WO2013021325A1

WO2013021325A1 - Methods and devices for cooking food

Info

Publication number: WO2013021325A1
Application number: PCT/IB2012/053970
Authority: WO
Inventors: Jingwei Tan; Qi Zhou; Eng Cheng KHAW
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2011-08-05
Filing date: 2012-08-02
Publication date: 2013-02-14

Abstract

The invention provides a method and a device for cooking food. The device for cooking food comprises: a first container (100) for containing food and water; a first unit (101) for obtaining information related to the food; a first heater (102) for heating the food and the water in the first container; and a second unit (103) for applying steam to the food according to the information, during the process of heating the food and the water. By means of the device of the invention, the physical and chemical changes of the food being cooked in water may be adjusted during the cooking process, so that the cooked food obtained can meet different requirements.

Description

METHODS AND DEVICES FOR COOKING FOOD

Technical field

The present invention relates to kitchenware, and particularly to food cookers.

Background of the invention

Rice is a common staple food in East Asia. Nowadays various automatic rice cookers are commercially available. Japan Patent Application with Publication Number 2006-110127 discloses a rice cooker, including a pot, a lid, a pot heating means that heats the pan, a steam generation means for generating steam, and a high-pressure means for applying high pressure to the steam generated by the steam generation means. The high pressure steam is applied to the rice in the pan for heating the rice when the water in the pan is exhausted. The high pressure steam can arrive at the bottom of the pan through the crevices between boiled rice grains, and spreads uniformly over the top surface of boiled rice and rice near the bottom of the pan, thereby solving the technical problem of preventing the boiled rice near the bottom getting burnt.

Summary of the invention

The cooking of starch-rich food, for example rice, is a complex progressive process. Starch is present in rice grains in two forms: amylose (straight-chain polysaccharide) and amylopectin (branched polysaccharide). Amylose and amylopectin react differently with water during the heating process, due to their structural difference, which leads to three phenomena, namely:

a) Amylose leach-out (from the rice grain): When rice is soaked in water, amylose, with its straight-chain structure, will leach out from the grain, whereas amylopectin will not.

b) Amylose pasting (in the rice-solute): When amylose is heated in water, it will form longer and more complex chains and it will reduce the viscosity of the rice solute. c) Amylopectin water-absorption (in the rice grain): As the heating step progresses, the branch-chain of amylopectin will be opened up and absorb the water molecules by weak bonding between its hydroxyl stems.

All these three phenomena take place concurrently, but they have individual peak moments, according to temperature and water conditions. At a fixed water dose and an ascending temperature, amylose leach-out will reach its peak at around 60degC, and will slow down as the solute becomes saturated. Pasting will reach its peak at around 70degC, as the amylose chains will start to mutually attract each other and affect the viscosity of the rice-solute. As the temperature increases, however, the effect of amylopectin water-absorption will prevail, as the branch-chains of the grain will open up and attract more water molecules. The rice grain will eventually absorb all the water and become swollen and tender.

The physical and chemical changes of rice grains due to these three phenomena will eventually contribute to a different sensory character of cooked rice. The sensory character of cooked rice comprises texture, taste, appearance and aroma. The dose of water, the temperature and the timing are key factors in determining the impact of these three phenomena.

As water is present in the cooking process in the form of liquid and vapor, the proportion of both forms (vapor and liquid) will have an impact on the quality of the cooked rice. For example: in the conventional stewing-only approach (in which only water is provided in the rice cooking process), the proportion of grain:water:vapour (typically Japonica short-grain rice) is 1 : 1.2:0, and these ingredients are successively soaked for 20 minutes, after which the temperature is increased for 5 minutes, and then boiled for 20 minutes, thereby increasing the water content of the cooked rice to 60-62%. To achieve a similar level of water content of the cooked rice in the case of a hybrid stew-steam approach (hybrid stew-steam approach means that both water and steam are applied in the rice cooking process), a typical proportion by weight of grain:water:vapour is 1:0.8:0.7. The 1 :0.8 grain: water ratio is for covering the grain surface during the 20 minute soaking stage and heating-up stage, whereas, the 0.7 portion of steam will be applied to the rice when the water and rice being cooked are in the boiling stage. Despite the same level of water content in the cooked rice, these two methods deliver a different taste quality, such as adhesiveness and hardness. By exploring this difference, a method was found for the cooker to control the cooked-rice quality by adjusting the water/steam proportion.

