IT201600117537A1 - Process for the production of whole grain flours - Google Patents

Description

DESCRIPTION

Field of application

The present invention relates to the food industry sector. More specifically, the invention relates to a process for the production of wholemeal flours obtained from cereals.

Known art

Cereals (e.g. wheat, rice, corn, barley, sorghum, etc.) are consumed worldwide as the basis of the diet as they are a primary source of carbohydrates due to the high starch content present in the endosperm, which is found in the central part of the caryopsis.

Taking wheat as an example, in the caryopsis there are, starting from the outside, the following layers, which make up the bran: pericarp, head, nucellar layer (or hyaline layer) and aleurone, while the inner part consists of endosperm and germ.

Flour is the main product of the soft wheat milling process and consists of the innermost starchy parts of the caryopsis (endosperm) after separation from the most external ones (the bran, which represents about 15% of the total content of the caryopsis, and the germ, which constitutes about 3%) traditionally intended for animal feed.

Flours are conventionally produced by breaking (grinding) the kernels as such, followed by sieving of the generated fragments, which may contain only endosperm or parts of endosperm accompanied by bran and germ. The aforementioned fragments are then sent to successive stages of grinding and separation aimed at freeing and separating as much as possible the endosperm fractions from the other components of the caryopsis.

Traditionally “white” flours have been used, ie refined flours for almost total removal of the bran, because these refined flours can be stored for a long time at room temperature.

In recent decades, however, there has been a re-evaluation of the nutritional value of "whole" cereal flours, that is, containing the greatest possible quantity of the original components of the caryopsis, and therefore also the bran.

In fact, the bran contains various substances, such as dietary fibers (insoluble and soluble), minerals, vitamins, lipids and other components with protective action (antioxidant) in cellular metabolism and in phenomena related to aging and there is unanimous recognition about the benefits achieved with the daily consumption of whole grain products.

The above with reference to wheat also applies to other cereals.

However, wholemeal flours obtained by simply grinding the kernels as they are, omitting the bran and germ separation phases, have the drawback of poor shelf life.

We then resorted to the use of processes for the production of cereal flours, which include a preliminary removal of the outer layers of the kernels by means of friction and abrasion operations, before the grinding of the kernels is carried out. Examples of such processes are reported in patent applications EP 0 295 774, EP 0 373 274 and WO 2004/028694.

The wholemeal flours available on the market are obtained by adding the bran obtained with the aforementioned abrasion and decortication processes to a "white" flour, obtained essentially from the endosperm alone, after it has been subjected to re-milling treatments, to reduce the size particles, and thermal stabilization, to prevent oxidative phenomena caused by enzymatic degradation.

The bran obtained in this way is in fact subject to degradation, even after a short time, due to the occurrence of oxidation reactions (rancidity) on the lipid components present in the bran, which may also contain parts of germ, very rich in lipids. Rancidity is generally caused by the activation of enzymes (lipase and lipoxygenase) located in the bran that attack the lipid portion present.

Consequently, attempts are made to prevent this phenomenon by deactivating these enzymes with heat. However, the heat treatment of the bran, in addition to entailing additional costs, can cause a darkening of the bran, the development of unpleasant flavors and a chemical degradation of the lipid portion.

Wholemeal flours obtained by adding to "white" bran flours obtained by abrasion and decortication operations and subjected to stabilization heat treatments, in addition to not being true "wholemeal" flours, often have satisfactory organoleptic characteristics, resulting from these treatments thermal.

The problem underlying the present invention was to make available a flour that can be correctly defined as "integral", as it is obtained by grinding the entire kernel, which can be stored for a long time at room temperature without being subject to rancidity or degradation and that it has good organoleptic characteristics.

Summary of the invention

This problem has been solved, according to the invention, by providing a process for the production of a wholemeal flour of cereals, which includes the steps of:

a) grind cereal kernels until they are reduced to particles with a diameter of no less than 2 mm;

b) provide a reactor for wet heat treatment comprising a cylindrical tubular body with a horizontal axis, equipped with at least one inlet opening for the introduction of the ground kernels referred to in step a) and of water or an aqueous solution and of at least one discharge opening, a heating jacket to bring the temperature of said tubular body to a temperature of at least 80 ° C, and a rotor, arranged in the cylindrical tubular body and comprising a shaft provided with elements radially projecting therefrom ;

