Preparing a blend of polysaccharide and ingredient

Abstract

The invention is directed to a method of preparing a blend comprising a polysaccharide and a water soluble or dispersible ingredient. More in particular, the invention relates to the preparation of such blend using a filter centrifuge. The method of the invention comprises a. feeding a polysaccharide slurry to a filter centrifuge via a first inlet; b. rotating the filter centrifuge at a first centrifuge speed to provide a polysaccharide cake; c. feeding a sprayable ingredient to the filter centrifuge via a second inlet; and d. spraying the sprayable ingredient onto the polysaccharide cake while rotating the filter centrifuge at a second centrifuge speed to produce a blend of the polysaccharide and the ingredient.

Claims

1. A method of preparing a blend comprising a polysaccharide and an ingredient, the method comprising: a) feeding a polysaccharide slurry to a filter centrifuge via a first inlet; b) rotating the filter centrifuge at a first centrifuge speed of 300-1500 rpm to provide a polysaccharide cake; c) feeding a sprayable ingredient to the filter centrifuge via a second inlet; and d) spraying the sprayable ingredient onto the polysaccharide cake while rotating the filter centrifuge at a second centrifuge speed of 50-1000 rpm to produce a blend of the polysaccharide and the ingredient; wherein: the polysaccharide slurry that is fed to the filter centrifuge has a slurry solvent content of 40-90% by total weight of the slurry; the polysaccharide cake at the start of spraying the sprayable ingredient has a solvent content above 45% and up to 60% by total weight of the polysaccharide cake; and the sprayable ingredient is sprayed for over a period of 5 min to 60 min.

2. The method according to claim 1, wherein the polysaccharide is one or more selected from the group consisting of hydrocolloids, cellulose, cellulose derivatives, starch, starch derivatives, maltodextrin, dextrin manno-oligosaccharides, xylo-oligosaccharides, polydextrose, glycogen, citrus fibres, cocoa fibres, and glucans.

3. The method according to claim 1, wherein the ingredient is one or more selected from the group consisting of salts, such as sodium carbonate, potassium carbonate, ammonium carbonate, calcium carbonate, sodium persulphate, potassium persulphate, ammonium persulphate, sodium sulphate, potassium sulphate, ammonium sulphate, sodium citrate, potassium citrate, ammonium citrate, lime; and additives, such as biocides, pH buffers; pH adjusting chemicals, such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, hydrogen chloride, sulphuric acid; processing aids, antifoaming agents, flowing agents, and bleaching agents.

4. The method according to claim 1, wherein the polysaccharide slurry that is fed to the filter centrifuge has a slurry-solvent content of 50-80%.

5. The method according to claim 1, wherein the first centrifuge speed is 400-1200 rpm; and/or wherein the second centrifuge speed is 200-500 rpm.

6. The method according to claim 1, wherein sprayable ingredient is a sprayable mixture of the ingredient in an ingredient-solvent.

7. The method according to claim 6, wherein the concentration of the ingredient in the sprayable mixture is 0.1-400 g/l.

8. The method according to claim 1, wherein the sprayable ingredient is sprayed over the polysaccharide cake using a spray bar.

9. The method according to claim 1, wherein the amount of sprayable ingredient sprayed is 0.1-0.6 1 per kg of polysaccharide cake.

10. The method according to claim 1, wherein the sprayable ingredient is sprayed at a rate of 10-1000 ml/min/kg polysaccharide.

11. The method according to claim 1, wherein the sprayable ingredient is sprayed for over a period of 5 to 35 min.

12. The method according to claim 1, wherein the polysaccharide cake has a thickness of 0.5-10 cm.

13. The method according to claim 1 further comprising removing solvent from the polysaccharide cake before spraying the sprayable ingredient.

