Process for producing a quick-cooking grain food product

Abstract

A process for producing a quick-cooking grain food product comprises a step of imbibing with water the pre-arranged grain food product by means of nebulisation, which ends when the grain food product has an average moisture content of 17% - 19%. The product rests while moving in a closed environment preferably for a period of time ranging from one to six hours and is pre-cooked inside a cooking chamber of a rotating batch-type autoclave (4) into which saturated vapour is injected at a pre-cooking pressure of 3-5 bar (300000 - 500000 Pa) and at a maximum temperature of 165°C while the autoclave (4) is set in rotation. When finished, the product has an average moisture content of 22% - 24%.

Description

[0001] PROCESS FOR PRODUCING A QUICK-COOKING GRAIN FOOD

[0002] PRODUCT

[0003] DESCRIPTION

[0004] The present invention relates to a process for producing a quick-cooking grain food product, in particular consisting in a cereal or a legume.

[0005] Starch, consisting of amylose (linear polymer of glucose) and amylopectin (branched polymer of glucose), is a complex water insoluble polysaccharide. It is present in large amounts in cereals and legumes, in crystalline form, within the cytoplasm.

[0006] For the starch in the grains to become digestible, it must lose its crystalline and ordered structure and switch to a disordered structure having the characteristics of a gel (gelatinisation).

[0007] The gelatinisation process of starch takes place by means of heating in an aqueous environment. With sufficient moisture and temperature, the grains gradually swell and the starch loses its crystalline structure; amylose and amylopectin enter the solution, forming bonds with water molecules.

[0008] Following gelatinisation, the amylose and amylopectin chains become exposed to the hydrolytic action of digestive enzymes, and this process is necessary to promote the metabolic utilisation of the starch contained in food.

[0009] Cooling promotes the restoration of the ordered structure resulting in starch “recrystallisation or retrogradation”.

[0010] Several processes are known for producing a quick-cooking grain food product in which the product, particularly rice, undergoes a gelatinisation process.

[0011] Among modern technologies, parboiling is certainly the most common.

[0012] According to known techniques, parboiling basically involves three steps: maceration up to about 30% moisture, cooking up to 34-36 % moisture and drying up to 12% moisture. Known maceration systems comprise a step of preparing water in a tank provided with pH and temperature control. The maceration tanks are provided with a water recirculation system, with integration thereof to compensate for the water absorbed, and a recirculation water temperature control to obtain a constant temperature. The temperature of the water is always lower than the gelatinisation temperature of the product, in order to control swelling of the grains which, in the case of bracted cereals, would cause the husk to open.

[0013] Known cooking systems involve, after maceration, the passage into a pressure-tight autoclave. The autoclave can be of various types including: continuous vertical, continuous mat or batch autoclave.

[0014] Conventional quick-cooking parboiling techniques, however, are still very expensive in terms of energy and water consumption.

[0015] In fact, in traditional parboiling processes, about 1 ,200 litres of water are used to macerate one tonne of rice, which is very expensive, especially considering waste water purification and disposal treatments.

[0016] On the other hand, with the new, increasingly restrictive environmental protection regulations, the price for these types of processes is constantly rising.

[0017] Another important aspect is the total consumption of electrical energy and thermal energy required to achieve, by means of the drying process, the correct moisture content of the grain.

[0018] In addition to conventional techniques, Patent Application WO201 5 / 033053 A1 (Benoit Jean-Louis) discloses a process for the pretreatment of cereals, in particular rice, wherein the product is placed in an autoclave without preliminary soaking.

[0019] Once the autoclave is filled and closed, the grain undergoes a treatment cycle in which vapour is injected at a pressure of 6-10 bar (600000-10000 Pa) and a temperature of 140°C - 190°C for a period of time of 5-40 seconds, preferably 20 seconds. Once the vapour relief valve is opened, a vacuum is applied in the autoclave chamber for a period of 10-90 seconds. WO201 5 / 033053 A1 also further discloses an additional step consisting in drying to bring the moisture content of the grain back to about 14%.

