PROCESS FOR THE OXIDATION OF STARCH-BASED MATERIALS

Abstract

A process for the oxidation of powder materials containing starch, which comprises the successive steps of mixing a powder material comprising starch with an aqueous solution of hydrogen peroxide (H.sub.2O.sub.2) and adding to the mixture thus obtained an aqueous solution of ammonia and reacting it with said mixture; the process may also comprise a further step of drying the aforementioned mixture to obtain a powder material containing oxidized starch; the process may advantageously comprise the steps of:feeding a continuous flow of powder material containing starch into a first reactor (R) comprising a cylindrical tubular body (1) and a rotor, arranged in the cylindrical tubular body, comprising a shaft (8) provided with elements (9) projecting radially therefrom and rotated at a speed greater than or equal to 50 rpm,feeding into said reactor also a continuous flow of an aqueous solution of hydrogen peroxidereacting the powder material containing starch and the hydrogen peroxide;discharging from a discharge opening (7) of the first reactor a continuous flow of a wet powder and feeding this continuous flow into a second reactor (R) comprising a cylindrical tubular body (101) and a rotor, arranged in the cylindrical tubular body, comprising a shaft (108) provided with elements (109) projecting radially therefrom and rotated at a speed greater than or equal to 50 rpm;feeding into the second reactor (R) also a continuous flow of an aqueous solution of ammonia,discharging from a discharge opening (107) of the second reactor a continuous flow of a wet powder comprising oxidized starch;drying the wet powder to a moisture content less than or equal to 20% by weight, thereby obtaining a powder material containing oxidized starch.

Claims

1. A process for the oxidation of powder materials containing starch, which is carried out in the absence of any metal compounds and which comprises the successive steps of: a) providing a powder material comprising starch; b) mixing said material with an aqueous solution of hydrogen peroxide (H.sub.2O.sub.2); and c) adding to the mixture thus obtained an aqueous solution of ammonia, which is reacted with said mixture.

2. The process according to claim 1, further comprising drying said mixture of step c), to obtain a powder material containing oxidized starch.

3. The process according to claim 2, wherein said powder material containing starch is selected from the group comprising starch of different origin, in particular starch from corn, potato, wheat, tapioca, rice and legumes, meal from cereals, in particular wheat, rice, corn, barley, rye, oats, buckwheat, amaranth and quinoa, and meal from legumes, especially beans, peas, chickpeas, broad beans, lentils, lupins, grass peas and soybeans.

4. The process according to claims 2, wherein said aqueous solution of hydrogen peroxide has a w/v concentration comprised between 5% and 20%.

5. The process according to claim 4, wherein said aqueous ammonia solution has a w/v concentration comprised between 5% and 20%.

6. The process according to claim 2, wherein the weight ratio between said powder material containing starch and said aqueous solution of hydrogen peroxide is comprised between 3 and 20.

7. The process according to claim 6, wherein the weight ratio between said aqueous solution of hydrogen peroxide and said aqueous solution of ammonia is comprised between 1 and 10.

8. The process according to claim 2, wherein the moisture content of said powder material containing oxidized starch is brought, by means of said drying step, to a value of less than or equal to 20% by weight of the total weight of said powder material containing oxidized starch.

