EP3893667A1

EP3893667A1 - Method for treating a rice grain, and treated rice grain

Info

Publication number: EP3893667A1
Application number: EP19818080.4A
Authority: EP
Inventors: Emna CHICHTI; Isabelle Françoise AREKION
Original assignee: Panzani SAS
Current assignee: Panzani SAS
Priority date: 2018-12-13
Filing date: 2019-12-13
Publication date: 2021-10-20
Also published as: WO2020120758A1; FR3089760B1; FR3089760A1

Abstract

The invention relates to a method for treating a grain of paddy or cargo rice, comprising the following successive steps: - a step of hydration of the rice grain so as to bring the moisture content thereof to a value such that the starch of said rice grain can be gelatinised to a degree of between 80% and 100%; - a heat treatment step during which the hydrated rice grain is placed in an autoclave, a pressurised stream of steam is injected and the rice grain is kept under superatmospheric pressure, at a predefined temperature of between 120-160°C, for a predetermined treatment time of between 10 s and 15 min, in order to gelatinise the starch of the rice grain to a degree of between 80% and 100%, and once the treatment time has elapsed, the treated rice grain is immediately removed from the autoclave, in order to bring it directly back to atmospheric pressure. The invention also relates to methods for treating rice grains and to treated rice grains.

Description

PROCESS FOR TREATING A GRAIN OF RICE AND TREATED RICE GRAIN

TECHNICAL AREA

The present invention relates to the general technical field of methods for treating grains of rice intended for human or animal consumption. The present invention also relates to the general technical field of rice grains thus treated and intended to be cooked subsequently, before being consumed by an end consumer.

PRIOR ART

Parboiling is a well-known process for treating paddy rice grains, that is, raw, unhulled rice grains. This process essentially aims to improve the nutritional value of the rice obtained after husking the paddy rice and after cooking, in particular by promoting the migration of vitamins and mineral salts from the outermost layers to the inside of the rice grain. Nutrient losses linked to hulling and cooking rice are thus reduced. In addition, parboiling rice is known to improve the resistance of rice to cooking and overcooking, so that parboiled rice is generally considered to be non-stick.

However, parboiling the rice involves gelatinization of the starch in the treated rice grains, which generally has the effect of increasing the time necessary for the final cooking of the parboiled rice obtained. In addition, parboiled rice generally has, before cooking, a yellowish color deemed unattractive by consumers. Also, parboiled rice generally has, after cooking, a particular characteristic taste which discourages certain consumers.

If the known rice parboiling processes are regularly subject to improvements and optimizations, in particular with a view to reducing the necessary cooking time of the parboiled rice grains, the organoleptic qualities of the parboiled rice obtained remain however still perfectible, in the eyes of consumers, particularly in terms of texture, consistency, taste or appearance.

STATEMENT OF THE INVENTION

The objects assigned to the invention therefore aim to remedy the various drawbacks listed above by proposing a new process for treating grains rice which, while allowing good control of the cooking time of the treated rice grains, allows rice grains to be obtained with significantly improved organoleptic qualities.

Another object of the invention is to propose a new grain of rice which, while having the advantages generally conferred by parboiling, has a well-controlled final cooking time and significantly improved organoleptic qualities.

Another object of the invention is to propose a new process which enables large quantities of rice grains to be treated quickly, efficiently and economically.

Another object of the invention is to propose a new process which, while allowing good control of the cooking time of the treated rice grains and obtaining rice grains with improved organoleptic qualities, also allows good control of the breaking rate.

The objects assigned to the invention are achieved using a process for processing a grain of paddy or cargo rice, comprising the following successive steps:

a step of hydration of said rice grain, to bring the moisture content of said rice grain to a value sufficient for the starch of said rice grain to be able to be gelatinized at a rate substantially between 80 and 100%, and preferably substantially equal to 100%;

a heat treatment step during which: o said grain of hydrated rice is placed in an autoclave, o a stream of pressurized steam is injected into the autoclave and said said is maintained grain of rice under super atmospheric pressure, at a predefined temperature between 120 and 160 ° C, for a predetermined treatment time between 10 s and 15 min, so as to gelatinize the starch of the rice grain at a substantially understood rate between 80 and 100%, and preferably substantially equal to 100%; o then, after the said predetermined treatment time has elapsed, the rice grain thus treated is immediately extracted from the autoclave, to bring the rice grain treated directly to atmospheric pressure. The objects assigned to the invention are also achieved using a grain of parboiled rice and intended to be cooked by immersion in an excess of water before being consumed, which grain of rice has: before cooking, a starch with a gelatinization rate substantially between 80 and 100%, and preferably substantially equal to 100%, and

- after cooking by immersion in excess water for about 10 min:

i. firmness F such that ii. an elasticity R such that where e; represents the thickness of the grain of cooked rice after application to said grain of cooked rice of a compression force under a load 700 g for 40 s, E is the initial thickness of the grain of rice cooked before the application of the effort compression, and e? represents the thickness of the grain of cooked rice measured 20 s after the end of the application of the compression force.

Other objects and advantages of the invention will appear more clearly on reading the detailed description which follows.