14. The method according to claim 1 further comprising drying the blend.

15. The method according to claim 14, wherein drying the blend comprises centrifuging and/or blowing of hot air.

16. A method of preparing a blend comprising a polysaccharide and an ingredient, the method comprising: a) feeding a polysaccharide slurry to a filter centrifuge via a first inlet; b) rotating the filter centrifuge at a first centrifuge speed to provide a polysaccharide cake; c) feeding a sprayable ingredient to the filter centrifuge via a second inlet; and d) spraying the sprayable ingredient onto the polysaccharide cake while rotating the filter centrifuge at a second centrifuge speed of at least 10 rpm to produce a blend of the polysaccharide and the ingredient, wherein the sprayable ingredient is sprayed over the polysaccharide cake using a spray bar over a period of 1-60 min; wherein: the polysaccharide slurry that is fed to the filter centrifuge has a slurry solvent content of 40-90% by total weight of the slurry; the polysaccharide cake at the start of spraying the sprayable ingredient has a solvent content of above 45% and up to 60% by total weight of the polysaccharide cake; and the sprayable ingredient is selected from the group consisting of sodium carbonate, potassium carbonate, ammonium carbonate, sodium persulphate, potassium persulphate, ammonium persulphate, calcium carbonate, sodium sulphate, potassium sulphate, ammonium sulphate, sodium citrate, potassium citrate, ammonium citrate, lime, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, hydrogen chloride, sulphuric acid, sodium trimetaphosphate (STMP), phosphorylchloride (POCl.sub.3, sodium hypochlorite (NaCIO), hydrogen peroxide, adipic acid, acetic anhydride, p-octenyl succinic anhydride, 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHPT), propylene oxide, and epichlorohydrine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates an exemplary schematic of a centrifuge for employing the method of the invention.

(2) FIG. 2 illustrates a graph of the percent salt remaining in the cake as a function of time.

(3) FIG. 3 illustrates the viscosity profiles of starch slurries as described in Inventive Example 5.

(4) FIG. 4 illustrates the viscosity profiles of starch slurries as described in Inventive Example 6.

(5) FIG. 5 illustrates the viscosity profiles of starch slurries as described in Inventive Example 7.

(6) A schematic exemplary illustration of employing the method of the invention in a centrifuge is shown in FIG. 1. In this figure, basket centrifuge (1) is rotating by means of central shaft (2). Feed pipe (3) is used to feed suspension into centrifuge (1), thereby forming polysaccharide cake (4), which is kept in place on filter plate (5). Subsequently, ingredient is sprayed onto the polysaccharide cake via spraying bar (6).

(7) When starting spraying of the sprayable ingredient, the polysaccharide cake preferably has a slurry solvent content of 20-60% by total weight of the polysaccharide cake, such as 25-50%, or 30-45%. The inventors surprisingly found that good mixing of the polysaccharide with the ingredient is achieved when the polysaccharide cake has a relatively low slurry solvent content of 20-60% by total weight of the polysaccharide cake, such as 25-50%, or 30-45%.

(8) The second centrifuge speed may be the same as the first centrifuge speed, but preferably the second centrifuge speed is lower than the first centrifuge speed. The second centrifuge speed is preferably at least 10 rpm, more preferably at least 30 rpm, most preferably at least 50 rpm. The second centrifuge speed may, for instance, be 50-1000 rpm, 200-500 rpm, or 250-400 rpm.

(9) Spraying the sprayable ingredient may take 1-60 min, such as 2-50 min, 3-35 min, or 4-20 min, or 5-15 min. For example, a sprayable solution, dispersion and/or suspension of the ingredient in the ingredient-solvent having a concentration of ingredient of 0.1-50 g/l, such as 0.5-25 g/l, or 1-10 g/l, can be sprayed over the polysaccharide cake over a period of 20-60 min, such as 25-45 min.

(10) The total amount of sprayable ingredient sprayed over the polysaccharide cake depends on what needs to be achieved and/or the concentration of the ingredient. Most typical amounts are at least 0.01 l/Kg of polysaccharide cake, preferably at least 0.05 l/Kg of polysaccharide cake, more preferably at least 0.1 l/Kg of polysaccharide cake. Said amount can be as high as at most 10 l/Kg of polysaccharide cake, preferably at most 5 l/Kg of polysaccharide cake, more preferably at most 1 l/Kg of polysaccharide cake. Typical amounts may be 0.1-0.6 l per kg of polysaccharide cake, such as 0.1-0.5 l, or 0.15-0.4 l. Higher levels may results in losses of the ingredient. Depending on the ingredient used, spraying may, for example, be done at a rate of 10-1000 ml/min/kg polysaccharide, such as 100-500 ml/min/kg polysaccharide.

