Method and equipment for the continuous production of a porous powdered product

Abstract

The present invention relates to a method for producing a powdered porous product from at least one starting powdery and/or viscous product, characterised in that it comprises the continuous following steps without exposing the product to open air: a) preparing the starting product in order to make it viscous; b) in a thermo-mechanical machine ( 10 ) for continuously realising transport and/or mixing functions of viscous products or dry-material rich products, lowering the viscosity of the viscous product without changing its dry-material content, by intimate mixing with a gas injected into the processing machine ( 10 ) and simultaneously initiating the porosity in the viscous product; c) continuously with the processing machine ( 10 ), statically or dynamically intensifying the intimate mixture of the viscous product with a gas in order to obtain an aerated and porous mass; and d), dividing said mass in order to obtain aerated and porous particles.

1 . Method for the production of a porous powdered product from at least one pulverulent and/or viscous starting product, wherein the following steps are carried out continuously and without exposing the product to the open air:
 a) the starting product is prepared in order to bring it into a viscous state of viscosity greater than 100 mPa·s and preferably greater than 200 mPa·s,   b) in a thermomechanical treatment machine ( 10 ) for continuously carrying out at least transport and/or mixing functions for viscous products or products rich in dry matter:
 the viscosity of the product in the viscous state is lowered without changing its content of dry matter by a first operation of intimate mixing with a gas injected into the thermomechanical treatment machine ( 10 ), and 
 porosity is simultaneously initiated in the product in the viscous state; 
   c) continuously with the thermomechanical treatment machine ( 10 ), the intimate mixing of the product in the viscous state is intensified in a static or dynamic manner by a second operation of mixing with a gas in order to obtain an aerated and porous mass, and   d) the mass is divided in order to obtain aerated and porous particles having a content of dry matter of from 50 to 90% and a particle size less than or equal to 3 mm.   
   
   
       2 . Method according to  claim 1 , wherein the product in the viscous state is prepared in the thermomechanical treatment machine ( 10 ) from at least one pulverulent product having a content of dry matter of from 70 to 98% and by carrying out at least one step of mixing with at least one ingredient and/or at least one shearing step and/or at least one heat treatment step before the viscosity of the product in the viscous state is lowered. 
   
   
       3 . Method according to  claim 1 , wherein the product in the viscous state is prepared in the thermomechanical treatment machine ( 10 ) from at least one pulverulent product having a content of dry matter of from 70 to 98% and by carrying out at least one step of mixing with at least one ingredient and subsequently a step of mixing with a product in the viscous state and/or at least one shearing step and/or at least one heat treatment step before the viscosity of the product in the viscous state is lowered. 
   
   
       4 . Method according to  claim 1 , wherein the product in the viscous state from the same family as the product to be obtained is prepared before it is introduced into the thermomechanical treatment machine ( 10 ), the product in the viscous state is introduced into said thermomechanical treatment machine ( 10 ) and, before the viscosity of the product in the viscous state is lowered, at least one step of mixing with at least one ingredient and/or at least one shearing step and/or at least one heat treatment step is carried out. 
   
   
       5 . Method according to  claim 1 , wherein the first and second operations of mixing the product in the viscous state and the gas are carried out starting from an injection of the gas. 
   
   
       6 . Method according to  claim 3 , wherein the product in the viscous state from the same family as the product to be obtained has a viscosity greater than 100 mPa·s and a content of dry matter of from 50 to 90%. 
   
   
       7 . Method according to  claim 1 , wherein drying of the aerated and porous particles is carried out. 
   
   
       8 . Method according to  claim 1 , wherein the resulting particles have a concentration of dry matter of the order of 96%, after additional drying. 
   
   
       9 . Method according to  claim 1 , wherein the gas mixed with the product in the viscous state in the thermomechanical treatment machine ( 10 ) is identical with or different from the gas mixed with the product in the viscous state downstream of said machine. 
   
   
       10 . Method according to  claim 9 , wherein the gas is, for example, carbon dioxide, air, steam, nitrogen or an oxide thereof. 
   
