Patent Application
20080317926
Production of carrageenan can be traced back to Ireland where plants of the red seaweed algae species of chondrus crispus were first harvested with rakes during low tide or by gathering seaweed that had washed ashore. After harvesting, the weeds were typically washed, sun-bleached, dried and boiled with milk to form a pudding. The weeds themselves were dubbed “Irish Moss” and after making it familiar to most of Europe, Nineteenth Century Irish immigrants carried it to the U.S. and Canada as well.
Today, this seaweed pudding is mostly confined to Ireland's cultural history, but carrageenan has become much more important because of its effectiveness as a functional food additive in forming gels in an aqueous system, which make it useful in a wide variety of applications, including beer (in which it has been used for over 150 years as a fining) to processed meat and food products like milk drinks and deserts; pharmaceutical preparations such as orally-administered gelcaps; personal care products such as toothpaste and skin care care preparations; and household products such air-freshener gel and cleaning gels. The temperature at which carrageenan gels and melts is dependent on a number of factors that include especially the concentration of gelling cations such as potassium and calcium ions. Generally speaking, the higher the concentration of gelling cations the higher the gelling and melting temperature of the carrageenan. Such cations may come not only from the composition to which the carrageenan is added as a gelling agent, but also from the carrageenan itself.
Thus, carrageenans with relatively high gelling cation concentrations also require relatively high-temperature processing. Generally, lower temperature processes are preferred since these save processing time, are less expensive and don't negatively affect the preparation of the composition in which the carrageenan is being included—this is especially important for food compositions, where higher temperatures may impair the base foodstuffs that are included in the food product. Thus, in order to produce carrageenan materials that promote gelling at even lower temperatures there is a continuing need for carrageenan extraction methods that reduce the concentration of gelling cations in the carrageenan.
Contemporary methods of carrageenan extraction and production have advanced considerably in the last fifty years. Perhaps most significantly is that today, rather than being gathered from wild-grown seaweed, carrageenan-containing plants such as Kappaphycus cottonii (Kappaphycus alvarezii), Euchema spinosum (Euchema denticilatum), and the above mentioned Chondrus crispus are more commonly seeded along nylon ropes and harvested in massive aqua-culture farming operations particularly in parts of the Mediterranean and throughout much of the Indian Ocean and along the Asian Pacific Ocean Coastline. Just as in the Nineteenth-century process, in contemporary processes before further processing the seaweed raw materials are first thoroughly cleaned in water to remove impurities and then dried. Then, as described in U.S. Pat. No. 3,094,517 to Stanley et al. the carrageenan is extracted from the cleaned seaweed while also at the same time being subjected to alkali modification by placing the seaweed in solution made slightly alkaline by the addition of a low concentration of alkali salt (i.e., a pH of the solution is raised to a range of, e.g., 9-10) and then heating this solution to a temperature of around 80° C. for a period of time of about 20 minutes to as long as two hours.
Subjecting the carrageenan-containing seaweed to alkali modification has the desired result of reducing the gelling cation concentration in the resulting carrageenan product; however, the extent to which the gelling cation levels can be reduced is limited because only relatively low concentrations of alkali may be used so as to not depolymerise (and thus damage) the carrageenan in the seaweed. So even though the gelling cation concentrations are reduced, they still remain high.
For example, when an alkali modification process is NOT used, typical cation concentration levels are:
When an alkali modification step is used to reduce these gelling cation concentrations, such as in U.S. Pat. No. 3,094,517 (Stanley et al.), which makes use of calcium hydroxide as alkali modification agent, the resulting cation concentration levels are:
As can be seen, the alkali modification step taught in U.S. Pat. No. 3,094,517 significantly reduced the levels of magnesium and sodium ions, but not other gelling cations such as potassium and calcium. Accordingly, other alkalis have been proposed. For example in U.S. Pat. No. 6,063,915 to Hansen et al., sodium hydroxide and sodium bicarbonate were used as alkalis, producing carrageenans with the following cation concentrations:
While the process taught in U.S. Pat. No. 6,063,915 produces the carrageenan having the best cation gelling concentration profile currently available, the levels of other gelling cations are still somewhat high, making it impossible to further reduce the gelling and melting temperature of compositions containing the carrageenans.
