Method for producing high quality maltodextrin

Abstract

The disclosure herein relates to a method for producing high-quality maltodextrin, and belongs to the technical field of maltodextrin. On the basis of a traditional enzymatic production process of maltodextrin, starch branching enzyme derived from Rhodothermus obamensis is introduced, an α-1,4-glycosidic bond is cleaved, the cleaved short chain is ligated to a receptor chain to form an α-1,6-branch point, so the degree of branching is increased and the maltodextrin has more cluster structures. Thereby, the aims that the stability of the maltodextrin is enhanced and the maltodextrin is not easy to retrograde are achieved, and the freeze-thaw stability of the maltodextrin is also improved. The method specifically comprises the steps of slurry preparation, spray liquefaction, starch branching enzyme action, filtration, decolorization, ion exchange, concentration, spray drying, and the like. The method can produce high-quality maltodextrin with good solubility and high transparency, good viscosity stability and good freeze-thaw stability during storage.

Claims

1. A method for producing branched maltodextrin, the method comprises: preparing a slurry of a starch by heating the starch in the presence of α-amylase and stirring, liquifying the starch slurry by spray liquefaction to generate liquified starch, cooling the liquified starch to 50° C. or lower, adding Rhodothermus obamensis-derived starch branching enzyme to the liquified starch, wherein 200 to 500 Units enzyme is added per gram of the liquified starch by dry weight, incubating the branching enzyme with the liquified starch at pH 6.5 to 7.0, at a temperature of 65° C. to 70° C., for a period of 6 hours to 12 hours, filtering the branching enzyme-treated starch, decolorizing the filtered starch, carrying out ion-exchange on the decolored starch, and concentrating the ion-exchanged starch to obtain the branched maltodextrin.

2. The method of claim 1, wherein the step of adding Rhodothermus obamensis-derived starch branching enzyme to the liquified starch comprises: adding 500 Units starch branching enzyme per gram of the liquefied starch on a dry basis; adjusting the pH to 6.5, and incubating the starch branching enzyme with the liquified starch at 70° C. for 6 to 8 hours.

3. The method of claim 1, wherein the method further comprises a step of spray drying.

4. The method of claim 2, wherein the method further comprises a step of spray drying.

5. The method of claim 2, wherein the step of preparing a slurry of a starch by heating the starch in the presence of α-amylase and stirring, comprises: preparing starch milk from the starch, heating the starch milk, adding α-amylase and calcium chloride to the starch milk, and stirring the starch milk; wherein after the step of incubating the branching enzyme with the liquified starch, the starch branching enzyme is deactivated by heating; wherein the step of decolorizing comprises adding activated carbon; and wherein the step of carrying out ion-exchange, thereby, removes metal salt and pigment from the decolored starch.

6. The method of claim 5, wherein a dextrose equivalent (DE) value of the branched maltodextrin produced by the method is 2 to 20.

7. The method of claim 5, wherein the starch is selected from a group of consisting of: common maize starch, tapioca starch, potato starch, waxy maize starch, sweet potato starch, rice starch, and wheat starch; wherein the concentration of the starch milk is 5% to 45% by weight; wherein the starch milk is heated to 60° C. to 70° C.; wherein the α-amylase is added in an amount of 10 to 15 Units per gram of the starch milk on a dry basis, and pH is then adjusted to 5.5 to 6.5 after the α-amylase is added; and wherein calcium chloride is added in an amount of 0.1% to 0.2% on a dry basis.

8. The method of claim 5, wherein the step of liquifying the starch slurry comprises two rounds of spray liquefaction.

9. The method of claim 5, wherein the two rounds of spray liquefaction comprises a first round of spraying and a second round of spraying, wherein the first round of spraying is performed at a material pressure of 0.35 MPa, a steam pressure of 0.1 MPa, and a temperature of 102° C. to 110° C. for 5 minutes to 15 minutes; and wherein the second round of spraying is performed at a material pressure of 0.35 MPa, a steam pressure of 0.3 MPa, and a temperature of 130° C. to 140° C., for 5 minutes.

10. The method of claim 5, wherein the step of incubating the branching enzyme with the liquified starch is performed at 65° C. to 70° C. for 6 hours.

