IE67646B1 - Process for the production of kappa carrageenans - Google Patents

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

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, - process such as described in particular in Industrial Gums by R.L.

Whistler, Academic Press, New York and London, 1973, pages 90-91, point 4 -, 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 utilises 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 KCL 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. Such a process is described in particular in Industrial Gums by R. L. Whistler, Academic Press, New York and London, 1973, pages 125-126, point 3.

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) hot-filtering the hot suspension to give a clarified extract; 3) precipitating the carrageenan contained in said extract; 4) removing the major part of the water from said carrageenan.

In characteristic manner: - the K+ ion content of the extract obtained in step 2) is adjusted to a 5 value comprised between 10 and 20 g/Z, K+ ions being added, if necessary, before or after frltration; and - in step 3), said clarified extract, whose temperature is comprised between 80*C and 95*C, is sprayed into a cooled ventilated enclosure, so as to form a mass - impregnated with water - of miniparticles whose temperature is comprised between 35*C and 45eC.

In order to have solutions fluid 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/Z to 40 g/Z of kappa carrageenan and preferably from 20 to 25 g/Z. An inorganic base, preferably sodium hydroxide, is added to the water in a sufficient amount to convert the mu carrageenan to kappa carrageenan; between 30 and 80 g of said base are generally added per liter of water. In the first step of the process, the suspension of algae is kept under stirring at a temperature of between 80*C and 100*C, preferably 90*C, for the time which is necessary for all the carrageenarr present to dissolve, generally between 10 and 20 hours, after which the suspension is practically homogenous.

Before the solid particles are separated off, a sufficient amount of potassium ions, in the form of an inorganic potassium salt, such as KCZ or K2SO4, 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 μχη.

The resulting more or less transparent clarified extract, whose temperature is between 80*C and 95*C, is then gelled into miniparticles 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 nozzle or nozzles marketed by Giesler or Emani.

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

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

The whole of the enclosure is also cooled, for example by a liquid circulating in its jacket-lined wall, so that the miniparticles which fall under gravity to the bottom of the enclosure 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 comprised of 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 enclosure at a temperature comprised 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 enclosure 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, 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 obtained is between 5% and 15% by weight, which is the percentage generally accepted in commercially available carrageenans, before it is packaged; to obtain a kappa carrageenan of higher grade, especially colourless, 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 two following examples of embodiment are given to illustrate the invention.

Example 1 1.7 t of dry algae of the Euchema cottonii type are dispersed in 20 0001 of water at 90*C containing 80 kg of sodium hydroxide. The mixture is kept under stirring at that temperature for 15 hours. 90 kg of potassium chloride and then 500 kg of diatomaceous earth or perlite are then added, still at that 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 enclosure of 5000 to 20 0001 through 1 to 5 hollow-cone nozzles of 4 mm diameter, the pressure at which it is introduced into each nozzle being 3 x 10^ Pa. The formed miniparticles of gel, which have a high water content, fall to the bottom of the enclosure, where they remain under stirring for 0.5 to 3 hours at a temperature of 42‘C, 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/Z of KCZ at a rate of 2000 I per 1000 I 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. 400 kg of carrageenan containing 5% by weight of water and 10% by weight of KCL are thus obtained.

Example 2 The carrageenan in the algae are solubilized as in Example 1. Then, the suspension obtained after the addition of potassium chloride is passed over a screen equipped with cloths having meshes of 500 μπι 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, to finally obtain, after drying, 540 kg of carrageenan, mixed with the cellulose from the alga, containing 10% by weight of KC/ and 50% of water.

Claims (10)

CLAIMS 1. ,000 /an.

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

2. Process according to claim 1, characterized in that filtration is 20 performed on a screen equipped with cloths having meshes of between 250 fan and 2) filtering under heat the obtained hot suspension to produce a clarified extract;

3. Process according to one of claims 1 or 2, characterized in that the clarified extract contains from 10 g/1 to 40 g/1 of carrageenan. 3) precipitating the carrageenan contained in said extract; 10 4) removing the major part of the water from said carrageenan; said process being characterized in that: - the content of K + ions of the extract produced in step 2) is adjusted to a value of between 10 and 20 g/1, K + ions being added, if necessary, before or after filtration; and in that 15 - in step 3), said clarified extract, whose temperature is between 80*C and 95*C, is sprayed into a cooled ventilated vessel so as to form a mass impregnated with water - of miniparticles whose temperature is between 35*Cand45*C.

4. Process according to any one of claims 1 to 3, characterized in that 25 the clarified extract is sprayed under a pressure of between 2 x 10^ Pa and 10^ Pa through at least one hollow-cone nozzle.

5. Process according to any one of claims 1 to 4, characterized in that 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 30 step 4). 5 1) treating algae of the Euchema cottonii type with a basic aqueous solution, at a temperature of between 80*C and 100 e C, in order to solubilize the carrageenan;

6. Process according to any one of claims 1 to 5, characterized in that the major part of the water of the mass of the miniparticles is removed by pressing on a filter.

7. Process according to claim 6, characterized in that said pressing 35 operation is performed in a filter with a continuous conveying belt.

8. Process according to any one of claims 1 to 7, characterized in that the carrageenan is finally dried in a stream of hot air.

9. A process according to claim 1 for the production of a kappa carrageenan, substantially as hereinbefore described and exem5 plified.

10. A kappa carrageenan whenever produced by a process claimed in a preceding claim.