For example: the impact of the steam/water ratio on the adhesiveness of the cooked rice. The adhesiveness of the cooked rice is very much caused by the leached-out amylose, which then undergoes the pasting process, and eventually is attached on the surface of rice-grains when the water absorption is completed. However, if the water appears as steam (instead of in liquid form) in these three stages of rice cooking, this will substantially reduce the degree of leach-out and pasting, but it will promote the amylopectin water-absorption as a result of a higher heat-transfer due to steam condensation. Thus, by exploring the quantity and ratio of vapor/liquid phases of water in these three stages of rice-cooking, it is possible to manipulate the final quality (texture, appearance, taste and aroma) of the cooked rice. Therefore, extended from this concept, the invention aims to propose a method and a device for cooking food, which are capable of adjusting the physical and chemical changes of the food by manipulating the supply of steam and water during the cooking process, and hence change the sensory character of the cooked food.

According to the above description, in a first aspect of the invention, a method of cooking food contained in a container is proposed, wherein a series of food cooking steps take place. The steps comprise:

a) obtaining information related to the food;

b) determining a cooking scheme according to the information, wherein the cooking scheme comprises a steam application scheme;

c) cooking the food according to the cooking scheme; wherein said cooking step comprises applying steam to the food according to the steam application scheme.

It is to be noted that the term "cooking food" in the context of this invention means processing raw food to obtain cooked food which is ready for consumption. The term "information related to the food" includes information related to raw food and information related to cooked food.

In the above embodiment, a steam application scheme is determined according to the information related to the food, and the steam is applied to the food during the cooking process according to the steam application scheme; therefore, the embodiment provides a more flexible way of cooking food, and the cooked food may present various sensory characters within a single container.

In one preferred embodiment of the first aspect, the steam application scheme comprises at least one of the following: time point at which the steam is to be applied; temperature at which the steam is to be applied; the amount of steam to be applied and the time duration that the steam is to be applied.

This embodiment provides more specific ways of timing when to apply steam and how much steam is to be applied. The parameters may include:

a) the time point at which the steam is to be applied. This is determined in the steam-application scheme. For example: the time point can be dictated by the temperature of the food being cooked.

b) the temperature or the amount of the steam are also determined in the steam-application scheme.

Thus, the application of steam is more accurate and cooked food having desired requirements can be obtained.

In general, the heating process of starch-rich food can be defined by four stages: i. amylose leach-out stage, defined by a first temperature range, in which range the amylose leaching-out from the rice is the main phenomenon. The temperature range of the leach-out stage is from room temperature to the temperature at the start of the amylose pasting stage which will be described below. For example, for some rice varieties, it is from room temperature to 60°C, and the temperature range may differ a bit depending on the rice varieties used.

ii. amylose pasting stage, defined by a second temperature range, in which range the main phenomenon is the pasting of the amylose. The temperature range of this stage begins from the temperature at which the pasting of the amylose becomes the main phenomenon instead of the amylose leach-out, and this stage ends when the amylopectin water absorption stage begins, which will be described below. For example, for some rice varieties, the range of this stage is from 60°C to 80°C. In particular, 70°C is the temperature at which pasting of rice reaches its peak level. In order to achieve sufficient pasting of rice, a great amount of water is needed. It is to be noted that amylose leach-out still takes place at this stage; however, it is not the prominent phenomenon, due to the change of the temperature and the rice-solute concentration level.

iii. amylopectin water absorption stage, defined by a third temperature range, in which range the water absorption of the amylopectin is the main phenomenon, and it starts when the amylopectin starts to absorb water and lasts substantially until the start of the boiling stage. For example, for some Japonica rice, this temperature range is from 80°C to 100°C.

iv. boiling stage, defined by the boiling temperature, in which stage water and rice are kept boiling. Generally, it is around 100°C. Though the main phenomenon of this stage remains water-absorption in amylopectin, the effect is augmented by vigorous vaporization and convection. The effects of steam application at this stage will be less significant, considering the already vigorous heat transfer.