Given the foregoing there is a need in the art for a process for reducing the concentration of gelling cations, and thereby lowering the gelling and melting temperatures, without depolymerising the carrageenan or damaging it in some other way.
The present invention relates to a process for producing a carrageenan composition, comprising the steps of: cleaning iota carrageenan-containing seaweed in water;treating the cleaned seaweed with an aqueous treatment solution, the aqueous treatment solution containing about 3-30 wt %, preferably 10-25 wt %, and most preferably 15-20 wt %, of a treatment compound; subjecting the treated seaweed to washing with water; and processing the washed seaweed to produce the carrageenan composition.
The present invention also relates to a process for producing a carrageenan composition, comprising the steps of: cleaning the iota carrageenan-containing seaweed in water; treating, in a first treating step, the washed seaweed with an aqueous treatment solution, the aqueous treatment solution containing about 3-30 wt %, preferably about 10-25 wt %, and most preferably about 15-20 wt %, of a first treatment compound; rinsing the treated seaweed to remove excess of the first treatment compound;treating, in a second treating step, the rinsed seaweed with a second aqueous treatment solution, the second aqueous treatment solution containing about 3-30 wt %, preferably about 10-25 wt %, and most preferably about 15-20 wt % of a second treatment compound to form a seaweed preproduct; washing the seaweed preproduct in water or a mixture of water and alcohol; and drying the washed seaweed preproduct to produce a carrageenan composition.
The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings;
All parts, percentages and ratios used herein are expressed by weight unless otherwise specified. All documents cited herein are incorporated by reference.
The present invention is directed to iota carrageenans, which may be more specifically described as generic repeating galactose and 3,6-anhydrogalactose residues linked b-(1-4) and a-(1-3), respectively and with characteristic 4-linked 3,6-anhydro-a-D-galactose-2-sulphate and 3-linked-b-D-galactose-4-sulphate groups. The molecules arrange themselves in a right-handed double helix with the strands parallel and threefold. The helix is stabilized by interchain hydrogen bonds through the only unsubstituted positions at O-2 and O-6 with the sulphate groups projecting outward from the helix. As mentioned above, there is a strong correlation between the presence of gelling cations and gellation. Without being limited by theory, it is believed that gels are formed in iota carrageenan through gelling (primarily monovalent) cations such as Na, K, Rb, Cs, NH4, Ca2+ as well as some divalent cations like calcium atoms that facilitate side-by-side interaction of the strands to form a three dimensional gel network. The exact transformation mechanism from the carrageenan as randomly-oriented coils at higher temperatures to a gelled network is the subject of some dispute. As the temperature is lowered the random coils of carrageenan molecules reaggregate to form gels. In one model of gellation, a gel is created by the formation of the carrageenan molecules into double helices; in certain forms of carrageenan (such as kappa carrageenan) these double helices may themselves aggregate side-by-side due to the influence of the aforementioned gelling cations forming aggregates of double helices and eventually even forming domains of a three-dimensional ordered gel network. Alternatively it has been suggested that upon cooling the random coils of the carrageenan molecules do not form double helices but only single helix structures, and that these single helix structures form single helices in which the gelling cations nested in the bends of the helix promote intermolecular aggregation.
Accordingly, the present invention is directed towards a process for treating fresh or dried iota carrageenan-containing seaweed so as to substantially reduce to amount of gelling cations from the iota carrageenan in the seaweed. Of equal importance is that this treatment process reduces the gelling cation concentration without extracting the carrageenan; in other words, depleting the gelling cations of the carrageenan by performing the alkali modification process essentially in situ. By modifying the polymer in situ in the seaweed, depolymerisaton of the carrageenan polymer is avoided and a iota carrageenan preparation is produced that forms gels having lower gelling and melting temperatures than were hitherto known.