11. The method of claim 2, (a) wherein the step of preparing a slurry of a starch by heating the starch in the presence of α-amylase and stirring, comprises: preparing starch milk from the starch, heating the starch milk to 60° C. to 70° C., adding α-amylase to the starch milk in an amount of 10 to 15 Units per gram of the starch milk on a dry basis and calcium chloride in an amount of 0.1% to 0.2% on a dry basis, stirring, and adjusting the pH to 5.5 to 6.5, wherein the starch is selected from a group of consisting of: common maize starch, tapioca starch, potato starch, waxy maize starch, sweet potato starch, rice starch and wheat starch; wherein the concentration of the starch milk is 5% to 45% by weight; (b) wherein the step of liquifying the starch slurry by spray liquefaction to generate liquified starch is performed in two rounds of spray liquefaction, wherein the two rounds of spray liquefaction comprises a first round of spraying and a second round of spraying, wherein the first round of spraying is performed at a material pressure of 0.35 MPa, a steam pressure of 0.1 MPa, and a temperature of 102° C. to 110° C. for 5 minutes; and wherein the second round of spraying is performed at a material pressure of 0.35 MPa, a steam pressure of 0.3 MPa, and a temperature of 130° C. to 140° C. for 5 minutes.

12. A branched maltodextrin produced by the method of claim 2.

13. The method of claim 1, wherein transparency of the branched maltodextrin produced by the method is selected from one of 99.8%, 99.8% and 99.9% transmittance with DE values of 5, 10 and 15, respectively, when stored at 4° C. for 10 days, wherein the transparency is based on a 30% by weight aqueous solution of the branched maltodextrin.

14. The method of claim 13, wherein the transparency is one of 97.6% and 98.7% transmittance after 60 days of storage at 4° C. for branched maltodextrin having DE values of 10 and 15, respectively.

Description

DETAILED DESCRIPTION

Example 1: Effect of Additive Amount of Starch Branching Enzyme on Properties of Maltodextrin

(1) (1) Slurry preparation: Starch milk of 35% was prepared from starch, and was thermally insulated at 70° C. for 30 min, high temperature resistant α-amylase in an amount of 12 U/g starch on a dry basis and 0.2% calcium chloride were added, and the pH was adjusted to 6.5 after uniform stirring.

(2) (2) Spray liquefaction: Spraying was carried out with a low pressure steam spray liquefier, where first spraying was carried out at a material pressure of 0.35 MPa, a steam pressure of 0.1 MPa and a temperature of 105° C. for 8 min; then thermal insulation liquefying was carried out at 90° C. for 40 min; and second spraying enzyme deactivation was carried out at a material pressure of 0.35 MPa, a steam pressure of 0.3 MPa and a temperature of 140° C. for 5 min.

(3) (3) Starch branching enzyme action: After liquefied liquid in (2) was cooled to 50° C. or lower, starch branching enzyme derived from Rhodothermus obamensis was added in an amount of 100, 200, 300, 400 and 500 U/g on a dry basis respectively, the pH was adjusted to 7.0, a reaction was carried out at 65° C. for 6 h, and reaction liquid was obtained after enzyme deactivation by heating.

(4) (4) Filtration: After the reaction liquid was cooled, filtration was carried out by a plate-and-frame filter press to obtain a settled solution.

(5) (5) Decolorization: The pH of the solution was adjusted to 4.5, 1% activated carbon was added, and the solution was stirred for decolorization at 85° C. for 40 min.

(6) (6) Ion exchange: Metal salt and pigment were removed from the solution at 45° C. using strongly acidic cation-weakly basic anion-strongly acidic cation exchange resin.

(7) (7) Concentration: The solution was concentrated to a concentration of 50% at a vacuum degree of 85 KPa and a temperature of 45° C.

(8) (8) Spray drying: The concentrated liquid obtained in (7) was spray-dried into powder at an inlet air temperature of 170° C., an outlet air temperature of 85° C., and a feed flow rate of 18 mL/min, and the DE value of the powder was measured.

(9) The effect of the additive amount of the starch branching enzyme on the properties of maltodextrin is shown in Tables 1 and 2. After the starch branching enzyme derived from Rhodothermus obamensis was introduced, the solubility, transparency and viscosity stability of the maltodextrin were all significantly improved without changing the DE value of the maltodextrin, and high-quality maltodextrin was obtained. When the additive amount of the starch branching enzyme was increased to 200 U/g or more, the difference in the properties of maltodextrin was small and the production cost was increased. When the starch branching enzyme derived from G. thermoglucosidans was introduced, almost no effect was found.

(10) Control A represents the maltodextrin produced in case of lacking step (3).

(11) Control B represents the maltodextrin produced by the starch branching enzyme derived from G. thermoglucosidans substituted for the Rhodothermus obamensis-derived starch branching enzyme in step (3) in an amount of 200 U/g.

(12) Control C represents the maltodextrin prepared by the starch branching enzyme derived from G. thermoglucosidans substituted for the Rhodothermus obamensis-derived starch branching enzyme in step (3) by reaction under the optimum reaction conditions of G. thermoglucosidans. The optimum reaction conditions were specifically as follows: the amount of the starch branching enzyme added was 0.12 U/g, the reaction temperature was 45° C., the reaction time was 4 h, and the pH of the reaction was adjusted to 6.5.

