Title of Invention	"A PROCESS FOR PREPARATION OF HYDROCOLLOID GUM ESTERS"
Abstract	The invention relates to a process for the preparation of hydrocolloid gum esters. More particularly it relates to a preparation at ambient or elevated temperature and mild base as a catalyst along with the respective acid anhydrides to obtain derivatives, which could be recovered by simple and well known methods and with desirable degree of substitution for specific end uses.

Full Text

This invention relates to a process for the preparation of hydrocolloid gum esters. Esterification, such as acetylation succinylation, and octenylsuccinylation of starches, gums and other biopolymers, which possess several important properties such as suspension or foam stabilization, emulsification, etc. is one of the commonly used modification methods for carbohydrates wherein the reaction is carried out using respective acid anhydrides and strong base as catalyst at ambient or elevated temperature. Occasionally pyridine is used as a solvent cum catalyst. Acetylation Reference may be made to Agboola (Production of low substituted cassava starch acetates and citrates, Starch/Starke, 43, 1991, 13-15) 1, wherein starch acetates were prepared by treating starch with dil. NaOH / acetic anhydride at room temperature with and without H2S04 as catalyst. Low degree of substitution and possible starch degradations were the drawbacks of this method. Reference may be made to Wang and Wang (Characterization of acetylated waxymaize starches prepared under catalysis by different alkali and alkaline hydroxides, Starch/Starke, 54, 2002, 25-30) 2, wherein the effects of alkaline catalysts on the degree of acetylation of waxymaize starch are investigated. Ca (OH) 2 - catalyzed acetylated starch exhibited a slightly higher pasting temperature and lower (3- amylolysis limit compared to NaOH or KOH catalyzed derivatives. Nevertheless, the residual calcium ions posed a potential barrier to enzymatic hydrolysis, thus potentially reducing the digestibility of acetylated starch. Reference may be made to Gonzalez and Perez (Effect of acetylation on some properties of rice starch, Starch/Starke, 54, 2002, 148-154) 3, wherein commercial rice starch was acetylated in NaOH (to maintain a pH of 8-8.4) with acetic anhydride at ambient temperature, to a low degree of substitution (DS 0.03,aqueous slurry and later energy required for drying the derivative, long reaction times and tedious follow up steps. Reference may be made to Singh (Influence of acetic anhydride on physicochemical, morphological and thermal properties of corn and potato starch, Food Chemistry, 2003) 4, wherein acetylated starches were prepared with acetic anhydride in the presence of an alkaline reagent (NaOH) in aqueous medium to very low degree of acetylation. Although sufficient to modify several of the properties' the method did not prevent starch degradation taking place in the alkaline medium and also did not prove to be cost effective. Succinylation: Reference may be made to Wang and Shogren (Preparation of starch succinates by reactive extrusion, Starch/Strake, 49, 1997,116-120) 5, wherein succinylation of corn starch was carried out by thin screw extrusion processing in a very short time (1 min) compared to much longer times normally required for typical batch reactions. Though short reaction times are possible, the extruder was operated at high temperature and high reactant concentrations, and the DS obtained was low 0.5. Also the initial investment on the extruder was very high. Octenyl succinylation Reference may be made to Shogren (Distribution of octenyl succinate groups in octenyl succinic anhydride modified waxymaize starch), Starch/Starke, 52, 2000, 196-204)6, wherein octenyl succinate modified waxymaize starch was prepared by base catalyzed reaction of alkenyl succinic anhydride with granular starch in aqueous suspension, with retention of granular structure after the reaction. The method did not pay attention to alkaline degradation of the reactant and reagent taking place during the reaction carried out for long interval of time. Thus, the available methods suffer from several disadvantages including use of toxic organic solvents, cost ineffectiveness and lengthy procedural steps.Hence, modification of the existing methods with emphasis to overcome above problems was felt desirable. The main objective of the present invention is to provide a process for the preparation of hydrocolloid gum esters, which obviates many of the drawbacks discussed above. Another objective of this invention is to describe a novel method for acetylation, succinylation and octenyl succinylation of galactomannans and other biopolymers such as starch. Another objective of this method is to minimize alkali- induced degradation of the reactant and reagent by using a very mild base catalyst at ambient or slightly elevated temperature Yet another objective of this method is to aim at cost effectiveness and easy recovery of derivatized hydrocolloid/ biopolymer in the entire operation process, especially