9. The process according to claim 2, comprising the steps of: a) providing a first reactor comprising a cylindrical tubular body with horizontal axis, having at least one opening for the introduction of reagents and at least one opening for discharging the final product, an optional heating or cooling jacket for bringing the temperature of said tubular body to a predetermined temperature, and a rotor, arranged in the cylindrical tubular body and comprising a shaft provided with elements projecting radially therefrom, and feeding a continuous flow of powder material containing starch into said first reactor, in which the rotor is rotated at a speed greater than or equal to 50 rpm, so as to disperse said continuous flow of said powder material containing starch into a flow of particles of said material, b) feeding into said reactor, together with said flow of powder material containing starch, a continuous flow of said aqueous solution of hydrogen peroxide, which is dispersed by said rotor into a flow of minute droplets, c) centrifuging said particles and said droplets against the inner wall of said first reactor, with formation of a highly turbulent, dynamic, thin, tubular, fluid layer in which the particles of powder material containing starch and said droplets of aqueous solution of hydrogen peroxide are kept mechanically in intimate contact by the radially projecting elements of said rotor, while advancing in substantial contact with said inner wall of the reactor towards the discharge opening; d) reacting the powder material containing starch and the hydrogen peroxide in said thin layer while it advances substantially in contact with said inner wall of the turbo-reactor towards the discharge opening; e) discharging from said discharge opening a continuous flow of a wet powder and feeding said continuous flow into a second reactor, comprising a cylindrical tubular body with horizontal axis, provided with at least one opening for the introduction of reagents and at least one opening for discharging the final product, an optional heating or cooling jacket for bringing the temperature of said tubular body to a predetermined temperature, and a rotor, arranged in the cylindrical tubular body and comprising a shaft having elements projecting radially therefrom, the rotor being rotated at a speed greater than or equal to 50 rpm; f) feeding into said second reactor, together with said flow of wet powder, a continuous flow of said aqueous solution of ammonia, which is dispersed by said rotor into a flow of minute droplets; g) centrifuging said continuous flows against the inner wall of said second reactor, through the action of said radially projecting elements of said rotor, causing them to move forwards in substantial contact with said inner wall of said second reactor towards the discharge opening; h) discharging from said discharge opening a continuous flow of a wet powder comprising oxidized starch; i) drying said wet powder to a moisture content which is less than or equal to 20% by weight, thereby obtaining said powder material containing oxidized starch.

10. A process for the oxidation of powder material containing starch, comprising the steps of: a) providing a reactor comprising a cylindrical tubular body with horizontal axis, provided with a first opening and a second opening for the introduction of reagents, arranged in the vicinity of one end of said cylindrical tubular body, a third opening for the introduction of reagents arranged in a position situated in between said first end of said cylindrical tubular body and the opposite end of said cylindrical tubular body, at least one opening for discharging the final product, an optional heating or cooling jacket for bringing the temperature of said tubular body to a predetermined temperature, and a rotor, arranged in the cylindrical tubular body and comprising a shaft provided with elements projecting radially therefrom, and feeding into said reactor a continuous flow of powder material containing starch through said first inlet opening, the rotor being rotated at a speed greater than or equal 50 rpm, so as to disperse said continuous flow of powder material containing starch into a flow of particles of said material, b) feeding into said reactor, through said second inlet opening, a continuous flow of an aqueous solution of hydrogen peroxide, which is dispersed by said rotor into a flow of minute droplets, c) centrifuging said particles and said droplets against the inner wall of said reactor, with formation of a highly turbulent, dynamic, thin, tubular, fluid layer in which the particles of powder material containing starch and said droplets of aqueous solution of hydrogen peroxide are kept mechanically in intimate contact by the radially projecting elements of said rotor, while advancing in substantial contact with said inner wall of the reactor toward the discharge opening; d) causing the powder material containing starch to interact with the hydrogen peroxide in said thin layer while it advances substantially in contact with said inner wall of the reactor towards the discharge opening; e) feeding into said reactor, through said third inlet opening, a continuous flow of an aqueous solution of ammonia, which is dispersed by said rotor into a flow of minute droplets; f) centrifuging said continuous flows against the inner wall of said reactor, through the action of said radially projecting elements of said rotor, causing them to move forwards in substantial contact with said inner wall of said reactor towards the discharge opening; g) discharging from said discharge opening a continuous flow of a wet powder comprising oxidized starch; h) drying said wet powder to a moisture content which is less than or equal to 20% by weight, thereby obtaining a powder material containing oxidized starch.

11. The process according to claim 10, wherein said respective drying steps i) and h) are carried out by means of a turbo-dryer, comprising a cylindrical tubular body with horizontal axis, provided with at least one inlet opening and at least one discharge opening, a heating jacket for bringing the temperature of said tubular body to a predetermined temperature, and a rotor arranged in the cylindrical tubular body and comprising a shaft having elements projecting radially therefrom, feeding said wet powder exiting from said reactor into said turbo-dryer through said at least one inlet opening, the inner wall of the turbo-dryer being kept at a temperature of at least 70 C. by means of said heating jacket and the rotor being rotated at a speed of at least 150 rpm; centrifuging and causing said wet powder to advance inside the turbo-dryer through the action of said rotor; and discharging from the outlet opening of the turbo-dryer a continuous flow of powder material containing oxidized starch having a moisture content less than or equal to 20% by weight.

