Carrageenan
Carrageenan.
Carrageenan [9000-07-1].
»Carrageenan is the hydrocolloid obtained by extraction with water or aqueous alkali,from some members of the class Rhodophyceae(red seaweeds).Carrageenan consists chiefly of potassium,sodium,calcium,magnesium,and ammonium sulfate esters of galactose and 3,6-anhydrogalactose copolymers.These hexoses are alternately linked a-1,3and b-1,4in the polymer.The prevalent copolymers in the hydrocolloid are designated kappa-,iota-,and lambda-carrageenan.Kappa-carrageenan is mostly the alternating polymer of D-galactose-4-sulfate and 3,6-anhydro-D-galactose.Iota-carrageenan is similar,except that the 3,6-anhydrogalactose is sulfated at carbon 2.Between kappa-carrageenan and iota-carrageenan there is a continuum of intermediate compositions differing in degree of sulfation at carbon 2.In lambda-carrageenan,the alternating monomeric units are mostly D-galactose-2-sulfate (1,3-linked)and D-galactose-2,6-disulfate (1,4-linked).The ester sulfate content for Carrageenan ranges from 18percent to 40percent.In addition,it contains inorganic salts that originate from the seaweed and from the process of recovery from the extract.
Carrageenan is recovered by alcohol precipitation,by drum drying,or by freezing.The alcohols used during recovery and purification are restricted to methanol,alcohol,and isopropyl alcohol.Carrageenan that is recovered by drum-roll drying may contain mono-and di-glycerides or up to 5percent of polysorbate 80used as roll-stripping agents.
Packaging and storage—
Preserve in tight containers,preferably in a cool place.
Solubility in water—
Not more than 30mLof water is required to dissolve 1g at a temperature of 80
.
.
Identification—
A:
Asolution (1in 50)prepared by heating a uniform dispersion in a hot water bath to 80(Solution A)becomes more viscous upon cooling and may form a gel.
(Solution A)becomes more viscous upon cooling and may form a gel.
B:
To 10mLof Solution A,while still hot,add 4drops of potassium chloride solution (1in 10),mix,and cool.Ashort-textured (“brittle”)gel indicates a carrageenan of a predominantly kappatype;a compliant (“elastic”)gel indicates a predominantly iotatype.If the solution does not gel,the carrageenan is of a predominantly lambdatype.
C:
Dilute a portion of Solution Awith about 4parts of water,and add 2to 3drops of methylene blue TS:a blue,stringy precipitate is formed (also positive for furcellaran,a similar colloid).
D:
Obtain IRabsorption spectra on the gelling and non-gelling fractions of the specimen by the following procedure.Disperse 2g in 200mLof potassium chloride solution (1in 40),and stir for 1hour.Allow to stand for 18hours,stir again for 1hour,and transfer to a centrifuge tube.(If the transfer cannot be made because the dispersion is too viscous,dilute with up to 200mLof the potassium chloride solution.)Centrifuge at approximately 1000g for 15minutes.
Remove the clear supernatant,resuspend the residue in 200mLof potassium chloride solution (1in 40),and centrifuge again.Coagulate the combined supernatants by adding 2volumes of dilute alcohol (9in 10).(Retain the sediment for use subsequently as directed.)Recover the coagulum,and wash with 250mLof the dilute alcohol.Press the excess liquid from the coagulum,and dry it at 60for 2hours:the material so obtained is the nongelling fraction (lambdacarrageenan).
for 2hours:the material so obtained is the nongelling fraction (lambdacarrageenan).Disperse the sediment retained from the foregoing procedure in 250mLof cold water,heat at 90for 10minutes,and cool to 60.Coagulate the mixture,then recover,wash,and dry the coagulum as described above:the material so obtained is the gelling fraction (kappa-and iota-carrageenan).
for 10minutes,and cool to 60.Coagulate the mixture,then recover,wash,and dry the coagulum as described above:the material so obtained is the gelling fraction (kappa-and iota-carrageenan).Prepare a solution (1in 500)of each fraction,cast films 5µm thick (when dry)on a suitable nonsticking surface,and obtain the IRabsorption spectrum of each film.Carrageenan has strong,broad absorption bands,typical of all polysaccharides,in the 1000to 1100cm-1region.Absorption maxima are 1065cm-1and 1020cm-1for gelling and nongelling types,respectively.Other characteristic absorption bands and their intensities relative to the absorbance at 1050cm-1are as shown in the accompanying table.