(11) Optionally, after having sprayed the sprayable ingredient over the polysaccharide cake in step d), the filter centrifuge may be rotated for an additional period in order to dry the blend of polysaccharide and ingredient. This may suitably be done at a centrifuge speed that is the same or higher than the second centrifuge speed. For example, the centrifuge speed for drying the blend may be 500-2500 rpm, preferably 800-2000 rpm, such as 1000-1600 rpm. This optional drying step may be performed for a period sufficient to achieve a moisture content in said cake of at most 30 wt %, more preferably at most 20 wt %, most preferably at most 15 wt %. Typical periods include those of 1-30 min, such as 2-20 min, 3-15 min, or 5-12 min. Further lowering of the solvent content of the blend may also, or in addition, be accomplished by blowing hot air through the blend.

(12) Depending on the type of polysaccharide and ingredient, the content of the ingredient in the resulting blend may vary. For example, in case of a starch cake having a moisture content of about 40%, the maximum amount of ingredient will be around 100-400 g/l/kg sprayed. Lower limits could lie around 10-500 ppm based on dry weight of the blend.

(13) The blend of polysaccharide and ingredient can then be collected from the filter centrifuge and optionally subjected to further treatment and/or processing.

(14) The inventors found that the method of the invention yields a blend wherein the ingredient is optimally distributed within the polysaccharide, as shown below in the examples.

(15) The inventors also found that the method of the invention can be utilized to carry out various polysaccharide modifications or chemical reactions involving polysaccharides. Examples of such reactions are well known for example from BeMiller et al. Starch; Chemistry and Technology ISBN: 978-0-12-746275-2, included herein by reference. In particular the method of the invention proved suitable to carry out polysaccharide cationization, polysaccharide cross-linking, polysaccharide acid-thinning and polysaccharide oxidation.

(16) The invention therefore relates to a process for a cationization of a polysaccharide, said polysaccharide being preferably a starch, comprising: (a) Providing a polysaccharide slurry, preferably having a dry solids concentration of between 10 and 50 wt %, more preferably between 20 and 45 wt %, most preferably between 30 and 40 wt %, said slurry preferably having a pH of between 9.0 and 12.0, more preferably between 10.0 and 11.8, most preferably between 11.0 and 11.6 and containing a basic catalyst, said catalyst being preferably chosen from NaOH or Ca(OH).sub.2; (b) providing an aqueous cationizing additive, said additive comprising a cationizing reagent, said reagent preferably comprising 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHPT) or 2,3-epoxypropyltrimethylammonium chloride (EPTC), the reagent being in an amount of preferably between 1.0 and 50 wt % relative to the dry starch weight, more preferably between 2.0 and 30 wt %, most preferably between 3.0 and 10 wt %, wherein when the reagent is CHPT, said additive comprises NaOH or Ca(OH).sub.2 in an amount of between 0.20 and 10 wt %, more preferably between 0.6 and 2.0 wt %; (c) feeding the polysaccharide slurry to a filter centrifuge via a first inlet; (d) rotating the filter centrifuge at a first centrifuge speed to provide a polysaccharide cake; (e) feeding the aqueous cationizing additive to the filter centrifuge via a second inlet; and (f) spraying said additive onto the polysaccharide cake while rotating the filter centrifuge at a second centrifuge speed, said additive being sprayed in an amount of preferably between 20 and 50 wt % relative to the mass of dry solids in the cake, more preferably between 25 and 40 wt %, most preferably between 30 and 35 wt %; (g) preferably drying and/or grinding the product obtained in step (f); (h) optionally curing before, during or after step (g), preferably at a temperature of between room temperature (about 20 C.) and 80 C., the product of step (f) or step (g).

