Mixing apparatus and method of preparing edible dispersions

1. A mixing apparatus comprising two elements ( 1 , 5 ) which are rotatable relative to each other about a predetermined axis ( 10 ) , said two elements being an outer ( 5 ) and an inner element ( 1 ), whereby said outer element is circumferent about said inner element, and between which is defined a flow path extending between inlet ( 6 ) for material to be mixed and an outlet ( 7 ), wherein the flow path is defined between surfaces of the elements ( 9 , 11 , 13 , 14 ) each of which surfaces defines a senes of annular projections ( 8 ; 12 ) centered on the predetermined axis ( 10 ), the surfaces are positioned such that projections defined by one element ( 1 ) extend towards spaces between projections defined by the other element ( 5 ), cavities are formed in each surface to define flow passages bridging the projections ( 8 ; 12 ), cavities formed in one surface being offset in the axial direction relative to cavities in the other surface, and cavities in one surface overlapping in the axial direction with cavities in the other surface such that material moving between the surfaces from the inlet to the outlet is transferred between the overlapping cavities, wherein the cavities ( 16 , 17 , 18 , 19 , 20 , 21 ; 23 , 24 , 25 , 26 , 27 , 28 ) have curved bases, characterized in that the maximum outer diameter of the inner element ( 22 ), as measured in mm, is

greater than 108 plus A, wherein A is the average diameter of the surface area of said cavities times 1.47, and

greater than 8.5 plus B, wherein B is the average diameter of the surface area of said cavities times 3.85, and

smaller than 468, and

wherein the diameter, as measured in mm, of the surface area of a cavity, as measured in mm 2 , is defined as the diameter being derived from a circle with equal surface area as said cavity and, wherein at least one annular projection does not have cavities ( 15 ) and is an annular projection with an above average diameter compared to annular projections as defined by the same surface.

2. A mixing apparatus according to claim 1 , wherein said maximum outer diameter of the inner element ( 22 ), as measured in mm, is

greater than 120 plus A, wherein A is the average diameter of the surface area of said cavities times 2, and

greater than −24 plus B, wherein B is the average diameter of the surface area of said cavities times 4.5, and

smaller than 390,

and preferably,

greater than 20 plus A, wherein A is the average diameter of the surface area of said cavities times 4,5, and

from 200 to 340,

and most preferably,

greater than 20 plus A, wherein A is the average diameter of the surface area of said cavities times 4.5, and

from 250 to 300.

3. A mixing apparatus comprising two elements ( 30 , 34 ) which are rotatable relative to each other about a predetermined axis ( 39 ), said two elements being an outer and an inner element, whereby said outer element is circumferent about said inner element, and between which is defined a flow path extending between inlet ( 35 ) for material to be mixed and an outlet ( 36 ), wherein the flow path is defined between surfaces of the elements ( 38 , 40 , 42 , 43 ) each of which surfaces defines a series of annular projections ( 37 ; 41 ) centered on the predetermined axis ( 39 ), the surfaces are positioned such that projections defined by one element ( 37 ) extend towards spaces between projections defined by the other element ( 41 ), cavities are formed in each surface to define flow passages bridging the projections ( 37 ; 41 ), cavities formed in one surface being offset in the axial direction relative to cavities in the other surface, and cavities in one surface overlapping in the axial direction with cavities in the other surface such that material moving between the surfaces from the inlet to the outlet is transferred between the overlapping cavities, wherein the cavities ( 45 , 46 , 47 , 48 , 49 , 50 ; 52 , 53 , 54 , 55 , 56 , 57 , 58 ) have curved bases, characterized in that the maximum outer diameter of the inner element ( 51 ), as measured in mm, is

greater than 108 plus A, wherein A is the average diameter of the surface area of said cavities times 1.47 and,

greater than 8.5 plus B, wherein B is the average diameter of the surface area of said cavities times 3.85 and,

smaller than 468 plus C, wherein C is the average diameter of he surface area of said cavities times −2.92,

wherein the diameter, as measured in mm, of the surface area of a cavity, as measured in mm 2 , is defined as the diameter being derived from a circle with equal surface area as said cavity.

