IE912360A1

IE912360A1 - Process for the production of kappa carrageenans

Info

Publication number: IE912360A1
Application number: IE236091A
Authority: IE
Inventors: Jean-Pierre Lhonneur
Original assignee: Sanofi Sa
Priority date: 1990-07-06
Filing date: 1991-07-05
Publication date: 1992-01-15
Also published as: FR2664279A1; IE67646B1; EP0465373B1; JPH04226501A; ES2076487T3; FR2664279B1; EP0465373A3; DK0465373T3; EP0465373A2; PH30976A; CA2046187A1

Abstract

The invention relates to a process for obtaining kappa-carrageenes from Eucheuma cottonii type algae. The process may be carried out in continuous fashion.

Description

Process for the production of kappa carrageenans The present invention relates to an improvement to the process for the production of kappa carrageenans.

Kappa carrageenans are sulfated polysaccharides which are used in particular in the food and cosmetic industries for their gelling power. These carrageenans are naturally present in red algae ; the species Euchema cottonii, cultivated in the Philippines and in Indonesia, only contains carrageenans of the kappa and mu types and is used for the production of kappa carrageenans.

In the conventional industrial process for the production of various carrageenans, algae are treated with hot water until all the carrageenan has been solubilized. The insoluble materials are then separated off by hot filtration and the polysaccharide is precipitated by adding isopropyl alcohol to the extract ; the polysaccharide is finally isolated after draining, washing, pressing and drying. This process is the one used to obtain all the types of carrageenan, whereas pure kappa carrageenan is obtained by adding a base, generally an alkali metal hydroxide, to the Euchema cottonii extraction water.

In the case of kappa carrageenan, another isolation process is also employed which utilizes the fact that the solutions gel in the presence of potassium ions. In this case, the extract from which the insoluble materials have been removed is poured into a solution of potassium chloride containing from 100 g to 300 g of KC1 per 100 g of carrageenan introduced ; the gel formed is then drained until the polysaccharide concentration is 2 to 5% (w/v), and is subsequently frozen at a temperature of -5°C to -15°C ; in this step, the carrageenan gel releases water, which is separated off, and the remaining carrageenan is dried in conventional manner.

The process of the present invention is less expensive because it does not require the use of alcohol. Furthermore, it consumes less energy and is faster than the process which involves freezing ; moreover, in contrast to said process involving freezing, it can be carried out continuously.

The process according to the present invention comprises the steps of : 1° treating algae of the Euchema cottonii type with a basic aqueous solution, at a temperature of between 80°C and 100°C, to give a suspension in which the kappa carrageenan is solubilized ; 2° filtering the suspension hot to give a clarified extract whose content of potassium ions is adjusted to a value of between 10 and 20 g/1, potassium ions being added, if necessary, to said hot suspension before filtration or to said clarified extract after filtration ; 3° spraying the resulting clarified extract, at a temperature of between 80°C and 95°C, into a cooled ventilated vessel so that the temperature of the mass of miniparticules of carrageenan gel which deposit on the bottom of said vessel is between 35°C and 45°C ; and 4° removing the major part of the water from said mass.

In order to have fluid solutions at the treatment temperature and a sufficient concentration of kappa carrageenan in the clarified extract for the droplets formed by spraying to gel spontaneously, the dry algae are treated with a sufficient amount of water for the clarified extract to contain from 10 g/1 to 40 g/1 of kappa carrageenan and preferably from 20 to 25 g/1. An inorganic base, preferably sodium hydroxide, is added to the water in a suf25 ficient amount to convert the mu carrageenan to kappa carrageenan ; from 30 to 80 g of said base are generally added per liter of water. In the first step of the process, the suspension of algae is agitated at a temperature of between 80°C and 100°C, preferably 90°C, for the time which is necessary for all the carrageenan pre30 sent to dissolve, generally between 10 and 20 hours, after which the suspension is practically homogeneous.

Before the solid particles are separated off, a sufficient amount of potassium ions, in the form of an inorganic potassium salt such a KC1 or K^SO^, is added to the medium so that the extract contains between 50 and 100% by weight of potassium ions, based on the weight of carrageenan, it being understood that the starting alga itself contains potassium chloride (generally about 15% by weight) which remains in the extract.