during the final drying step. Accordingly, the present invention relates to a process for the preparation of hydrocolloid gum esters, which comprises; a. surface wetting galactomannans with 95% ethanol, b. acetylation of gum, catalyst and reagents are in the ratio of 1:0.5:5, Succinylation in the ratio of 1:0.5:1 and octenyl Succinylation in the ratio of 1:1:1 for guar gum and Tara gum at a temperature ranging between 28-60°C, c. mixing the ingredients to get a homogeneous slurry d. raising the temperature to 60°C for a period of 2-4 hr, e. precipitating the slurry with 3 to 4 vol. of ethanol, f. drying the precipitate to obtain the hydrocolloid gum ester. In an embodiment of the process the yield of acetylated, succinylated and octenylsuccinylated derivatives of guar and tara gums is 104-105%, 89-92% and 89-92% respectively. In an another embodiment of the process the acetylation of gum, catalyst and reagents are in the ratio of 1:0.5:5, Succinylation in the ratio of 1:0.5:1 and octenyl Succinylation in the ratio of 1:1:1 for guar gum and Tara gum at a temperature ranging between 28-60°C. In yet an another embodiment of the process the viscosity of the hydrocolloids is in the range of 350-5100 cps. Novelty: The novelty embodying the present invention is elimination of aqueous reaction conditions and use of mild base catalyst (NaHCO3), which is a commonly used chemical in foods, to prepare the respective esterified derivatives, helps in preserving the structural integrity of the sample (hydrocolloid gum) as well as the reagent. The method is novel, cost effective, eliminates the use of toxic organic solvent such as pyridine, and versatile. The following examples are given by way of illustration of the present invention and therefore should not be construed to limit the scope of the present invention. Examples Example 1. One g of guar gum and 0.5g of finely powdered NaHC03 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanol (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at ambient temperature (28°C) the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanol followed by repeated (x3) washing with 70 to 75% aqueous ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1 % solution of derivatized gum was determined (Tablel). Example 2. One g of guar gum and 1.5g of finely powdered NaHCO3 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanol (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at ambient temperature (28°C) the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanol followed by repeated (x3) washing with 70 to75% aqueous ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Tablel). Example 3. One g of guar gum and 1.5g of finely powdered NaHCO3 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanol (1ml) and then 10ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at ambient temperature (28°C) the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanol followed by repeated (x3) washing with 70 to 75% aqueous ethanoi, dried by solvent exchange with absolute ethanoi, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Tablel). Example 4. One g of guar gum and 1.5g of finely powdered NaHCO3 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanoi (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at 40°C the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanoi followed by repeated (x3) washing with 70 to75% aqueous ethanoi, dried by solvent exchange with absolute ethanoi, followed by solvent ether and air dried. The relative viscosity of 1 % solution of derivatized gum was determined by the known method (Tablel). Example 5. One g of guar gum and 1.5g of finely powdered NaHCO3 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanoi (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at 60°C the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanoi followed by repeated (x3) washing with 70 to75% aqueous ethanoi, dried by solvent exchange with absolute ethanoi, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Tablel). Example 6. One g of tara gum and 0.5g of finely powdered NaHCO3 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanoi (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at ambient temperature (28°C) the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3 vol. of ethanol followed by repeated (x3) washing with 70 to 75% aqueous ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Tablel). Example 7. One g of tara gum and 1,5g of finely powdered NaHC03 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanol (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at ambient temperature (28°C) the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanol followed by repeated (x3) washing with 70 to 75% aqueous ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of1 % solutions of derivatized gum were determined by the known method (Tablel). Example 8. One g of tara gum and 1.5g of finely powdered NaHC03 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanol (1ml) and then 10ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at