The Irish are given credit for the discovery of the seaweeds and their extracts. Some 600 years ago the shore residents of county Carragheen on the south Irish coast first used the weed or Irish moss (Chondrus crispus) as they are called, in food, medicine and as fertilizer and also noted its milk reactivity. The Irish settlers coming to America brought with them a taste for Irish moss and it was soon found to occur as a component of natural flora of the coast of Massachusetts. In the earlier literature the polysaccharide extract of Irish moss was named as carrageen and carrageenin but now these are dropped on the recommendation of Polysaccharide Nomenclature Committee and the name carrageenan is adopted.

Carrageenans are water-soluble gums which occur in certain species of red seaweeds of Gigartinaceae, Solieriaceae, Phyllophoraceae, Hypneaceae, Furcellariaceae, Rhabdoniaceae, Rhodophyllidaceae and some members of Rhodomelaceae, of which five families occur on Indian coasts. The important genera of carrageenophytes occurring in India are Acanthophora, Grateloupia, Halymenia, Hypnea, Laurencia, Portieria, Sarconema, Sebdenia and Solieria.

Chemical Nature:

All carrageenans have the common structural feature of being linear polysaccharides built up of alternating 1,3 linked b -D -galactopyranosyl and 1,4 linked a -D- galactopyranosyl units. Carrageenans are anionic polyelectrolytes. The charged nature of the sugar units and their structural arrangement within the macromolecules render the carrageenans chemically highly reactive and account for its gelling property. Carrageenans have a wealth of possibilities for substitution on the basic co - polymer, admits the possibility of a continuous spectrum of carrageenan types. However, these exist as variants and hybrids of a small number of ideal or limit polysaccharides of definite chemical nature.

In 1953 Smith and Cook separated from Chondrus crispus (Irish moss) two fractions of varying properties which they named as kappa and lambda
carrageenans. Kappa was defined as that fraction which was precipitated with KCl, while lambda was the fraction, which remained in solution. Chemical studies of these fractions revealed that nearly half of the sugar units in kappa carrageenan were 3,6- anhydro -D- galactose, while lambda carrageenan contained little or none of this sugar unit. Rees and his co-workers based on their investigations have defined carrageenans in terms of chemical structure which for convenience are named by Greek-letter prefixes as mu, kappa, nu, iota, lambda, theta, and xi carrageenans.

In kappa-carrageenan, the 1,3- and 1,4-linked units are D-galactose-4-sulphate and 3,6-anhydro-D-galactose respectively. Mu- is considered to be the biological precursor of kappa. Mu- differs from kappa- in that the anhydride is replaced by D-galactose-6-sulphate. In the seaweed, the change from mu- to kappa- is catalysed by the enzyme dikinkase. While kappa- forms gel with water in the presence of certain cations, notably potassium, its precursor mud- is non-gelling.

Similarly nu- is believed to be the precursor of iota. Chemically they differ from their respective counterparts, mu- and kappa- only in having a sulphate group at C2 on the 1,4-linked units. Again nu- is a non-gelling fraction and iota is the gelling fraction

Lambda is a non-gelling carrageenan, which differs from nu- in that about 70%
of the 1,3-linked units are sulphated at C2 rather than C4, the remainder being unsulphated. However, unlike either iota- or kappa-, the alkali-modified lambda-, which has been named theta-carrageenan, is non-gelling. Theta carrageenan is yet to be identified as occurring naturally.

Xi-carrageenan, which replaces lambda in some Gigartina species (G. chamissoi, and G. canaliculata) has not been completely characterised, but seems to differ from lambda- in that the 1,3-linked units are completely sulphated at C2, while at least some of the 1,4-linked units are unsubstituted at C6.

A new family of carrageenans with 1,3-linked units free of sulphates have been reported as the polysaccharide of Eucheuma gelatinae. This family consists of beta carrageenan, analogous to kappa carrageenan but lacking sulphate on the C4 of the 1,3-linked units and its precursor gamma carrageenan analogous to mu-

Lambda- and kappa- carrageenans were found to occur together in the carrageenan extracted from Chondrus crispus and some Gigartina species, although they do not occur on the same plant. It has been shown that kappa- occurs only on the haploid gametophytes of Irish moss and lambda- only on the diploid tetrasporic forms. Since the various forms grow together and harvested and used for extraction yields contain a mixture of two carrageenans. However, their ratio varies and averages about 70% kappa- and 30% of lambda-

Reactivity: The chemical reactivity of carrageenans is primarily due to half-ester sulphate groups that are strongly anionic, being comparable to sulphuric acid in this respect. The free acid is unstable and commercial carrageenans are available as stable potassium and calcium salts or a mixture of both. The associated cations together with the conformation of the sugar units in the polymer chain determine the physical properties of the carrageenans.