The process for producing iota carrageenans according to the present invention will now be described in greater detail.
The present process utilizes a first step which is a conventional cleaning step in which the carrageenan-containing seaweed, particularly seaweed of the species Eucheuma spinosum, is washed to remove impurities and unwanted particulates. The water may be sea water, tap water, rain water, deionised water, sodium chloride softened water or preferably demineralised water. Washing may be conducted at temperatures in the range 5-25° C. The washing may be conducted as a counter current wash or a batch wash, with a counter current process preferred because of its better utilisation of the treatment liquid. (In all subsequent steps of the process of the present invention, the water may be rain water, deionised water, sodium chloride softened water, but preferably demineralised water).
The second step in the process may be practiced in accordance with three different embodiments.
(a) Second step, first Embodiment
In the first embodiment, the second step is a treatment of the cleaned seaweed with an aqueous treatment solution containing alkali in water. The alkali supplies cations, which prevent the diffusion of potassium, calcium and magnesium ions into the carrageenan, while the concentration of the alkali in the treatment solution is held sufficiently high to reduce the aqueous solubility of the carrageenan thus preventing it from leaching out of the seaweed and dissolving into the water during this and subsequent steps.
Accordingly, by treating the carrageenan-containing seaweed in this way, the carrageenan is depleted from its gelling cat ions in situ.
Preferred alkalis are sodium hydroxide and its corresponding carbonates and bicarbonates, with sodium hydroxide being the most preferred. Sodium hydroxide is particularly notable for reducing the gelling and melting temperatures of carrageenan. Also suitable is calcium hydroxide. As discussed above, the concentration of the alkali must be such to provide sufficient monovalent cations while preventing solubilization of the carrageen in the water phase; an appropriate range to accomplish this dual purpose is a concentration of alkali in range of 3-30 wt %, preferably 10-25 wt % and most preferably 15-20 wt %.
In some cases alcohol may be added to the treatment solution to further reduce the leaching out of the carrageenan from the seaweed and its dissolving into water. It is particularly important to add alcohol when relatively small quantities of the aqueous treatment liquid are used. This is because excess water initially present in the wet seaweed and also remaining from the washing step could dilute the concentration of the cations in the aqueous treatment solution to the point that the carrageenan begins to leach out. The presence of alcohol in the treatment solution helps maintain high yields, especially as the treatment temperature is increased. Preferred alcohols are methanol, ethanol and isopropyl alcohol with ethanol being most preferred. The amount of alcohol ranges from 200-800 ml alcohol per 1000 ml treatment solution, preferably 200-600 ml alcohol per 1000 ml treatment solution and most preferably 500-600 ml alcohol per 1000 ml treatment solution.
The temperature during treatment ranges from 0-70° C., preferably 5-70° C. and most preferably 5-35° C. The treatment time is in the range 1-24 hours, preferably 2-17 hours, and most preferably 2-4 hours. Either a batch wise or counter current process may be used; although as mentioned above the counter current process is preferred because it makes better utilisation of the treatment liquid.
Carrageenan products prepared according to the first embodiment of the second step form gels having gelling temperatures of 7-30° C., preferably 7-18° C., more preferably 7-12° C.; and melting temperatures in the range 16-38° C., preferably 16-28° C., more preferably 16-24° C. In addition, carrageenan products according to the first embodiment of the second step are characterized by a sodium content in the range 5.410-8.230%, preferably 6.300-8.230% and more preferably 7.380-8.230%; a potassium content of 0.023%-0.248%, preferably 0.023-0.238% and more preferably 0.023-0.078%; a calcium content of 0.046-0.553%, preferably 0.046-0.446% and more preferably 0.046-0.325%; and a magnesium content of 0.051-0.338%, preferably 0.051-0.244% and more preferably 0.051-0.127%.