(13) TABLE-US-00001 TABLE 1 Effect of additive amount of starch branching enzyme on properties of maltodextrin Additive amount DE (U/g) value Solubility.sup.1 Transparency.sup.2 Control A 10.1 3 min 25 s 0.2% 100 10.0 3 min 14 s 57.4% 200 9.9 2 min 23 s 97.6% 300 10.3 2 min 19 s 97.9% 400 10.2 2 min 14 s 98.0% 500 10.2 2 min 08 s 98.0% Control B-200 10.3 3 min 25 s 0.5% Control C 10.1 3 min 24 s 0.7% Note: .sup.1Solubility: 5 g of sample was weighed and dissolved in 50 mL of distilled water, and the time when maltodextrin was completely dissolved was taken as an indicator. .sup.2Transparency: The transparency of a 30% aqueous solution of maltodextrin prepared and stored in a refrigerated (4° C.) state for 60 d.

(14) TABLE-US-00002 TABLE 2 Effect of additive amount of starch branching enzyme on viscosity stability of maltodextrin Additive amount Viscosity.sup.1 (mPa .Math. s) (U/g) 0 d 2 d 4 d 6 d 8 d 10 d Control A 97 104 129 153 187 219 100 94 98 103 114 121 132 200 93 93 94 95 97 97 300 91 92 91 93 93 94 400 93 93 94 94 94 93 500 92 92 92 92 93 93 Control B-200 98 102 128 151 189 213 Control C 96 102 127 149 182 209 Note: .sup.1Viscosity: The viscosity of a 50% aqueous solution of maltodextrin prepared and placed for 0, 2, 4, 6, 8 and 10 d respectively.

(15) TABLE-US-00003 TABLE 3 Effect of additive amount of starch branching enzyme on freeze-thaw stability of maltodextrin Additive amount DE (U/g) value FTC1.sup.1 FTC3.sup.1 FTC5.sup.1 Control A 10.1 92.0% 43.7% 4.1% 100 10.0 94.6% 68.1% 37.3% 200 9.9 98.6% 97.7% 96.8% 300 10.3 98.8% 97.9% 96.9% 400 10.2 99.4% 98.7% 97.5% 500 10.2 99.4% 98.6% 97.6% Control B-200 10.3 92.3% 44.5% 4.8% Control C 10.1 92.6% 45.0% 5.2% Note: .sup.1FTC (freeze-thaw cycle): indicating the freeze-thaw stability of maltodextrin. FTC1, 3, and 5 respectively indicate the transparency of 30% maltodextrin after 1, 3, and 5 freeze-thaw cycles.

(16) Transparency was represented by transmittance measured at 620 nm using a spectrophotometer.

Example 2: Effect of Action Time of Starch Branching Enzyme on Properties of Maltodextrin

(17) (1) Slurry preparation: Starch milk of 35% was prepared from starch, and was thermally insulated at 70° C. for 30 min, high temperature resistant α-amylase in an amount of 12 U/g starch on a dry basis and 0.2% calcium chloride were added, and the pH was adjusted to 6.5 after uniform stirring.

(18) (2) Spray liquefaction: Spraying was carried out with a low pressure steam spray liquefier, where first spraying was carried out at a material pressure of 0.35 MPa, a steam pressure of 0.1 MPa and a temperature of 105° C. for 8 min; then thermal insulation liquefying was carried out at 90° C. for 40 min; and second spraying enzyme deactivation was carried out at a material pressure of 0.35 MPa, a steam pressure of 0.3 MPa and a temperature of 140° C. for 5 min.

(19) (3) Starch branching enzyme action: After liquefied liquid in (2) was cooled to 50° C. or lower, the starch branching enzyme derived from Rhodothermus obamensis was added in an amount of 200 U/g on a dry basis, the pH was adjusted to 7.0, a reaction was carried out at 65° C. for 2, 4, 6, 8, 10 and 12 h respectively, and reaction liquid was obtained after enzyme deactivation by heating.

(20) (4) Filtration: After the reaction liquid was cooled, filtration was carried out by a plate-and-frame filter press to obtain a settled solution.

(21) (5) Decolorization: The pH of the solution was adjusted to 4.5, 1% activated carbon was added, and the solution was stirred for decolorization at 85° C. for 40 min.

(22) (6) Ion exchange: Metal salt and pigment were removed from the solution at 45° C. using strongly acidic cation-weakly basic anion-strongly acidic cation exchange resin.