Reactivity with proteins is exhibited by both gelling and non-gelling carrageenans. In most cases ion-ion interaction between sulphate groups of the carrageenans and the charged groups of the protein are involved. The reaction depends on protein/carrageenan net charge ratio and thus is a function of isoelectric point of protein, the pH of the system and the weight ratio of carrageenan to protein.

Carrageenan is an anionic polysaccharide gum having hydrocolloidal properties. The commercially important property referred to as milk reactivity is rather remarkable for carrageenan to stabilize casein micelles. In natural milk this is brought about by k-casein. On a weight for weight basis, kappa carrageenan is as effective a micelle-builder as k-casein, while lambda- carrageenan is less effective. Theta -carrageenan is more effective than lambda- though less effective than kappa-. The property of micelle stabilization may account for the effectiveness of carrageenan as stabilizer for evaporated milk and infant food formulae. Industrial importance of carrageenan is greatly due to its ability to cause agglomeration of protein solutions, in particular the casein particles in cow's milk. The carrageenan-protein reaction is quite specific and is influenced by the amount and location of O-sulphate groups on the molecule and molecular shape.

The less desirable property of carrageenan is its susceptibility to depolymerization through acid -catalysed hydrolysis. This is shown to be related to 3,6-anhydride content of carrageenans. Carrageenans in gel state are more stable to acid than those in sol state. The secondary and tertiary structures developed on gelation may exert a shielding effect on the glycosidic bonds. This effect permits the use of carrageenan in acid system, if enough potassium salt is present to develop a gel structure. The carrageenans can be induced to form thermally reversible gels in the presence of specific cations. The rate of acid catalysed degradation is proportional to hydrogen ion activity with maximum stability at a pH of about 9. The rate of acid-catalysed degradation increases with temperature. Carrageenans are relatively resistant to alkaline degradation.

As in other naturally occurring polysaccharides, carrageenans also do not have sharply defined molecular weights, but rather have average molecular weights representing a distribution of molecular species identical in structure but of varying chain length. Commercial food grade carrageenans typically have average molecular weights in the region of 2,00,000 Daltons. The functionality of carrageenans in most food and industrial application depends on molecular weight and is largely lost if it is below 1,00,000 Daltons.

PHYSICAL PROPERTIES:
Appearance: Commercial carrageenans are cream-coloured to light brown powders. Under low-power magnification, individual particles are seen to be short -fibre segments (alcohol-precipitated products), or as thin flakes (roll-dried products).

Density: Particle density averages about 1.7 gms. /cm3. Nominal bulk density is about 0.6g. /cm3 (39 lb./ ft3 ) for roll-dried products and 1g/cm3 (64 lb./ft3 ) for alcohol-precipitated products.

Solubility: Hot water: Carrageenans are soluble in hot (>75oC) water. Only the viscosity of the solution limits solubility. For commercial carrageenans, solutions containing up to 10% carrageenan can be prepared and handled with conventional mixing equipment.

Cold water: Sodium salts of kappa-and iota are soluble in cold water, while salts of other cations such as potassium and calcium do not dissolve completely but exhibit swelling. Lambda- is fully soluble in cold water, regardless of the cations with which it is associated.

Hot milk: All carrageenans are soluble in hot milk.
Cold milk: Lambda- carrageenan has the greatest ability to disperse and thicken milk without the need of solubilising salts. Its insensitivity to calcium and potassium ions, along with its high ester sulphate content, may account for this cold-milk reaction.
With regard to kappa- and iota- carrageenans, the 3,6 -AG content, and the lower ester sulphate content cause the greater insolubility in cold milk. This is attributable in part to the increased sensitivity of these carrageenans to potassium and calcium, which are the constituents of the milk. However even kappa- and iota types, which are practically insoluble in cold milk, may be used effectively for thickening and gelling if tetrasodiumpyrophosphate (TSPP) is used.