12. The process according to claim 11, wherein, simultaneously with the feeding of said flow of wet powder into the turbo-dryer, a flow of a gas heated to a temperature of at least 50 C. is also fed into said turbo-dryer, through said at least one inlet opening.

13. The process according to claim 12, wherein the temperature of the inner wall of said turbo-dryer is kept at 70-180 C. and the temperature of the gas flow fed into the turbo-dryer is between 50 C. and 250 C.

14. The process according to claim 9, wherein said elements projecting radially from the shaft of said rotor are in the form of rods, blades, V-blades or beaters.

15. The process according to claim 9, wherein said aqueous solution of hydrogen peroxide has a w/v concentration comprised between 5% and 20% and said aqueous solution of ammonia has a w/v concentration comprised between 5% and 20%.

16. (canceled)

17. The process according to claim 9, wherein the ratio between the flowrate of said flow of aqueous solution of hydrogen peroxide and the flowrate of said flow of powder material containing starch is comprised between 1:20 and 1:5.

18. The process according to claim 17, wherein the ratio between the flowrate of said flow of aqueous solution of ammonia and the flowrate of said flow of powder material containing starch is comprised between 1:20 and 1:5.

19. The process according to claim 9, wherein the moisture content of said powder material containing oxidized starch is brought, by means of said drying step, to a value of between 5 and 15% by weight of the total weight of said powder material containing oxidized starch.

20-26. (canceled)

27. The process according to claim 10, wherein said respective drying steps i) and h) are carried out by means of a turbo-dryer, comprising a cylindrical tubular body with horizontal axis, provided with at least one inlet opening and at least one discharge opening, a heating jacket for bringing the temperature of said tubular body to a predetermined temperature, and a rotor arranged in the cylindrical tubular body and comprising a shaft having elements projecting radially therefrom, feeding said wet powder exiting from said reactor into said turbo-dryer through said at least one inlet opening, the inner wall of the turbo-dryer being kept at a temperature of at least 70 C. by means of said heating jacket and the rotor being rotated at a speed of at least 150 rpm; centrifuging and causing said wet powder to advance inside the turbo-dryer through the action of said rotor; and discharging from the outlet opening of the turbo-dryer a continuous flow of powder material containing oxidized starch having a moisture content less than or equal to 20% by weight.

28. The process according to claim 27, wherein, simultaneously with the feeding of said flow of wet powder into the turbo-dryer, a flow of a gas, preferably air, heated to a temperature of at least 50 C. is also fed into said turbo-dryer, through said at least one inlet opening.

29. The process according to claim 28, wherein the temperature of the inner wall of said turbo-dryer is kept at 70-180 C. and the temperature of the gas flow fed into the turbo-dryer is between 50 C. and 250 C.

30. The process according to claim 20, wherein said elements projecting radially from the shaft of said rotor are in the form of rods, blades, V-blades or beaters.

31. The process according to claim 27, wherein said aqueous solution of hydrogen peroxide has a w/v concentration comprised between 5% and 20% and said aqueous solution of ammonia has a w/v concentration comprised between 5% and 20%.

32. The process according to claim 27, wherein the ratio between the flowrate of said flow of aqueous solution of hydrogen peroxide and the flowrate of said flow of powder material containing starch is comprised between 1:20 and 1:5.

33. The process according to claim 32, wherein the ratio between the flowrate of said flow of aqueous solution of ammonia and the flowrate of said flow of powder material containing starch is comprised between 1:20 and 1:5.

34. The process according to claim 27, wherein the moisture content of said powder material containing oxidized starch is brought, by means of said drying step, to a value of between 5 and 15% by weight of the total weight of said powder material containing oxidized starch.

35. The process according to claim 8, wherein the moisture content of said powder material containing oxidized starch is brought, by means of said drying step, to a value between 5% and 15% by weight of the total weight of said powder material containing oxidized starch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0093] The advantages and characteristic features of this invention will emerge more clearly from the description below of an example of implementation of the starch cationization process, provided hereinbelow with reference to the apparatus schematically shown in FIGS. 1 and 2 of the attached drawings, provided purely by way of example.

