FR2816480A1 - Hard wheat grain treatment procedure for human consumption consists of immersing in boiling water to gelatinize starch - Google Patents

Abstract

The hard wheat grains are processed for human consumption by immersing 100 g of the grains in 1 liter of boiling water for 5 minutes, when they will take up over 100 per cent of their weight in water. After immersion, the grains are drained and cooled in a 60 mm Petri dish, passed over a moist sponge and covered with a 80 mm Petri dish. The hard wheat grains are processed for human consumption by immersing 100 g of the grains in 1 liter of boiling water for 5 minutes, when they will take up over 100 per cent of their weight in water. The grains used for the procedure have a density above 0.7 and a thickness of 32 - 2.4 mm, and during the process at least 90 per cent and preferably at least 99 per cent of them will have a gelatinized core. After immersion, the grains are drained for 1 minute and cooled for 15 minutes in a 60 mm Petri dish, passed over a moist sponge and covered with a 80 mm Petri dish. The heat treatment of the grains can be carried out in a vibrated metal coil (8) with ends (9, 10) connected to a heating circuit (11) with a generator (12); the vibration is carried out by motors (4) on a support (3) mounted on a base (1).

Description

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Durum wheat grains and their preparation process The present invention relates to durum wheat seeds and their preparation process.

In European patent 561092, a method of manufacturing a product intended for human consumption is described, which consists in subjecting durum wheat grains to hot hydration, to hot rest, to cooking, to a drying and cooling, hulling and hot expansion. The fourth fundamental step of the process consists in a treatment causing an expansion of the grains of the order 1, 1 times to 2, 0 times their initial volume, which makes them porous. This porosity is essential to accelerate the time of household cooking which is then reduced to 10 to 20 min, without altering the taste qualities of the grains.

In U.S. Patent 5,520,949, a process for the preparation of wheat grains is described which consists of increasing the moisture content of the grains to about 20 to 45%, carrying the hydrated grains between 100oC and 130oC for 7 to 50 min, dehydrating the grains to a moisture content of around 18 to 30%, compressing the grains and drying them quickly after compression. The grains produced look like puffed grains close to breakfast cereals because they have undergone drying in a dehydrating unit after compression, so as to produce the expansion necessary for rapid cooking.

The present invention relates to durum wheat grains which, having not undergone an expansion treatment, retain their initial density, but which however have a porosity such that they cook in 5 min in water

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 boiling.

 Durum wheat grains can be prepared according to the invention by a process which consists in soaking them in water at a temperature between 40 and 65 ° C., and preferably between 50 and 65 ° C. for a time such that obtains, after draining and spinning, soaked grains having a moisture content by weight of between 30 and 45% and preferably between 35 and 40%, to bring the soaked grains to a temperature above 100 ° C., for a period such as grains of wheat are obtained in which gelatinization of the starch has taken place, dehydrating the grains in which gelatinization of the starch has taken place, so as to obtain dehydrated grains having a weight content by moisture of between 15 and 18%, to flatten the dehydrated grains into flattened grains, then to dry the flattened grains to reduce the moisture content by weight between 11 and 13%. According to the invention, the stage of obtaining wheat grains in which gelatinization of the starch has taken place is carried out by passing the grains soaked continuously in an enclosure, so as to limit by the balance which establishes in the enclosure between the moisture content of the grains which undergo gelatinization and the moisture content of the gaseous atmosphere of the enclosure, the quantity of vapor which is released from the grains during gelatinization to maintain the weight humidity of the grains in the course of gelatinization at a value between 25 and 35% and preferably between 28 and 32%, so as to obtain a gelatinization of at least 95% and preferably of at least 99% and to dehydrate the grains to a maximum temperature of 90oC.