Concentrated sugar and salt solutions: Kappa- and lambda- carrageenans are soluble in hot sucrose solutions with concentrations as high as 65%. Iota-carrageenan, however, is sparingly soluble under these conditions. On the other hand, iota- and lambda- solutions will tolerate high concentrations of strong electrolytes (20 to 25% of NaCl), while kappa- will be salted out.

Water - miscible solvents: Alcohol, propylene glycol, glycerin, dimethyl sulphoxide and other such water-miscible solvents may be incorporated into carrageenan solutions. The concentration of the solvent, which can be tolerated, depends upon the molecular weight of carrageenan and the type of carrageenan and cations present, as well as the method of incorporation of the solvent. Thus the higher the ester sulphate contents of the carrageenan and the lower its molecular weight, the higher is the solvent tolerance. Also, the lower the concentration of salts present, the higher is the tolerance.

Organic solvents: All carrageenan products are insoluble in organic solvents, even the most polar ones.

Biological / Toxicological properties: Carrageenan is listed as GRAS (Generally Recognised As Safe) food product by the FDA, of U.S.A. Intensive investigations into carrageenan's safety carried out by the FDA and other medical institutes proved that no gastrointestinal ulceration is caused by the carrageenans; carrageenan is not teratogenic and it is not carcinogenic either.

Rheological properties:
Viscosity: Carrageenans typically form highly viscous solutions. This is due to their unbranched, linear macromolecular structure and polyelectrolyte nature. Viscosity depends on concentration, temperature, the presence of other solutes and the type of carrageenan and its molecular weight. The viscosity increases nearly exponentially with concentration. Salts lower the viscosity of carrageenan solutions by reducing the electrostatic repulsion among the sulphate groups. The viscosity decreases with the increase in temperature. Again the change is exponential and also reversible under specific conditions. The viscosity increases with molecular weight. Commercial carrageenans are generally available in viscosities ranging from about 0.005 to 0.800 Pa.s (5 to 800 cP) when measured at 1.5% concentration at 75oC. Lambda- type or the sodium salt of unmodified mixed lambda- and kappa- carrageenans are used for water thickening applications. Here, high water viscosities are desirable which is contributed by the high molecular weight and the hydrophilicity of lambda- carrageenan.

Gelation: Water gels: Kappa - and iota- carrageenans have the ability to form gels on cooling of a hot solution. These gels are thermally reversible, i.e. they melt on heating and gel again on cooling. Kappa- and iota - carrageenans will not gel in the sodium form but will form gel with potassium, calcium or ammonia. In the case of kappa- carrageenan, potassium ions produce strongest gels whereas iota carrageenan produces the strongest gel with calcium. Pure potassium kappa produces a gel that is clear and compliant, and usually subjected to syneresis. Iota- carrageenan by itself yields compliant and transparent gels that are not subject to syneresis. The gelling temperature of a specific type of carrageenan is relatively insensitive to carrageenan concentration and is primarily a function of the concentration of gelling cations present. The melting temperature of a carrageenan gel is higher than its settling temperature. The melting and gelling temperatures of kappa- carrageenan are increased by the presence of sucrose. Aqueous kappa- gels do not normally exhibit freeze-thaw stability. Considerable change in gel structure, as well as substantial water release, may take place. The more hydrophilic iota- shows better stability in the freeze-thaw cycle.
Milk gels: All carrageenan products have the ability to form gels on cooling a solution of the carrageenan in hot milk. Even lambda-, which does not gel in water, regardless of the cations present, will form milk gels at levels of 0.2% by weight of the milk. This gelation is attributed to the formation of carrageenan-protein bonds. The presence of fat also influences the behaviour of carrageenans in milk. Strongly gelling kappa- carrageenan can be used in high -fat systems. Kappa- produces gels in milk, which have the same brittle nature that they have in water. Moreover, they are very prone to syneresis. These undesirable properties can be ameliorated with the addition of salts such as orthophosphates, carbonates, citrates etc. Iota-carrageenan does not produce the same syneresis -free gels in milk that it does with water. If TSPP is included, however, syneresis is markedly reduced and the gels become more compliant. In cold-milk systems, soft gels can be produced by lambda- or theta- when used at sufficient concentration.