BEST WAY TO IMPLEMENT THE INVENTION

The present invention relates firstly to a method of treating a grain of paddy rice or cargo, that is to say a grain of rice in the raw state, typically not intended to be consumed in the state .

Advantageously, the process of the invention is an easily industrializable process, which can be implemented on a large scale in order to treat simultaneously, and preferably substantially continuously, a large quantity of rice grains. It is however conceivable that certain steps of the process of the invention are carried out by hand or by hand.

In general, the treatment method according to the invention aims to modify the characteristics of the rice grain concerned, prior to its final cooking and its consumption by a final consumer, human or animal. In particular, the method according to the invention aims advantageously to obtain a grain of rice having all or part of the qualities usually expected of a grain of parboiled rice, in particular in terms of control of the nutritional profile and resistance to overcooking (in particular in terms of firmness and unbeatable character ), and which also has excellent organoleptic characteristics after cooking and, in particular, after rapid cooking for approximately 10 min in an excess of water, preferably boiling. The cooked character of a grain of rice results in particular in a rehydration and a complete gelatinization (if the latter is not already the consequence of the heat treatment to which the grain of rice has previously been subjected) at the heart of the grain. Typically, a perfectly cooked grain of rice leaves behind, after being crushed between two sheets of plexiglass, no whitish and opaque granules, and on the contrary appears substantially entirely transparent or translucent.

In addition, the method according to the invention advantageously aims to obtain a grain of rice which, after drying and machining, and before final cooking for consumption, has a higher whiteness, a less yellow coloring, than a grain of traditional parboiled rice, so as to be visually more attractive to the consumer.

The improvement, brought by the treatment method according to the invention, in terms of textural characteristics of the grain of cooked rice, can advantageously be observed by monitoring the viscoelastic properties of the latter in terms of firmness and elasticity. These firmness and elasticity parameters can be evaluated using a Chopin viscoelastograph, advantageously according to the method defined in standard NF ISO 6648: 1993 - Rice - Determination of viscoelastic properties at different cooking times - Method using viscoelastograph. The measurement protocol, which can be implemented with a TA.XT Plus® texturometer marketed by the company Texture Technologies, is typically as follows: in a saucepan, using a hot plate, the mixture is brought to a boil 1 L of water, then cook 100 g of rice in boiling water for the desired cooking time (for example, 10 min); the rice is drained, then cooled for 1 min in cold water; the cooked rice is then stored for 15 min in a petri dish, all on a wet sponge to create a humid atmosphere; three cooked grains of rice are placed on the lower tray of the viscoelastograph / texturometer; - After the waiting time possibly required by the texturometer, the following measurement cycle is started:

o we measure the initial thickness E of the cooked rice grains,

o a compression force is applied to the cooked rice grains under a load of 700 g for 40 s, and the thickness ei of the cooked rice grains is measured after application of the compression force,

o then, 20 s after the end of the application of the compression force, the thickness e2 of the cooked rice grains is measured.

The firmness F, representative of the capacity of the grain of rice to resist the deformation imposed by the application of the compressive force, is then calculated according to the following formula:

F = ¾ x 100

E

The elasticity R (or elastic recovery), representative of the rice's capacity to return to its initial shape after the compression force has been released, is calculated according to the following formula:

(C-> “i? I)

R = - K 100

(6 - <? I)

The measurement and calculation cycle is repeated several times, preferably 6 to 10 times, for better reliability of the results, then the mean and G standard deviation of the 6 to 10 values F and R obtained are calculated.

Another interesting parameter to study in connection with the textural and taste characteristics of the cooked rice grain is the water-taking capacity of the rice grain during its final cooking. Indeed, good water intake during cooking contributes to the softness of the grain of cooked rice. Typically, the water intake can be measured as follows:

100 g of rice is cooked in excess boiling water for the desired cooking time (for example, 10 min);

the rice is then drained, so as to evacuate the surface water; then, the drained cooked rice is weighed, and the weight thus obtained is compared with that of the rice before cooking.

To characterize the whiteness and color, after drying and machining and before final cooking, of the rice grain obtained using the process according to the invention, advantageously: a measurement of the whiteness index "Kett" is carried out, using a rice whiteness tester sold by the company Kett Electric Laboratory (for example, a rice whiteness tester C-300-3); a measurement of the color, using a colorimeter or spectrocolorimeter (for example, a Konica Minolta® CM-3500d spectrocolorimeter), in the chromatic space L * a * b * CIELAB (1976), where Z * represents clarity, between 0 (black) and 100 (reference white), the a * parameter represents the value on a red green axis, and the b * parameter represents the value on a blue yellow axis.

As such, these characterization methods and the equipment capable of enabling their implementation are well known in the field.

The method according to the invention corresponds, at least in part, to a method of steaming the grain of rice, that is to say to a method implementing a hydrothermal treatment of the grain of rice. As such, and as will be explained below, the method according to the invention comprises a step of hydration of said grain of rice, followed by a step of heat treatment of the grain of hydrated rice, during which this the latter is subjected to a flow of water vapor.