   
       11 . Method according to  claim 1 , wherein the percentage of gas in total injected into the thermomechanical treatment machine ( 10 ), expressed as percent by volume based on the dry mass of the product treated in said machine, is from 0.01 nl·kg −1 ·mn −1  to 10 nl·kg −1 ·mn −1 . 
   
   
       12 . Method according to  claim 1 , wherein at least 10% of the gas mixed with the product is injected into the thermomechanical treatment machine ( 10 ). 
   
   
       13 . Method according to  claim 1 , wherein the product in the viscous state is milk, powdered milk thereby being obtained. 
   
   
       14 . Method according to  claim 1 , wherein the product in the viscous state is a natural or (physically and/or chemically) modified starchy product based on cereal (wheat, oat, maize, barley, etc.) flours, potato flour, potato granules, potato flakes and/or tapioca flour, the product initially being in the form of a mixture of the solution, suspension or emulsion type in an aqueous medium, the method yielding the product in pulverulent form. 
   
   
       15 . Method according to  claim 1 , wherein the product in the viscous state is a natural or (physically and/or chemically) modified protein product selected from milk casein, wheat gluten, maize zein, soybean proteins, legume proteins, in particular pea proteins and/or proteins of oleaproteaginous crops, in particular sunflower or rape, the product initially being in the form of a mixture of the solution, suspension or emulsion type in an aqueous medium, the method yielding the product in pulverulent form. 
   
   
       16 . Method according to  claim 1 , wherein the product in the viscous state is a milk fractionation co-product/by-product obtained by fractionating milk by centrifugation, filtration, nanofiltration, ultrafiltration and/or reverse osmosis, or a co-product obtained by coagulation of milk. 
   
   
       17 . Equipment for the production of a porous powdered product from at least one pulverulent and/or viscous starting product, wherein it comprises, continuously and without exposing the product to the open air:
 means for preparing the starting product in order to bring it into a viscous state of viscosity greater than 100 mPa·s and preferably greater than 200 mPa·s,   a thermomechanical treatment machine ( 10 ) comprising at least one transport and/or mixing step for the viscous products or products rich in dry matter, and a step of aeration of the product in the viscous state by a first operation of intimate mixing with a gas in order to lower the viscosity of the product and simultaneously initiate porosity in said product without changing its content of dry matter,   a static or dynamic aeration device ( 20 ) connected directly to the thermomechanical treatment machine ( 10 ) in order to carry out a second operation of mixing the product with a gas, intensifying the reduction in viscosity of said product, and obtain an aerated and porous mass, and   a means of separating the mass into aerated and porous particles having a content of dry matter of from 50 to 90% and a particle size less than or equal to 3 mm.   
   
   
       18 . Equipment according to  claim 17 , wherein the means for preparing the product are incorporated into the thermomechanical treatment machine ( 10 ). 
   
   
       19 . Equipment according to  claim 17 , wherein the thermomechanical treatment machine is a machine having rotating screw(s). 
   
   
       20 . Equipment according to  claim 17 , wherein the thermomechanical treatment machine is an extrusion machine ( 10 ) having two co-rotating and co-penetrating screws. 
   
   
       21 . Equipment according to  claim 20 , wherein the screws of the extrusion machine ( 10 ) are driven in rotation at a speed of from 50 to 1200 rpm. 
   
   
       22 . Equipment according to  claim 17 , wherein in the aeration step of the extrusion machine ( 10 ), the ratio between the length of the screws and the diameter of said screws is from 3 to 12. 
   
   
       23 . Equipment according to  claim 17 , wherein the thermomechanical treatment machine ( 10 ) is a single-screw extrusion machine. 
   
   
       24 . Equipment according to  claim 17 , wherein it comprises, at the outlet from the aeration device ( 20 ), a drying device formed by at least one fluidized-bed dryer. 
   
   
       25 . Equipment according to  claim 17 , wherein it comprises, at the outlet from the aeration device ( 20 ), a drying device formed by at least one atomizing tower.