(17) The invention also relates to an acid-thinning process of a polysaccharide, said polysaccharide being preferably a starch, comprising: (a) Providing a polysaccharide slurry, preferably having a dry solids content of at least 10 wt %; (b) Providing an aqueous acid-thinning additive, said additive comprising an acid; (c) feeding the polysaccharide slurry to a filter centrifuge via a first inlet; (d) rotating the filter centrifuge at a first centrifuge speed to provide a polysaccharide cake; (e) feeding the aqueous acid-thinning additive to the filter centrifuge via a second inlet in a sufficient amount to achieve a pH of the polysaccharide cake to at most 7, more preferably at most 5, most preferably between 1 and 4; and (f) spraying said additive onto the polysaccharide cake while rotating the filter centrifuge at a second centrifuge speed, said additive being sprayed in an amount of preferably between 20 and 50 wt % relative to the mass of dry solids in the cake, more preferably between 25 and 40 wt %, most preferably between 30 and 35 wt %; (g) preferably drying and/or grinding the product obtained in step (f); (h) optionally curing before, during or after step (g), preferably at a temperature of between room temperature (about 20 C.) and 80 C., the product of step (f) or step (g).

(18) The invention also relates to a cross-linking process of a polysaccharide, said polysaccharide being preferably a starch, comprising: (a) Providing a polysaccharide slurry, preferably having a dry solids content of at least 10 wt %, said slurry preferably having a pH of between 9.0 and 12.0, more preferably between 10.0 and 11.8, most preferably between 11.0 and 11.6; (b) Providing an aqueous cross-linking additive, said additive comprising a cross-linking reagent, said reagent preferably comprising sodium trimetaphosphate (STMP), the reagent being in an amount of preferably between 0.1 and 1000 ppm relative to the dry starch weight, more preferably between 1 and 500 ppm, most preferably between 10 and 350 ppm; (c) feeding the polysaccharide slurry to a filter centrifuge via a first inlet; (d) rotating the filter centrifuge at a first centrifuge speed to provide a polysaccharide cake; (e) feeding the aqueous cross-linking additive to the filter centrifuge via a second inlet; and (f) spraying said additive onto the polysaccharide cake while rotating the filter centrifuge at a second centrifuge speed, said additive being sprayed in an amount of preferably between 20 and 50 wt % relative to the mass of dry solids in the cake, more preferably between 25 and 40 wt %, most preferably between 30 and 35 wt %; (g) preferably drying and/or grinding the product obtained in step (f); (h) optionally curing before, during or after step (g), preferably at a temperature of between room temperature (about 20 C.) and 80 C., the product of step (f) or step (g).

(19) The invention also relates to an oxidation process of a polysaccharide, said polysaccharide being preferably a starch, comprising: (a) Providing a polysaccharide slurry, preferably having a dry solids content of at least 10 wt %; (b) Providing an aqueous oxidation additive, said additive comprising active chlorine in an amount of preferably between 0.1 and 10.0 wt % relative to the dry polysaccharide weight, more preferably between 0.1 and 5.0 wt % and most preferably between 0.1 and 2.5 wt %. (c) feeding the polysaccharide slurry to a filter centrifuge via a first inlet; (d) rotating the filter centrifuge at a first centrifuge speed to provide a polysaccharide cake; (e) feeding the aqueous oxidation additive to the filter centrifuge via a second inlet; and (f) spraying said additive onto the polysaccharide cake while rotating the filter centrifuge at a second centrifuge speed, said additive being sprayed in an amount of preferably between 20 and 50 wt % relative to the mass of dry solids in the cake, more preferably between 25 and 40 wt %, most preferably between 30 and 35 wt %; (g) preferably drying and/or grinding the product obtained in step (f); (h) optionally curing before, during or after step (g), preferably at a temperature of between room temperature (about 20 C.) and 80 C., the product of step (f) or step (g).

(20) The pH of slurries or polysaccharide cakes described above can be measured according to known methods in the art, e.g. a pH-meter or a pH paper. For a cake, forming a slurry from the cake (e.g. about 20 wt % dry solids) before the pH measurement helps with achieving more precise values.

(21) The invention has been described by reference to various embodiments, and methods. The skilled person understands that features of various embodiments and methods can be combined with each other.