c) feeding a continuous flow of said ground kernels into said reactor, in which the rotor is rotated at a speed greater than or equal to 150 rpm;

d) feeding into said reactor, together with said flow of ground kernels, a continuous flow of water or aqueous solution, which is dispersed in minute drops;

e) centrifuging said flows against the internal wall of the reactor, with the formation of a thin, dynamic, highly turbulent tubular fluid layer, in which the ground kernels particles and the drops of water or aqueous solution are mechanically kept in intimate contact by the elements radially projecting of said rotor, while advancing in substantial contact with said inner wall of the reactor towards the discharge opening;

f) discharge from the discharge opening a continuous flow of wet ground kernels particles (moisture content 20-30%);

g) providing a reactor for thermal treatment and dehydration, comprising a cylindrical tubular body with a horizontal axis, equipped with at least one inlet opening and at least one discharge opening, a heating jacket to bring the temperature of said tubular body at a predetermined temperature, and a rotor disposed in the cylindrical tubular body and comprising a shaft provided with elements radially projecting therefrom;

h) feeding said wet ground kernels into said reactor through the at least one inlet opening, the inner wall of the reactor being maintained at a temperature of at least 100 ° C by said heating jacket and the rotor being rotated at a speed at least 150 rpm;

i) centrifuging and advancing said wet ground kernels within the reactor by the action of said rotor;

1) discharging from the reactor outlet a continuous flow of ground kernels having a moisture content between 2% and 15%;

m) subjecting said ground kernels to a further grinding step, to reduce the size of the particles to a value less than or equal to 0.5 mm, obtaining said integral flour.

Preferably, in step d) a continuous flow of water vapor is fed through the aforementioned at least one inlet opening into the reactor for wet heat treatment.

Preferably, in concomitance with the feeding of the aforementioned flow of wet ground kernels particles into the reactor for thermal treatment and dehydration referred to in step g), a flow of a gas, preferably air, heated to a temperature of at least 100 ° C.

The aforementioned aqueous solution may contain one or more water-soluble ingredients, selected from the group comprising salts, in particular sodium chloride, flavoring, water-soluble vitamins, in particular ascorbic acid, and natural antioxidants.

The temperature of the inner wall of the wet heat treatment reactor is preferably maintained at 100-160 ° C, conveniently at 100-120 ° C.

The rotational speed of the rotor of the wet heat treatment reactor is preferably set at 500-3000 rpm.

The residence time of the ground kernels inside the reactor for wet heat treatment is preferably between 20 and 60 seconds.

The temperature of the inner wall of the reactor for thermal treatment and dehydration is preferably maintained at 120-280 ° C, conveniently at 150-190 ° C.

The rotational speed of the rotor of the reactor for thermal treatment and dehydration is preferably set at 300-1200 rpm.

The temperature of the gas flow fed into the reactor for thermal treatment and dehydration is preferably between 120 ° C and 250 ° C, conveniently between 140 ° C and 190 ° C.

The residence time of the ground kernels inside the reactor for thermal treatment and dehydration is preferably between 30 and 70 seconds.

The water or aqueous solution fed into the reactor for wet heat treatment preferably has a temperature of 80-110 ° C, conveniently 90 ° -100 ° C.

The ratio between the flow rate of the water or aqueous solution fed into the wet heat treatment reactor and the flow rate of wet ground kernel particles fed into the wet heat treatment reactor is preferably between 1: 10 and 1: 2, conveniently between 1: 4 and 1: 2.5.

The aforementioned elements protruding radially from the rotor shaft can be for example rod-shaped or in the form of blades or plowshares or reels.

The process according to the invention can also comprise, before the aforementioned step b), a step of immersing the aforementioned ground cereal kernels into particles with a diameter of not less than 2 mm in water at 80 ° -100 ° C for a time ranging from 15 and 60 minutes.

By "flour" we mean a finely divided product obtained from the grinding of cereal seeds, which can be in the form of flour, semolina or fine granulate.

The term "cereals" refers to plants belonging to different families, in particular Graminaceae (wheat, rice, barley, rye, oats, corn, sorghum and teff), Polygonaceae (buckwheat), Amaranthaceae (amaranth) and Chenopodiaceae (quinoa) .

The present invention also relates to a wholemeal flour of cereals obtained by means of the process described above, as well as to a bakery product obtained starting from such wholemeal flour.