 By respecting these conditions very precisely, durum wheat grains are obtained which, after having immersed 100 g thereof for 5 min in 1 l of boiling water, exhibit a water uptake greater than 100% by weight, but which retain their original density, this density being in particular greater than 0.7. We succeeded for the first time in creating a porosity in the wheat grains, without however that they are expanded and that their density as well as the resulting aspect suffer from it. The consumer thus has at his disposal grains of wheat which can cook quickly, but which appreciably preserve the appearance of natural wheat, which is essential to make a market product which pleases the consumer.

 The thickness of the grains is between 2 and 2.4 mm. This

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 thickness is obtained by the flattening stage, the flattening operation reduces the thickness of the grain and therefore allows hydration to the heart faster. It creates a large micro-cracking of the surface, thus increasing the porosity of the grain. At least 90% and preferably 99% of the grains are gelatinized to the core according to the alkali test.

 When the grains, after immersion for 5 min in water, then draining for 1 min and cooling for 15 min in a 60 mm diameter petri dish placed on a damp sponge and covered with a petri dish 80 mm in diameter so that the latter creates a watertight seal with the water which soaks the sponge, are subjected to a texture test with a Chopin viscoelastograph, it is found that the grains have a firmness of less than 45 and a higher elastic recovery to 30, which makes them have excellent taste properties.

 In addition, the grains according to the invention are characterized by a color on the Minolta chromameter by a clarity index L less than 65 by a yellow index b greater than 27 and by a red index a less than 2. The grains are thus particularly appetizing.

 The first stage of the process according to the invention consists in dipping durum wheat grains in water. The water temperature is between 40 and 65 C and preferably between 50 and 65OC. Depending on the water temperature, the soaking is carried out for approximately 1 to 3 hours, so that the grain moisture is between 30 and 45% at the end of the soaking and preferably between 35 and 40% . At the end of the soaking, the surface water is removed by draining or spinning.

 The second stage of the process according to the invention consists in heat treating the soaked grains in an enclosure. The heat treatment is carried out at a temperature above 100oC, for a period which is normally between 4 and 10 min. The temperature used is generally between 120 and 160oC. We can make sure that in stationary mode, the grains occupy from 5 to 30% of the volume of the enclosure. To prevent certain grains from continuously staying in contact with the heated enclosure and from roasting, it is preferable to move them in the enclosure by vibrating it so that it is never the same grains which are in contact with the enclosure. By confining the grains in an enclosure and heating them by conduction and not by convection in the hot fluid state,

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 in particular by contact with the metallic enclosure heated by current flow or by an external jacket in which heat transfer fluid passes, the temperature of the enclosure being able to reach 130 to 180oC, one is well mastered of the moisture content of the grains then that the temperature is raised to gelatinize them, so that no expansion takes place.

 The next stage of the process according to the invention consists in dehydrating the grains in which gelatinization of the starch has taken place, so as to obtain dehydrated grains having a weightable moisture content of between 15 and 18%, and preferably close 17%. This dehydration can be carried out in a drying column with a stream of hot air having a maximum temperature of 90oC.

 According to an advantageous embodiment of the invention, it is then possible to interpose a stage of dehulling of the grains by abrasion in a vertical dehuller composed of 5 to 9 grindstones stacked on an axis, separated by perforated spacers and rotating inside d '' a perforated coat for sound evacuation. Three to four passes may be necessary to properly shell the grain, with the exception of the furrow, and to reach a weight ratio of husking of 15 to 25% and preferably 20%.

 The next stage of the process according to the invention is that of flattening, which can be carried out by passing between rollers whose spacing is adjusted between 0.2 and 0.5 mm and preferably between 0.25 and 0 , 4 mm. The speed of the rollers can be adjusted between 20 and 60 rpm. Before flattening, the grains are heated under infrared panels to give them sufficient plasticity so that they can be flattened without breaking them. Reheating allows to go from 25 C to 85 C in less than 30 s, without modifying the humidity of the wheat.

 The last stage of the process according to the invention consists in drying the grains in order to bring their weight humidity between 11 and 13%, and preferably between 12.5 and 13% so that the grains keep well.

 Figure 1 of the accompanying drawing illustrates the heat treatment installation in an enclosure.