(22) All references cited herein are hereby completely incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

(23) Hereinafter, the invention will be illustrated in more detail, according to specific examples. However, the invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these example embodiments are provided so that this description will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

EXAMPLES

Comparative Example 1Addition of Salt in Last Fraction of Slurry

(24) A starch slurry (38% dry solids) was prepared by mixing 11.5 kg of starch with 15.5 kg of water. Sodium chloride salt was mixed into the slurry in a conventional mixer in an amount of 10% based on total slurry weight (2 kg). The slurry was fed to a filter centrifuge, which was rotated at a centrifuge speed of 700 rpm, at a rate of 350 l/h. After all slurry was fed to the centrifuge, the centrifuge speed was increased to 1400 rpm and the filter cake was centrifuged for 10 min. The resulting blend had a moisture content of 35-42% based on total weight.

Comparative Example 2Addition of Salt in Last Fraction of Slurry

(25) A starch slurry (38% dry solids) was prepared by mixing 11.5 kg of starch with 15.5 kg of water. Sodium chloride salt was mixed into the slurry in a conventional mixer in an amount of 10% based on total slurry weight (1 kg). The slurry was fed to a filter centrifuge, which was rotated at a centrifuge speed of 700 rpm, at a rate of 350 l/h. After all slurry was fed to the centrifuge, the centrifuge speed was increased to 1400 rpm and the filter cake was centrifuged for 10 min. The resulting blend had a moisture content of 35-42% based on total weight.

Comparative Example 3Addition of Salt in Last Fraction of Slurry

(26) A starch slurry (38% dry solids) was prepared by mixing 11.5 kg of starch with 15.5 kg of water. Sodium chloride salt was mixed into the slurry in a conventional mixer in an amount of 10% based on total slurry weight (1 kg). The slurry was fed to a filter centrifuge, which was rotated at a centrifuge speed of 700 rpm, at a rate of 750 l/h. After all slurry was fed to the centrifuge, the centrifuge speed was increased to 1400 rpm and the filter cake was centrifuged for 10 min. The resulting blend had a moisture content of 35-42% based on total weight.

Inventive Example 1Spray Salt Solution on Partially Dewatered Cake

(27) A starch slurry (38% dry solids) was prepared by mixing 11.5 kg of starch with 15.5 kg of water. The starch slurry was fed to a filter centrifuge, which was rotated at a centrifuge speed of 700 rpm, at a rate of 350 l/h. After all slurry was fed to the centrifuge, the centrifuge speed was increased to 1400 rpm. Then, a salt solution (5 l of 5% sodium chloride) was sprayed over the filter cake over a period of about 30 min. Subsequently, the filter cake was centrifuged at 1400 rpm for another 5 min. The resulting blend had a moisture content of 35-42% based on total weight.

Inventive Example 2Spray Salt Solution on Dewatered Cake

(28) A starch slurry (38% dry solids) was prepared by mixing 11.5 kg of starch with 15.5 kg of water. The starch slurry was fed to a filter centrifuge, which was rotated at a centrifuge speed of 700 rpm, at a rate of 750 l/h. After all slurry was fed to the centrifuge, the centrifuge speed was increased to 1400 rpm. The filter cake was then dewatered by centrifuging at 1400 rpm for a period of 10 min. Then, a salt solution (5 l of 5% sodium chloride) was sprayed over the filter cake over a period of about 30 min. Subsequently, the filter cake was centrifuged at 1400 rpm for another 5 min. The resulting blend had a moisture content of 35-42% based on total weight.

Results

(29) An overview of the Examples and the mass balance for each example is shown in Tables 1 and 2 below.