(b) Second Step, Second Embodiment
In a second embodiment of the present invention, the second step is a treatment of the washed seaweed with an aqueous treatment solution containing a sodium salt. The effect is similar as described above with respect to the first embodiment where the sodium salt provides monovalent cations to prevent the diffusion of potassium, calcium and magnesium ions into the carrageenan while the concentration of the sodium salt in the treatment solution is held sufficiently high to reduce the aqueous solubility of the carrageenan thus reducing its leaching out from seaweed and dissolution into water. Thus similarly as above, by treating the carrageenan-containing seaweed in this way, the carrageenan is depleted from its gelling cat ions in situ.
Sodium salts include, but are not limited to sodium chloride, sodium sulphate, sodium phosphate, sodium tripolyphosphate and sodium hexametaphosphate. The concentration of sodium salt in the water phase is in the range 3-30 wt %, preferably 10-25 wt %, and more preferably 15-20 wt %.
As described above in the section entitled “Second Step, First Embodiment”, alcohol may optionally be added to the treatment solution to further reduce the leaching out of the carrageenan from the seaweed and dissolving into water. Similarly, the same temperature and time parameters are used in this embodiment of the process as in the previous two mentioned above.
In this embodiment, the temperature during treatment ranges from 0-25° C., preferably 0-10° C., and more preferably 0-5° C. The treatment time is in the range 1-24 hours, preferably 2-17 hours, and most preferably 2-4 hours. Either a batch wise or counter current process may be used; the counter current process is preferred because it makes better utilisation of the treatment liquid.
Carrageenan products prepared according to the second embodiment of the second step form gels having gelling temperatures in the range 0-13° C., preferably 0-8° C., more preferably 0-5° C.; and melting temperatures in the range 13-24° C., preferably 13-15° C. In addition, carrageenan products according to the second embodiment of the second step are characterized by a sodium content in the range 7.200-10.120%, preferably 7.360-10.120%, more preferably 7.860-10.120%; a potassium content of 0.030-0.330%, preferably 0.030-0.140% and most preferably 0.030-0.057%; a calcium content of 0.055-0.574%, preferably 0.055-0.450% and more preferably 0.055-0.330%; and a magnesium content of 0.019-0.110%, preferably 0.019-0.090%, and more preferably 0.019-0.073%.
(C) Second Step, Third Embodiment
In a third embodiment of the present invention, this second step is essentially split into three substeps which include a first substep of treating the washed seaweed with a first aqueous treatment solution containing about 3-30 wt %, preferably 10-25 wt %, and most preferably 15-20 wt %, of a first treatment compound, a second substep of washing or rinsing the treated seaweed to remove excess of the first treatment compound, and a third substep of treating the washed seaweed with a second aqueous treatment solution containing about 3-30 wt %, preferably 10-25 wt %, and most preferably 15-20 wt %, of a second treatment compound. (For purposes of clarity, exactness and completeness to persons of ordinary skill in the art these substeps are referred to as separate processing steps in the claims.).
The third embodiment can thus be practiced in two subembodiments. In the first subembodiment, the first treatment compound is an alkali, and the second treatment compound is an salt; in the second subembodiment, the first treatment compound is an salt, and the second treatment compound is an alkali.
As described above in the section entitled “Second Step, First Embodiment”, alcohol may optionally be added to the treatment solution to further reduce the leaching out of the carrageenan from the seaweed and dissolving into water. Similarly, the same temperature and time parameters are used in this embodiment of the process as in the previous two mentioned above.