 The installation comprises a base 1 mounted on damping pads 2. From this base 1, an upright 3 leaves on which motors 4 are mounted.

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 unbalance that vibrates a plate 5.

 On this plate 5 is bolted an internal barrel 6 and coaxially to it a barrel 7. The interval between the barrels 6 and 7 is filled with a thermally and electrically insulating material. A metal coil 8 is fixed around the barrel 6 and winds from an inlet 9 to an outlet 6. The outlets 9 and 10 are connected by an electric heating circuit 11 and to a generator 12 of electric current. The input 9 is supplied from a vibrating filter serving as a draining device, itself supplied with wheat grains by a conveyor belt coming from a soaking tank.

 The following examples illustrate the invention.

 500 kg of durum wheat of the Orjaune variety are soaked for 1 hour 30 minutes in water at 55 C and then drained on a vibrating filter. The humidity of the wheat is then 35.4%.

 The product is then transferred to the heat treatment enclosure, the walls of which have been heated to 150oC. The residence time is 8 min in the enclosure. Wheat comes out at 106OC and 29.2% humidity.

 It is then transferred to a drying column to be dried to 17% humidity with hot air at 80 ° C and then shelled by passage through 4 vertical shellers to remove 20% of bran.

 The peeled grains are then reheated for 20 s by passing in a monolayer under infrared panels to reach 85 C and flattened by passing between 2 rollers whose spacing is 0.25 mm and rotating at 40 rpm. At the exit of the rollers, the flattened grains are conveyed to the drying columns where their humidity is reduced to 12.5%.

 The product from this preparation has an average thickness of 2.20 mm, its density is 0.72 and its color measured with the Minolta chromameter has an index L = 63.96, a = 1.72 and b = 28, 86. The alkali test shows 100% of gelatinized grains.

 This wheat, after cooking for 5 min in boiling water has a water intake of 108%, its firmness measured with a viscoelastograph is 41.0 and its elastic recovery of 31.1.

Comparative example
We use the previous example, but without flattening the grains.

Peeled and dried kernels that have not been flattened set

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 77% water after cooking for 5 min. in boiling water. They are not hydrated in the heart and are much too firm to be consumed.

Comparative analysis of previous products
Commercial durum wheat according to EP-561 092-A has a density of 0.6, the clarity index L is 70.29, and the water intake in 5 minutes of cooking is only 85 %.

 Another durum wheat product has a water uptake in 5 minutes of cooking greater than 100% (130%) but has a density of 0.26 and a yellowness index equal to 26.12.

 The methods of analysis for characterizing the grains are given below.

Alkali test
100 wheat grains are placed in a 1.7% by weight KOH solution for 20 h. after 20 hours of reaction, the degradation undergone by the grains is observed.

 - Opaque, white grains: non-gelatinized grains.

 - Grains dispersed in a yellow ocher mass: slightly gelatinized grains.

 - Completely translucent grains: totally gelatinized grains.

Density measurement
The wheat is gradually poured into a graduated one-liter glass test tube, 470 mm high, using a powder funnel with a stem diameter of 40 mm, which makes it possible to standardize the packing of the grains.

When the volume of a liter is appreciably reached, complete slowly to adjust to the liter, avoiding any movement of the test piece which could modify the compaction of the grains.

 The quantity of grains corresponding to the volume of a liter is then weighed.

 The operation is repeated five times. The result D is the average of the five measurements.

 D = weight of a liter of grain / 1000 (weight of a liter of water).

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Color The measurement is carried out with the Minolta chromameter calibrated with a white plate in the L * a * b system on 15 g of grains placed in the measuring cell. L being the index of clarity, a the index of red and b the index of yellow. The measurement is carried out on five different samples, the average and the standard deviation are then calculated.

Grain thickness The thickness taken into account is the measurement of the smallest section made in the middle of the grain. It is carried out with the caliper on the middle of the grain seen in profile.

The result is the average of the measurement of 50 representative grains of the sample.