[0020] Despite reducing the amount of water required, the process disclosed in WO201 5 / 033053 A1 requires a high consumption of energy in order to reach the pressures indicated inside the autoclave and, precisely because of the pressures reached, it risks compromising the physical and organoleptic characteristics of the grain.

[0021] In this context, the technical task underlying the present invention is to propose a process for producing a quick-cooking grain food product that overcomes at least some of the drawbacks of the prior art mentioned above.

[0022] In particular, the object of the present invention is to make available a process for producing a quick-cooking grain food product that makes it possible to substantially save water, thermal and electrical energy consumption, achieving a reduction in cooking time without compromising the physical integrity and appearance of the grain.

[0023] The defined technical task and the specified objects are substantially achieved by a process for producing a quick-cooking grain food product comprising the technical characteristics set forth in one or more of the appended claims. The dependent claims, herein incorporated for reference, correspond to possible different embodiments of the invention.

[0024] Further characteristics and advantages of the present invention will become more apparent from the approximate and thus non-limiting description of a preferred, but not exclusive, embodiment of a process for producing a quick-cooking grain food product.

[0025] This description will be set forth hereinbelow with reference to Figure 1 , which is provided for merely illustrative and therefore non-limiting purposes, and which represents a schematic view of a possible plant 1 for producing a quick-cooking grain food product comprising an imbibition apparatus 2, a rest apparatus 3 and an autoclave 4 of the batch type with a vapour input device 4a. Plant variants, differing from what shown, are possible.

[0026] The grain food product can be a cereal, e.g. rice, or a legume.

[0027] The plant is configured to implement a process for producing a quickcooking grain food product according to the present invention.

[0028] According to this process, the grain food product is pre-arranged to undergo an imbibition step with water.

[0029] If the imbibition apparatus 2 is used, the product preferably consisting in a cereal is introduced into the imbibition apparatus 2 to undergo the imbibition step.

[0030] Alternatively, the imbibition apparatus 2 is not provided and the product, preferably consisting in a legume, is introduced directly into the autoclave 4 to undergo the imbibition step.

[0031] The imbibition step takes place by means of nebulisation and ends when the grain food product has an average moisture content of 17% - 19%, preferably of about 18%.

[0032] Saturated water vapour at atmospheric pressure and water are preferably nebulised during the imbibition step.

[0033] During the imbibition step, the product is kept at a temperature lower than the gelatinisation temperature of the product itself, preferably at a temperature 2-4° C lower than the gelatinisation temperature of the product itself.

[0034] The imbibition step has a duration ranging from 90-300 seconds, preferably 90-120 seconds to reach the indicated moisture content.

[0035] The imbibition apparatus 2, if present, is preferably of the vertical type with handling of the raw material by means of helicoids and is preferably configured so that the product is loaded from below at an inlet 2a of the imbibition apparatus 2. In this case, the plant 1 preferably comprises a feed silo “S” and a conveyor screw “C” connecting the feed silo “S” to the imbibition apparatus 2 at the inlet 2a. The imbibition apparatus 2 is also preferably configured so that the product is discharged from above at an outlet 2b. The imbibition apparatus 2 preferably comprises a central shaft 5. Even more preferably, a plurality of atomising nozzles 6 are positioned on the central shaft 5. Furthermore, the imbibition apparatus 2 is rotating, driven by the central shaft 5, and is preferably set in rotation so that moisture is continuously absorbed by the product. Vapour and water are mixed and atomised by the plurality of nozzles 6 so as to create a sort of dew.

[0036] If the imbibition apparatus 2 is not provided, the atomising nozzles are arranged inside the autoclave 4.

[0037] In the process described, the amount of water required to imbibe approximately one tonne of product is only 120 litres, compared to the 1200 litres of water used in traditional maceration processes.

[0038] In addition, it is advantageously possible to treat condensation water, resulting from imbibition, with an osmotic process. During the osmotic process, the condensation water is purified and recirculated, greatly reducing the amount of waste.