DETAILED DESCRIPTION

[0094] With reference to FIG. 1, an apparatus used for the process according to the invention comprises a reactor R consisting essentially of a cylindrical tubular body 1, closed at the opposite ends by end plates 2, 3 and coaxially provided with a heating (or cooling) jacket 4 intended to be passed through by a fluid, for example diathermic oil, so as to keep the inner wall of the body 1 at a predefined temperature.

[0095] The tubular body 1 is provided with inlet openings 5, 6 for the powder material containing starch and the aqueous solution of hydrogen peroxide, respectively, as well as a discharge opening 7.

[0096] The tubular body 1 rotatably supports internally a rotor comprising a shaft 8 provided with elements 9 projecting radially therefrom, in the form of blades, these blades 9 being arranged helically and oriented so as to centrifuge and at the same time convey towards the discharge opening 7 the flows of powder material containing starch and aqueous solution of hydrogen peroxide and the wet powder formed following mixing of the powder material with the hydroperoxide solution and its reaction therewith.

[0097] A motor M is envisaged for operation of the bladed rotor at variable speeds ranging from 50 to 1500 rpm.

[0098] When it exits from the reactor, the aforementioned wet powder is fed via a pipe 11, communicating with the discharge opening 7 of the reactor, to the injector device 51.

[0099] The body of the injector device 51 has a tubular shape and is provided with an inlet opening 55 which receives the wet powder from the pipe 11, and an outlet opening 57.

[0100] The tubular body 51 rotatably supports internally a bladed or screw rotor 58, which imparts to the wet powder an advancing thrust towards the outlet opening 57, which transfers the wet powder to the inlet opening 105 of a second reactor R. This second reactor R, which has a structure entirely similar to that of the first reactor described above, is not described in detail. The components of the second reactor which are identical to those of the first reactor are indicated by the same reference numbers increased by 100. It is merely mentioned that the inlet opening 106 is for supplying a flow of aqueous ammonia solution.

[0101] The wet powder output from the discharge opening 107 is fed via a pipe 111, communicating with the discharge opening 107 of the second reactor R, to the injector device 151. The components of the injector device 151 which are identical to those of the injector device 51 are indicated by the same reference numbers increased by 100.

[0102] Via the outlet opening 157 of the injector device 151, the wet powder is discharged and fed into the turbo-dryer T through the inlet opening 205.

[0103] The turbo-dryer T consists essentially of a cylindrical tubular body 201, closed at the opposite ends by end plates 202, 203 and coaxially provided with a heating (or cooling) jacket 204 intended to be passed through by a fluid, for example diathermic oil, so as to keep the inner wall of the body 201 at a predefined temperature.

[0104] The tubular body 201 is provided with openings 205, 206 for the introduction of the wet powder discharged by the injector device 151 and hot air, and also with a discharge opening 7.

[0105] The tubular body 201 rotatably supports internally a rotor comprising a shaft 108 provided with elements 209 radially projecting therefrom in the form of blades, these blades 209 being arranged helically and oriented so as to centrifuge and at the same time convey towards the outlet 207 the flows of hot air and wet powder. The discharge opening 207 is used to discharge continuous flows of hot air and water vapour and a powder material containing oxidized starch, resulting from drying of the aforementioned wet powder following the heat exchange of the latter with the wall of the turbo-dryer heated by the heating jacket 204 and with the flow of hot air.

[0106] The flows of powder material containing oxidized starch and hot air and water vapour are finally conveyed to a container 18 for collecting and separating the vapour and the air also exiting from the turbo-dryer.

[0107] With reference to FIG. 2, an apparatus used for the process according to the invention, in an alternative embodiment thereof, comprises a first reactor R consisting essentially of a cylindrical tubular body 301, closed at the opposite ends by end plates 302, 303 and coaxially provided with a heating (or cooling) jacket 304 intended to be passed through by a fluid, for example diathermic oil, so as to keep the inner wall of the body 301 at a predefined temperature.