| Wave Number cm-1 | Molecular Assignment | Absorbance Relative to 1050cm-1 | ||
| Kappa | Iota | Lambda | ||
| 1220to 1260 | Ester sulfate | 0.7to 1.2 | 1.2to 1.6 | 1.4to 2.0 |
| 928to 933 | 3,6-anhydrogalactose | 0.3to 0.6 | 0.2to 0.4 | 0to 0.2 |
| 840to 850 | Galactose-4-sulfate | 0.3to 0.5 | 0.2to 0.4 | — |
| 825to 830 | Galactose-2-sulfate | — | — | 0.2to 0.4 |
| 810to 820 | Galactose-6-sulfate | — | — | 0.1to 0.3 |
| 800to 805 | 3,6-anhydrogalactose-2-sulfate | 0to 0.2 | 0.2to 0.4 | — |
Viscosity á911ñ—
Transfer 7.5g to a tared,tall-form,600-mLbeaker,add 450mLof water,and disperse with agitation for about 15minutes.Add water to bring the weight to 500g,and heat in a water bath,with continuous agitation,until a temperature of 80is reached.Add water to adjust for loss by evaporation,cool to between 76and 77,and place in a constant-temperature bath maintained at 75.Provide a suitable rotational viscosimeter with a spindle 1.88cm in diameter and 6.51cm high,using an immersion depth of 8.10cm (No.1spindle).Allow the spindle to rotate in the solution at 30rpm for 6revolutions,then observe the scale reading.Convert the scale reading to centipoises by multiplying by the constant for the spindle and speed employed.The viscosity at 75is not less than 5centipoises.
is reached.Add water to adjust for loss by evaporation,cool to between 76and 77,and place in a constant-temperature bath maintained at 75.Provide a suitable rotational viscosimeter with a spindle 1.88cm in diameter and 6.51cm high,using an immersion depth of 8.10cm (No.1spindle).Allow the spindle to rotate in the solution at 30rpm for 6revolutions,then observe the scale reading.Convert the scale reading to centipoises by multiplying by the constant for the spindle and speed employed.The viscosity at 75is not less than 5centipoises.
Microbial limits á61ñ—
The total bacterial count does not exceed 200cfu per g,and the tests for Salmonellaspecies and Escherichia coliare negative.
Loss on drying á731ñ—
Dry it at a pressure not exceeding 10mm of mercury at 70for 18hours,cool in a desiccator,and weigh:it loses not more than 12.5%of its weight.
for 18hours,cool in a desiccator,and weigh:it loses not more than 12.5%of its weight.
Acid-insoluble matter—
Transfer about 2g,accurately weighed,to a 250-mLbeaker containing 150mLof water and 1.5mLof sulfuric acid.Cover with a watch glass,and heat on a steam bath for 6hours,rubbing down the wall of the beaker frequently with a rubber-tipped stirring rod,and replacing any water lost by evaporation.Transfer about 500mg of a suitable filter aid,accurately weighed,to the beaker,and filter through a tared filtering crucible provided with a 2.4-cm glass fiber filter.Wash the residue several times with hot water,dry at 105for 3hours,cool in a desiccator,and weigh.The difference between the total weight and the sum of the weights of the filter aid,crucible,and glass fiber filter is the weight of the acid-insoluble matter.It is not more than 2.0%of the weight of Carrageenan taken.
for 3hours,cool in a desiccator,and weigh.The difference between the total weight and the sum of the weights of the filter aid,crucible,and glass fiber filter is the weight of the acid-insoluble matter.It is not more than 2.0%of the weight of Carrageenan taken.
Total ash á561ñ:
not more than 35.0%.
Arsenic á211ñ:
3ppm.
Lead á251ñ:
0.001%.
Heavy metals,Method IIá231ñ:
0.004%.
Auxiliary Information—
Staff Liaison:Catherine Sheehan,B.Sc.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 2979
Phone Number:1-301-816-8262