ambient temperature (28°C) the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanol followed by repeated (x3) washing with 70 to75% aqueous ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Tablel). Example 9. One g of tara gum and 1.5g of finely powdered NaHCO3 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanol (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at 40°C the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanol followed by repeated (x3) washing with 70 to 75% aqueous ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Tablel). Example 10. One g of guar gum and 0.5g of finely powdered NaHCO3 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanol (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs 60°C at the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanol followed by repeated (x3) washing with 70 to 75% aqueous ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Tablel). Example 11. One gram of locust bean gum and 1.5g of finely powdered NaHCO3 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanol (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at 40°C the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanol followed by repeated (x3) washing with 70 to 75% aqueous ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the Known method (Tablel). Example 12. One g of starch and 1.5g of finely powdered NaHCO3 were mixed in a pestle and mortar. This was moistened with distilled water (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at 40°C the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3 vol. of ethanol followed by repeated (x3) washing with 70 to 75% aqueous ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Tablel). Example 13. One g of starch and 1.5g of finely powdered NaHCO3 were mixed in a pestle and mortar. This was moistened with 95% aqueous ethanol (1ml) and then 5ml of distilled acetic anhydride was added dropwise and mixed well. After 2 hrs at 40°C the slurry pH was adjusted to 7.0 by adding either 1N HCI or NaOH, and the derivatized product was recovered by precipitation with 3vol. of ethanol followed by repeated (x3) washing with 70 to 75% aqueous ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1 % solution of derivatized gum was determined by the known method (Tablel). Example 14 One g of tara gum was mixed with 1 g of finely powdered NaHCO3 and wetted with 0.2 ml of absolute ethyl alcohol and then 1g of succinic anhydride was added. The reaction was allowed to take be for 4 hrs at 28°C. The derivatized product was precipitated with 3 vol of ethanol followed by centrifugation (10 min at 4000 rpm). The sediment was repeatedly (x3) washed with 70% ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1 % solution of derivatized gum was determined by the known method (Table 2). Example 15. One g of tara gum was mixed with 1 g of finely powdered NaHCO3 and wetted with 0.2 ml of absolute ethyl alcohol and then 2g of succinic anhydride was added. The reaction was allowed to take place for 4 hrs at 28°C. The derivatized product was precipitated with 3 vol. of ethanol followed by centrifugation (10 min at 4000 rpm). The sediment was repeatedly (x3) washed with 70% ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Table 2). Example 16. One g of guar gum was mixed with 1g of finely powdered NaHC03 and wetted with 0.2 ml of absolute ethyl alcohol and then 1g of succinic anhydride was added. The reaction was allowed to take place for 4 hrs at 28°C. The derivatized product was precipitated with 3 vol of ethanol followed by centrifugation (10 min at 4000 rpm). The sediment was repeatedly (x3) washed with 70% ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1 % solution of derivatized gum was determined by the known method (Table 2). Example 17. One g of guar gum was mixed with 1g of finely powdered NaHC03 and wetted with 0.2 ml of absolute ethyl alcohol and then 2g of succinic anhydride was added. The reaction was allowed to take place for 4 hrs at 28°C. The derivatized product was precipitated with 3 vol. of ethanol followed by centrifugation (10 min at 4000 rpm). The sediment was repeatedly (x3) washed with 70% ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Table 2). Example 18. Two g of tara gum was mixed with 0.5 g of finely powdered NaHCO3 followed by the slow addition of 0.2 ml of octenyl succinic anhydride kept for 2 hrs with occasional stirring. The derivatized product was precipitated with 3 vol. of ethanol followed by centrifugation (10 min at 4000 rpm). The sediment was repeatedly (x3) washed with 70% ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Table 3). Example 19. Two g of tara gum was mixed with 2 g of finely powdered NaHCO3 followed by the slow addition of 2 ml of octenyl succinic anhydride kept for 4 hrs with occasional stirring. The derivatized product was precipitated by 3 vol. of ethanol followed by centrifugation (10 min at 4000 rpm). The sediment was repeatedly (x3) washed with 70% ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1 % solution of derivatized gum