[Code of Federal Regulations]
[Title 21, Volume 3]
[Revised as of January 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 21CFR172.695]
[Page 71-72]
TITLE 21--FOOD AND DRUGS
CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN
SERVICES (CONTINUED)
PART 172 FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN
Subpart G Gums, Chewing Gum Bases and Related Substances
Sec. 172.695 Xanthan gum.
The food additive xanthan gum may be safely used in food in
accordance with the following prescribed conditions:
(a) The additive is a polysaccharide gum derived from Xanthomonas
campestris by a pure-culture fermentation process and purified by
recovery with isopropyl alcohol. It contains D-glucose, D-mannose, and
D-glucuronic acid as the dominant hexose units and is manufactured as
the sodium, potassium, or calcium salt.
(b) The strain of Xanthomonas campestris is nonpathogenic and
nontoxic in man or other animals.
(c) The additive is produced by a process that renders it free of
viable cells of Xanthomonas campestris.
(d) The additive meets the following specifications:
(1) Residual isopropyl alcohol not to exceed 750 parts per million.
(2) An aqueous solution containing 1 percent of the additive and 1
percent of potassium chloride stirred for 2 hours has a minimum
viscosity of 600 centipoises at 75 [deg]F, as determined by Brookfield
Viscometer, Model LVF (or equivalent), using a No. 3 spindle at 60
r.p.m., and the ratio of viscosities at 75 [deg]F and 150 [deg]F is in
the range of 1.02 to 1.45.
(3) Positive for xanthan gum when subjected to the following
procedure:
Locust Bean Gum Gel Test
Blend on a weighing paper or in a weighing pan 1.0 gram of powdered
locust bean gum with 1.0 gram of the powdered polysaccharide to be
tested. Add the blend slowly (approximately \1/2\ minute) at the point
of maximum agitation to a stirred solution of 200 milliliters of
distilled water previously heated to 80 [deg]C in a 400-milliliter
beaker. Continue mechanical stirring until the mixture is in solution,
but stir for a minimum time of 30 minutes. Do not allow the water
temperature to drop below 60 [deg]C.
Set the beaker and its contents aside to cool in the absence of
agitation. Allow a minimum time of 2 hours for cooling. Examine the
cooled beaker contents for a firm rubbery gel formation after the
temperature drops below 40 [deg]C.
In the event that a gel is obtained, make up a 1 percent solution of
the polysaccharide to be tested in 200 milliliters of distilled water
previously heated to 80 [deg]C (omit the locust bean gum). Allow the
solution to cool without agitation as before. Formation of a gel on
cooling indicates that the sample is a gelling polysaccharide and not
xanthan gum.
Record the sample as ``positive'' for xanthan gum if a firm, rubbery
gel forms in the presence of locust bean gum but not in its absence.
Record the sample as ``negative'' for xanthan gum if no gel forms or if
a soft or brittle gel forms both with locust bean gum and in a 1 percent
solution of the sample (containing no locust bean gum).
(4) Positive for xanthan gum when subjected to the following
procedure:
Pyruvic Acid Test
Pipet 10 milliliters of an 0.6 percent solution of the
polysaccharide in distilled water (60 milligrams of water-soluble gum)
into a 50-milliliter flask equipped with a standard taper glass joint.
Pipet in 20 milliliters of 1N hydrochloric acid. Weigh the flask. Reflux
the mixture for 3 hours. Take precautions to avoid loss of vapor during
the refluxing. Cool the solution to room temperature. Add distilled
water to make up any weight loss from the flask contents.
Pipet 1 milliliter of a 2,4-dinitro phenyl hydrazine reagent (0.5
percent in 2N hydrochloric acid) into a 30-milliliter separatory funnel
followed by a 2-milliliter aliquot (4 milligrams of water-soluble gum)
of the polysaccharide hydrolyzate. Mix and allow the reaction mixture to
stand at room temperature for 5 minutes. Extract the mixture with 5
milliliters of ethyl acetate. Discard the aqueous layer.
Extract the hydrazone from the ethyl acetate with three 5 milliliter
portions of 10 percent sodium carbonate solution. Dilute the combined
sodium carbonate extracts to 100 milliliters with additional 10 percent
sodium carbonate in a 10-milliliter volumetric flask. Measure the
optical density of the sodium carbonate solution at 375 millimicrons.
Compare the results with a curve of the optical density versus
concentration of an authentic sample of pyruvic acid that has been run
through the procedure starting with the preparation of the hydrazone.
Record the percent by weight of pyruvic acid in the test
polysaccharide. Note ``positive'' for xanthan gum if the sample contains
more than 1.5 percent of pyruvic acid and ``negative'' for xanthan gum
if the sample contains less than 1.5 percent of pyruvic acid by weight.
(e) The additive is used or intended for use in accordance with good
manufacturing practice as a stabilizer, emulsifier, thickener,
suspending agent, bodying agent, or foam enhancer in foods for which
standards of identity established under section 401 of the Act do not
preclude such use.
[[Page 72]]
(f) To assure safe use of the additive:
(1) The label of its container shall bear, in addition to other
information required by the Act, the name of the additive and the
designation ``food grade''.
(2) The label or labeling of the food additive container shall bear
adequate directions for use.
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