Xanthan gum is treated with surfactants. This treatment produces a readily dispersible xanthan gum.

BACKGROUND OF THE INVENTION 
Xanthan gum has been used widely to prepare a variety of aqueous solutions 
having high viscosity and good suspending properties. A difficulty with 
xanthan gum in common with other high molecular weight, water soluble 
polymers has been its resistance to dispersibility and hydration. 
Typically, xanthan gum powder must be subjected to high agitation, as in a 
typical kitchen blender, to get it to disperse and hydrate. 
Various approaches to the problem of preparing a dispersible xanthan gum 
have been described. For example, U.S. Pat. No. 4,357,260, Sandford, et 
al., describes the additiion of silica to a xanthan gum solution, which is 
then precipitated with a non-solvent, dried, and milled. U.S. Pat. No. 
4,363,669, Cottrell et al., describes blends of glyoxal treated xanthan 
gum with certain non-dispersible plant gums. 
SUMMARY OF THE INVENTION 
It has now been found that the blending of certain surfactants with dry 
xanthan gum, optionally with the addition of sugar, produces a dispersible 
xanthan gum. 
DETAILED DESCRIPTION OF THE INVENTION 
Xanthan gum as used herein, refers to the biosynthetic polysaccharide 
produced by the organism Xanthomonas campestris by the whole culture 
fermentation of a medium comprising a fermentable carbohydrate, a nitrogen 
source, and appropriate other nutrients. 
Xanthan gum preparation is described in numerous publications and patents, 
e.g., U.S. Pat. Nos. 3,671,398; 3,594,280; 3,591,578; 3,481,889 3,433,708; 
3,427,226; 3,391,061; 3,391,060 3,271,267; 3,251,749; 3,020,206. 
The surfactants of this invention are any of various food approved wetting 
agents such as acetylated monoglycerides, glycerol esters, lecithin, mono- 
and di-glycerides, polyglycerol esters, propylene glycol esters, 
polyoxyethylene sorbitan esters, sorbitan esters, sodium 
stearoyl-2-lactylate, stearyl-2-lactylic acid, and also other industrial 
surfactants, e.g. polyoxylstearates (e.g. Myrj-52). Combinations of two or 
more of these agents are also within the scope of this invention. The 
amount of surfactant can be reduced by the addition of sugar (e.g., 
sucrose, fructose, maltose, dextrose, maltodextrins, etc.) to the blend. 
Several methods can be used to blend the various blend components. The 
surfactants are used in a liquid or dissolved state. For example, liquid 
(at room temperature) surfactants are added directly to xanthan gum powder 
and continually mixed as with a Hobart N-50 blender using a wire beater so 
as to substantially uniformly coat the xanthan gum particles. Sugar can 
then be blended in if desired to form a substantially homogeneous blend of 
coated xanthan gum and sugar. Solid surfactants are melted first and then 
the liquid surfactants are blended with the xanthan gum as above, 
optionally with sugar, as above. Instead of melting the solid surfactants, 
these can be dissolved in alcohol, such as isopropanol (IPA), and added to 
the xanthan gum as above. When the blending is completed the IPA is 
evaporated off as by gentle heating or forced aeration. 
Pan agglomeration is a different technique for forming the blends of this 
invention. The two (or three) components are dry mixed and then tumbled on 
a rotating pan. The mix is treated with a fine mist while tumbling until 
the components form beads. These damp beads are then dried, as in a fluid 
bed dryer. The mist comprises water or a water/lower alcohol (e.g., IPA) 
mixture, with or without added surfactant. The beads generally have a mesh 
size ranging from about through 20 to on 80 mesh (U.S. standard sieves). A 
commercially available device for this process is The Ferrotech Pan 
Agglomerator, model FC 016-02 (Ferrotech Co., Wyandotte, Mich.). 
The ratios of xanthan gum:surfactant within the scope of this invention 
range from 95:5 to 80:20 by weight. When sugar is used, the ratios are 
20:0.5:80 to 20:5:80. 
The dispersible blends of this invention are useful in all applications 
where it is desirable to use xanthan gum as a thickening agent, especially 
in consumer products which require in-home preparation by the end-user, 
such as dry-mixed salad dressings. A typical formulation for such a mix 
is: 
______________________________________ 
Parts by Weight 
______________________________________ 
Salt/sugar/spices dry blend 
8.35 
Tap water 12.81 
Vinegar (50 grain) 56.23 
Vegetable oil 130.00 
Gum/surfactant blend 
0.15 
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Dispersibility is evaluated by visual observation. Typically, a 0.5-1.0% 
blend (based on weight of xanthan gum) is added to the vortex of 150 ml 
Standard Tap Water (STW is a solution comprising 1000 ppm NaCl and 143 ppm 
CaCl.sub.2.2H.sub.2 O in deionized water) in a 300 ml beaker stirred with 
a magnetic bar at 500 rpm for 1 minute. This is compared to 0.5-1% 
untreated xanthan gum. The test blend is described as dispersible if there 
are fewer lumps than with untreated gum.

EXAMPLE 1 
Two blends of xanthan gum and surfactant (90:10 and 85:15) were prepared as 
follows: Stearolac-S.RTM. (sodium stearoyl-2-lactylate) was first melted 
before adding KELTROL.RTM.F (xanthan gum, Kelco Div. of Merck & Co., 
Inc.). The mixture was stirred while hot for approximately 20 minutes 
using a Hobart mixer equipped with a wire whip. The mixture was then 
cooled and stirring continued until the Stearolac S resolidified giving a 
uniform coating on the xanthan gum. 