More specifically, while said paddy or cargo grain of rice initially has a moisture content typically close to 12% on a wet basis, said hydration step of the process according to the invention is designed to carry the moisture content of said grain of rice at a threshold value, which is chosen sufficient for the starch of said grain of rice to be capable of being gelatinized at a rate substantially between 80 and 100%, preferably greater than 90%, and more preferably substantially equal to 100% , during the following heat treatment step. Typically, the hydration step aims to increase the moisture content of said rice grain to a value advantageously between 30 and 35%, preferably between 30 and 33%, on a wet basis. If a moisture content of a value greater than these ranges of preferential values could make the starch of the rice grain suitable for being subsequently gelatinized at a substantially understood rate between 80 and 100%, it would nevertheless be liable to lead to a deterioration in the integrity of the rice grain.

The hydration step thus aims to increase the humidity of the rice grain to ensure the most complete gelatinization possible, and advantageously homogeneous, of the starch of the rice grain during the heat treatment step. to which the grain of hydrated rice will then be subjected.

Preferably, said hydration step is carried out by soaking, that is to say by immersion, the grain of rice in water, using a suitable soaking installation. More preferably, said hydration step is carried out by soaking the grain of rice in water at a temperature above room temperature and at atmospheric pressure. Advantageously, the water temperature is at least equal to approximately 50 ° C, and preferably between approximately 55 and 70 ° C.

The precise duration and temperature of the soaking (and more generally, the parameters of the hydration step) are, in practice, chosen and adjusted according to the nature and morphology of the grain of rice used as raw material. For example, for an indica long grain cargo rice grain, hydrated by soaking in a water bath, the rice grain can thus, for example, be soaked for 90 min in water at a temperature of 65 ° C. . In particular, the duration and the temperature of the soaking will be adapted to avoid any gelatinization effect of the rice starch during the hydration step, so that the starch of the hydrated rice grain, obtained at resulting from the hydration step, is not substantially gelatinized.

The soaking step can, alternatively, be carried out at a water temperature lower than the values mentioned above, for example at room temperature (typically around 20-25 ° C) or even at a temperature below ambient temperature. In this case, a much longer soaking time will be necessary to impart the desired moisture content to the grain of rice.

Advantageously, the method according to the invention comprises, after said hydration step, a step of resting the hydrated rice grain, for a predetermined rest time, to balance the humidity in said hydrated rice grain. Typically, said predetermined rest time is at least 30 min. The homogeneity of the gelatinization is thus further promoted starch from the rice grain during the heat treatment step to which the hydrated rice grain will then be subjected. This resting step can be carried out after a prior draining step of the hydrated rice grain or, more preferably, simultaneously with said draining step. Advantageously, said steps of draining and of resting the grain of hydrated rice are both carried out at atmospheric pressure and at room temperature.

The method according to the invention comprises, after said hydration step (and if necessary, also after said resting step), a step of heat treatment of the rice grain, as mentioned above, during from which: the hydrated rice grain obtained at the end of said hydration step is placed in an autoclave (or equivalent device); then, after having closed said autoclave, a flow of steam (preferably saturated) is pressurized within the autoclave and said grain of rice is kept under super atmospheric pressure (ie higher than atmospheric pressure ), at a predefined temperature between 120 and 160 ° C, for a predetermined treatment time between 10 s and 15 min, so as to gelatinize the starch of the rice grain at a rate substantially between 80 and 100%, and preferably substantially equal to 100%.

The term “predefined temperature” is understood here to mean a treatment temperature known in advance and kept substantially constant throughout the predetermined treatment time. The term “predetermined treatment time” is understood to mean a duration defined in advance during which the grain of rice is maintained, within the autoclave, under the aforementioned temperature and pressure conditions.

The heat treatment step of the process according to the invention therefore consists in gelatinizing the starch of the rice grain at a rate substantially between 80 and 100%, preferably greater than 90%, and more preferably substantially equal to 100%. , by subjecting the rice grain to a steam treatment under high temperature, high pressure, for a short treatment time. The fullest possible gelatinization of the rice grain contributes to the strengthening of the structure of the latter, which in particular leads to the production of a treated rice grain which is more resistant to cooking and overcooking.

The gelatinization rate of the starch of the rice grain can be measured by any known method. In particular, the total gelatinization of the starch of a grain of rice treated in accordance with the invention can be observed, for example, by the absence of a motif (“Maltese cross”) of birefringence of the starch particles observable under a polarizing microscope. Another known method for observing the starch transformation of the rice grain consists in exposing the treated rice grain to an alkaline solution (or "alkali test"). A grain of rice whose starch is not gelatinized will retain a substantially intact, opaque white appearance, while a grain of rice whose starch is completely transformed will be attacked by the alkaline solution and made substantially translucent. This method is described in particular in ALI, SZ and BHATTACHARYA, KR, An alkali reaction test for parboiled rice, Lebensmittel Wissenschaft Technologie, 1972, vol. 5 (6), pages 216-218, and in BIENVENIDO O. Juliano, Rice: Chemistry and Technology, American Association of Cereal Chemists, 1985.

While it is generally considered that a high gelatinization rate of the starch of a grain of rice tends to lengthen the final cooking time of the latter, it has been found that the method according to the invention makes it possible to obtain a grain of treated rice capable of being cooked in about 10 min in an excess of water, while having once cooked excellent taste characteristics.