(23) (7) Concentration: The solution was concentrated to a concentration of 50% at a vacuum degree of 85 KPa and a temperature of 45° C.

(24) (8) Spray drying: The concentrated liquid obtained in (7) was spray-dried into powder at an inlet air temperature of 170° C., an outlet air temperature of 85° C., and a feed flow rate of 18 mL/min, and the DE value of the powder was measured.

(25) The effect of the action time of the starch branching enzyme on the properties of maltodextrin is shown in Tables 3 and 4. After the starch branching enzyme derived from Rhodothermus obamensis was introduced, the solubility, transparency and viscosity stability of the maltodextrin were all significantly improved without changing the DE value of the maltodextrin, and high-quality maltodextrin was obtained. When the action time of the starch branching enzyme was increased to 6 h or more, the difference in the properties of maltodextrin was small and the production cost was increased. When the starch branching enzyme derived from G. thermoglucosidans was introduced, almost no effect was found.

(26) Control A represents the maltodextrin produced in case of lacking step (3).

(27) Control B represents the maltodextrin produced by the starch branching enzyme derived from G. thermoglucosidans substituted for the Rhodothermus obamensis-derived starch branching enzyme in step (3), and the action time was 6 h.

(28) Control C represents the maltodextrin prepared by the starch branching enzyme derived from G. thermoglucosidans substituted for the Rhodothermus obamensis-derived starch branching enzyme in step (3) by reaction under the optimum reaction conditions of G. thermoglucosidans. The optimum reaction conditions were specifically as follows: the amount of the starch branching enzyme added was 0.12 U/g, the reaction temperature was 45° C., the reaction time was 4 h, and the pH of the reaction was adjusted to 6.5.

(29) TABLE-US-00004 TABLE 4 Effect of action time of starch branching enzyme on properties of maltodextrin Action time DE (h) value Solubility.sup.1 Transparency.sup.2 Control A 10.1 3 min 25 s 0.2% 2 9.9 3 min 09 s 37.1% 4 10.0 2 min 58 s 66.0% 6 9.9 2 min 23 s 97.6% 8 10.1 2 min 18 s 98.3% 10 10.3 2 min 15 s 98.0% 12 10.2 2 min 07 s 98.7% Control B-6 10.3 3 min 25 s 0.5% Control C 10.1 3 min 24 s 0.7% Note: .sup.1Solubility: 5 g of sample was weighed and dissolved in 50 mL of distilled water, and the time when maltodextrin was completely dissolved was taken as an indicator. .sup.2Transparency: The transparency of a 30% aqueous solution of maltodextrin prepared and stored in a refrigerated (4° C.) state for 60 d.

(30) TABLE-US-00005 TABLE 5 Effect of action temperature of starch branching enzyme on viscosity stability of maltodextrin Action time Viscosity.sup.1 (mPa .Math. s) (h) 0 d 2 d 4 d 6 d 8 d 10 d Control A 97 104 129 153 187 219  2 99 106 125 141 169 188  4 96 102 114 127 144 159  6 93 93 94 95 97 97  8 93 94 96 95 96 95 10 94 93 93 95 94 95 12 92 92 93 93 94 94 Control B-6 98 102 128 151 189 213 Control C 96 102 127 149 182 209 Note: .sup.1Viscosity: The viscosity of a 50% aqueous solution of maltodextrin prepared and placed for 0, 2, 4, 6, 8 and 10 d respectively.

(31) TABLE-US-00006 TABLE 6 Effect of action time of starch branching enzyme on freeze-thaw stability of maltodextrin Action time DE (h) value FTC1.sup.1 FTC3.sup.1 FTC5.sup.1 Control 10.1 92.0% 43.7% 4.1% 2 9.9 94.5% 56.7% 21.3% 4 10.0 94.6% 70.1% 39.9% 6 9.9 98.6% 97.7% 96.8% 8 10.1 99.0% 98.2% 97.7% 10 10.3 99.5% 98.9% 98.0% 12 10.2 99.3% 98.7% 97.9% Control B-6 10.3 92.3% 44.5% 4.8% Control C 10.1 92.6% 45.0% 5.2% Note: .sup.1FTC (freeze-thaw cycle): indicating the freeze-thaw stability of maltodextrin. FTC1, 3, and 5 respectively indicate the transparency of 30% maltodextrin after 1, 3, and 5 freeze-thaw cycles.

(32) Transparency was represented by transmittance measured at 620 nm using a spectrophotometer.

Example 3: Effect of Action Temperature of Starch Branching Enzyme on Properties of Maltodextrin

(33) (1) Slurry preparation: Starch milk of 35% was prepared from starch, and was thermally insulated at 70° C. for 30 min, high temperature resistant α-amylase in an amount of 12 U/g starch on a dry basis and 0.2% calcium chloride were added, and the pH was adjusted to 6.5 after uniform stirring.