[0039] The overall reduction of water use and its disposal cost is therefore evident.

[0040] Waste water from traditional maceration processes in fact requires purification treatments that, in compliance with the latest restrictive environmental protection regulations, entail cost increases.

[0041] After the imbibition step, a rest step is provided to allow water to penetrate to the core of the grains. During the rest step, the product is kept moving in a closed environment. Preferably the duration of the rest step ranges from one to six hours, preferably from one to three hours.

[0042] Preferably during the rest step, the temperature is kept substantially constant and preferably at 50-70°C, even more preferably at 60°C, however lower than the gelatinisation temperature. It is possible, by keeping the temperature constant (thus preventing the temperature from dropping), to avoid condensation and drying phenomena.

[0043] During the rest step, excess moisture is expelled from the closed environment in a controlled manner based on the detection of the temperature and moisture in the closed environment and based on the moisture detection of the product.

[0044] The closed environment may be formed by means of the rest apparatus 3 comprising a plurality of conveyor belts 30, preferably comprising eight conveyor belts 30.

[0045] The product preferably consisting in a cereal is loaded into the rest apparatus 3 from above at an inlet 3a and is moved by means of an upper conveyor belt 30a of the plurality of conveyor belts 30.

[0046] At the end of the rest step, the product exits from below the rest apparatus 3 at an outlet 3b by means of a lower conveyor belt 30b of the plurality of conveyor belts 30.

[0047] The conveyor belts 30 are positioned in parallel on different planes of the height of the closed environment in a staggered manner and are moved in such a way that the product falls from one conveyor belt onto the conveyor belt immediately below. Advantageously, the closed environment and preferably the rest apparatus 3 comprises one or more fans for introducing warm air. Fans are preferably arranged vertically on both sides of the rest apparatus 3.

[0048] The conveyor belts 30 are perforated and advantageously closed at the sides, so as to let air in from the outside and limit the loss of moisture from the product. In fact, if air were to come into contact with the product, evaporation phenomena would occur, whereas the purpose of this step is to keep the product in a warm environment, so as to allow the homogeneous redistribution of moisture between the grains and within each individual grain.

[0049] During the rest step, the product is continuously transported by conveyor belts 30 within the rest apparatus 3, preferably passing up to eight times between the upper belt 30a and the lower belt 30b, so as to ensure a moving rest and the consequent process uniformity on the product.

[0050] Alternatively, the closed environment can be formed by the autoclave 4. The product preferably consisting in a legume remains in the autoclave 4 for the rest step by keeping the autoclave rotating.

[0051] After the rest step, the product undergoes a pre-cooking step with saturated vapour at a pre-cooking pressure of 3-5 bar (300000-500000 Pa) and a maximum temperature of 165°C inside the autoclave 4 set in rotation. The pre-cooking step ends when the grain food product has an average moisture content of 22% - 24%.

[0052] During this pre-cooking step, the maximum pre-cooking pressure is reached in about 30-40 seconds and held constant for 2-5 minutes. Pressure relief then lasts for approximately 30-40 seconds, preferably until the pressure inside the autoclave 4 is restored to the atmospheric pressure by discharging vapour through a relief valve. In this case as well, condensation can be recovered and treated by osmotic treatment.

[0053] The pressure will then quickly return to atmospheric pressure (101325 Pa). The sudden drop in pressure causes a porosity of the grains in combination with a change in the starch structure. After cooling, it can be noted that the amylose contained in the grains has an elongated chain structure with the formation of pores and micro-channels extending from the surface pores. These channels facilitate the exchange of water to and from the starch granules, enabling rapid cooking in just 10 minutes.

[0054] It is possible, by setting the process parameters in the imbibition step and the pre-cooking step, to adjust the grain consistency, resulting in a softer or firmer product.

[0055] Preferably the rotating autoclave 4 is made of stainless steel and consists of a cooking chamber and a gap, both fed with saturated vapour. The autoclave comprises probes for detecting process temperatures and pressures, a product imbibition system and a vacuum system for the drying process (first sub-step of autoclave drying). In addition, the autoclave allows to adjust various parameters including time, temperature, pressure, amount of vapour, amount of water, speed of rotation.