Amylose leach-out, amylose pasting, amylopectin water absorption are concurrent phenomena, however, the abovementioned stage i, stage ii and stage iii refer to conditions where each of them prevails.

Based on the above defined stages, in another embodiment of the first aspect, the food is rich in starch, and the temperature for cooking the food according to the steam-application scheme may correspond to the temperature of the amylose pasting stage of the starch-rich food. The above embodiment is based on the fact that the amount of water is one of the factors that influence the cooking of rice, and in particular, it has great influence on amylose pasting. After the rice is fully soaked in the water, that is, after the amylose leach-out stage, the larger the quantity of water in the amylose pasting stage, the more active the amylose pasting stage, and the better the cohesion of the cooked food is. However, the form in which the water is applied, either vapour or liquid, is another factor that determines the adhesion of the starch-based food. If more vapour and less liquid is applied, this will reduce the pasting effects and lead to less adhesive food.

In this embodiment, steam may be applied to the rice during the food-pasting stage, so as to adjust the sensory character of the cooked food, and particularly the cohesion and adhesion of the cooked food.

In another embodiment of the first aspect, the cooking temperature of the food comprised in the steam-application scheme may correspond to the temperature during the water absorption stage of the starch-rich food.

The above embodiment is based on the fact that the amount of water influences the water absorption of the amylopectin in the food. For example, the larger the quantity of water in the water absorption stage, the more water the food will absorb, and the more the food will expand. In this embodiment, the steam is applied to the rice in the amylopectin water-absorption stage, but the form in which the water is applied, either steam or liquid, will give a different level of kinetics in the water-absorption process, and this can be explored as an adjustment technique to control the expansion of the amylopectin, so as to further influence the taste of the rice.

Besides, the application of steam in the water absorption stage will lead to less friction among grains and will reduce the broken starch-chain in the solute and hence reduce the potential amylose pasting, so that the cooked rice is less sticky.

Additionally, the application of steam causes the water absorption to be smooth and gradual, and this will produce a gradually swollen texture from the surface to the core of the grain, and thus improve the chewiness of the rice without adversely affecting the fluffiness of the rice.

Further, steaming could help preserve some nutrients like folic acid and vitamin C, which are mainly dissolved in boiling water.

In another embodiment of the first aspect, the step of applying steam comprises at least one of the following:

- supplying the steam from outside of the container;

- generating the steam by boiling the water in the container.

This embodiment provides two more specific ways of generating steam: steam may be generated either by boiling water outside of the container that contains the food; or steam may be generated by boiling the water in the container. The first way enables the generation of steam to be controlled more accurately, while the second way can be implemented using a more compact design. Of course, the two methods may be combined with each other.

In another embodiment of the first aspect, the water in the container may also be adjusted according to the water application scheme. Since both the water and the steam influence the cooking process, this embodiment integrates applying steam and adjusting water to provide a more flexible scheme. Of course, the adjusting of water and the applying of steam may be performed simultaneously or successively in order to produce food with various sensory characters.

In another embodiment of the first aspect, the cooking scheme comprises a water application scheme, and the water application scheme comprises at least one of the following:

- time points at which the water is to be introduced into the container and/or drained from the container;

- the amount of water to be introduced into the container and/or drained from the container;

wherein the method further comprises adjusting the water level in the container according to the determined water application scheme during the cooking process.