(34) (2) Spray liquefaction: Spraying was carried out with a low pressure steam spray liquefier, where first spraying was carried out at a material pressure of 0.35 MPa, a steam pressure of 0.1 MPa and a temperature of 105° C. for 8 min; then thermal insulation liquefying was carried out at 90° C. for 40 min; and second spraying enzyme deactivation was carried out at a material pressure of 0.35 MPa, a steam pressure of 0.3 MPa and a temperature of 140° C. for 5 min.

(35) (3) Starch branching enzyme action: After liquefied liquid in (2) was cooled to 50° C. or lower, the starch branching enzyme derived from Rhodothermus obamensis was added in an amount of 200 U/g, the pH was adjusted to 7.0, a reaction was carried out at 50, 55, 60, 65 and 70° C. respectively for 6 h, and reaction liquid was obtained after enzyme deactivation by heating.

(36) (4) Filtration: After the reaction liquid was cooled, filtration was carried out by a plate-and-frame filter press to obtain a settled solution.

(37) (5) Decolorization: The pH of the solution was adjusted to 4.5, 1% activated carbon was added, and the solution was stirred for decolorization at 85° C. for 40 min.

(38) (6) Ion exchange: Metal salt and pigment were removed from the solution at 45° C. using strongly acidic cation-weakly basic anion-strongly acidic cation exchange resin.

(39) (7) Concentration: The solution was concentrated to a concentration of 50% at a vacuum degree of 85 KPa and a temperature of 45° C.

(40) (8) Spray drying: The concentrated liquid obtained in (7) was spray-dried into powder at an inlet air temperature of 170° C., an outlet air temperature of 85° C., and a feed flow rate of 18 mL/min, and the DE value of the powder was measured.

(41) The effect of the action temperature of the starch branching enzyme on the properties of maltodextrin is shown in Tables 5 and 6. After the starch branching enzyme derived from Rhodothermus obamensis was introduced, the solubility, transparency and viscosity stability of the maltodextrin were all significantly improved without changing the DE value of the maltodextrin, and high-quality maltodextrin was obtained. When the action temperature of the starch branching enzyme was 65° C., the maltodextrin has the best properties. When the starch branching enzyme derived from G. thermoglucosidans was introduced, almost no effect was found.

(42) Control A represents the maltodextrin produced in case of lacking step (3).

(43) Control B represents the maltodextrin produced by the starch branching enzyme derived from G. thermoglucosidans substituted for the Rhodothermus obamensis-derived starch branching enzyme in step (3), and the action temperature was 65° C.

(44) Control C represents the maltodextrin prepared by the starch branching enzyme derived from G. thermoglucosidans substituted for the Rhodothermus obamensis-derived starch branching enzyme in step (3) by reaction under the optimum reaction conditions of G. thermoglucosidans. The optimum reaction conditions were specifically as follows: the amount of the starch branching enzyme added was 0.12 U/g, the reaction temperature was 45° C., the reaction time was 4 h, and the pH of the reaction was adjusted to 6.5.

(45) TABLE-US-00007 TABLE 7 Effect of action temperature of starch branching enzyme on properties of maltodextrin Action temperature DE (° C.) value Solubility.sup.1 Transparency.sup.2 Control A 10.1 3 min 25 s 0.2% 50 10.2 3 min 22 s 1.7% 55 10.3 3 min 13 s 21.6% 60 10.2 2 min 58 s 85.9% 65 9.9 2 min 23 s 97.6% 70 10.0 2 min 47 s 94.3% Control B-65 10.3 3 min 25 s 0.5% Control C 10.1 3 min 24 s 0.7% Note: .sup.1Solubility: 5 g of sample was weighed and dissolved in 50 mL of distilled water, and the time when maltodextrin was completely dissolved was taken as an indicator. .sup.2Transparency: The transparency of a 30% aqueous solution of maltodextrin prepared and stored in a refrigerated (4° C.) state for 60 d.

(46) TABLE-US-00008 TABLE 8 Effect of action temperature of starch branching enzyme on viscosity stability of maltodextrin Action temperature Viscosity.sup.1 (mPa .Math. s) (° C.) 0 d 2 d 4 d 6 d 8 d 10 d Control A 97 104 129 153 187 219 50 98 103 130 149 181 203 55 99 100 123 136 169 182 60 97 99 104 117 131 148 65 93 93 94 95 97 97 70 94 98 104 112 117 124 Control B-65 98 102 128 151 189 213 Control C 96 102 127 149 182 209 Note: .sup.1Viscosity: The viscosity of a 50% aqueous solution of maltodextrin prepared and placed for 0, 2, 4, 6, 8 and 10 d respectively.