[0056] Product handling is also ensured by an inner helical structure, which improves the homogeneity of treatment during the processes. Resistance to high pressures and temperatures is ensured by mechanical seals and / or packings and wall expanders. Inside the autoclave, in the cooking chamber, there is a manifold provided with nozzles, which allow the amount of liquid to be calibrated, particularly on leguminous products. In addition, the cooking chamber may comprise a system provided with coils that allow a more homogeneous distribution of heat within the mass of product, also performing an important mixing action thereof.

[0057] The cooking chamber is maintained at a constant temperature, also thanks to the presence of the outer jacket, into which the heating vapour is conveyed. The presence of the jacket allows easy control of the first drying sub-step, using more heat during the early drying steps and reducing the intensity of treatment progressively until the desired moisture level is reached.

[0058] The vacuum drying process, performed inside the autoclave, ensures an efficient result by using a special pump which allows to remove the air and moisture present in the chamber. The vacuum allows to speed up the drying process and also allows temperatures that are not too high to be used, preserving the nutritional value of the processed food.

[0059] Advantageously, a drying step subsequent to the pre-drying step may be provided, wherein preferably the drying step comprises at least a first drying sub-step carried out at a first drying temperature and, thereafter, a second drying sub-step carried out at a second drying temperature other than the first drying temperature, preferably lower than the first drying temperature.

[0060] Preferably, the first drying sub-step is followed by a first cooling step in which the product is brought to room temperature. This cooling allows the fat materials contained in the husks or bran not to stick to the grains during scraping or light refining.

[0061] The drying step is very fast and requires little consumption of thermal energy since the product is at a maximum of 24% moisture when leaving the autoclave 4, instead of 34% as in traditional processes. Preferably, the drying step (or at least the first drying sub-step) is performed inside the autoclave 4 by introducing vapour in a controlled manner inside a jacket surrounding the cooking chamber to control the drying temperature of the product until the grain food product has an average moisture content of about 16-18%. In this case, the first drying sub-step can be performed under vacuum.

[0062] Alternatively, the system can comprise a fluidised bed dryer 7a in which the first drying sub-step is performed at an air temperature of 120-150°C, preferably for 5-20 minutes, even more preferably for 10 minutes, until the grain food product has an average moisture content of about 16-18%. The core of the grain has a higher moisture content than the average content while the surface layers have a lower moisture content than the average content, e.g. around 8-10%. The body of the grain is flexible.

[0063] The second drying sub-step can be performed by radio frequency until the grain food product has an average moisture content of 12-14%.

[0064] Alternatively, the second drying sub-step can be performed in the autoclave, preferably operating under vacuum and controlling the temperatures by introducing vapour into the outer jacket of the autoclave.

[0065] Alternatively, the second drying sub-step can be performed using an additional fluidised bed dryer 7b until the grain food product has an average moisture content of 12-14%. The air temperature is preferably of about 45°C and the duration of the second drying sub-step is preferably of about 20 minutes.

[0066] Advantageously, fluidised bed dryers comprise vibrating plates 8 to facilitate the drying step. Fluidised bed dryers advantageously comprise ventilation, air emission and suction systems.

[0067] Between the first and second drying sub-steps, there may be a dehulling or light refining step to remove the husk that encloses the bracted grains i.e. barley, oats, rice and wheat. This is done, for example, with counterrotating rubber rollers, with vertical rice or corn refiners, with stone discs. A single pass is made for cracking or two passes for light refining, followed by a pass in a horizontal water cleaner to make the grains clean and shiny. After refining, the centre of the grain is moist while the surface is dry. For this reason, it is preferable to perform the second drying sub-step using radio frequency so that drying takes place by rubbing between the water molecules and starts from the wettest region, then from the centre towards the surface. In this way, the centre of the grain gradually dries out, until it reaches a uniform moisture content of 12-14% in all the grains.