These two blends were tested for dispersibility as follows: dispersibility 
(0.5% based on xanthan gum) was measured one minute after adding the 
sample to 150 ml STW in a 300 ml beaker. The solution was stirred (500 
rpm, magnetic stir bar) for one minute. A "good" rating was given if the 
dispersibility was better than the untreated control (Keltrol F, xanthan 
gum). The data of Table 1-1 were obtained. 
TABLE 1-1 
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Sample Rating 
______________________________________ 
Untreated Control (0.5% x.g.) 
Poor 
90/10 blend Good 
85/15 blend Good 
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EXAMPLE 2 
Sterolac-S was first melted before adding 200 g. xanthan gum. The mixture 
was stirred while hot for 20 minutes using a Hobart mixer equipped with a 
wire whip. The mixture was then cooled and stirring continued until the 
Sterolac-S resolidified giving a uniform coating on the xanthan gum 
particles. Two commercially available grades of xanthan gum were tested: 
KELTROL.RTM. and KELTROL.RTM.F. 
Dispersibility (0.5% based on x.g.) was measured one minute after adding 
the sample (milled through 200 mesh for KELTROL.RTM.F xanthan gum and 
through 60 mesh for KELTROL.RTM. xanthan gum samples) to 150 ml STW in a 
300 ml beaker. The solution was stirred (500 rpm, magnetic stir bar) for 
one minute. A "good" rating was given if the dispersibility was better 
than the untreated control. The data of Table 2-1 were obtained. 
All blends hydrated to give essentially equivalent viscosities upon 
prolonged stirring demonstrating that blends were soluble. 
TABLE 2-1 
______________________________________ 
Amt. of blend 
used in test 
(g) Disper. 
______________________________________ 
1. KELTROL/Stearolac- 
0.54 good 
S(200:15) 
2. KELTROL/Stearolac- 
0.55 good 
S(200:20) 
3. Untreated Control 
0.5 poor 
(KELTROL) 
5. Untreated Control 
0.5 poor 
(KELTROL F) 
6. KELTROL F/Stearolac- 
0.55 good 
S(200:20) 
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EXAMPLE 3 
Dispersible blends were prepared by adding surfactants to xanthan gum 
(KELTROL.RTM.) prior to blending with sucrose. Two solid low melting point 
surfactants (Myrj-52.RTM., a polyoxyl (40) stearate, and Tween-65.RTM., a 
polysorbate-65) were first melted before adding to the xanthan gum whereas 
liquid surfactants (Tween 20.RTM. and Tween-80.RTM.) were added directly 
to xanthan gum. Uniform coating was achieved by mixing with the Hobart 
N-50 using the wire beater. The ratio of xanthan gum to surfactant was 
varied from 20/10 to 20/0.8 and varying amounts of sugar were added. 
Dispersibility was measured (0.5% xanthan gum final concentration) one 
minute after adding material to be tested to 150 ml STW in a 300 ml 
beaker. The solution was stirred (500 rpm, magnetic stir bar) for one 
minute. An excellent rating was given if no lumps were present, a good 
rating if the number of lumps was significantly less than for the control, 
and fair if marginally less than the control. The data of Table 3-1 were 
obtained. 
All blends hydrated to give essentially equivalent viscosities upon 
prolonged stirring demonstrating that the blends were soluble. 
TABLE 3-1 
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Blend Ratio Dispersibility 
______________________________________ 
X.G.:Tween-20:sucrose 
(20:10:80) Excellent 
:Tween-65:sucrose 
(20:10:80) Good 
:Tween-80:sucrose 
(20:10:80) Good 
:Myrj-52:sucrose (20:10:80) Excellent 
X.G.:Tween-20:sucrose 
(20:0.8:20) Good 
:Tween-65:sucrose 
(20:0.8:20) Good 
:Tween-80:sucrose 
(20:0.8:20) Good 
:Myrj-52:sucrose (20:0.8:20) Good 
X.G.:Tween-80:sucrose 
(200:5:800) Good 
(200:10:800) 
Good 
(200:20:800) 
Good 
(200:5:0) Poor 
(200:10:0) Poor 
X.G.:Stearolac-S:sucrose 
(200:5:800) Fair 
(200:10:800) 
Fair 
(200:15:800) 
Excellent 
(200:20:800) 
Excellent 
(200:5:0) Fair 
(200:10:0) Fair 
(200:15:0) Excellent 
(200:20:0) Excellent 
Controls 
X.G.:surfactant:sugar 
(200:0:0) Poor 
(200:0:800) Poor 
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EXAMPLE 4 
Dry blends of KELTROL-F.RTM. xanthan gum/Stearolac-S.RTM./sucrose were 
agglomerated using a rotary pan agglomerator. The pan agglomerator used 
comprised a 9" diameter dish, set at a 45.degree. angle, and rotating at 
20 rpm, capable of suitably holding 200 grams of blend. A fine mist of 
water was applied to the blend, while tumbling, that caused the product to 
bead. These damp beads were then dried in a fluid bed dryer and the beads 
(through 20 and on 80 mesh) were tested and evaluated for dispersibility. 
The controls were dry blends of xanthan gum and xanthan gum with sugar. 
The data of Table 4-1 were obtained. 
TABLE 4-1 
______________________________________ 
Blend composition 
Ratios Dispersibility 
______________________________________ 
X.g.:Stearolac-S:sugar 
20:2:80 Excellent 
X.g.:Stearolac-S:sugar 
20:0:80 Poor 
X.g.:Stearolac-S:sugar 
20:0:0 Poor 
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