(30) TABLE-US-00001 TABLE 1 Speed Salt Salt Salt slurry addition addition addition Salt feeding by by in slurry introduced (l/h) spraying spraying phase (g) CE1 350 10% of 2 kg 200 slurry CE2 350 10% of 1 kg 100 slurry CE3 750 10% of 1 kg 100 slurry IE1 350 51 of 5% 250 salt solution IE2 750 51 of 5% 250 salt solution

(31) TABLE-US-00002 TABLE 2 Mass balance Starch Water Salt Water for for solution Cake Cake left in Filtrate slurry slurry sprayed weight moisture cake weight (kg) (kg) (l) (kg) (%) (kg) (kg) CE1 11.5 15.5 15.85 6.3 10.7 CE2 11.5 15.5 15.8 5.2 11.8 CE3 11.5 15.5 15.6 42 6.7 10.3 IE1 11.5 15.5 5 16 37 6.2 15.8 IE2 11.5 15.5 5 15.3 40 6.7 15.3

(32) FIG. 2 shows the percentage of salt that is contained in the cake compared to what was introduced. In this figure Trial 15 option 1 corresponds to IE2, Trial 4 option 2 corresponds to IE1, Trial 16 option 3 corresponds to CE3, Trial 3 option 3 corresponds to CE2, and Trial 2 option 3 corresponds to CE1.

(33) Homogeneity of the salt dispersion throughout the starch filter cake was measured by conductivity of the cake. Conductivity was measured at three different positions along the y-axis of the centrifuge as well as at the inner and outer surface of the cake. The results are shown in Tables 3, 4 and 5.

(34) TABLE-US-00003 TABLE 3 Cake conductivity for CE3 Position in Cake Conductivity Conductivity Moisture centrifuge thickness of cake x = 0 of cake x = 4 cm cake (y-axis) (cm) (x-axis) (S/cm) (S/cm) (%) Top 4 1686 73 42 Middle 4 988 70 42 Bottom 4 2120 75 42

(35) TABLE-US-00004 TABLE 4 Cake conductivity for IE1 Position in Cake Conductivity Moisture centrifuge thickness of cake x = 0 cake (y-axis) (cm) (x-axis) (S/cm) (%) Top 4.5 3620 34 Bottom 3.5 6530 40

(36) TABLE-US-00005 TABLE 5 Cake conductivity for IE2 Position in Cake Conductivity Conductivity Moisture centrifuge thickness of cake x = 0 of cake x = 4 cm cake (y-axis) (cm) (x-axis) (S/cm) (S/cm) (%) Top 4 511 103 40 Middle 4 1302 1279 40 Bottom 4 1109 704 40

(37) These results show that the feeding flow of the slurry has an impact on the thickness and on the moisture of the filter cake. With a higher feeding flow (750 l/h) the cake has a better homogeneity in moisture and thickness.

(38) Additionally, the starch filter cake has a better salt distribution with the salt addition by spraying according to the invention. Salt is present throughout the filter cake.

Inventive Example 3Performing a Cationic Modification of a Native Wheat Starch

(39) A starch slurry at 38% of dry solids was prepared by mixing 1100 g of native wheat starch with 1400 g of water, 55 g of sodium chloride (5% wNaCl/wstarch) was added to it. The pH of the slurry was adjusted to 11.6 with a 4% sodium hydroxide solution, the mixing occurred at 21 C. and under high level of stirring to ensure quick dispersion and avoid gelatinization of the starch.

(40) The slurry was then fed to a filter centrifuge (model CEPA LS L3386), it was operating at 2100 rpm and dewatering took less than one minute. Immediately after the dewatering, 320 g of the spraying solution was prepared by mixing 68 g of a 60% 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHPT) solution with 85 g of a 10% sodium hydroxide solution and 167 g of water. CHPT is transformed in the presence of NaOH into GMAC (glycidyl trimethylammonium chloride). The resulting solution is sprayed in the filter centrifuge on the filter cake with a spray bar using a pump (480-500 mL/min) within 1 minute, the centrifuge is then turned off. Finally, a piece of the wet cake (37-43% moisture) was sliced vertically, crumbled, mixed and dried (14% moisture), it was then stored in a closed vessel and placed in an oven set at 45 C. for 18 hours.

(41) To determine the degree of substitution of cationic modified starch, the standard Kjeldahl method to study nitrogen content was performed, details of the technique and underlying methods are thoroughly explained in Sez-Plaza, Purificacin, et al. An overview of the Kjeldahl method of nitrogen determination. Part I. Early history, chemistry of the procedure, and titrimetric finish. Critical Reviews in Analytical Chemistry 43.4 (2013): 178-223 and in Sez-Plaza, Purificacin, et al. An overview of the Kjeldahl method of nitrogen determination. Part II. Sample preparation, working scale, instrumental finish, and quality control. Critical Reviews in Analytical Chemistry 43.4 (2013): 224-272.