(47) TABLE-US-00009 TABLE 9 Effect of action temperature of starch branching enzyme on freeze-thaw stability of maltodextrin Action temperature DE (° C.) value FTC1.sup.1 FTC3.sup.1 FTC5.sup.1 Control 10.1 92.0% 43.7% 4.1% 50 10.2 92.1% 47.5% 10.2% 55 10.3 93.0% 55.0% 32.3% 60 10.2 95.8% 78.1% 59.2% 65 9.9 98.6% 97.7% 96.8% 70 10.0 97.1% 89.2% 79.9% Control B-65 10.3 92.3% 44.5% 4.8% Control C 10.1 92.6% 45.0% 5.2% Note: .sup.1FTC (freeze-thaw cycle): indicating the freeze-thaw stability of maltodextrin. FTC1, 3, and 5 respectively indicate the transparency of 30% maltodextrin after 1, 3, and 5 freeze-thaw cycles.

(48) Transparency was represented by transmittance measured at 620 nm using a spectrophotometer.

Example 4: Effect of Action pH of Starch Branching Enzyme on Properties of Maltodextrin

(49) (1) Slurry preparation: Starch milk of 35% was prepared from starch, and was thermally insulated at 70° C. for 30 min, high temperature resistant α-amylase in an amount of 12 U/g starch on a dry basis and 0.2% calcium chloride were added, and the pH was adjusted to 6.5 after uniform stirring.

(50) (2) Spray liquefaction: Spraying was carried out with a low pressure steam spray liquefier, where first spraying was carried out at a material pressure of 0.35 MPa, a steam pressure of 0.1 MPa and a temperature of 105° C. for 8 min; then thermal insulation liquefying was carried out at 90° C. for 40 min; and second spraying enzyme deactivation was carried out at a material pressure of 0.35 MPa, a steam pressure of 0.3 MPa and a temperature of 140° C. for 5 min.

(51) (3) Starch branching enzyme action: After liquefied liquid in (2) was cooled to 50° C. or lower, the starch branching enzyme derived from Rhodothermus obamensis was added in an amount of 200 U/g, the pH was adjusted to 6.0, 6.5, 7.0 and 7.5 respectively, a reaction was carried out at 65° C. for 6 h, and reaction liquid was obtained after enzyme deactivation by heating.

(52) (4) Filtration: After the reaction liquid was cooled, filtration was carried out by a plate-and-frame filter press to obtain a settled solution.

(53) (5) Decolorization: The pH of the solution was adjusted to 4.5, 1% activated carbon was added, and the solution was stirred for decolorization at 85° C. for 40 min.

(54) (6) Ion exchange: Metal salt and pigment were removed from the solution at 45° C. using strongly acidic cation-weakly basic anion-strongly acidic cation exchange resin.

(55) (7) Concentration: The solution was concentrated to a concentration of 50% at a vacuum degree of 85 KPa and a temperature of 45° C.

(56) (8) Spray drying: The concentrated liquid obtained in (7) was spray-dried into powder at an inlet air temperature of 170° C., an outlet air temperature of 85° C., and a feed flow rate of 18 mL/min, and the DE value of the powder was measured.

(57) The effect of the action pH of the starch branching enzyme on the properties of maltodextrin is shown in Tables 7 and 8. After the starch branching enzyme derived from Rhodothermus obamensis was introduced, the solubility, transparency and viscosity stability of the maltodextrin were all significantly improved without changing the DE value of the maltodextrin, and high-quality maltodextrin was obtained. When the action pH of the starch branching enzyme was 7.0, the maltodextrin has the best properties. When the starch branching enzyme derived from G. thermoglucosidans was introduced, almost no effect was found.

(58) Control A represents the maltodextrin produced in case of lacking step (3).

(59) Control B represents the maltodextrin produced by the starch branching enzyme derived from G. thermoglucosidans substituted for the Rhodothermus obamensis-derived starch branching enzyme in step (3), and the action pH was 7.0.

(60) Control C represents the maltodextrin prepared by the starch branching enzyme derived from G. thermoglucosidans substituted for the Rhodothermus obamensis-derived starch branching enzyme in step (3) by reaction under the optimum reaction conditions of G. thermoglucosidans. The optimum reaction conditions were specifically as follows: the amount of the starch branching enzyme added was 0.12 U/g, the reaction temperature was 45° C., the reaction time was 4 h, and the pH of the reaction was adjusted to 6.5.

