GELLAN GUM
Prepared at the 49th JECFA (1997), published in FNP 52 Add 5 (1997)
superding specifications prepared at the 46th JECFA (1996), published in
FNP 52 Add 4 (1996). An ADI 'not specified' was established at the 37th
JECFA (1990)
SYNONYM INS No. 418
DEFINITION Gellan gum is a high molecular weight polysaccharide gum produced by a
pure culture fermentation of a carbohydrate by Pudomonas elodea,
purified by recovery with isopropyl alcohol, dried, and milled. The high
molecular weight polysaccharide is principally compod of a
tetrasaccharide repeating unit of one rhamno, one glucuronic acid, and
钢笔抠图two gluco units, and is substituted with acyl (glyceryl and acetyl) groups
as the O-glycosidically-linked esters. The glucuronic acid is neutralized to a
mixed potassium, sodium, calcium, and magnesium salt. It usually contains
书香校园的手抄报a small amount of nitrogen containing compounds resulting from the
fermentation procedures.
C.A.S. number 71010-52-1n4000
Formula weight Approximately 500,000
Assay Yields, on the dried basis, not less than 3.3% and not more than 6.8% of
carbon dioxide (CO2).
DESCRIPTION Off-white powder
FUNCTIONAL USES Thickening agent, gelling agent, stabilizer
CHARACTERISTICS
IDENTIFICATION
Solubility(Vol. 4) Soluble in water, forming a viscous solution; insoluble in ethanol
Gel test with calcium ion Add 1.0 g of the sample to 99 ml of water, and stir for about 2 h, using a
motorized stirrer having a propeller-type stirring blade. Draw a small amount
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of this solution into a wide bore pipet and transfer into a 10% solution of
calcium chloride. A tough worm-like gel will be formed immediately.
Gel test with sodium ion Add 1.0 g of the sample to 99 ml of water, and stir for about 2 h, using a
motorized stirrer having a propeller-type stirring blade. Add 0.50 g of sodium
chloride, heat to 80° with stirring, and hold at 80° for 1 min. Allow the
solution to cool to room temperature. A firm gel is formed.
PURITY
Loss on drying(Vol. 4) Not more than 15% (105°, 2½ h)
Nitrogen(Vol. 4) Not more than 3%
Isopropyl alcohol Not more than 750 mg/kg
See description under TESTS
Microbiological criteria Total plate count: Not more than 10,000 colonies per gram
E. coli: Negative by test
Salmonella: Negative by test
Yeasts and moulds: Not more than 400 colonies per gram
See description under TESTS
Lead (Vol. 4) Not more than 2 mg/kg
Determine using an atomic absorption technique appropriate to the
specified level. The lection of sample size and method of sample
preparation may be bad on the principles of the method described in
Volume 4, “Instrumental Methods.”
TESTS
PURITY TESTS
学号英语Isopropyl alcohol Isopropyl alcohol (IPA) Standard Solution
Transfer 500.0 mg of chromatographic quality isopropyl alcohol into a 50-ml
volumetric flask, dilute to volume with water, and mix. Pipet 10 ml of this
solution into a 100-ml volumetric flask, dilute to volume with water, and mix.
Tertiary butyl alcohol (TBA) Standard Solution
Transfer 500.0 mg of chromatographic quality tert-butyl alcohol into a 50-ml
volumetric flask, dilute to volume with water, and mix. Pipet 10 ml of this
solution into a 100-ml volumetric flask, dilute to volume with water, and mix.
Mixed Standard Solution
Pipet 4 ml each of the IPA standard solution and of the TBA standard
solution into a 125-ml graduated Erlenmeyer flask, dilute to about 100 ml
with water, and mix. This solution contains approximately 40 µg each of
isopropyl alcohol and of tert-butyl alcohol per ml.
Sample preparation
Disper 1 ml of a suitable antifoam emulsion, such as Dow-Corning G-10
or equivalent, in 200 ml of water contained in a 1000-ml round-bottom
distilling flask. Add about 5 g of the sample, accurately weighed, and shake
the flask for 1 h, on a wrist-action mechanical shaker. Connect the flask to a
fractionating column and distil about 100 ml; adjust the heat so that foam
does not enter the column. Add 4.0 ml of TBA Standard Solution to the
distillate to obtain the Sample Preparation.
Procedure
Inject about 5 µl of the Mixed Standard Solution into a suitable gas
chromatograph equipped with a flame-ionization detector and a 1.8-m x 2.3-
浙江二批分数线mm stainless steel column packed with 80/100-mesh Porapak QS or
equivalent. The carrier is helium flowing at 80 ml per min. The injection port
temperature is 200°, the column temperature 165°, and the detector
temperature 200°. The retention time of isopropyl alcohol is about 2 min,
and that of tert-butyl alcohol about 3 min.