The wholemeal flours obtained with the process according to the present invention are particularly suitable for obtaining baked products, which, compared to baked products obtained with refined flours, have the great advantage of containing the components of high nutritional value present in the bran ( fiber, minerals, vitamins), while presenting organoleptic and structural characteristics (color, flavor, "texture") that are completely similar to those of corresponding products obtained from flours completely deprived of the bran. Furthermore, these organoleptic-structural characteristics remain substantially unchanged for the entire shelf-life of the finished product.

This is probably due to the fact that the treatment undergone by the particles of kernels ground in the reactor allows to deactivate the enzymes (lipase and lipoxygenase) localized in the bran, preventing them from attacking the lipid portion present in the bran and causing oxidation reactions, which lead to to rancidity. Furthermore, the relatively short residence time of the ground kernels inside the reactor for wet heat treatment allows to avoid the drawbacks encountered for the heat treatments of the known art, to which the bran is subjected which is added to the white flour to "recreate" a flour " whole wheat". In fact, during these heat treatments there is a darkening of the bran, the development of abnormal flavors (burnt and bitter) and the triggering of chemical degradation (due to heat) in the lipid part.

Brief description of the drawings

Further features and advantages of the present invention will become clearer from the following detailed description made with reference to the single attached figure (Fig. 1), which schematically shows an embodiment of a plant for carrying out the process according to the present invention.

Detailed description of the invention

With reference to the aforementioned figure, an apparatus used for the process according to the present invention comprises a reactor for wet heat treatment essentially consisting of a cylindrical tubular body 1, closed at the opposite ends by bottoms 2, 3, and coaxially provided with a jacket for heating / cooling intended to be traversed by a fluid, for example diathermic oil, to maintain the internal wall of the body 1 at a predetermined temperature.

The tubular body 1 is equipped with inlet openings 5, 6 and 10 respectively 5 for the water or aqueous solution, 6 for the kernels of ground cereals and 10 for the steam, as well as a discharge opening 7.

A rotor 8 is rotatably supported in the tubular body 1 comprising a shaft 8 provided with elements radially projecting therefrom in the form of vanes 9, which are arranged helically and oriented to centrifuge and at the same time convey towards the outlet the flows of ground kernels and water or aqueous solution.

An M motor is designed to drive the rotor at variable speeds from 150 to 3000 rpm.

As they leave the reactor, the wet ground kernels are fed through a conduit 11, in communication with the discharge opening 7 of the wet heat treatment reactor, to the injector device 51.

The body of the injector device 51 is tubular in shape and provided with an inlet opening 55, which receives the wet ground kernels from the duct 11 and with an outlet opening 57.

A bladed or helical rotor 58 is rotatably supported in the tubular body 51, which gives the wet ground kernels an advance thrust towards the outlet opening 57, which gives these wet ground kernels to the inlet opening 105 of a reactor for thermal treatment and dehydration 101. This reactor 101, having a structure entirely similar to the aforementioned wet thermal treatment reactor, is not described in detail. The components of the reactor for thermal treatment and dehydration equal to those of the reactor for wet thermal treatment are indicated with the same reference numerals increased by 100.

The dried ground kernels leaving the reactor for thermal treatment and dehydration are sent to a container 18 for collecting and separating the steam and air also leaving this reactor.

Finally, the dried ground kernels are fed to a conventional grain mill, to further reduce the particle size and obtain corresponding whole grain flours.

The whole grain flours obtained with the process according to the present invention, in addition to the previously mentioned advantages (presence of components of high nutritional value (fiber, minerals, vitamins) associated with organoleptic-structural characteristics quite similar to those of corresponding completely flours without bran and long shelf life at room temperature), have the further advantage of allowing cooking in a shorter time than previously known wholemeal flours.

This is because the wet heat treatment undergone by the ground kernels determines a partial gelatinization of the starch contained in them.

Consequently, the doughs for different types of bakery products (bread, cakes, biscuits, etc.) obtained with wholemeal flours produced with the process according to the invention require a cooking time in the oven significantly lower than that required by doughs prepared with flours. wholemeal (but also with non-wholemeal flours) conventional. The cooking time can be reduced by approximately 30% -40%.

EXAMPLE 1

In the wet heat treatment reactor 1, in which the bladed rotor 8 was rotated at a speed of 700 rpm, a flow of soft wheat kernels previously coarsely ground was fed continuously through the opening 6 of a flax mill to obtain particles having a diameter of not less than 2 mm (average diameter 2.5 mm) (80 kg / h) having a moisture content of 13.5%. At the same time, through opening 5 a flow of water at 80 ° C (20 kg / h) was continuously fed and through opening 10 a flow of water vapor (105 ° C) (15 kg / h) was continuously fed. .