(42) In order to calculate the cationic degree of substitution in starch and therefore the yield, it was necessary to slightly adapt the procedure: remove all the unreacted chemicals by washing 30 g of the dry starch for 30 minutes with 1.5 L of a 70:30 ethanol and water solution. The washed sample was prepared for analysis following the Kjeldahl procedure for starch, known in prior art and in the referenced article. The analysis showed, after correcting for nitrogen content for the base material, a cationic degree of substitution of 0.012 mol cationic unit/mol anhydroglucose unit (reaction efficiency: 62%).

(43) Moreover, literature reports comparable results in terms of efficiency for the same levels of substitution. BeMiller, J. N., & Whistler, R. L. (Eds.). (2009). Starch: chemistry and technology. Academic Press. Third Edition. Pages 632-635 mentions that wet processes, aiming at 0.02-0.05 degree of substitution, can achieve up to 70-85% reaction efficiencies for the same CHPT modification.

Inventive Example 5Performing an Acid-thinning of a Native Corn Starch

(44) A starch slurry at 41% of dry solids was prepared by mixing 1165 g of native corn starch with 1335 g of water. The 2.5 kg of slurry was kept under constant mixing to ensure an effective dispersion of the solids. Additionally, a 320 g of a diluted acid solution was prepared by mixing 91 g of a 3M solution of hydrochloric acid with 229 g of water.

(45) The starch slurry was fed to a filter centrifuge (model CEPA LS L3386) operating at 2100 rpm and dewatering took less than one minute. Immediately after the dewatering the diluted acid solution was sprayed in the filter centrifuge on the filter cake with a spray bar using a pump (480-500 mL/min) within 1 minute. Finally, pieces of the wet cake (37-43% moisture) were sliced vertically, crumbled, mixed, stored in a closed vessel, placed in an oven at different temperatures (50 C. and 65 C.) and left to react for 6 and 18 hours. Final product moisture was between 11%-14%.

(46) To assess the extent of thinning of the samples, the common approach is to measure the viscosity of the starch slurry, the viscometer Brabender Viscograph-E has been used for such analysis. Each sample was neutralized with sodium hydroxide until a pH of 6-7 and left to dry once again. Final product moisture was between 11%-14%. The dry products were slurrified (40 g of dry starch and 440 g of water), placed in the viscometer and viscosity profiles at different temperatures have been obtained. Table 6 and FIG. 3 display these results.

(47) TABLE-US-00006 TABLE 6 Reaction conditions for different thinned starch samples. HCl REACTION REACTION CONTENT TEMPERATURE TIME SAMPLE (g.sub.HCl/kg.sub.starch) ( C.) (hours) Unmodified native corn starch (CONTROL) Example 5A 4.5 50 6 Example 5B 4.5 65 6 Example 5C 4.5 50 18

Inventive Example 6Performing Cross-linking on a Native Corn Starch

(48) A starch slurry at 38% of dry solids was prepared by mixing 1100 g of native corn starch with 1400 g of water. 55 g of sodium chloride (5% wNaCl/wstarch) was also added to into the slurry. The pH of the slurry was adjusted to 11.5 with a 4% sodium hydroxide solution, the mixing occurred at 21 C. and under high level of stirring to ensure quick dispersion and avoid gelatinization of the starch. Additionally, 320 g of dilute spraying solutions were prepared by mixing different amounts (0.18 g-0.34 g) of sodium trimetaphosphate (STMP-cross linker) and topping up the rest of the weight with demineralized water.

(49) The starch slurry was fed to a filter centrifuge (model CEPA LS L3386) operating at 2100 rpm and dewatering took less than one minute. Immediately after the dewatering the dilute STMP solution was sprayed in the filter centrifuge on the filter cake with a spray bar using a pump (480-500 mL/min) within 1 minute. Finally, pieces of the wet cake (37-43% moisture) were sliced vertically, crumbled, mixed, stored in a closed vessel, placed in an oven at 45 C. and left to react for 4 hours. Post to modification, the semi dry cake was slurrified, neutralized with hydrochloric acid until pH 6-7 and left to dry overnight. Final product moisture was between 11%-14%.