Determine the areas of the IPA and TBA peaks, and calculate the respon
factor, f, by the formula A IPA/A TBA, in which A IPA is the area of the isopropyl
alcohol peak, and A TBA is the area of the tert-butyl alcohol peak.
Similarly, inject about 5 µl of the Sample Preparation, and determine the
peak areas, recording the area of the isopropyl alcohol peak as a IPA, and
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that of the tert-butyl alcohol peak as a TBA.
Calculate the isopropyl alcohol content, in mg/kg, in the sample taken by the
formula:
(a IPA x 4000)(f x a TBA x W)
where W is the weight of the sample taken, in g.
Microbiological criteria Total plate count
Using aptic technique, disper 1 g of sample into 99 ml of phosphate
buffer and u a Stomacher, shaker or stirrer to fully dissolve. Limit
dissolving time to about 10 min and then pipette 1 ml of the solution into
parate, duplicate, appropriately marked petri dishes. Pour over the aliquot
of sample in each petri dish 12-15 ml of Plate Count Agar previously
tempered to 44-46°. Mix well by alternate rotation and back and forth motion
of the plates, allow the agar to solidify. Invert the plates and incubate for
48±2 h at 35±1°.
After incubation count the growing colonies visible on each plate and record
the number of colonies. Take the average of both plates, and multiply by the
sample dilution factor, 100. Where no colonies are visible, express the
result as less than 100 cfu/g.
E. coli determination
Using aptic technique, disper 1 g of sample in 99 ml of Lacto broth
using either a Stomacher, shaker or stirrer to fully dissolve the sample. Limit
the dissolving time to about 15 min and then lightly al the container and
incubate the broth for 18-24 h at 35±1°. Using a sterile pipette, inoculate 1
ml of the incubate into a tube containing 10 ml GN broth. Incubate for 18-24
h and then streak any GN broths showing positive growth or gas production
onto duplicate plates of Levine EMB agar. Incubate the plates for 24±2 h at
35±1° and then examine for colonies typical of E. showing strong
purple growth with dark centre and a green metallic sheen sometimes
spreading onto the agar. Record any typical E. coli colonies as presumptive
positive, otherwi negative.
Streak any well isolated suspect colonies onto a plate of PCA and incubate
for 18-24 h at 35±1°. Perform a Gram stain on any growth to confirm it is
Gram negative. If so, disper any colony growth into a small volume of
0.85% saline and perform chemical tests to confirm the identity of the
bacterial growth. This can most conveniently be done by using API 20E or
Micro ID strips or equivalent systems.
After completion of the tests, identify the organism from the Identification
manual of the system ud and record the final result.
Media一尘不染什么意思
GN Broth (Gram Negative Broth)
Peptone 20.0 g
Dextro 1.0 g
Mannitol 2.0 g
Sodium citrate 5.0 g
Sodium deoxycholate 0.5 g
Potassium phosphate (dibasic) 4.0 g
Potassium phosphate (monobasic) 1.5 g
Sodium chloride 5.0 g
Make up to 1 litre with distilled or de-ionid water, pH 7.0±0.2 at 25°. Salmonella determination
Using aptic technique, disper 5 g of sample into 200 ml of sterile lacto broth using either a Stomacher, shaker or stirrer to maximi dissolution over a 15 min period. Looly al the container and incubate at 35±1° for 24±2 h.
Continue as per method on page 221 of FNP 5/Rev. 2 (1991). Identification can be more conveniently done using API or Micro ID systems or equivalent.
Yeasts and moulds
Using aptic technique, disper 1 g of sample into 99 ml of phosphate buffer and u a Stomacher, shaker or stirrer to fully dissolve. Limit dissolving time to about 10 min and then pipette 1 ml of the solution into parate, duplicate, appropriately marked petri dishes. Pour over the aliquot of sample in each petri dish 15-20 ml of Potato dextro Agar (either acidified or containing antibiotic) previously tempered to 44-46°. Mix well by alternate rotation and back and forth motion of the plates, and allow the agar to solidify. Invert the plates and incubate for 5 days at 20-25°.
After incubation, count the growing colonies visible on each plate using a colony counter and record
the number of colonies. Separate the yeasts from the moulds according to their morphology and count them parately. Take the average of both plates and multiply by the sample dilution factor, 100. Where no colonies are visible, express the result as less than 100 cfu/g.
METHOD OF ASSAY Procesd as directed in the test for Carbon Dioxide Determination by Decarboxylation in the General Methods, Volume 4, using about 1.2 g of the sample weighed accurately.