Carrageenan products according to the third embodiment of the second step produce gels having gelling temperatures in the range 4-35° C., preferably 4-25° C. and most preferably 4-9° C.; and melting temperatures in the range 15-45° C., preferably 15-35° C. and most preferably 15-18° C. In addition, carrageenan products according to the third embodiment of the second step are characterized by a sodium content in the range 6.720-7.546%, preferably 6.920-7.546% and more preferably 7.200-7.546%; a potassium content of 0.017-0.078%, preferably 0.017-0.030% and more preferably 0.017-0.026%; a calcium content of 0.140-0.250%, preferably 0.140-0.220% and most preferably 0.140-0.160%; and a magnesium content of 0.083-0.210%, preferably 0.083-0.120% and more preferably 0.083-0.094%
In the third step in the process (which is common to all three embodiments of the second step discussed above) the treated seaweed is subjected to washing to remove the excess of the last reagent that was used in the second or treatment step. The reagent can of course be either an salt or an alkali. Washing is done with slow agitation and the number of washings is in the range 1-4, preferably 1-2, and washing time is in the range 10-30 minutes per wash, preferably 15 minutes per wash. Controlling the number of washing steps is important because the yield decreases with time (possible reasons for this are discussed below) and because the number of washing steps affects the gelling and melting temperatures (again, this is discussed in greater detail, below). As above to limit leaching out of the carrageenan from the seaweed the temperature during washing is held in the range 0-25° C., preferably 0-5° C.
In the fourth and final step of the process the treated seaweed can be dried and ground into a powder of semi-refined carrageenan products, which in addition to carrageenan also contain the cellulosic material from the seaweed.
Alternatively, pure carrageenan can be extracted from the treated seaweed in pure water, such as one of the water types described above (again demineralised water is preferred). Of primary importance is that the extraction step does not re-introduce the gelling cations. Extraction temperatures are in the range 0-90° C., preferably 25-90° C. and most preferably 50-90° C. Typically, higher extraction temperatures result in greater yields.
Other aspects of the processes for production of carrageenan according to the present invention are not particularly limited, and where necessary conventional carrageenan technology may be used. In addition to the specific steps set forth herein, processes of the present invention may further comprise additional processes typically associated with carrageenan production.
An additional important aspect of this present invention is that because the relationship between the gelling and melting temperatures and the several processing parameters has been determined with such specificity, then these temperatures can be controlled depending on the specific properties desired in the carrageenan. In other words, by specially controlling the processing parameters, a carrageenan having particular properties can be produced.
The present invention will now be explained in greater details with respect to the following several experiments. These experiments and their accompanying textual descriptions, will present detailed descriptions of the process of the present invention as well as results obtained from the experimental process. Additionally analysis of the results will be presented and supplemented by possible theoretical explanations. The following experimental equipment, materials and methods were used in carrying out the present experiments. Application of these experimental methods are introduced in the specific examples section below that illustrate the present invention and place it within the context of the prior art.
Equipment
Chemicals:
Treatment of seaweed:
The Determination of gelling and melting temperatures of carrageenan-compositions was made using a composition with the following carrageen-incorporating composition:
This composition was prepared as follows:
The gelling and melting temperatures were measured by temperature sweeps on Haake RheoStress RS100, using cooling and heating rates of 1° C./min. The following program was generally used, however, in some instances where gelling and melting temperatures were higher; the program was run at higher starting temperatures and lower end-temperatures:
Fig. A and Fig. B show typical temperature sweep graphs.
The following procedure was used for gelling and melting temperatures in demineralized water:
The following procedure for gelling and melting temperatures in demineralized water with salts;
The Viscosity in Toothpaste was measured using the following equipment, chemicals, formula, and procedure:
Equipment
Chemicals
Process
The invention will now be described in more detail with respect to the following non-limiting examples which were performed with the above described equipment, materials and methods.
The following Examples with data set forth in tables 1-8 relate to results obtained by treating the red seaweed Eucheuma spinosum with an alkali according to the present invention. The results obtained from the present invention were compared with comparative, prior art neutral extractions, in which the washed seaweed was extracted in demineralized water for one hour at 90° C.