It is also possible to adjust the content of potassium ions only after the filtration.

It is possible to separate off all the solid particles or simply the foreign particles such as, for example, sand or shellfish fragments. In the second case, the semi-refined carrageenan which is finally isolated still contains the cellulose from the algae.

To obtain the pure polysaccharide, the suspension, still at a temperature of between 80°C and 100°C, is filtered in conventional manner, for example in a sealed pressure filter, with a sufficient amount of a filter aid such as a diatomaceous earth or a perlite, which will form a bed retaining all the particles.

To obtain a semi-refined product, the filtration is performed on a vibrating or rotary screen equipped with cloths having meshes of between 250 and 1 000 pm.

The resulting clarified extract, which is more or less transparent and is at a temperature of between 80°C and 95°C, is then gelled into miniparticules by passage under slight pressure through one or more spray nozzles of the so-called hollow cone type, i.e. whose shape makes it possible to obtain a hollow cone of particles downstream, such as the spray nozzles marketed by Giesler or Emani.

The pressure at which the extract is introduced into each 6 nozzle is generally between 2 x 10 Pa and 10 Pa.

Said nozzle(s) emerge in the upper part of an open vessel ; a gentle stream of air at ambient temperature, i.e. about 20°C, runs through the top of this vessel so that the water is removed in the form of vapor and does not fall to the bottom of the vessel with the miniparticles of gel ; the temperature in the top of the vessel is thus about 65°C.

The whole of the vessel is also cooled, for example by a liquid circulating in a jacket, so that the miniparticles which fall under gravity to the bottom of the vessel are finally at a temperature below 45°C.

In addition, and particularly for continuous operations, the bottom of the vessel is equipped with a device which makes it possible to remove the deposited mass comprising water and carrageenan. It has been found that the miniparticles of gel, kept for some time at a temperature below 45°C, preferably while stirring, lose part of their water by the phenomenon of syneresis, thereby facilitating the subsequent pressing operations, and it is preferred to effect the removal in such a way that the miniparticles remain in the bottom of the vessel at a temperature of between 35 and 45°C, preferably 40 to 45°C, for 0,5 hour to 3 hours.

The mass which is finally extracted from the vessel contains more than 90% of water, the major part of which is then removed by pressing on a filter, preferably very gradually so as to favor syneresis and not to clog the pores of said filter ; this operation can be carried out in a pressure-filter with plate or membrane filter press, generally in a thin layer with a thickness of less than 5 cm, or preferably in a continuous conveyor belt filter of the type commonly used to concentrate the waste sludges from water or paper treatments.

The wet mass of carrageenan obtained is then dried in conventional manner in a stream of hot air, for example in a fluidized air bed dryer, until the amount of residual water is between 5% and 15% by weight - the percentage generally accepted in commercially available carrageenans - before it is packaged ; to obtain a kappa carrageenan of higher grade, especially colorless, the mass produced by pressing is preferably washed, before drying, with an aqueous solution of potassium chloride containing from 25 to 50 g of potassium chloride per liter ; the water is then removed by renewed pressing and the product is dried.

The following examples illustrate the invention without limiting it.

Example 1 1.7 t of dry algae of the Euchema cottonii type are dis35 persed in 20,000 1 of water containing 80 kg of sodium hydroxide, at 90°C. The mixture is agitated at this temperature for 15 hours. kg of potassium chloride and then 500 kg of diatomaceous earth or perlite are then added, still at this temperature. The suspension is then filtered at 90°C in a sealed pressure filter and the filtrate, still at 90°C, is introduced into a cooled vessel of 5000 to 20,000 1 through i to 5 hollow-cone nozzles of diameter 4 mm, the pressure at which it is introduced into each nozzle being 5 x 10 Pa. The miniparticles of gel formed, which have a high water content, fall to the bottom of the vessel, where they remain for 0.5 to 3 hours at a temperature of 42°C, while stirring, before being drawn off. This mass of carrageenan particles, containing 96% of water and still at a temperature of 42°C, is then introduced into a pressing belt filter in a thickness of 6 to 8 cm, the film of carrageenan obtained at the outlet having a thickness of about 1 cm and still containing 80% of water. The mass is then suspended in water containing 30 g/1 of KC1 at a rate of 2000 1 per 1000 1 of pressed product, then pressed again to a solids content of 20% to 25% and finally ground and dried in a fluidized air bed dryer in conventional manner.