EXTRACTION OF CARRAGEENANS

Carrageenan is a complex process and there are methods available. In this manual two simple methods are described in some detail. One describes extraction with alkaline water and the other with a solution of sodium bicarbonate.
A product similar to carrageenan in all properties and feasible of application in
All formulations in which carrageenan is used, is obtained by cooking the seaweed in a solution of potassium hydroxide. This product is called semi-finished carrageenan. Procedure preparation of this product is also given below.

Before extraction, the seaweed is pulverized, bleached and dried. For semi-finished carrageenan, it may not be necessary to pulverize the seaweed, but bleaching is necessary.

Pulverizing the seaweed : This can be achieved using a dry grinder and sieving the powder through 40-mesh sieve. If, however, the quantity of seaweed is limited, mechanically grind with mortar and pestle. Grinding is not necessary for semi-finished carrageenan.

Bleaching : The seaweed powder or seaweed thalli should be bleached by treating first with 5 volumes of acetone with stirring. Filter to get rid of the green liquid. Treat the residue with boiling 80% alcohol for a few minutes and then with absolute alcohol. A final treatment with diethyl ether at room temperature completes the bleaching process. The seaweed powder is recovered by filtration and is then dried in an oven at 60o C.
The dry bleached seaweed is used in the extraction process.
I. Extraction with alkaline water :
1. Soak 5 gms. of dried seaweed powder in about 100 ml. of distilled water made alkaline (pH 8) with 1N NaOH for 15 mints. Use 500 ml. Ehrlenmeyer flask.
2. Cover the flask with aluminium foil. Make a small hole in the foil. Autoclave for 11/2 hrs.
3. Filter the viscous solution while it is hot, into a suitable beaker (500 ml.)
4. Cool the extracts to the room temperature.
5. Observe if the extract gels immediately on cooling.
6. If the extract does not gel on cooling, but remains highly viscous, the carrageenan can be precipitated by adding 2.5 times the volume of isopropanol
7. Remove carrageenan by filtration and dry in an oven at 60o C overnight.
8. If gel is formed, place the gel in a freezer. The following day, frozen gel can be thawed and then dried.
9. Weigh the dry carrageenan obtained and calculate the yield. Of carrageenan from dry weight of seaweed used.
10. Save the product for further testing.

II. Extraction with sodium bicarbonate
1. Treat 5gms. of dried seaweed with 100 ml. of 0.5M sodium bicarbonate solution (1:20 W/V)
2. Autoclave for 11/2 hrs.
3 to 10 - Repeat process as in I above

III. Semi-finished carrageenan:
1. Soak 5 gms of dry seaweed in 20 volumes of distilled water for 20 minutes.
2. Place the soaked seaweed in a cloth bag and secure the bag.
3. Immerse in 150 ml. of 1N solution of potassium hydroxide and cook for 1 hr in a water bath.
4. Remove the bag containing cooked seaweed and soak in fresh water for 1 hour to remove the residual alkali.
5. After soaking, take the bag out and rinse thoroughly in running water.
6. Dry overnight in an oven at 60oC.

TESTS FOR CARRAGEENAN
KCl solubility:
1. Prepare 0.1% solution of the carrageenan by dissolving 100mg.of dry powder in 100 ml. of distilled water at 70o C..
2. Add 10 ml. of 3M KCl solution.
3. Observe if a precipitate is formed and record your observation. (The solution can be subsequently filtered and reprecipitated with 2.5 volumes of isopropanol)
Methylene blue test:
1. Prepare 1% solution of carrageenan in distilled water.
2. To 10 ml of the sample solution add 4-5 drops of 1% aqueous solution of methylene blue.
3. Observe the interface part of the solution for fibrous agglomeration.
Milk reactivity:
1. Prepare 10 ml. of 0.154% solution of carrageenan.
2. Add this to 10 ml. of hot homogenised milk.
3. Look for flocculation of milk casein.
Gel formation
1. Dissolve 1 gm. of carrageenans in 100 ml. of 1% KCl solution at 70oC.
2. Transfer part of the solution to a 50ml. beaker and allow it to cool down to room temperature.
3. Observe if gel is formed.
Viscosity measurements using Ostwald's viscometer
The apparatus : Ostwald's viscometer makes use of the rate of flow of a fluid through a capillary tube of a given length. The figure below gives the details of construction of the apparatus.
The determination of the viscosity of carrageenan solution with this viscometer involves the following steps :
1. Determination of viscometer constant
2. Determination of density of solvent
3. Determination of the absolute viscosity of the solvent
4. Preparation of carrageenan solutions
5. Determination of density of carrageenan solutions
6. Determination of rate of flow of carrageenan solutions and
7. Calculation of viscosity