TG and TM stand for gelling temperature and melting temperature, respectively, while TD is the dissolution temperature, and η stands for intrinsic viscosity at 60° C. The “% yield” is calculated as: % yield=(g. dry precipitate×1500×100)/(g. seaweed×g. precipitated extract×seaweed dry matter). Since yield of polymer from seaweed changes with season and with seaweed harvesting location, the yield of neutral extractions of seaweed have been assigned an index of 100, and subsequent calculations of yield index utilize that baseline figure.
The results for the neutral, prior art, extraction were as follows:
Effect of washing temperature. The process of the present invention involves the treatment of seaweed with salts and/or an alkali, and thus, the new process involves a washing step subsequent to the treatment with salts and/or alkali. This washing is done in order to prevent residues of salts and alkalis in the final extract. Accordingly, in this example, after treatment with salts and/or alkali, the seaweed was washed 4 times for a period of 30 minutes with demineralized water at various temperatures. The seaweed was treated with different concentrations of sodium hydroxide for 2 hours at 5° C.: The results are set forth in Table 2 and shown graphically in
As can be seen in Table 2 and
These results indicate that regardless of the alkali concentration, the washing temperature should be held as low as possible, preferably at about 5° C. or lower.
Table 2 and
Effect of the number of washing step. The next step was to look at the number of washing steps. Each washing step took 15 minutes and was performed at 5° C., and the seaweed was treated with 15% and 3% sodium hydroxide for 2 hours at 5° C.:
A selection of the results from Table 3 are shown graphically in
In table 3, the pH of the extract is indicia of the excess of alkali, and at least one washing step seems to be adequate in order to remove excess alkali. The yields at or above 100% for the zero washing are believed to be caused by alkali being co-precipitated with the carrageenan polymer.
Without being limited by theory, it is believed that this residue of sodium hydroxide in itself reduces the solubility and increases gelling and melting temperatures. Additionally, the higher content of potassium ions in the carrageenan polymer accounts for at least some of the increased gelling and melting temperatures. As the number of washing steps is increased, the content of potassium ions in the polymer is reduced, and correspondingly the pH of the extract is reduced, which explains the proportional drop in gelling and melting temperatures with increasing number of washing steps. However, the measured concentration of cations may be somewhat misleading, because the concentration is averaged over the entire polymer. But it is strongly believed that the cation concentration is not homogeneous throughout, but instead that different fractions of the polymer molecule have been subjected to different levels of ion-exchange between potassium cations and monovalent cations like sodium, with some monovalent-rich fractions reflecting a high amount of ion-exchange activity. This heterogeneity is believed to explain why the gelling and melting temperatures increase with further washing steps because further washing eliminates the monovalnt-rich portions (i.e., those subjected to greater ion exchange) more readily than further washing eliminates the potassium-rich portions (i.e., those subjected to less ion exchange).
Effect of alcohol concentration in the wash. Alcohol will prevent the polymer in the seaweed from dissolving, and the next step was to look at washing the treated seaweed in different concentrations of alcohol in demineralized water. The seaweed was treated with 15% sodium hydroxide for 2 hours at 5° C. before washing 4 times 15 minutes in ethanol and water:
A selection of the results tabulated in Table 4, are shown graphically in
Effect of alkali treatment time. The next experiment looked at the yield index as a function of alkali treatment time. The seaweed was treated at 25° C. and 5° C. for 2 hours, and subsequently washed at 25° C. and at 5° C. with a mixture of 300 ml ethanol and 200 ml demineralized water. G′ is the elastic modulus, which indicates the stiffness of the gel and which is measured during the cooling sweep at the point where the elastic modulus, G′ intersects with the viscous modulus, G″. For comparison, a neutral extraction provides a polymer having G′ of about 4.5 Pa.