Immediately upon entering the reactor 1, the flow of ground kernels was mechanically dispersed into particles, which were immediately centrifuged against the inner wall of the reactor itself, where they formed a thin, fluid, tubular and dynamic layer. At the same time, the water fed through the opening 5 was finely atomized by the blades of the rotor 8, which also provided for the immediate centrifugation of the tiny drops obtained. These were thus introduced into the thin dynamic tubular fluid layer of particles, with which they could interact intimately, even in the presence of the steam fed through the opening 10. The rotational speed of the bladed rotor 8 was loaves at 700 rpm.

After an average residence time of about 30 seconds in the reactor, a flow of heat-treated wet ground kernels was discharged continuously from opening 7. The wet ground kernels in question had a moisture content of 26.2%.

These wet ground kernels were fed continuously into the reactor for thermal treatment and dehydration 101, by means of pumping 51, with a flow rate of 80 kg / h, in equicurrent to a flow of air at a temperature of 180 ° C (flow rate 385 m <3 > / h).

In the reactor 101 the wall temperature was controlled at a value of 180 ° C while the rotation speed of the bladed rotor 108 was kept constantly at 1000 rpm.

After an average stay in the reactor for 20 seconds, ground kernels having a moisture content of 12% were continuously discharged from it.

These ground kernels were then fed to a cylinder mill, in which they were subjected to further grinding until a wholemeal soft wheat flour with a grain size lower than or equal to 300 pm (diameter) was obtained.

EXAMPLE 2

With the wholemeal soft wheat flour obtained according to example 1, a dough for shortcrust pastry biscuits was prepared having the following composition

Ingredients% (by weight on weight

total)

Whole wheat flour of 56.00

Wheat

according to the example

1

Sugar 16.55

Vegetable fats 13.00

salt

0.30

Raising agents 0.35

Water 6.80

Eggs 5.00

Total 100.00

The ingredients of the shortbread biscuit (shortbread) were processed according to conventional mixing methods in a planetary mixer with a reel, mixing sugar and fat from the basic recipe until a homogeneous mixture was obtained and then adding the remaining ingredients.

The dough thus obtained was then subjected to conventional forming operations, obtaining semi-finished products in the shape of the desired shortbread, which were then subjected to baking in the oven at a temperature of 200 ° C for 6 minutes.

EXAMPLE 3 (comparative)

For comparative purposes, shortbread biscuits were prepared starting from a dough with a composition equal to the one reported above but in which, instead of the whole soft wheat flour of example 1, a type 0 flour was used. processing operations of Example 1 were repeated in an identical manner.

However, the time needed to bake the shortbread biscuits in the oven at 200 ° C was 9 minutes.

The shortbread biscuits obtained from examples 2 and 3 were subjected to the evaluation of a panel of trained tasters, who expressed judgments on various characteristics of the biscuits, such as the overall appearance, the texture on the palate, the crispness, the fragrance, assigning a score from 1 to 10 for each of the characteristics evaluated. The overall average score was 8.1 for the shortbread according to example 2 and 8.2 for the shortbread according to example 3, that is a substantial parity of evaluation, despite the presence in the shortbread of example 2 of a consistent quantity of bran, which notoriously tends to negatively affect the organoleptic and structural characteristics of baked products.

Brio che s, croissants, and cakes were also prepared with the wholemeal flour of example 2, obtained starting from both cast doughs and Danish doughs, always with excellent results in terms of organoleptic-structural properties and noting constantly the significant reduction of the cooking times mentioned above.