1. Determination of viscometer constant : Take one litre of filtered and deaerated distilled water in a suitable vessel. Immerse the viscometer in the water upto about 2 cms. above the upper graduation mark. The viscometer should be clamped vertically. Using a serological pipette with a long tip, add 3 ml. of distilled water to the wider arm of the viscometer (if its capacity is 5 ml.) carefully, avoiding air bubbles. Allow to equilibrate for 5 mints. With a soft rubber bulb, gently draw the liquid up the capillary arm to a level just above the upper graduation mark. Using a stop-watch, time the flow of water from the upper graduation mark to the lower mark, to the nearest 0.1 sec. Repeat the process five times and average the five recorded times.
Calculate the viscometer constant k using the formula k = h / td , where h is the absolute viscosity of water = 0.8937 cps at 25 oC t is the time in seconds and d is the density of water = 0.9978 ml -1 at 25oC.
Repeat these proceedings for each viscometer.

2. Determining density of solvent
Carrageenan solution is prepared only by using 0.1M sodium chloride as solvent. Therefore, density of the solvent has to be determined.
Use a clean volumetric flask of 10 ml. capacity. Accurately determine its tare. Fill the flask upto the graduation mark with deaerated distilled water. Determine the weight. Determine the exact volume of the flask from the formula V = M /D where V is volume in millilitres, M is weight in grams and D is the density of water = 0.9978 ml -1 at 25oC.
Using this calibrated flask, determine the density of 0.1 M NaCl using the formula Do = M /V where Do is the density of the solvent, M is the weight of the solvent and V is the volume of the flask, as determined above.

3. Determining the absolute viscosity of the solvent
Prepare 500 ml. of 0.1 M NaCl solution using deaeratd distilled water and filter through a membrane. Determine the absolute viscosity of this solution using an Ostwald viscometer, following the procedure given in (1) above.

4. Preparation of carrageenan solutions
Use 0.1 M NaCl solution as solvent. Accurately weigh out 75 mg. of carrageenan into a volumetric flask. Add approximately 40 ml. of the solvent and stir vigorously for 30 to 45 mts. at room temperature, until all the carrageenan is dissolved. (A magnetic stirring bar can be used. In that case, after dissolution, the magnetic bar should be retrieved and rinsed with a small amount of the solvent into the flask.) Allow to remain for 10 mts. to equilibrate and then make up the volume with the solvent. The stock solution will have 0.15% concentration.
Prepare three dilutions in the following proportions between stock and the solvent.
(i) 15 ml. stock - 25 ml. solvent
(ii) 15 ml. stock - 50 ml. solvent
(iii) 3.0 ml. stock - 25 ml. solvent

The final concentrations of the solutions will be
Stock - 0.15%
Dilution (i) - 0.09%
Dilution (ii) - 0.045%
Dilution (iii) - 0.018%

The above dilutions will serve well for k-carrageenan; if lambda- carrageenan is used, use only half the above concentrations.

5. Determination of densities of carrageenan solutions
Follow procedure given in (2) above, but with the carrageenan solutions (all dilutions) prepared.

6. Determination of flow of carrageenan solutions
Follow procedure given for water in (1)

7. Calculation of viscosity
i. Calculate the absolute viscosity h for each solution from the formula h = ktd, where k is viscometer constant, t is the time of flow in seconds and d is the density of the solution
ii. Calculate the specific viscosity using the formula h sp = (h - ho ) / h0 where ho is absolute viscosity of the solvent.
iii. Calculate the reduced specific viscosity h sp / C where C is the percentage concentration of the solution
iv. Plot h sp / C against C in a linear graph and draw a straight line through the data using a least squares fit.