was determined by the known method (Table 3). Example 20. Two g of guar gum was mixed with 0.5 g of finely powdered NaHCO3d followed by the slow addition of 0.2 ml of octenyl succinic anhydride kept for 2 hrs with occasional stirring. The derivatized product was precipitated with 3 vol. of ethanol followed by centrifugation (10 min at 4000 rpm). The sediment was repeatedly (x3) washed with 70% ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Table 3). Example 21. Two g of guar gum was mixed with 2 g of finely powdered NaHCO3 followed by the slow addition of 2 ml of octenyl succinic anhydride kept for 4 hrs with occasional stirring. The derivatized product was precipitated with 3 vol. of ethanol followed by centrifugation (10 min at 4000 rpm). The sediment was repeatedly (x3) washed with 70% ethanol, dried by solvent exchange with absolute ethanol, followed by solvent ether and air dried. The relative viscosity of 1% solution of derivatized gum was determined by the known method (Table 3). Further confirmation of esterification in the derivatives was obtained by FT-IR data, which revealed characteristic absorption bands due to various functional groups (Table 4). Table 1: Acetylation data (Table Removed) G= gum; C= base catalyst; R= reagents (acetic anhydride); *Apparent viscosity of the samples is as determined using Brookfield Synchroelectric viscometer, LVT model spindle No. 4, measured at 30 rpm. Table 2: Succinylation data. (Table Removed) Reaction carried out at 28°C. *Apparent viscosity of the samples is as determined using Brookfield Synchroelectric viscometer, LVT model spindle No. 4, measured at 30 rpm. Table 3: Octenyl succinylation data. (Table Removed) Temperature - 28°C, Amount of gum- 2g *Apparent viscosity of the samples is as determined using Brookfield Synchroelectric viscometer, LVT model spindle No. 4, measured at 30 rpm. Table 4: IR characterization of gum derivatives (Table Removed) * Ambient temperature; ** 40°C and *** 60°C DS = Log [A-OH, cm -1/ A -c = o, cm -1], Where A is the absorbance at these wavelengths, calculated from baseline drawing. Summary • The results indicated that galactomannans with different galactose to mannose ratios could be derivatized using this method. Guar gum showed higher degree of substitution for acetylated and octenylsuccinylated esters followed by esterified tara gum, while succinylated ester showed a significantly higher value of degree of substitution for tara compared to guar gum. • The yield of acetylated guar and tara gums was 104 to 105% and that of acetylated starch was 95 to 96%. Yield of succinylated and octenylsuccinylated gums was 89 to 92%. • Derivatized gums showed easy despersibility compared to native gum. • The apparent viscosity showed a significant decrease after derivatization • Acetylation could be carried out eliminating the use of toxic solvent such as pyridine by using mild catalyst such as sodium bicarbonate. Further confirmation of esterification in the polymeric derivatives was obtained by FT-IR data, which revealed characteristic absorption bands due to various functional groups. Advantages: The main advantages of the present invention are 1. A novel process for esterification of hydrocolloid gums and other biopolymers. 2. Use of inexpensive, mild base (solid NaHCO3, which is a commonly used chemical in foods) as the catalyst for the reaction. 3. Quantitative removal of catalysts/ reagent is easily accomplished by successive treatment with ethanol (70 to 75%) washings. 4. Use of anhydrous reaction conditions also saves on energy consumption required for drying the derivatized materials in the final step. Hence, the method is cost effective. 5. By suitable manipulation of the reaction conditions, a range of tailor-made derivatives of defined DS could be prepared. 6. With slight variation of the method, other biopolymers such as starch could also be conveniently derivatized. 7. Thus, the described process is novel, efficient, cost effective and versatile. We Claim: 1. A process for the preparation of hydrocolloid gum esters, which comprises: a. mixing galactomannans or starch and finely powdered catalyst- NaHC03, b. moisturizing with 95% ethanol, c. adding esterifying agent selected from distilled acetic anhydride, succinic anhydride, octenyl succinic anhydride at a level of 0.2-10 ml, d. mixing the ingredients acetylation of gum, catalyst and esterifying agent in the ratio of 1:0.5:5, Succinylation in the ratio of 1:0.5:1 and octenyl Succinylation in the ratio of 1:1:1 for guar gum and Tara gum at a temperature ranging between 28-60°C for 2-4 hours to get a homogeneous slurry, e. precipitating the slurry with 3 to 4 vol. of ethanol, f. drying the precipitate to obtain the hydrocolloid gum ester. 2. A process as claimed in claim 1, wherein galactomannas is selected from guar gum or tara gum. 3. A process for the preparation of hydrocolloid gum esters substantially as herein described with reference to the examples and graphs accompanying this specification.

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