Water intake 100g of grains weighed to the nearest 0.1 g are immersed for 5 min in 1 1 of boiling water. The grains are then drained for 1 min in a colander of 20 cm in diameter and weighed immediately.

The water intake result (PE) is the average of three measurements and is expressed as a percentage of the starting rice weight.

Texture measurement with viscoastoscope 100 g of wheat grains are immersed for 5 min in boiling water. Then the grains are drained for 1 min, and allowed to cool for 15 min in a 60 mm petri dish placed on a damp sponge plate and covered by a 80 mm larger petri dish so that the latter creates a waterproof seal with the water which soaks the sponge plate. Three grains thus cooled are placed on the viscoelastograph tray. A force of 700 g is applied with the piston to the grains. The thickness E of the grains is noted before application of the force, the thickness e1 after application and e2 after release of the force.

From these values we calculate the firmness F = 100 (e1 / E) and the elastic recovery RE = 100 [(e2-e1) / (E-e1)].

Claims (10)

1. Durum wheat grains which, after having been immersed 100 g for 5 min in 1 1 boiling water, have a water uptake greater than 100% by weight, characterized by a grain density greater than 0 , 7, and a thickness of the grains is between 2 and 2.4 mm.  2. Grains according to claim 1, characterized in that at least 90% and preferably at least 99% of the grains are gelatinized to the core according to the alkali test.  3. Grains according to claim 1 or 2, characterized in that after immersion for 5 min in water then draining for 1 min and cooling for 15 min in a Petri dish of 60 mm in diameter, passed over a sponge wet and covered with a 80 mm diameter petri dish so that the latter creates a tight seal with the water which soaks the sponge, the grains have a firmness less than 45 and an elastic recovery greater than 30 with a viscoelastograph Chopin.  4. Grains according to one of the preceding claims, characterized by a color on the Minolta chromameter such that the clarity index L is less than 65, that the red index a is less than 2 and that the yellow index b is greater than 27.  5. Process for the preparation of durum wheat grains which consists in soaking them in water at a temperature between 40 and 65 C and preferably between 50 and 65 C for a time such as is obtained, after draining or spinning, soaked grains having a moisture content by weight between 30 and 45% and preferably between 35 and 40%, to bring the soaked grains to a temperature above 100oC for a <Desc / Clms Page number 9>  duration such as to obtain grains in which gelatinization of starch has taken place, to dehydrate the grains in which gelatinization of starch has taken place so as to obtain dehydrated grains having a weight content of moisture included between 15 and 18% and preferably around 17%, to flatten the dehydrated grains into flattened grains, then to dry the flattened grains to reduce the weight content by moisture between 11 and 13% and preferably between 12.5 and 13%, characterized in that it consists in carrying out the stage of obtaining grains in which gelatinization of the starch has taken place by passing the grains soaked continuously in an enclosure so as to limit, by equilibrium which is established in the enclosure between the moisture content of the grains which undergo gelatinization and the moisture content of the gaseous atmosphere of the enclosure, the quantity of vapor which is released from the grains during t the gelatinization to maintain the weight humidity of the grains in the course of gelatinization at a value between 25 and 35% and preferably between 28 and 32% and to obtain a gelatinization of at least 95% and preferably at least 99% of the beans and to carry out the dehydration stage at a maximum temperature of 90oC.  6. Method according to claim 5, characterized in that it consists in hulling the dehydrated grains up to a hulling rate of 15 to 25% and preferably 20% by weight.  7. Method according to claim 5 or 6, characterized in that the duration of passage of the grains soaked in the enclosure is between 4 and 10 min.  8. Method according to one of claims 5 to 7, characterized in that in stationary regime, the grains occupy from 5 to 30% of the volume of the enclosure.  9. Method according to one of claims 5 to 8, characterized in that it consists in moving the grains in the enclosure by vibrating the enclosure.  10. Method according to one of claims 5 to 9, characterized in that it consists, before the flattening stage, in heating the grains to a temperature below 85 C in less than 30 s.