Infrared spectroscopic analysis can be done for the samples if extracts and can be compared with Authentic samples of kappa-, lambda- and iota carrageenan

CHEMICAL ANALYSES OF CARRAGEENAN

I. Estimation of galactose (Total carbohydrate)
Phenol-sulphuric acid method
Reagents:
5% phenol: 5 gms. of phenol crystals dissolved in 100 ml. of glass distilled water.
Sulphuric acid (analytical reagent - 96%)
Procedure:
1. Take 1 ml of the carrageenan solution provided.
2. Add 1 ml. of 5% phenol and 5 ml. of sulphuric acid and mix thoroughly by shaking (or using a cyclomixer)
3. Allow the solution to stand for 10 mints.
4. Read optical density at 490 nm.
5. Compare with standard graphs prepared with different concentrations of D- galactose ranging from 10 to 100mg/ml.
6. Express the result as mg. of galactose per mg. of carrageenan.

Estimation of 3, 6 anhydrogalactose:
Acetol -resorcinol method (Yaphe and Arsenault, 1965)
Reagents
I. Preparation of acetol :
1. Place 50gms. of anhydrous calcium chloride and 260 gms. (323 ml.) of 95% ethyl alcohol in a 1 litre narrow necked bottle and cool the mixture below 8oC.
2. Introduce 120 gms. of fresh acetaldehyde (Boiling point 20-25oC) slowly down the sides of the bottle to form a layer of alcoholic solution.
3. Stopper the bottle and mix by shaking for 3-4 mins.
4. Allow the bottle to stand for 20-30 hrs.,with intermittent shaking.
5. After final shaking, leave undisturbed for 1-2 hrs. till the mixture separates into two layers.
6. Separate the upper layer.
7. Wash three times with 80 ml. distilled water.
8. Dry for several hours over 6gms. Anhydrous potassium carbonate and fractionate.
The fraction collected is pure acetol, boiling point 101-104oC. Specific gravity ml = 850 mg. Yield - 200 gms.
Stock solutions:
A. Take 0.1 ml of acetol and make up to 10.3 ml. with glass-distilled water.
B. Take 0.1 ml. of stock A and make up to 2.5 ml. with glass distilled water
II. Resorcinol:
Dissolve 150 mgs. of resorcinol in 100 ml. of glass distilled water. Keep in refrigerator until required.
Procedure:
a. To 1 ml. of carrageenan solution taken in ice-bath, add 5 ml. of cold acetol-resorcinol reagent and mix thoroughly by shaking.
ii. Transfer the sample to an oven maintained at 80oC for 30 mins. until a permanent light violet colour appears and then transfer back to the ice- bath for three mins. Read O.D. at 555 nm. in a spectrophotometer. Compare with standard graphs prepared with different concentrations of D-fructose ( 10 - 100 mg / ml.)

Estimation of sulphate content in carrageenan:
Reagents:
1N HCl 6M HCl.
70% solution of sorbitol Barium chloride
Procedure
a. Take 10 ml. of the carrageenan solution and add 1 ml. 6M HCl and 5 ml. of 70% sorbitol followed by 1 gm. Of barium chloride, shake in a rotor and then read absorbance at 470 nm.
b. Compare with standard graphs made with different concentrations of potassium sulphate (10 to50mm / ml)

ECONOMIC IMPORTANCE
Carrageenan is employed in food application primarily to gel, thicken or stabilize. Secondary advantage includes improved palatability and appearance. It is used in both milk and water systems.

Food applications:
Carrageenans are valuable gelling agents as well as viscosity improvers in foods and they are effective at relatively low concentrations, which can offset their somewhat high cost. They are used in dry mixes such as cooked puddings and pie fillings, cooked flans and custards. In chocolate milk, chocolate syrup, ice creams and sherbets, canned milk, infant food formulations, whipped cream etc. All these are milk-based applications.
As for as water applications are concerned they are used in fruit drinks, jellies, relishes, pizza, fish gels, pet foods etc. While using carrageenan in most cases locust bean gum is used which alters the structure of the carrageenan gel and gives a smoother texture.

Medical and pharmaceutical uses:
A discovery by Elsner, Broser and Burger, which is important from the medical point of view is that carrageenan even in very great dilution acts as an anti-coagulant of blood. Among the carrageenans lambda type was found to be most potently anticoagulant at low concentrations. In France and Great Britain carrageenan is used in control of stomach ulcers.
Lambda carrageenan at concentrations of 0.1 to 1.0 may be used as hand lotions and creams to provide slip and improved rub-out. It is interesting to know that it is frequently noted that fishermen who collect Irish moss have surprisingly soft skin on their hands.
In toothpaste carrageenans function as a "binder" to impart the desired rheological properties to the paste and to provide the cosmetic "sheen". Carrageenan suffers severe competition with sodium carboxymethyl cellulose, a much cheaper gum. Despite this, carrageenan has maintained a strong position in this application due to its superior quality and its immunity to degradation by enzymes, which attack cellulose gums. Apart from toothpaste, carrageenan is also used in the production of shaving soaps, hair creams etc. The extractive plus potassium salts are used for tablet binding in pharmaceuticals.