(61) TABLE-US-00010 TABLE 10 Effect of action pH of starch branching enzyme on properties of maltodextrin DE Action pH value Solubility.sup.1 Transparency.sup.2 Control A 10.1 3 min 25 s 0.2% 6.0 10.2 3 min 11 s 28.5% 6.5 10.0 2 min 37 s 90.2% 7.0 9.9 2 min 23 s 97.6% 7.5 10.1 2 min 58 s 78.0% Control B-7.0 10.3 3 min 25 s 0.5% Control C 10.1 3 min 24 s 0.7% Note: .sup.1Solubility: 5 g of sample was weighed and dissolved in 50 mL of distilled water, and the time when maltodextrin was completely dissolved was taken as an indicator. .sup.2Transparency: The transparency of a 30% aqueous solution of maltodextrin prepared and stored in a refrigerated (4° C.) state for 60 d.

(62) TABLE-US-00011 TABLE 11 Effect of action pH of starch branching enzyme on viscosity stability of maltodextrin Viscosity.sup.1 (mPa .Math. s) Action pH 0 d 2 d 4 d 6 d 8 d 10 d Control A 97 104 129 153 187 219 6.0 98 103 121 142 160 185 6.5 94 103 105 114 121 133 7.0 93 93 94 95 97 97 7.5 96 105 113 127 140 156 Control B- 98 102 128 151 189 213 7.0 Control C 96 102 127 149 182 209 Note: .sup.1Viscosity: The viscosity of a 50% aqueous solution of maltodextrin prepared and placed for 0, 2, 4, 6, 8 and 10 d respectively.

(63) TABLE-US-00012 TABLE 12 Effect of action pH of starch branching enzyme on freeze-thaw stability of maltodextrin DE Action pH value FTC1.sup.1 FTC3.sup.1 FTC5.sup.1 Control 10.1 92.0% 43.7% 4.1% 6.0 10.2 92.9% 52.5% 29.3% 6.5 10.0 96.7% 87.4% 72.9% 7.0 9.9 98.6% 97.7% 96.8% 7.5 10.1 94.1% 78.4% 61.1% Control B-7.0 10.3 92.3% 44.5% 4.8% Control C 10.1 92.6% 45.0% 5.2% Note: .sup.1FTC (freeze-thaw cycle): indicating the freeze-thaw stability of maltodextrin. FTC1, 3, and 5 respectively indicate the transparency of 30% maltodextrin after 1, 3, and 5 freeze-thaw cycles.

(64) Transparency was represented by transmittance measured at 620 nm using a spectrophotometer.

Example 5: Effect of Starch Branching Enzyme on Properties of Maltodextrin with Different DE Values

(65) (1) Slurry preparation: Starch milk of 35% was prepared from starch, and was thermally insulated at 70° C. for 30 min, high temperature resistant α-amylase in an amount of 12 U/g starch on a dry basis and 0.2% calcium chloride were added, and the pH was adjusted to 6.5 after uniform stirring.

(66) (2) Spray liquefaction: Spraying was carried out with a low pressure steam spray liquefier, where first spraying was carried out at a material pressure of 0.35 MPa, a steam pressure of 0.1 MPa and a temperature of 105° C. for 8 min; then thermal insulation liquefying was carried out at 90° C. for 15, 40 and 60 min respectively; and second spraying enzyme deactivation was carried out at a material pressure of 0.35 MPa, a steam pressure of 0.3 MPa and a temperature of 140° C. for 5 min.

(67) (3) Starch branching enzyme action: After liquefied liquid in (2) was cooled to 50° C. or lower, the starch branching enzyme derived from Rhodothermus obamensis was added in an amount of 200 U/g, the pH was adjusted to 7.0, a reaction was carried out at 65° C. for 6 h, and reaction liquid was obtained after enzyme deactivation by heating.

(68) (4) Filtration: After the reaction liquid was cooled, filtration was carried out by a plate-and-frame filter press to obtain a settled solution.

(69) (5) Decolorization: The pH of the solution was adjusted to 4.5, 1% activated carbon was added, and the solution was stirred for decolorization at 85° C. for 40 min.

(70) (6) Ion exchange: Metal salt and pigment were removed from the solution at 45° C. using strongly acidic cation-weakly basic anion-strongly acidic cation exchange resin.

(71) (7) Concentration: The solution was concentrated to a concentration of 50% at a vacuum degree of 85 KPa and a temperature of 45° C.

(72) (8) Spray drying: The concentrated liquid obtained in (7) was spray-dried into powder at an inlet air temperature of 170° C., an outlet air temperature of 85° C., and a feed flow rate of 18 mL/min, and the DE value of the powder was measured.