[0108] The tubular body 301 is provided with inlet openings 305, 306 for the powder material containing starch and the aqueous solution of hydrogen peroxide, respectively, arranged in the vicinity of the end plate 302, an inlet opening 310 for an aqueous solution of ammonia, arranged along the tubular body 301 in a position approximately equidistant from the end plates 302 and 303, and a discharge opening 307.

[0109] The tubular body 301 rotatably supports internally a rotor comprising a shaft 308 provided with elements 309 projecting radially therefrom, in the form of blades, these blades 309 being arranged helically and oriented so as to centrifuge and at the same time convey towards the discharge opening 307 the flows of powder material containing starch, aqueous solution of hydrogen peroxide and aqueous solution of ammonia as well as the wet powder formed following mixing and reaction of the powder material with the hydroperoxide solution and with the ammonia solution.

[0110] A motor M is envisaged for operation of the bladed rotor at variable speeds ranging from 50 to 1500 rpm.

[0111] When it exits from the reactor, the aforementioned wet powder is fed via a pipe 311, communicating with the discharge opening 307 of the reactor, to the injector device 351.

[0112] The body of the injector device 351 has a tubular shape and is provided with an inlet opening 355 which receives the wet powder from the pipe 311, and an outlet opening 357.

[0113] The apparatus further comprises a turbo-dryer T entirely similar to the turbo-dryer T described further above, and therefore not described in detail. The components of this turbo-dryer T which are identical to those of the turbo-dryer described further above are indicated by the same reference numbers increased by 200.

[0114] The apparatus comprises, finally, a container 18 for collecting the powder material containing oxidized starch and separating it from the vapour and the air which are also output from the turbo-dryer.

EXAMPLE 1

[0115] A flow of potato starch in powder form with a moisture content of 20% was continuously fed (100 kg/h), through the opening 6, into the reactor R, inside which the bladed rotor 8 was rotated at a speed of 700 rpm. At the same time a flow of aqueous solution of hydrogen peroxide in 36 volumes, corresponding to about 10.9% w/v was continuously fed (10 l/h) through the opening 5.

[0116] The temperature of the inner wall was kept at about 20 C.

[0117] Immediately at the inlet of the reactor R, the flow of starch was mechanically dispersed into particles which were immediately centrifuged against the inner wall of the reactor, where a dynamic, tubular, thin, fluid layer was formed. At the same time, the aqueous solution of hydrogen peroxide fed through the opening 5 was finely atomized by the blades of the rotor 8 which also performed the immediate centrifuging of the very fine droplets obtained. The latter were thus introduced into the dynamic, tubular, thin, fluid layer of starch particles, with which they were able to interact intimately.

[0118] After an average residence time of about 30 seconds inside the reactor, a powder with a moisture content of 28% was continuously discharged from the opening 7.

[0119] This wet powder was continuously fed into the reactor R, through the opening 105, by means of the injector 51, with a flowrate of 100 kg/h.

[0120] Inside the reactor R the wall temperature was kept at a value of about 20 C., while the rotational speed of the bladed rotor 108 was kept constantly at 800 rpm.

[0121] A continuous flow of an aqueous solution of ammonia (10% w/v) was fed through the opening 106 into the reactor R (flowrate 10 l/h).

[0122] After an average residence of 20 seconds inside the reactor, a wet powder with a moisture content of 35% was continuously discharged from said reactor though the opening 107.

[0123] This wet powder was continuously fed into the turbo-dryer T, through the opening 205, by means of the injector 151, with a flowrate of 100 kg/h, in parallel with a flow of air at a temperature of 100 C. (flowrate 500 m.sup.3/h), fed through the opening 206.

[0124] Inside the turbo-dryer T the wall temperature was kept at a value of 150 C., while the rotational speed of the bladed rotor 108 was kept constantly at 1000 rpm.

[0125] After an average residence time of 20 seconds inside the turbo-dryer T, oxidized potato starch in powder form with a moisture content of 10% was continuously discharged from said turbo-dryer.

[0126] The viscosity of a 10% aqueous solution of this oxidized starch powder was determined, obtaining a value of 10 cps where the viscosity of a 10% aqueous solution of the starting starch powder was equal to 1450 cps.