(50) To assess the extent of crosslinking of the samples, the common approach is to measure the viscosity of the starch slurry, the viscometer Brabender Viscograph-E has been used for such analysis. The dry products were slurrified (40 g of dry starch and 440 g of water), placed in the viscometer and viscosity profiles at different temperatures have been obtained. Table 7 and FIG. 4 display these results.

(51) TABLE-US-00007 STMP REACTION REACTION CONTENT TEMPERATURE TIME SAMPLE (ppm) ( C.) (hours) Unmodified native corn starch (CONTROL) Example 6A 135 45 4 Example 6B 250 45 4

(52) As can be observed in FIG. 4, the processes of Examples 6A and 6B successfully managed to create a link between molecular chains, as demonstrated by the shift in the hold viscosity and overall shape of the curve.

Inventive Example 7Performing Oxidation on a Native Corn Starch

(53) A starch slurry at 41% of dry solids was prepared by mixing 1165 g of native corn starch with 1335 g of water. The 2.5 kg of slurry was kept under constant mixing to ensure an effective dispersion of the solids. Additionally, 320 g of spray solutions were prepared by mixing different amounts (30.8 g-61.6 g) of a sodium hypochlorite solution (163 g of active chlorine per kilogram of NaOCl solution) and topping up the leftover volume with demineralized water.

(54) The starch slurry was fed to a filter centrifuge (model CEPA LS L3386) operating at 2100 rpm and dewatering took less than one minute. Immediately after the dewatering the NaOCl solution was sprayed in the filter centrifuge on the filter cake with a spray bar using a pump (480-500 mL/min) within 1 minute. Finally, pieces of the wet cake (37-43% moisture) were sliced vertically, crumbled, mixed and left to react and dry overnight at room temperature. Final product moisture was between 11%-14%.

(55) To assess the extent of oxidation in the samples, the common approach is to measure the viscosity of the starch slurry, the viscometer Brabender Viscograph-E has been used for such analysis. The dry products were slurrified (40 g of dry starch and 440 g of water), placed in the viscometer and viscosity profiles at different temperatures have been obtained. FIG. 3 displays these results.

(56) Furthermore, the content of carboxyl groups has been measured using the procedure described by Kuakpetoon et al. [4]: 2 g of starch was mixed with 25 mL of 0.1N HCl solution and stirred for 30 minutes, the slurry was filtered through a paper filter and washed with 500 mL of demineralized water. The filtered wet cake was transferred to a beaker, 300 mL of demineralized water was added to it and the slurry was heated until complete gelatinization of the starch (95 C.). Afterwards, 150 mL of demineralized water was added to the slurry and the solution was titrated with 0.01N NaOH until pH 8.3, the whole procedure was repeated for a blank test with unmodified corn starch. The following equations were used to calculate the percentage of carboxyl groups:
m.sub.eq/100 g.sub.starch=([(V.sub.SampleV.sub.Blank)N.sub.NaOH100])/(Sample.Weight)
% COOH=m.sub.eq/100g.sub.starch0.045

(57) With V.sub.Sample and V.sub.Blank expressed in milliliters and sample weight in grams.

(58) By analyzing the data in FIG. 5, it is possible to see the shift of the pasting on-set from roughly 21 minutes for the native starch to roundabout 18 minutes in the most oxidized sample, also noticeable is the decrease in the slurry viscosity with increasing chlorine concentration. The carboxyl group content was measured for a separate sample containing 2% (20 g/kg) active chlorine, the analysis yielded 0.13% of COOH groups in the molecular starch matrix, a value very similar to the one reported by Kuakpetoon, Daris, and Ya-Jane Wang. Characterization of different starches oxidized by hypochlorite. Starch-Strke 53.5 (2001): 211-218. (0.14% for 2% active chlorine via wet modification).