(73) The effect of the starch branching enzyme on the properties of maltodextrin with different DE values is shown in Tables 9 and 10. For maltodextrin with any DE value, the introduction of the Rhodothermus obamensis-derived starch branching enzyme may significantly enhance the solubility, transparency and viscosity stability to obtain high-quality maltodextrin. When the starch branching enzyme derived from G. thermoglucosidans was introduced, almost no effect was found.

(74) Control A represents the maltodextrin produced in case of lacking step (3).

(75) Control B represents the maltodextrin produced by the starch branching enzyme derived from G. thermoglucosidans substituted for the Rhodothermus obamensis-derived starch branching enzyme in step (3).

(76) Control C represents the maltodextrin prepared by the starch branching enzyme derived from G. thermoglucosidans substituted for the Rhodothermus obamensis-derived starch branching enzyme in step (3) by reaction under optimum reaction conditions of G. thermoglucosidans. The optimum reaction conditions were specifically as follows: the amount of the starch branching enzyme added was 0.12 U/g, the reaction temperature was 45° C., the reaction time was 4 h, and the pH of the reaction was adjusted to 6.5.

(77) Controls 1, 2 and 3 respectively represent maltodextrin with DE values of 5, 10 and 15 produced in step (2) for the thermal insulation liquefying time of 15, 40 and 60 min.

(78) TABLE-US-00013 TABLE 13 Effect of starch branching enzyme on properties of maltodextrin with different DE values Thermal insulation liquefying DE time (min) value Solubility.sup.1 Transparency.sup.2 Control A1 5.2 8 min 47 s 0.1% 15 5.0 5 min 25 s 53.7% Control B1 5.1 8 min 44 s 0.3% Control C1 5.2 8 min 42 s 0.4% Control A2 10.1 3 min 25 s 0.2% 40 9.9 2 min 23 s 97.6% Control B2 10.3 3 min 25 s 0.5% Control C2 10.1 3 min 24 s 0.7% Control A3 15.0 2 min 37 s 24.5% 60 15.2 1 min 28 s 98.7% Control B3 15.1 2 min 35 s 24.9% Control C3 14.9 2 min 33 s 25.3% Note: .sup.1Solubility: 5 g of sample was weighed and dissolved in 50 mL of distilled water, and the time when maltodextrin was completely dissolved was taken as an indicator. .sup.2Transparency: The transparency of a 30% aqueous solution of maltodextrin prepared and stored in a refrigerated (4° C.) state for 60 d.

(79) TABLE-US-00014 TABLE 14 Effect of starch branching enzyme on viscosity stability of maltodextrin with different DE values Thermal insulation liquefying time Viscosity.sup.1 (mPa .Math. s) (min) 0 d 2 d 4 d 6 d 8 d 10 d Control A1 148 179 222 251 307 379 15 142 151 165 189 197 203 Control B1 149 177 219 250 305 376 Control C1 147 176 218 248 303 375 Control 2 97 104 129 153 187 219 40 93 93 94 95 97 97 Control B2 98 102 128 151 189 213 Control C2 96 102 127 149 182 209 Control 3 79 93 118 139 155 179 60 78 79 80 79 79 80 Control B3 80 92 117 139 156 178 Control C3 79 91 115 137 154 176 Note: .sup.1Viscosity: The viscosity of a 50% aqueous solution of maltodextrin prepared and placed for 0, 2, 4, 6, 8 and 10 d respectively.

(80) TABLE-US-00015 TABLE 15 Effect of starch branching enzyme on freeze-thaw stability of maltodextrin with different DE values Thermal insulation liquefying DE time (min) value FTC1.sup.1 FTC3.sup.1 FTC5.sup.1 Control A1 5.2 78.2% 10.3% 1.7% 15 5.0 91.2% 69.6% 38.2% Control B1 5.1 78.9% 10.8% 1.9% Control C1 5.2 79.2% 11.0% 2.2% Control A2 10.1 92.0% 43.7% 4.1% 40 9.9 98.6% 97.7% 96.8% Control B2 10.3 92.3% 44.5% 4.8% Control C2 10.1 92.6% 45.0% 5.2% Control A3 15.0 93.8% 77.2% 52.1% 60 15.2 99.5% 98.3% 97.7% Control B3 15.1 94.0% 77.5% 52.8% Control C3 14.9 93.9% 78.2% 53.1% Note: .sup.1FTC (freeze-thaw cycle): indicating the freeze-thaw stability of maltodextrin. FTC1, 3 and 5 respectively indicate the transparency of 30% maltodextrin after 1, 3, and 5 freeze-thaw cycles.

(81) Transparency was represented by transmittance measured at 620 nm using a spectrophotometer.