DESCRIPTION

Field of application

The present invention relates to the sector of the food industry. More particularly, the invention relates to a process for the production of whole grain meal obtained from cereals.

Prior art

Cereals (e.g. wheat, rice, corn, barley, sorghum, etc.) are consumed the world over as the basis of an alimentary diet since they are the primary source of carbohydrates owing to the high starch content of the endosperm which is located in the central part of the caryopsis.

Considering for example wheat, the following layers, which form the bran, are located as follows in the caryopsis, starting from the outside: pericarp, testa, nucellar layer (or hyaline layer) and aleurone, while the internal part consists of endosperm and germ.

Flour is the main product obtained from the process of grinding the soft wheat and consists of the innermost starchy parts of the caryopsis (endosperm) after separation from the outermost parts (the bran, which represents about 15% of the total content of the caryopsis, and the germ, which forms about 3%) traditionally intended for livestock feeding.

Meal is conventionally produced by breaking (grinding) the caryopses as such, followed by sieving of the fragments produced, which may contain only endosperm or parts of endosperm accompanied by bran and germ. The aforementioned fragments are then conveyed away for successive grinding and separation steps aimed at releasing and separating as far as possible the fractions of endosperm from the other components of the caryopsis.

Traditionally "white" flours, namely refined flours where the bran is almost fully removed are used, because these refined flours may be stored for a long time at room temperature. During the last few decades, however, there has been a reassessment of the nutritional value of "whole grain" cereal meal, i.e. meal containing the largest possible amount of the original components of caryopsis, and therefore also the bran. The bran in fact contains various substances, such as (insoluble and soluble) dietary fibers, minerals, vitamins, lipids and other component which have a protective (anti-oxidizing) action in the cellular metabolism and in ageing phenomena and there is unanimous recognition of the benefits resulting from the daily consumption of whole grain products. The above comments made with reference to wheat are also applicable to other cereals.

However, the whole grain meal obtained by means of simple grinding of the caryopses as such, omitting the bran and germ separation steps, has the drawback of poor conservation properties. Processes for the production of cereal meal, which comprise preliminary removal of the outer layers of the caryopsis by means of friction and abrasion operations, before grinding of the caryopses, have therefore been adopted. Examples of these processes are illustrated in patent applications EP 0 295 774, EP 0 373 274 and WO 2004/028694. The whole grain flours which are commercially available are obtained by adding to a "white" flour, obtained essentially from the endosperm alone, the bran obtained by means of the aforementioned abrasion and decortication operations, after the same has undergone regrinding treatment, in order to reduce the particle size, and heat stabilization treatment, in order to prevent the oxidation caused by enzymatic degradation.

The bran obtained in this way is in fact subject to degradation, even after a short period of time, owing to occurrence of oxidation reactions (rancidity) affecting the lipid components present in the bran, which may also contain germ parts very rich in lipids. Rancidity is generally caused by the activation of enzymes (lipase and lipoxygenase) which are present in the bran and attack the lipid portion present. Consequently, attempts have been made to prevent this phenomenon by deactivating these enzymes with heat. The heat treatment of bran, however, in addition to involving extra costs, may result in darkening of the bran, the creation of unpleasant tastes and chemical degradation affecting the lipid portion.

The whole grain flours obtained by the addition to "white" flours of bran obtained by means of abrasion and decortication operations and subjected to stabilization heat treatment, apart from not being authentic "whole grain" flours, have organoleptic characteristics which are often unsatisfactory following such heat treatment.

The problem underlying the present invention has therefore been that of providing a meal which may be correctly defined as "whole grain", since obtained from the grinding of the entire caryopsis, said meal being able to be stored for a long period of time at room temperature without being affected by rancidity or degradation and having optimum organoleptic properties.

Summary of the invention

This problem has been solved, according to the invention, by providing a process for the production of a whole grain cereal meal, which comprises the steps of: a) grinding cereal caryopses into particles of diameter of not less than 2 mm; b) providing a wet heat treatment reactor comprising a cylindrical tubular body with horizontal axis, having at least one opening for the introduction of the ground caryopses of step a) and water or an aqueous solution and at least one discharge opening, a heating jacket for raising the temperature of said tubular body to a temperature of at least 80°C, and a rotor, arranged inside the cylindrical tubular body and comprising a shaft provided with elements projecting radially therefrom; c) feeding a continuous flow of said ground caryopses into said reactor, wherein 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 caryopses, a continuous flow of water or aqueous solution, which is dispersed into minute droplets; e) centrifuging said flows against the inner wall of the reactor, thus forming a highly turbulent, dynamic, thin, tubular fluid layer, in which the particles of ground caryopses and the droplets of water or aqueous solution 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; f) discharging from the discharge opening a continuous flow of wet ground caryopses particles (moisture content 20-30%); g) providing a thermal dehydration and treatment reactor, comprising a cylindrical tubular body with horizontal axis, having at least one inlet opening and at least one discharge opening, a heating jacket for raising the temperature of said tubular body to a predetermined temperature and a rotor arranged inside the cylindrical tubular body and comprising a shaft provided with elements projecting radially therefrom; h) feeding said wet ground caryopses into said reactor through the at least one inlet opening, the inner wall of the reactor being kept at a temperature of at least 100°C by means of said heating jacket and the rotor being rotated at a speed of at least 150 rpm; i) centrifuging and causing said wet ground caryopses to advance inside the reactor by means of the action of said rotor;

1) discharging from the discharge opening of the reactor a continuous flow of ground caryopses having a moisture content of between 2% and 15%. m) subjecting said ground caryopses to a further grinding step, to reduce the particle size to a value less than or equal to 0.5 mm, thus obtaining said whole grain meal.