[0068] The second drying sub-step is preferably followed by a second cooling step wherein the product is brought to room temperature.

[0069] The process according to the invention is able to balance on the one hand the result in terms of product quality and on the other hand the need to reduce energy and water consumption by providing an imbibition step by means of nebulisation, a rest step while moving and a pre-cooking (gelatinisation) step in a batch autoclave 4 at a pressure of 3-5 bar.

[0070] As explained above, costs in the use of thermal energy are reduced mainly during the drying step, because the grains have a moisture content of 24% and not 34-36%, as is the case in traditional processes. The drying process is much faster and uses fewer calories.

[0071] As explained above, the amount of water required for imbibition of the grains is only 120 litres per tonne of product. All condensation water, or water from the amount used in imbibition, is treated by an osmotic process, purified and returned to circulation. For these reasons, there is only a very small amount of waste.

[0072] The entire process has an electrical energy consumption 30-40% lower than a conventional parboiling process. Savings result in particular from reduced imbibition, gelatinisation and drying times.

[0073] This does not affect the quality of the product obtained, in particular the reduction in cooking time. Cooking of the rice is achieved after only 10 minutes, with no need for further treatment thanks to the pre-cooking step at 3-5 bar with a quick return to atmospheric pressure, during which the starch structure of the grain is changed, allowing faster hydration. In fact, the product obtained has a typical colour and taste, without being negatively affected by the pre-cooking process, which, in the abovedescribed embodiment applied to cereals, does not allow the pentoses contained in the husk to migrate.

[0074] In the case of rice, the peculiar characteristics of the product at the end of the process are: a light colour of the rice grain; a taste and smell typical of natural rice; a non-gummy texture of the grain.

[0075] Furthermore, the process described is very flexible and allows to produce a customised product according to user specifications.

[0076] The recommended cooking time of 10 minutes for rice is preferred in Europe; whereas cooking time of 12 minutes is more popular in the USA. This variability is achieved by appropriately controlling the duration of the autoclave treatment (maintaining pre-cooking pressure).

[0077] It is further possible to carry out a fortification by including added substances in the grains.

[0078] Before the second drying step, an amount of 2-4% of water can be added, mixed with fortification substances such as fibre, minerals and vitamins. The aqueous solution can be micronised and sprayed onto the product in a rotating cylinder. Afterwards, a rest step of 15-20 minutes is preferably provided, during which the mixture is absorbed into the grains. Thus, fortification does not take place by surface covering but by inclusion, avoiding dispersion during home cooking. Subsequently, the second drying sub-step is performed.

[0079] If necessary, it is possible to obtain ancient grains and legumes with cooking times of 5 minutes or instantaneous, subjecting the products to a process chosen between extrusion, chemical treatment, rolling and expansion, preferably hot air expansion without rolling. In this process, cereals or legumes with a moisture content of 18%, after the first sub-step of drying and dehulling / refining, are subjected to a current of hot air at 180-260°C for 25-35 seconds, depending on the product and the desired cooking time: 5 minutes or instant. The equipment is a fluidised bed wherein the product is in suspension and is not damaged by heat from contact with the underlying perforated metal sheet.

Claims

CLAIMS1 . Process for producing a quick-cooking grain food product comprising:- a step of pre-arranging a grain food product consisting of a cereal or a legume,- a step of imbibing with water the pre-arranged grain food product, wherein the imbibition step is carried out by means of nebulisation and ends when the grain food product has an average moisture content of 17% - 19%, preferably of about 18%,- a rest step wherein the imbibed grain food product is kept moving in a closed environment preferably for a period of time ranging from one to six hours,- a pre-cooking step wherein saturated vapour at a pre-cooking pressure of 3 - 5 bar (300000 - 500000 Pa) and at a maximum temperature of 165°C is injected into a cooking chamber of a rotating batch-type autoclave (4) containing the grain food product, while the autoclave (4) is set in rotation and wherein the pre-cooking step ends when the grain food product has an average moisture content of 22% - 24%.