A selection of the results tabulated in Table 5, are shown graphically in
Effect of other alkali types. The next step was to look at the effect on the yield when using different alkalis during treatment of the seaweed. For this, a new batch of Eucheuma spinosum was used. The following results were obtained:
In order to obtain the polymers from these experiments in predominantly sodium-cation form, the seaweed was treated with the alkali at 25° C., and subsequently washed at 25° C. twice with 500 ml. 30% sodium chloride and finally twice with 250 ml methanol in 250 ml demineraiised water:
A selection of the results tabulated in Tables 6 and 7 are shown graphically in
Effect of calcium hydroxide. In order to further evaluate to effect of calcium hydroxide, tests were performed in which the seaweed was treated with various concentrations of calcium hydroxide at 25° C. The treated seaweed was subsequently treated for 2 hours at 25° C. in 1000 ml 30% sodium chloride and finally washed twice with 250 ml methanol in 250 ml deminerialized water. The results were as follows:
A selection of the results tabulated in Table 8 is shown graphically in
The following Examples relate to results obtained using the red seaweed Eucheuma spinosum and treatment, with salt.
A new batch of Eucheuma spinosum was used to prepare an additional comparative example representing the prior art:
A first experiment looked at treatment with sodium chloride at various concentrations and times at 25° C. The treated seaweed was subsequently washed twice in 500 ml demineralised water at 5° C.
A selection of the results tabulated in Table 10 is shown graphically in
Effect of other salts. The Next step was to evaluate the effect of other salts, where seaweed was treated for two hours with a 10% solution of the salt at 25° C. The treated seaweed was subsequently washed twice in a mixture of 500 ml ethanol and 500 ml demineralized water at 5° C.
A selection of the results tabulated in Table 10 is shown graphically in
Effect of treatment with alkali and salt. The effect of using both an alkali and a salt was then studied by first treating seaweed with 15% alkali for 73 hours at 5° C., and then washed twice for 15 minutes in 30% sodium chloride solution at 25° C. The treated and washed seaweed was then treated for 4 hours at 25° C. with a 30% sodium chloride solution and finally washed twice with a mixture of 250 ml methanol and 250 ml demineralized water at 25° C.
A selection of the results tabulated in Table 12 is shown graphically in
The following were examples and experiments, the results of which are set forth in Tables 13-14, were performed, in order to provide a means for maintaining the yield when using sodium hydroxide as the alkali before treatment with sodium chloride. The process involved the following steps: the washed seaweed was treated with 20% sodium hydroxide in the water phase and varying quantities of ethanol for 3 hours at 5° C. The treated seaweed was then washed once in 30% sodium chloride solution at 5° C. and treated with a 20% sodium chloride solution for 2 hours at 5° C. The seaweed was then washed twice in a mixture of 600 ml ethanol and 400 ml demineralized water at 5° C. before being extracted in demineralized water at 90° C. for 1 hour, filtered and precipitated in three volumes of 100% isopropyl alcohol, dried and milled.
Effect of alcohol during alkali treatment. As comparison, one test was done using a mixture of 600 ml ethanol and 400 ml demineralized water instead of a 30% sodium chloride solution during the wash after alkali treatment.
A selection of the results tabulated in Table 13 is shown graphically in
Effect of temperature during alkali treatment. In further experiments, the effect of temperature during alkali treatment was evaluated. The process was the same as the process used for the data in Table 13, using salt in the first wash, but while varying the temperature during alkali treatment.
A selection of the results tabulated in Table 14 is shown graphically in
With ethanol concentrations in the range from about 200 ml. ethanol per litre to about 600 ml. ethanol per litre, the gelling temperature can be controlled in the range from about 6° C. to about 27° C. Similarly, the melting temperature can be controlled in the range from about 16° C. to about 36° C. This by varying the treatment temperature within the range from about 5° C. to about 35°° C.
However, when using lower concentrations of ethanol during the alkali treatment, the gelling and melting temperatures can be controlled in a wider range. The gelling temperature can be controlled in the range from about 6° C. to about at least 35° C., Similarly, the melting temperature can be controlled in the range from about 16° C. to about at least 45° C. This by varying the treatment temperature from about 5° C. to about at least 50° C.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood therefore that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