Other applications:
Air freshener gels: Mixture of kappa- carrageenan, other gums and a gelling salt such as potassium chloride are used to prepare air freshener gels. Volatile odour-absorbing compounds and fragrant oils incorporated in the gel are released uniformly from the gel surface as the gel dries down.
In textile industry carrageenan is extensively used at a concentration of about 5% as a stiffening and binding material. It produces a soft finish and a surface to which the printing will adhere.
For beverage clarification, for metal fabrication, to thicken latex emulsion paints, as abrasive suspensions, for ceramic glazing etc also carrageenans are used.
A new important use is in connection with antibiotic ice used in fishing boats in order to preserve the fish. The antibiotic is far better distributed through the ice in the presence of carrageenan.
Carrageenan and locust bean gum provided the greatest range of condition at which recrystallisation rate of ice is inhibited.

TRY OUT THESE RECIPES
Desserts : Water Gel
Ingredients :
Carrageenan 6gms
Sugar 80gms
Trisodium citrate 0.8gm
Adipic acid 3gms
Flavour and colour 0.3 gm
The ingredients are mixed well and dissolved completely in one (8 oz.) of boiling water. Then one cup of cold water is added. The solution is frozen in a zero degree constant temperature for 24 hrs. The gel is removed and thawed at room temperature for 4 hrs. and then served.
Milk pudding :
Ingredients :
Lambda carrageenan 270 mesh 4gms
Non-fat milk solids 20gms
Sugar 47gms
Colour and flavour as desired
Blend dry ingredients and place in small electric mixer bowl. Mix in one cup (237 ml. ) of cold milk at low speed. Whip at high speed for 3 mns. Fold in one cup of cold milk at low speed for 1 min. Pour into mold; refrigerate. Unmold after one hour. Pudding may be consumed after 5 to 10 minutes.
Cooked custard:
Ingredients :
Iota - carrageenan 1.4 g.
Mixed kappa- and lambda- carrageenan 0.3 g.
Tetrasodium pyrophosphate 0.8 g.
Salt 0.3 g.
Sugar 54.2 g.
Colour and flavour as desired
Blend the dry ingredients, add one pint of milk, and stir thoroughly in a saucepan until completely dispersed. Bring to a full boil over medium heat, stirring constantly to prevent sticking. Remove from heat, pour into molds, and refrigerate.
Chocolate milk
Ingredients :
Fine sugar 32.3 g
Cocoa 6.9 g
Mixed kappa- and lambda- carrageenan 0.15 g
Vanillin 0.08 g
Blend the above ingredients and disperse in one pint of 2% butterfat milk with agitation. Heat the milk to 71oC. Maintain this temperature for several minutes under agitation, then cool the mixture rapidly with constant agitation as over a surface cooler

FOR FURTHER READING

1. Anderson , N.S., T.C.S. Dolan, A. Penman, D.A. Rees, G.P. Mueller, D.J.Stancioff and N.F.Stanley. 1968 Carrageenans Part IV. Variations in the structure and gel properties of carrageenan, and the characterization of sulphate esters by infrared spectroscopy. J.Chem. Soc. (C) : 602 - 06
2. Chapman, V.J., and D.J. 1980 Seaweeds and their uses (Third Ed.) Chapman and Hall, New York pp. 334
3. Craigie J.S., and C.Leigh 1978. Carrageenans and agars. In : J.A. Hellebust and J.S. Craigie, (eds.) Handbook of Phycological methods : Physiological and Biochemical Methods. Cambridge University Press, Cambridge. Pp. 109 - 131.
4. Doshi, Y.A., R.G.Parekh, V.D.Chauhan and M.M.Taqui Khan. 1984. Polysaccharides fro Indian seaweeds. Proc. Industrial carbohydrates conference. ATIRA, Ahemadabad pp. 286 - 302
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