additional work is required to further clarify the emulsification power of xanthan
gum.
REFERENCES
1.
Dickinson, E., Ed. Food Emulsions and Foams, Royal Society of Chemistry, London,
1987.
2.
Darling, D.F. and Birkett, R.J., Food Colloids in Practice, in Food Emulsions and
Foams, Dickinson, E., Ed., Royal Society of Chemistry, London, 1987, 1.
3.
Bee, R.D., Richmond, P. and Mingins, J., Eds., Food Colloids, Royal Society of
Chemistry, Bristol, U.K., 1989.
4.
Larsson, K. and Friberg, S.E., Eds., Food Emulsions, Marcel Dekker, New York, 1990.
5.
Krog, N.J., Riisom, T.H. and Larsson, K., Applications in the food industry, I. in
Encyclopedia of Emulsion Technology, Becher, P., Ed., Marcel Dekker, New York,
1985, 321.
6.
Tornberg, E., Olsson, A. and Persson, K., The structural and interfacial properties of
food proteins in relation to their function in emulsions, in Food Emulsions, Larsson,
K. and Friberg, S.E., Eds., Marcel Dekker, New York, 1990, 247.
7.
Dickinson, E. and Stainsby, G., Advances in Food Emulsions and Foams, Elsevier
Applied Science, London, 1988.
8.
Dickinson, E. and Stainsby, G., Colloids in Foods, Applied Science Publishers,
London, 1982.
9.
Jaynes, E.N., Applications in the food industry, II. in Encyclopedia of Emulsion
Technology, Becher, P., Ed., Marcel Dekker, New York, 1985, 367.
 
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