Then, once said predetermined treatment time has elapsed, the grain of rice thus treated is then immediately extracted from the autoclave, to bring the grain of rice treated directly to atmospheric pressure. The rice grain is thus removed from the autoclave as soon as the predetermined treatment time is reached. In other words, the method according to the invention therefore comprises a phase of reducing the pressure exerted on said grain of rice, making it possible to immediately bring the latter from said super-atmospheric treatment pressure to atmospheric pressure, said grain of rice remaining permanently, during said pressure reduction phase, at a pressure greater than or equal to atmospheric pressure. The grain of treated rice is thus thus brought directly to atmospheric pressure, in the sense that it is, in particular, at no time subjected to any intermediate phase of depression during which it would be subjected to a pressure below the atmospheric pressure. This advantageously avoids the risk of mechanical degradation, bursting, of the grain of rice. For the purposes of the invention, “immediately” means the fact that the grain of treated rice is extracted from the autoclave, once said predetermined treatment time has elapsed, rapidly, almost instantaneously. Advantageously, the grain of treated rice thus passes from said super atmospheric pressure of treatment to atmospheric pressure in 1 s to 10 s, preferably in 1 s to 5 s, during its extraction from the autoclave. The reduction of the pressure exerted on the grain of rice is thus appreciably faster than in the case of conventional steaming methods. The reduction, during extraction, of the pressure exerted on said grain of rice, is preferably not specifically controlled. In particular, the reduction of the pressure takes place in a single operation, and not in successive stages of a predefined duration, the variation of the pressure over time is not necessarily linear. Although rapid, the return of the treated rice grain to atmospheric pressure is nevertheless advantageously carried out so as to avoid any phenomenon of self-evaporation of the water and sudden change in the structure of the treated rice grain when it is extracted from the autoclave. Advantageously, the grain of treated rice extracted has, once brought back to atmospheric pressure, a moisture content substantially close to the moisture content that said grain of rice exhibits at the end of said hydration step, and whatever in is preferably less than or equal to 35%. Moist at heart, the grain of rice is advantageously dry to the touch. Typically, the grain of treated rice exhibits, once brought back to atmospheric pressure after extraction from the autoclave, a temperature which still remains greater than or equal to approximately 100 ° C.

It was surprisingly found that the combination of the conditions mentioned above in terms of high pressure, high temperature and short treatment time in the autoclave, and control of the conditions for returning the grain of treated rice pressure allows obtaining a grain of treated rice, which after cooking - and in particular after a short cooking of about 10 min in an excess of water - has organoleptic (and in particular, textural) characteristics quite interesting facts. By immediately removing the grain of treated rice from the autoclave, the risk of continuing heat treatment is reduced, in particular due to the thermal inertia of the autoclave and residual super-atmospheric pressure. The method according to the invention thus allows very good control over the effective treatment time to which the rice grain is subjected. Furthermore, bringing the treated rice grain back to atmospheric pressure while extracting it from the autoclave, and not keeping it in the autoclave, advantageously makes it possible to quickly release the autoclave, so that almost continuously process new grains of rice. This optimizes the rate of implementation of the method according to the invention.

Typically, said heat treatment step of the process according to the invention can be carried out as follows:

- Introducing and positioning the hydrated rice grain inside the autoclave (sealed heating chamber), for example in a basket or at the bottom of the autoclave, then the autoclave is sealed; a pressure water vapor inlet valve is opened, in order to authorize the injection of water vapor into the autoclave in which the hydrated rice grain is positioned; once the conditions of super-atmospheric pressure and predefined temperature are reached (controlled using a suitable probe or sensor), the grain of rice is maintained in the autoclave for the predetermined treatment time. A purge can possibly be maintained throughout the duration of the treatment to evacuate potential condensates. The conditions prevailing in the autoclave are controlled, using any known means, so as to keep said superatmospheric pressure and said predefined temperature substantially constant.

- then, when the predefined treatment time has elapsed, an extraction valve or hatch (for example of the pneumatic ball valve type), preferably positioned in the lower part of the autoclave, is opened, to immediately evacuate the grain of rice treated, which thus returns very quickly to atmospheric pressure on leaving the autoclave.

The choice of the ranges of values of said predefined temperature and of said predetermined treatment time will now be explained.

Generally speaking, long processing times and temperatures favor a high gelatinization rate of the starch in the rice grain. However, if the high temperature treatment time is too long, structural damage to the treated rice grains can be observed. This results in obtaining a grain of treated rice which, after cooking, has a degraded texture, less firm and less elastic. When the treatment time is less than 10 s, said heat treatment step becomes relatively complex to implement in practice, in particular in the case of treatment of large quantities of rice grains. In addition, there is a risk of heterogeneity in the gelatinization rate of said rice grains, a part of the grains concerned being capable of not seeing its starch completely gelatinized at the end of the heat treatment step.

The table below compiles the results of measurements of firmness F, elasticity R and uptake of rice grains obtained by the process according to the invention from long grain indica cargo rice grains, and cooked for 10 min in excess boiling water.