[0127] The oxidized starch powder was perfectly white and odourless and also devoid of any metal compound residues and therefore perfectly suitable for all the intended uses of oxidized starch, in particular alimentary and pharmaceutical use.

EXAMPLE 2

[0128] A flow of corn starch in powder form with a moisture content of 18% was continuously fed (80 kg/h), through the opening 306, into the reactor R, inside which the bladed rotor 308 was rotated at a speed of 800 rpm. At the same time a flow of aqueous solution of hydrogen peroxide in 30 volumes, corresponding to about 9.1% w/v, was continuously fed (10 l/h) through the opening 305 and a continuous flow of aqueous solution of ammonia, 9% w/v, was continuously fed (10 l/h) through the inlet opening 310. The temperature of the inner wall was kept at about 20 C.

[0129] After an average residence time of about 30 seconds inside the reactor, a powder with a moisture content of 33% was continuously discharged from the opening 307.

[0130] This wet powder was continuously fed into the turbo-dryer T, through the opening 405, by means of the injector 351, with a flowrate of 80 kg/h, in parallel with a flow of air at a temperature of 100 C. (flowrate 400 m.sup.3/h), fed through the opening 406.

[0131] Inside the turbo-dryer T the wall temperature was kept at a value of 150 C., while the rotational speed of the bladed rotor 108 was kept constantly at 1000 rpm.

[0132] After an average residence time of 20 seconds inside the turbo-dryer T, oxidized corn starch powder with a moisture content of 10% was continuously discharged from said turbo-dryer.

[0133] The viscosity of a 10% aqueous solution of this oxidized starch powder was determined, obtaining a value of 11 cps where the viscosity of a 10% aqueous solution of the starting starch powder was equal to 1410 cps.

[0134] The oxidized starch powder was perfectly white and odourless and also devoid of any metal compound residues and therefore perfectly suitable for all the intended uses of oxidized starch, in particular alimentary and pharmaceutical use.

EXAMPLE 3

[0135] A flow of type O wheat flour starch with a moisture content of 14% was continuously fed (100 kg/h), through the opening 6, into the reactor R, inside which the bladed rotor 8 was rotated at a speed of 900 rpm. At the same time a flow of aqueous solution of hydrogen peroxide in 36 volumes, corresponding to about 10.9% w/v, was continuously fed (10 l/h) through the opening 5. The temperature of the inner wall was kept at about 20 C.

[0136] After an average residence time of about 30 seconds inside the reactor, a wet flour with a moisture content of 27% was continuously discharged from the opening 7.

[0137] This wet flour was fed continuously into the reactor R, through the opening 105, by means of the injector 51, with a flowrate of 100 kg/h.

[0138] Inside the reactor R the wall temperature was kept at a temperature of about 20 C., while the rotational speed of the bladed rotor 108 was kept constantly at 800 rpm.

[0139] A continuous flow of an aqueous solution of ammonia (10% w/v) was fed through the opening 106 into the reactor R (flowrate 10 l/h).

[0140] After an average residence of 20 seconds inside the reactor, a wet flour with a moisture content of 34% was continuously discharged from said reactor though the opening 107.

[0141] This wet flour was continuously fed into the turbo-dryer T, through the opening 205, by means of the injector 151, with a flowrate of 100 kg/h, in parallel with a flow of air at a temperature of 100 C. (flowrate 500 m.sup.3/h), fed through the opening 206.

[0142] Inside the turbo-dryer T the wall temperature was kept at a value of 150 C., while the rotational speed of the bladed rotor 108 was kept constantly at 900 rpm.

[0143] After an average residence time of 20 seconds inside the turbo-dryer T, wheat flour containing oxidized starch, with a moisture content of 13%, was continuously discharged from said turbo-dryer.

[0144] The flour obtained was white and odourless and also devoid of any metal compound residues and therefore perfectly suitable for human consumption.

[0145] The gliadin contact of the flour thus obtained was determined by means of electrophoresis on a polyacrylamide gel (SDS-PAGE), resulting in the substantial absence of gliadin, this showing that the process according to the present invention caused a total degradation of the gliadin contained in the flour.

[0146] This flour was therefore particularly suitable for consumption by persons suffering from coeliac disease or gluten intolerance.