Preferably, in step d), a continuous flow of steam is fed into the wet heat treatment reactor through the aforementioned at least one inlet opening. Preferably, at the same time as feeding of the aforementioned flow of wet ground caryopses into the thermal dehydration and treatment reactor according to step h), a flow of gas, preferably air, heated to a temperature of at least 100°C, is also fed into this reactor, through the aforementioned at least one inlet opening.

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

The temperature of the inner wall of the reactor for the wet heat treatment is preferably kept at 100- 160°C, conveniently at 100- 120°C. The rotational speed of the rotor of the reactor for wet heat treatment is preferably set to 500-3000 rpm.

The residence time of the ground caryopses inside the wet thermal treatment reactor is preferably between 20 and 60 seconds.

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

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

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

The residence time of the ground caryopses inside the thermal dehydration and treatment reactor is preferably between 30 and 70 seconds. The water or aqueous solution fed into the wet heat treatment has preferably a temperature of 80- 1 10°C, conveniently 90- 1 10°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 the wet ground caryopses particles fed into the wet heat treatment reactor is preferably comprised between 1 : 10 and 1 :2, conveniently between 1 :4 and 1 :2.5. The aforementioned elements radially projecting from the rotor shaft may be for example rod-like or in the form of vanes or V-blades or beaters.

The process according to the invention may also comprise, prior to the aforementioned step b), a step where the aforementioned cereal caryopses ground into particles of diameter of not less than 2 mm are immersed in water at 80- 100°C for a time of between 15 and 60 minutes.

"Meal" is understood as meaning a finely divided product which is obtained from the grinding of cereal seeds and may be in the form of flour, semolina or fine granules. The term "cereals" is understood as meaning plants belonging to different families, in particular Graminacee (wheat, rice, barley, rye, oat, corn, sorghum and teff), Polygonaceae (buckwheat), Amaranthaceae (amaranth) and Chenopodiaceae (quinoa).

The present invention also relates to a whole grain cereal meal obtained by means of the aforementioned process, such as a bakery product obtained from such whole grain meal.

The whole grain meal obtained with the process according to the present invention is particularly suitable for making bakery products which, compared to the bakery products made with refined flour, have the major advantage that they contain the components of high nutritional value present in the bran (fiber, minerals, vitamins), while at the same time they have organoleptic/ structural properties (color, taste, texture) entirely comparable to those of corresponding products obtained from completely bran-free meal. Moreover, these organoleptic/ structural properties remain substantially unchanged for the entire shelf-life of the finished product.

This is probably due to the fact that the treatment carried out on the particles of ground caryopses in the reactor allows the enzymes (lipase and lipoxygenase) present in the bran to be deactivated, preventing them from attacking the lipid portion present in the bran and causing oxidation reactions, resulting in rancidity. Moreover, the relatively short residence time of the ground caryopses inside the wet heat treatment reactor avoids the drawbacks encountered in the heat treatment of the prior art performed on the bran which is added to the white flour in order to "recreate" a "whole grain" flour. Such heat treatment in fact results in darkening of the bran, the creation of anomalous (burnt or bitter) tastes and the triggering of chemical degradation of the lipid fraction (due to heat) . Brief description of the drawings

Further characteristic features and advantages of the present invention will emerge more clearly from the following detailed description provided with reference to the single attached figure (Fig. 1), which shows in schematic form an embodiment of a plant for implementing 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 wet heat treatment reactor consisting essentially of a cylindrical tubular body 1 , closed at the opposite ends by end plates 2, 3 and coaxially provided with a heating/ cooling jacket 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.

The tubular body 1 is provided with inlet openings 5, 6 and 10, i.e. 5 for the water or aqueous solution, 6 for the caryopses and 10 for the steam, as well as a discharge opening 7.

The tubular body 1 rotatably supports a rotor 8 comprising a shaft 8 provided with elements radially projecting therefrom in the form of blades 9 which are arranged helically and oriented so as to centrifuge and at the same time convey towards the outlet the flows of ground caryopses and water or aqueous solution.

A motor M is provided for operation of the rotor at variable speeds ranging from 150 to 3000 rpm.

Upon exiting the reactor, the wet caryopses are fed via a pipe 1 1 , communicating with the discharge opening 7 of the wet heat treatment reactor, to the injector device 51. The body of the injector device 51 has a tubular shape and is provided with an inlet opening 55 which receives the ground caryopses from the pipe 1 1 , and an outlet opening 57.