Furthermore, it has been observed that, for a given predefined treatment temperature T, the increase in the predetermined treatment time t tends to decrease the Kett index and the clarity Z * of the grain of treated rice obtained. A short predetermined processing time t therefore appears to favor obtaining a high Kett index. The parameters a * and b * evolve in turn upward, when the predetermined treatment time t is increased for a given predefined treatment temperature T. An identical observation was made when, for a predetermined treatment time t given, the predefined treatment temperature T is increased.

The table below, which compiles results of measurements of the whiteness index Kett and of colorimetry L * a * b * of rice grains obtained by means of the process according to the invention from cargo rice grains long grain indica, illustrates these phenomena.

In addition, a negative effect of an increase in the predetermined treatment time t was observed on the rate of breakage, as illustrated by the results compiled in the table below.

Preferably, said predefined temperature is substantially between 130 and 150 ° C. Advantageously, said predetermined processing time is for its part substantially between 30 s and 10 min. Preferably, said superatmospheric pressure corresponds to an absolute pressure of between 2 and 6 bar (ie between 200 and 600 kPa), and more preferably substantially equal to approximately 4 bar (or 400 kPa). If a high pressure, typically greater than 2 bar (in absolute pressure), proves to be rapid and efficient transformation of the starch of the grain of rice, too high a pressure could, in particular in combination with high temperatures, cause undesirable degradation of the grain of rice.

The choice of the precise values of the pressures, predefined temperature T and predetermined treatment time l can also vary, within the ranges of values mentioned above, depending on whether the grain of rice chosen as raw material is a grain of paddy rice or cargo . Indeed, forming a barrier around the heart of the grain, the husk still has paddy rice grain tends to require the application of more severe treatment conditions to the rice grain, in particular in order to obtain the required gelatinization rate.

An optimum in terms of texture of the grain of rice after cooking seems to be advantageously achieved, in particular in the case where the grain of rice used as raw material is a grain of cargo rice, in particular a grain of indica long grain cargo rice, for a predefined temperature substantially between 140 and 150 ° C and a predetermined treatment time substantially between 30 s and 1 min.

Advantageously, the heat treatment step of the process according to the invention is unique, in the sense that it is carried out continuously, all at once, and where it constitutes the only step of the treatment process during which the rice grain is subjected to the combined action of a high pressure and a high temperature with a view to a transformation, a gelatinization, of its starch. The treatment process is thus particularly simple and quick to implement, and any risk of deterioration of the integrity of the rice grain (and therefore of its organoleptic properties) which could arise due to the production of a plurality is avoided. successive heat treatments.

The method according to the invention can be advantageously applied to any type of rice usually used in human and / or animal food. However, said grain of rice is preferably a grain of long rice ("long grain"). It can be a grain of rice called “long B”, typically of the indica species, that is to say a grain of rice with a length greater than or equal to 6 mm (long B), or even greater than 7, with a length to width ratio greater than or equal to 3. Alternatively, it could be a grain of rice called "long A", typically of the japonica species, that is to say a grain of rice with a length greater than 6 mm, with a length to width ratio greater than 2 and less than 3. Indeed, such a long grain of rice is particularly suitable to be subjected to the process according to the invention, its dimensions favoring the interaction with pressurized water vapor during the heat treatment step.

Preferably, the grain of rice concerned by the process according to the invention is a grain of cargo rice. Also known as "whole" or "brown" rice, cargo rice is paddy (or raw) rice which has been hulled to rid it of its husk and its outer husks (or lemmas) inedible members. A grain of cargo rice, however, still has its bran and germ. It has been observed, very interestingly, that the use of a grain of cargo rice as a raw material makes it possible to obtain, by means of the treatment process according to the invention, a grain of parboiled rice which, before cooking, is whiter (and more precisely, less yellow) and which, after cooking, has a more neutral taste, than a grain of parboiled rice which would respectively be obtained from a grain of paddy rice. In addition, the application of the process according to the invention to a grain of cargo rice, rather than to a grain of paddy rice, is more energy efficient, since less severe processing conditions, in terms of time and / or temperature (and possibly in terms of pressure) heat treatment, can be advantageously implemented to obtain in particular the highest possible gelatinization rate. This being the case, it is nevertheless conceivable, although less advantageous, that the grain of rice concerned by the process according to the invention is a grain of paddy rice, as is moreover usually the case with steaming techniques. classics.

The method according to the invention can be advantageously applied to a grain of rice having an amylose content greater than or equal to 20%, and preferably between 22 and 25%. That said, it has surprisingly been observed that it is possible to obtain, by means of the treatment method according to the invention and from a grain of rice with a low amylose content (typically less than 20 %), a grain of rice that has excellent textural characteristics, especially in terms of firmness and elasticity, after final cooking.

Advantageously, the method according to the invention comprises a step of enriching the grain of rice with at least one food substance designed to improve the nutritional and / or organoleptic properties of said grain of rice, that is to say by adding said grain of rice of at least one food substance having a particular nutritional and / or organoleptic function. Said enrichment step is advantageously carried out prior to said heat treatment step, so that the latter entails, by following, the penetration and inclusion of at least a fraction of said substance inside the grain of rice, and more preferably in the albumen, that is to say in the heart, of said grain of rice .