2. Process for producing a quick-cooking grain food product according to claim 1 , wherein saturated water vapour at atmospheric pressure and water are nebulised during the imbibition step.

3. Process for producing a quick-cooking grain food product according to claim 1 or 2, wherein a pre-arranged grain food product is introduced inside a rotating imbibition apparatus (2) preferably driven by a central shaft (5) on which nebulising nozzles (6) are placed, wherein the imbibition step is carried out inside the imbibition apparatus (2) and wherein the grain food product preferably consists in a cereal.

4. Process for producing a quick-cooking grain food product according to claim 1 or 2, wherein the pre-arranged grain food product is introducedinside the autoclave (4), wherein the imbibition step is carried out inside the autoclave (4) and wherein the grain food product preferably consists in a legume.

5. Process for producing a quick-cooking grain food product according to one or more of the preceding claims, wherein during the imbibition step the grain food product is maintained at a temperature below the gelatinisation temperature of the product, preferably at a temperature of 2-4 °C below the gelatinisation temperature of the product.

6. Process for producing a quick-cooking grain food product according to one or more of the preceding claims, wherein the imbibition step has a duration ranging from 90 to 300 seconds, preferably of 90-120 seconds.

7. Process for producing a quick-cooking grain food product according to one or more of the preceding claims, wherein during the rest step the closed environment is maintained at a temperature of 50°C - 70°C, preferably of 60°C and / or wherein during the rest step, the exceeding moisture is expelled from the closed environment in a controlled manner based on the detected temperature and moisture of the closed environment and based on the detected moisture of the product.

8. Process for producing a quick-cooking grain food product according to one or more of the preceding claims, wherein the rest step takes place in a rest apparatus (3) defining the closed environment within which conveyor belts (30) are provided for handling the grain food product and wherein the grain food product preferably consists in a cereal.

9. Process for producing a quick-cooking grain food product according to one or more of claims 1 to 7, wherein the rest step takes place in the autoclave (4) defining the closed environment, maintaining the rotation ofthe autoclave itself, and wherein the grain food product preferably consists in a legume.

10. Process for producing a quick-cooking grain food product according to one or more of the preceding claims, wherein in the pre-cooking step the maximum pre-cooking pressure is reached in about 30-40 seconds, is maintained for 2-5 minutes and then the discharge back to the atmospheric pressure takes place in about 30-40 seconds.11 . Process for producing a quick-cooking grain food product according to one or more of the preceding claims, comprising a drying step subsequent to the pre-cooking step comprising at least a first drying sub-step carried out at a first drying temperature, and subsequently, a second drying substep carried out at a second drying temperature different from the first drying temperature, preferably lower than the first drying temperature, wherein a first cooling step wherein the product is brought to room temperature is preferably carried out between the first drying sub-step and the second drying sub-step.

12. Process for producing a quick-cooking grain food product according to claim 11 , wherein the first drying sub-step is performed within the autoclave (4) by introducing vapour in a controlled manner within a jacket surrounding the cooking chamber to control the drying temperature of the product until the grain food product has an average moisture content of about 16-18%.

13. Process for producing a quick-cooking grain food product according to claim 11 , wherein the first drying sub-step is performed in a fluidised bed dryer (7a) at an air temperature of 120-150°C, preferably for 5-20 minutes, even more preferably for 10 minutes, until the grain food product has an average moisture content of about 16-18%.

14. Process for producing a quick-cooking grain food product according to one or more of claims 11 to 13, wherein the second drying sub-step is performed by radio frequency or in an additional fluidised bed dryer (7b), until the grain food product has an average moisture content of 12-14%, and wherein the second drying sub-step is preferably followed by a second cooling step wherein the product is brought to room temperature.

15. Process for producing a quick-cooking grain food product according to one or more of the preceding claims, comprising a step of treating, with an osmotic process, condensation water resulting from the imbibition step and a step of re-circulating the condensation water subjected to the osmotic process.

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