This gives 400 kg of carrageenan containing 5% by weight of water and 10% by weight of KC1.

Example 2 The carrageenan in the algae are solubilized as in Example 1. The suspension abtained after the addition of potassium chloride is then passed over a screen equipped with cloths having meshes of 500 pm so as to remove all the particles foreign to the algae (sand, shellfish fragments). The suspension purified in this way, still at 90°C, is sprayed as in Example 1 and finally gives, after drying, 540 kg of carrageenan mixed with the cellulose from the alga, containing 10% by weight of KC1 and 50% of water.

Claims

WHAT IS CLAIMED IS :

1. A process for the production of kappa carrageenans, which comprises the steps of :

2. A process according to claim 1 wherein the algae are treated with an aqueous solution of sodium hydroxide. 20 3. A process according to claim 1 wherein the clarified extract contains from 10 g/1 to 40 g/1 of carrageenan. 2) filtering the suspension hot to give a clarified extract whose content of K + ions is adjusted to a value of between

3. ) spraying the resulting clarified extract, at a temperature of between 80°C and 95°C, into a cooled ventilated vessel so that the recovered mass of miniparticles of carrageenan 15 gel - impregnated with water - is at a temperature of between 35°C and 45°C, and

4. A process according to claim 1 wherein the algae are treated with an aqueous solution of sodium hydroxide, and the clarified extract contains from 10 g/1 to 40 g/1 of carrageenan. 25 5. A process according to claim 1 wherein the clarified extract contains from 10 g/1 to 40 g/1 of carrageenan and is 5 6 sprayed under a pressure of between 2 x 10 Pa and 10° Pa through at least one hollow-cone nozzle. 4) removing the major part of the water from said mass.

5. 1) treating algae of the Euchema cottonii type with a basic aqueous solution, at a temperature of between 80°C and 100°C, in order to solubilize the carrageenan,

6. A process according to claim 1, wherein the algae are 30 treated with an aqueous solution of sodium hydroxide, the clarified extract contains from 10 g/1 to 40 g/1 of carrageenan and said 5 clarified extract is sprayed under a pressure of between 2 x 10 Pa g and 10 Pa through at least one hollow-cone nozzle.

7. A process according to claim 1 wherein the recovered 35 mass of miniparticles of carrageenan gel is kept at a temperature of between 35°C and 45°C for 0.5 to 3 hours, and the water is separated off before step 4).

8. A process according to claim 1, wherein the clarified extract contains 10 g/1 to 40 g/1 of carrageenan , the recovered mass of miniparticles of carrageenan gel is kept at a temperature of between 35°C and 45°C for 0.5 to 3 hours, and the water is separated off before step 4).

9. A process according to claim 1, wherein the clarified extract contains 10 g/1 to 40 g/1 of carrageenan, said clarified c c extract is sprayed under a pressure of between 2 χ 10 3 Pa and 10° Pa through at least one hollow-cone nozzle f the recovered mass of miniparticles of carrageenan gel is kept at a temperature of between 35°C and 45°C for 0.5 to 3 hours, and the water is separated off before step 4).

10. A process according to claim 1 wherein the major part the water is removed by pressing on a filter. 10 10 and 20 g/1, K + ions being added, if necessary, before or after filtration,

11. A process according to claim 1 wherein the recovered mass of miniparticles of carrageenan gel is kept at a temperature of between 35°C and 45°C for 0.5 to 3 hours, the water is separated off, and the remaining water is further removed by pressing on a filter.

12. A process according to claim 1 for the production of a Kappa carrageenan, substantially as hereinbefore described and exemplified.

13. A Kappa Carrageenan whenever produced by a process claimed in a preceding claim.