By food substance having a nutritional function, is meant here an edible substance (other than water), capable of ensuring a nutritional function, that is to say a substance including one or more ingredients capable of being used by the organism to satisfy its physiological needs, whether said ingredients are digestible and metabolizable (which is the case, for example, vitamins and minerals) or not (which is the case, for example, ingredients promoting transit intestinal). By food substance having an organoleptic function, is meant here an edible substance (other than water) capable of ensuring an organoleptic function, that is to say having properties perceptible by at least one sensory receptor (taste, odor , color, etc.) at the end consumer of the treated rice grain. Advantageously, the food substance having a nutritional and / or organoleptic function comprises one or more of the following ingredients: nutrients (and in particular vitamins and minerals), flavors. For example, the food substance in question advantageously comprises at least one vitamin, and preferably one or more of the following vitamins: B1, B3, B5, B6 and B9. In a particularly preferred manner, the food substance comprises all of the vitamins B1, B3, B5, B6 and B9 mentioned above, preferably added with minerals and in particular with phosphorus and / or magnesium.

The step of enriching the grain of rice with said food substance having a nutritional and / or organoleptic function advantageously consists in coating the grain of rice with said food substance, preferably so as to coat substantially the entire surface of the grain rice. According to a preferred operating mode, said enrichment step is carried out by spraying said food substance onto said hydrated rice grain, for example using one or more nozzles provided for this purpose. Said food substance can be sprayed in the solid state, in the form of dry powder, or in the liquid state, in concentrated solution. Such a spraying is particularly advantageous in that it makes it possible to quickly and effectively bring the food substance into intimate contact with the rice grain, by producing a substantially uniform covering of said rice grain by the food substance. Alternatively, and although less preferably, the enrichment step may be carried out by mixing the grain of rice with a highly concentrated liquid solution of said food substance. In this case, the grain of rice is for example immersed in a bath formed by or containing said liquid solution, so that after removal of the grain of rice out of the bath a film of said liquid solution remains on the surface of the rice grain. In this sense, said enrichment step can be carried out simultaneously with the soaking step, said food substance being introduced into the soaking water. Advantageously, said at least one food substance will be chosen to be heat-resistant and hydrophilic, and will thus be well suited to the subsequent heat treatment of the hydrated and enriched rice grain.

Thanks to such an enrichment step, it is thus advantageously possible to obtain a grain of rice having a nutritional profile (in particular in terms of content of vitamins and mineral salts and in particular vitamins and minerals) and / or organoleptic (for example , flavoring) improved compared to a traditional treated rice grain, or even an untreated paddy or cargo rice grain.

Advantageously, the method according to the invention comprises, after said heat treatment step, a step of drying the grain of rice treated. This drying step is designed to lower the moisture content of the treated rice grain to a value giving it microbiological stability, preferably to a value equal to 12-13% on a wet basis.

Preferably, said drying step is carried out in a single operation of passing said grain of rice treated in a flow of hot air, the temperature of which is advantageously between 55 and 130 ° C., with an optimum at 95 ° C. for a speed of the hot air flow of 0.9 m / s, typically for around 30 min. Indeed, it has been observed that such a preferential operating method is surprisingly particularly beneficial, both in terms of control of the rate of breaking, as in terms of color (in particular whiteness) of the grain of treated rice obtained (after machining and before cooking) and taste qualities perceived by the consumer after final cooking.

Alternatively, said drying step could nevertheless be carried out in two separate and successive operations, namely: a first rapid drying operation at high temperature (typically greater than or equal to 100 ° C.), designed to rapidly lower the moisture content of the grain rice treated from 32-35% to between 18 and 22% on a wet basis, followed by a second slow drying step at low temperature (typically substantially equal to 55 ° C), designed to allow homogeneous dehydration of the rice grain avoiding the risk of cleavage and breakage of said grain of rice. For example, the first drying step can be carried out at 130-135 ° C for about 7 to 15 min, and the second step can last between 80 and 110 min, or even up to about 6 h, depending on the equipment. drying used.

These two drying methods advantageously allow homogeneous dehydration of the grain of treated rice, limiting the risk of cleavage and breakage of the latter.

Preferably, the method according to the invention comprises a step of machining the treated grain of rice obtained at the end of said heat treatment step. During said machining step, at least one outer shell of the treated rice grain is removed, to obtain a processed and milled rice grain. This machining step can be carried out with conventional means for milling rice. Advantageously, said machining step is applied to the dried rice grain obtained at the end of said drying operation, in particular in the case where, as described above, said drying step is carried out in a single operation passage of said grain of treated rice in a flow of hot air. In the case where the drying step is carried out in two successive drying operations, as proposed as an alternative above, said machining step may advantageously be carried out between said first and second drying operations, and thus be applied to a partially dried rice grain, typically having a residual moisture content substantially between 18 and 22% on a wet basis.

Advantageously, the method according to the invention has no stage of flattening or crushing of the rice grain during which the dimensions of said rice grain would be mechanically modified, in particular to generate microcracking of treated rice grain and to promote setting. in fast water when cooking the latter. The process according to the invention is more advantageously devoid of a step for expanding the grain of rice, which would aim to increase the porosity and decrease the density of the grain of rice. Indeed, taking into account the particular parameters of the treatment method according to the invention, such steps prove to be unnecessary. In addition, in addition to making the process more complex and costly to implement, such steps of flattening and / or expanding the grain of rice are likely to generate a higher rate of breakage.