Claims (16)

CLAIMS 1. Process for the production of a wholemeal flour of cereals, which includes the phases of: a) grind cereal kernels until they are reduced to particles with a diameter of not less than 2 mm; b) provide a reactor for wet heat treatment comprising a cylindrical tubular body (1) with a horizontal axis, equipped with at least one inlet opening (5, 6, 10) for the introduction of the ground kernels referred to in step a) and of water or an aqueous solution and of at least one discharge opening (7), a heating jacket (4) for bringing the temperature of said tubular body to a temperature of at least 80 ° C, and a rotor (8), arranged in the cylindrical tubular body and comprising a shaft provided with elements (9) projecting radially therefrom; c) feeding a continuous flow of said ground kernels into said reactor, in which the rotor is rotated at a speed greater than or equal to 150 rpm; d) feeding into said reactor, together with said flow of ground kernels, a continuous flow of water or aqueous solution, which is dispersed in minute drops; e) centrifuging said flows against the internal wall of the reactor, with the formation of a thin, dynamic, highly turbulent tubular fluid layer, in which the ground kernels particles and the drops of water or aqueous solution are mechanically kept in intimate contact by the elements ( 9) protruding radially of said rotor (8), while advancing in substantial contact with said inner wall of the reactor towards the discharge opening (7); f) discharge from the discharge opening a continuous stream of wet ground kernels particles (moisture content 20-30%); g) providing a reactor for thermal treatment and dehydration, comprising a cylindrical tubular body (101) with a horizontal axis, equipped with at least one inlet opening (105) and at least one discharge opening (107), a jacket (104) heating to bring the temperature of said tubular body to a predetermined temperature, and a rotor (108) arranged in the cylindrical tubular body and comprising a shaft provided with elements (109) projecting radially therefrom; h) feeding said wet ground kernels into said reactor through the at least one inlet opening (105), the inner wall of the reactor being kept at <"> a temperature of at least 100 ° C by means of said heating jacket (104) and the rotor (108) being rotated at a speed of at least 150 rpm; i) centrifuge and advance said wet ground kernels inside the reactor by the action of said rotor; 1) discharging from the reactor outlet opening (107) a continuous flow of ground kernels having a moisture content between 2% and 15%; m) subjecting said ground kernels to a further grinding step, to reduce the size of the particles to a value less than or equal to 0.5 mm, obtaining said integral flour. 2. Process according to claim 1, in which, in step d), a continuous flow of water vapor is fed through said at least one inlet opening (10) into the reactor for wet heat treatment. 3. Process according to claim 1 or 2, wherein, in concomitance with the feeding of said stream of wet ground kernels particles into the reactor for thermal treatment and dehydration of step g), said reactor is also fed, through said at least one inlet opening, a flow of a gas, preferably air, heated to a temperature of at least 100 ° C. Process according to any one of claims 1-3, wherein the temperature of the inner wall of the wet heat treatment reactor is maintained at 100-160 ° C, preferably at 100-120 ° C. Process according to any one of claims 1-4, wherein the rotational speed of the rotor (8) of the wet heat treatment reactor is set at 500-3000 rpm. 6. Process according to claim 5, in which the residence time of said ground kernels inside the reactor for wet heat treatment is between 20 and 60 seconds. Process according to any one of claims 1-6, wherein the temperature of the inner wall of the reactor for thermal treatment and dehydration is maintained at 120-280 ° C, preferably at 150-190 ° C. Process according to any one of claims 1-7, wherein the rotational speed of the rotor (108) of the reactor for thermal treatment and dehydration is set at 300-1200 rpm. Process according to any one of claims 3-8, wherein the temperature of the gas flow fed into the reactor for thermal treatment and dehydration is comprised between 120 ° C and 250 ° C, preferably between 140 ° C and 190 ° C. Process according to any one of claims 1-9, wherein the residence time of the ground kernels inside the reactor for thermal treatment and dehydration is comprised between 30 and 70 seconds. 11. Process according to any one of claims 1-10, wherein the water or aqueous solution fed into the reactor for wet thermal treatment has a temperature of 80-110 ° C, preferably 90 ° -100 ° C. Process according to any one of claims 1-11, wherein the ratio between the flow rate of the water or aqueous solution fed into the wet heat treatment reactor and the flow rate of wet ground kernel particles fed into the reactor for wet heat treatment is between 1:10 and 1: 2, preferably between 1: 4 and 1: 2.5. 13. Process according to any one of claims 1-12, in which said elements (9, 109) protruding radially from the rotor shaft (8, 108) are rod-shaped or in the form of blades or plowshares or reels. 14. Process according to any one of claims 1-13, in which said kernels of ground cereals into particles having a diameter of not less than 2 mm as in step a) are immersed in water at 80 <0> -100 ° C for a time comprised between 15 and 60 minutes, before being fed into said reactor for wet heat treatment. 15. Wholemeal cereal flour obtained by the process according to any one of claims 1-14. 16. Bakery product obtained starting from a whole grain flour according to claim 15.