4. A mixing apparatus according to claim wherein said axium outer diameter of the inner element ( 51 ), as measured in mm

greater than 120 plus A, wherein A is the average diameter of the surface area of said cavities times 2 and,

greater than 10 plus B, wherein B is the average diameter of the surface area of said cavities times 5 and,

smaller than 468 plus C, wherein C is the average diameter ace area of said cavities times −3,

and preferably,

greater than 30 plus A, wherein A is the average diameter of he surface area of said cavities times 5, and

greater than 160, and

smaller than 400 plus C, wherein C is the average diameter of the surface area of said cavities times −3,

and most preferably,

greater than 30 plus A, wherein A is the average diameter of the surface area of said cavities times 5, and

greater than 160, and

smaller than 400 plus C, wherein C is the average diameter of the surface area of said cavities times −3.

5. A mixing apparatus according to claim 1 , wherein at least one annular projection does not have cavities ( 15 ) and is an annular projection with an above average diameter, preferably wherein said annular projection has the largest diameter compared to annular projections as defined by the same surface.

6. A mixing apparatus according to claim 1 , wherein at least 50%, preferably at least 75%, more preferably at east 90% and most preferably essentially all of said cavities 16 , 17 , 18 , 19 , 20 , 21 ; 23 , 24 , 25 , 26 , 27 , 28 ; 45 , 46 , 47 , 48 , 49 , 50 ; 52 , 53 , 54 , 55 , 56 , 57 , 58 ) are part spherical.

7. A mixing apparatus according to claim 1 , wherein the volume of said cavities ( 16 , 17 , 18 , 19 , 20 , 21 ; 23 , 24 , 25 , 26 , 27 , 28 ; 45 , 46 , 47 , 48 , 49 , 50 ; 52 , 53 , 54 , 55 , 56 , 57 , 58 ) is such that the volume of each cavity is from 0.02 to 10 times, more preferably from 0.05 to 3 times and most preferably from 0,2 to 0.5 times the volume of a sphere having an equal diameter.

8. A mixing apparatus according to claim 1 , wherein the number of annular projections ( 8 , 12 ; 37 , 41 ) as defined by the surface of inner element ( 1 , 30 ) and outer element ( 5 , 34 ) is from 4 to 20 and 4 to 20 respectively, preferably from 5 to 9 and from 5 to 9 respectively and most preferably from 5 to 7 and 5 to 7 respectively.

9. A mixing apparatus according to claim 1 , wherein the surfaces of the elements which define the projections are generally conical.

10. A mixing apparatus according to claim 1 , wherein each projection ( 8 , 12 ; 37 , 41 ) is defined between two side surfaces ( 9 , 11 , 13 , 14 ; 38 , 40 , 42 , 43 ) each of which is a surface of revolution swept out by a straight line rotated about the axis ( 10 ; 39 ).

11. A mixing apparatus according to claim 1 , wherein adjacent projections comprise cavities of different shapes.

12. A mixing apparatus according to claim 1 , wherein the projections ( 8 ; 37 ) defined by one element ( 5 : 34 ) extend into the space between the projections ( 12 ; 41 ) defined by the other element ( 1 ; 30 ).

13. A mixing apparatus according to claim 1 , wherein the average diameter of the cavities ( 16 , 17 , 18 , 19 , 20 , 21 ; 23 , 24 , 25 , 26 , 27 , 28 ; 45 , 46 , 47 , 48 , 49 , 50 ; 52 , 53 , 54 , 55 , 56 , 57 , 58 ) is from 2 to 119, more preferably from 10 to 80 mm, even more preferably from 15 to 65 mm and most preferably from 25 to 55 mm.

14. Method of manufacture of an edible dispersion, preferably a water-in-oil dispersion, comprising the step of mixing an aqueous phase and a fat phase, wherein said fat phase comprises fat powder, in a mixing apparatus, according to claim 1 .

15. Method of manufacture of an edible water-in-oil dispersion, according to claim 14 , wherein the mixing device is operated at a throughput from 0.1 to 25tons/hour and a rpm from 300 to 7500, preferably from 2 to 15 tons/hour and a rpm from 600 to 4500, and most preferably from 3 to 8 tons/hour and a rpm from 750 to 1500 rpm.