The tubular body 51 rotatably supports a bladed or screw rotor 58 which imparts to the wet ground caryopses an advancing thrust towards the outlet opening 57 so as to convey said wet ground caryopses to the inlet opening 105 of a thermal dehydration and treatment reactor 101. This reactor 101 , which has a structure entirely similar to the wet treatment reactor mentioned further above, is not described in detail. The components of the thermal dehydration and treatment reactor which are identical to those of the wet heat treatment reactor are indicated by the same reference numbers increased by 100.

The dried ground caryopses output from the thermal dehydration and treatment reactor are conveyed to a storage container 18 which separates them from the steam and air which are also output from this reactor.

Finally, the dried ground caryopses are fed to a conventional cereal mill in order to reduce further the particle size and obtain corresponding whole grain cereal meal.

The whole grain cereal meal obtained with the process according to the present invention, in addition to the aforementioned advantages (presence of components with a high nutritional value (fiber, minerals, vitamins) together with organoleptic/ structural properties entirely similar to those of corresponding entirely bran-free meal and long storage life at room temperature, offers the further advantage of rapid baking times compared to the previously known whole grain meal.

This is due to the fact that the wet heat treatment carried out on the ground caryopses results in partial gelatinization of the starch contained in them.

Consequently, the mixtures for different types of bakery products (bread, cakes, biscuits, etc.) obtained with the whole grain meal produced by the process according to the invention require an oven baking time which is substantially shorter than that required by mixtures prepared with conventional whole grain meal (but also non whole grain meal). The baking time may be reduced by about 30-40%. EXAMPLE 1

The wet heat treatment reactor 1 , in which the bladed rotor 8 was rotated at a speed of 700 rpm, was continuously fed, via the opening 6, with a flow of soft wheat caryopses rough-ground beforehand inside a mill to obtain particles with 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 a flow of water at 80°C was continuously fed (20 kg/h) through the opening 5, and a flow of steam was continuously fed (15 kg/h) through the opening 10 at 105°C.

Immediately at the inlet of the reactor 1 , the flow of caryopses was mechanically dispersed into particles which were immediately centrifuged against the inner wall of the reactor, where a thin, dynamic, tubular, fluid layer was formed. At the same time, the water 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. These droplets were thus introduced into the thin, dynamic, tubular, fluid layer of particles, with which they were able to interact intimately, in the presence also of the steam fed through the opening 10. The rotational speed of the bladed rotor 8 was 700 rpm.

After an average residence time of about 30 seconds inside the reactor, a flow of heat-treated, wet, ground caryopses was continuously discharged from the opening 7. The wet ground caryopses in question had a moisture content of 26.2%. These wet ground caryopses were continuously fed into the thermal dehydration and treatment reactor 101 , via the injector 51 , at a flow rate of 80 kg/h, in parallel with an air flow at a temperature of 180°C (flow rate 385 m ³ /h).

Inside the reactor 101 , the wall temperature was controlled to remain at a value of 180°C, while the rotational speed of the bladed rotor 108 was kept constantly at 1000 rpm.

After an average residence time of 20 seconds inside the reactor, ground caryopses with a moisture content of 12% were continuously discharged therefrom.

The ground caryopses were then fed to a cylinder mill where they underwent further grinding until a soft wheat whole grain flour with a grain size smaller than or equal to 300 μπι (diameter) was obtained.

EXAMPLE 2

A dough for short pastry biscuits with the composition shown below was prepared using the soft wheat whole grain flour according to Example 1 :

The ingredients of the short pastry biscuit were worked using conventional kneading methods inside a planetary machine with beater, mixing sugar and fat of the base recipe until a homogeneous dough was obtained and then adding the remaining ingredients.

The dough thus obtained was then subjected to conventional forming operations resulting in semi-finished products with the shape of the desired short pastry biscuits which were then baked in an oven at a temperature of 200°C for 6 minutes. EXAMPLE 3 (comparative)

For comparison purposes, short pastry biscuits were prepared from a dough which had a composition similar to that described above, but in which a type 0 flour was used instead of the soft wheat whole grain flour of Example 1. The processing steps of Example 1 were repeated in an identical manner.

The time needed to obtain oven-baking of the short pastry biscuits at 200°C was however 9 minutes.

The short pastry biscuits obtained from Examples 2 and 3 underwent evaluation by a panel of trained tasters who gave their opinion on various characteristics of the biscuits, such as the overall appearance, the consistency when tasted, the crumbliness and the fragrance, giving a score of 1 to 10 for each of the characteristics assessed. The overall average score was 8.1 for the short pastry biscuit according to Example 2 and 8.2 for the short pastry biscuit according to Example 3, namely substantially the same evaluation, despite the presence in the short pastry biscuit according to Example 2 of a significant amount of bran, which, as is well-known, tends to have a negative effect on the organoleptic and structural properties of the oven products. Brioches, croissants and cakes made using both batters and Danish pastry doughs were also prepared using the whole grain flour of Example 2, again with optimum results in terms of organoleptic/ structural properties and confirming in all cases the substantial reduction in the aforementioned baking times.