The invention also relates, as such, to a grain of parboiled rice intended to be cooked by immersion in an excess of water, preferably boiling, before being consumed. Advantageously, it is a grain of rice capable of being cooked in approximately 10 minutes, by immersion in an excess of preferably boiling water. Advantageously, said grain of parboiled rice is a grain of rice which has been obtained by treatment of a grain of paddy or cargo rice in accordance with the treatment process according to the invention described above. This being the case, it nevertheless remains conceivable that the grain of rice according to the invention can be obtained using a different treatment process.

Preferably, the grain of rice according to the invention is a grain of dry rice, which preferably has, before cooking, a moisture content less than or equal to 12-13% on a wet basis.

Preferably, the grain of rice according to the invention is a long grain of rice ("long grain"). It can be a grain of rice called “long B”, typically of the indica species, that is to say a grain of rice with a length greater than 6 mm (long B), or even greater. to 7, with a length to width ratio greater than or equal to 3. Alternatively, it could be a grain of rice called "long A", typically of the japonica species, that is to say a grain rice of a length greater than or equal to 6 mm, with a length to width ratio greater than 2 and less than 3 (said lengths and widths being measured before cooking said grain of rice, and therefore on a grain of raw rice). Indeed, in addition to the fact that they contribute to a rapid and uniform cooking of the grain of rice, such dimensions are particularly well appreciated, from a visual point of view, by the consumer. In addition, such a long grain of rice has the advantage of generally advantageously retaining its general shape and its dimensional ratio during cooking.

The grain of rice according to the invention has, before cooking, a starch with a gelatinization rate substantially between 80 and 100%, preferably greater than 90%, and more preferably substantially equal to 100%. It also has, after cooking by immersion in an excess of preferably boiling water for approximately 10 minutes, and according to the characterization method described previously in connection with the process according to the invention: a firmness F such that:

£ 45 £ 55

an elasticity R (elastic recovery) such that

40 <R £ 55 Organoleptic comparative tests, organized with a panel of 180 consumers of parboiled rice, have shown that such a pair of firmness F and elasticity R values gives the grain of rice a particularly appreciated texture in the mouth. An optimum even seems advantageously reached when the grain of rice has a firmness F and an elasticity R such that:

£ 46 F £ 52

£ 40 R <52

Preferably, the grain of rice according to the invention also has, after cooking by immersion in an excess of water, a water intake of between 130 and 150% on a wet basis, and preferably between 135 and 145% . Such a level of water intake, higher than what is usually found in parboiled rice, contributes in particular to obtaining a grain of cooked rice which is particularly soft.

Advantageously, the grain of rice according to the invention is a milled grain of rice, that is to say a grain of rice which, initially in the paddy or cargo state, was the subject of at least one step machining, such as that described above in connection with the method of the invention, during which at least one outer casing of the grain of rice has been removed. Typically, such a grain of milled rice is devoid of husks, lemmas, pericarp, integuments and germ.

Even more advantageously, said grain of rice has, before cooking, a whiteness index greater than or equal to 28 Kett, preferably greater than or equal to 30 Kett, more preferably still greater than or equal to 35 Kett.

Still before cooking, said grain of rice preferably has, and as measured using a colorimeter in the chromatic space L * a * b * CIELAB: clarity L * such that L * is greater than or equal to 67 , 0 a parameter a * such that a * is less than or equal to 2.5, and preferably such that a * is less than or equal to 2.3

- a parameter b * such that b * is less than or equal to 24.0, and preferably such that b * is less than or equal to 22.5. These whiteness and color index parameters can advantageously be measured using the corresponding methods and equipment which have been previously described in connection with the method according to the invention.

The rice grain according to the invention is thus whiter, less colored, than conventional parboiled rice grains, in particular those capable of cooking in 10 minutes. This advantage was clearly identified by the consumer panel mentioned above, during comparative organoleptic tests.

A grain of rice according to the invention, having such properties can, for example, be obtained by subjecting indica “long B” cargo rice of variety CL26 to a treatment process in accordance with the invention, including the treatment step Thermal is advantageously carried out at a super atmospheric pressure of approximately 4 bar (in absolute pressure), at a predefined treatment temperature of 143 ° C., and during a predetermined treatment time of 30 s.

Before cooking, the grain of rice thus treated typically has the following colorimetric properties:

After cooking by immersion in an excess of preferably boiling water for approximately 10 minutes, said grain of rice taken as an example has the following textural properties (on average):

In comparison, the same grain of indica "long B" cargo rice of variety CL26, this time subjected to a conventional treatment process (not in accordance with the invention) comprising a steaming step carried out at a temperature between 1 10 ° C and 115 ° C, for 10 to 15 min, then dried, has the following colorimetric properties before cooking (on average):

When cooked by immersion in an excess of preferably boiling water for about 10 minutes, the classic grain of rice has the following textural properties (on average):

In organoleptic tests, conventional parboiled rice is judged to be firmer and more elastic on the one hand, and much less white on the other hand, than the rice according to the invention, which therefore wins the preference of testers.

POSSIBILITY OF INDUSTRIAL APPLICATION

The invention finds its application in the food industry, and more specifically in the field of methods of treating rice grains intended for human or animal consumption, and in the field of treated rice grains intended to be cooked later, before being consumed by an end consumer.

Claims

1. Process for processing a grain of paddy or cargo rice, comprising the following successive steps:

a heat treatment step during which

said grain of hydrated rice is placed in an autoclave;

ii. a stream of pressurized steam is injected into the autoclave and said rice grain is kept under super atmospheric pressure, at a predefined temperature between 120 and 160 ° C., for a predetermined treatment time included between 10 s and 15 min, so as to gelatinize the starch of the rice grain at a rate substantially between 80 and 100%, and preferably substantially equal to 100%;

iii. then, after the said predetermined treatment time has elapsed, the grain of rice thus treated is immediately extracted from the autoclave, to bring the grain of rice treated directly to atmospheric pressure.

2. Method according to the preceding claim, wherein said predefined temperature is substantially between 130 and 150 ° C.

3. Method according to any one of the preceding claims, in which said predetermined treatment time is between 30 s and 10 min.

4. Method according to claims 2 and 3, wherein said predefined temperature is between 140 and 150 ° C, said predetermined treatment time being between 30 s and 1 min.

5. Method according to any one of the preceding claims, in which said superatmospheric pressure corresponds to an absolute pressure of between 2 and 6 bar, preferably substantially equal to approximately 4 bar.

6. Method according to any one of the preceding claims, in which said grain of treated rice passes from said super atmospheric pressure to atmospheric pressure in 1 s to 10 s, preferably in 1 s to 5 s, during the extracting the treated rice grain from the autoclave.

7. Method according to any one of the preceding claims, in which said grain of rice is a grain of cargo rice.

8. Method according to any one of the preceding claims, wherein said hydration step is carried out by soaking the grain of rice in water at a temperature above room temperature and at atmospheric pressure.

9. Method according to any one of the preceding claims, which method comprises, prior to said heat treatment step, a step of enriching the grain of rice with at least one food substance designed to improve the nutritional and / or organoleptic properties of said grain of rice, preferably by spraying said substance onto said grain of hydrated rice.

10. Method according to any one of the preceding claims, which method comprises, after said hydration step, a step of resting the grain of hydrated rice, for a predetermined rest time, to balance the moisture in said grain hydrated rice.

11. Method according to any one of the preceding claims, characterized in that it comprises, after said heat treatment step, a step of drying the treated rice grain to reduce the moisture content of the treated rice grain to a value giving it microbiological stability, preferably at a value equal to 12-13% on a wet basis.

12. Method according to the preceding claim, wherein said drying step is carried out in a single operation of passing said grain of rice treated in a flow of hot air, the temperature of which is between 55 and 130 ° C, and preferably equal to 95 ° C for a speed of said hot air flow of 0.9 m / s.

13. The method of claim 11 or 12, which method comprises a step of machining the dried rice grain obtained at the end of said drying operation, to obtain a processed and milled rice grain.

14. Parboiled rice grain and intended to be cooked by immersion in an excess of water before being consumed, which rice grain has:

before cooking, a starch with a gelatinization rate substantially between 80 and 100%, and preferably substantially equal to 100%, and

after cooking by immersion in excess water for about 10 minutes:

/ ^' . firmness F such that ii. an elasticity R such that

where ei represents the thickness of the grain of cooked rice after application to said grain of cooked rice of a compression force under a load of 700 g for 40 s, E is the initial thickness of the grain of cooked rice before the application of the compression force, and ei represents the thickness of the grain of cooked rice measured 20 s after the application of the compression force has stopped.

15. Rice grain according to the preceding claim, which grain of rice has: a firmness F is such that:

46 <F £ 52 an elasticity R is such that:

40 <R <52

16. Rice grain according to claim 14 or 15, which grain of rice has, after cooking, a water intake of between 130 and 150% on a wet basis, preferably between 135 and 145%.

17. Rice grain according to any one of claims 14 to 16, which grain of rice has, before cooking, a moisture content substantially less than or equal to 12-13% in wet basis.

18. Rice grain according to any one of claims 14 to 17, characterized in that it is a long grain of rice, of a length substantially greater than or equal to 6 mm before cooking, with a length to width ratio greater or equal to 3 or a length to width ratio greater than 2 and less than 3.

19. Rice grain according to any one of claims 14 to 18, characterized in that it is a grain of milled rice.

20. Rice grain according to the preceding claim, characterized in that, before cooking, a whiteness index greater than or equal to 28 Kett, preferably greater than or equal to 30 Kett, more preferably still greater than or equal to 35 Kett .

21. Rice grain according to claim 19 or 20, characterized in that it exhibits, before cooking, as measured using a colorimeter in the chromatic space L * a * b * CIELAB: clarity L * such that L * is greater than or equal to 67.0 a parameter a * such that a * is less than or equal to 2.5, and preferably such that a * is less than or equal to 2.3 a parameter b * such that b * is less than or equal to 24.0, and preferably such that b * is less than or equal to 22.5.