This embodiment provides more specific ways of adjusting the water level, so that the application of water is more accurate and the desired cooked food can be obtained. Besides, the time point or temperature for adjusting the water level can be either the same as or different from the time point when the steam is applied.

In another embodiment of the first aspect, the information related to the food comprises at least one of the following: features of the food; target requirement of the cooked food.

In another embodiment of the first aspect, the features of the food correspond to at least one of the following: amount of the food; species of the food; freshness degree of the food; region in which the food is produced; quality of the food. In this embodiment, various features of rice can be distinguished, enabling the application of steam to be more specific to the food item in question and providing more flexibility.

In another embodiment of the first aspect, the food is rich in starch, and the target requirement corresponds to at least one of the following: hardness; adhesiveness; resilience; cohesiveness; springiness; gumminess; chewiness, aroma and appearance. In this embodiment, various requirements can be met, so that the flexibility of target taste, aroma or appearance is further increased.

In a second aspect of the present invention, there is provided a food cooker comprising: a first container for containing food; a first unit for obtaining information related to the food; a controller, electrically coupled to the first unit, for determining a cooking scheme according to the information, wherein the cooking scheme comprises a steam application scheme; a first heater, coupled with the first container for cooking the food contained in the first container according to the cooking scheme; a second unit, electrically coupled to the controller, for applying steam to the food according to the steam application scheme.

Brief description of the drawings

Features, aspects and advantages of the present invention will become obvious by reading the following description of non-limiting embodiments with the aid of the appended drawings. In the drawings, same or similar reference numerals refer to the same or similar steps or means.

Fig. 1 shows a block diagram of a rice cooker 10 according to an embodiment of the invention;

Fig. 2 shows a flowchart of the method of cooking rice according to an embodiment of the invention;

Fig. 3 shows the correlation between the application of steam to rice in the heating process and respective taste aspects such as hardness, cohesiveness, springiness and chewiness of the cooked rice according to an embodiment of the present invention;

Fig. 4 shows the correlation between the temperatures in the heating process at which the steam is added to the rice and the adhesiveness of the cooked rice according to an embodiment of the present invention.

Fig. 5 shows the correlation between the steam dose in the heating process and respective taste aspects such as springiness and resilience of the cooked rice according to an embodiment of the present invention.

Fig. 6 shows a schematic view of a rice cooker 10 according to an embodiment of the invention.

Fig. 7 shows a schematic view of a rice cooker 10, according to another embodiment of the invention.

Detailed description of embodiments

As shown in Fig. 1, the rice cooker 10 comprises:

a first container 100 for containing food;

a first unit 101 for obtaining information related to the food;

a controller 104, electrically coupled to the first unit (101), for determining a cooking scheme according to the information, wherein the cooking scheme comprises a steam application scheme;

a first heater 102, coupled with the first container 100, for cooking the food contained in the first container 100 according to the cooking scheme;

a second unit 103, electrically coupled to the controller 104, for applying steam to the food according to the steam application scheme.

Preferably, as shown in Fig. 1, the rice cooker 10 further comprises a third unit 108 for introducing water into the first container 100 and/or a fourth unit 109 for draining water from the first container 100.

The second unit 103 further comprises a steam generator 105, a second heater (not shown in figures), and a steam feeding tube 106 (shown in Fig. 6). Alternatively, the second unit 103 may comprise a carrier 107 (shown in Fig. 7). The function of these units will be described in the following part in combination with the following figures.

The method of cooking food comprises:

- obtaining information related to the food;

- determining a cooking scheme according to the information, wherein the cooking scheme comprises a steam application scheme;

- cooking the food according to the cooking scheme;

wherein the cooking step comprises applying steam to the food according to the steam application scheme.

The device and method for cooking food according to an embodiment of the invention will be elucidated by referring to figures 1 to 7.

In the following, the method and device for cooking rice are taken as examples for elucidating the embodiments of the invention. However, those skilled in the art may appreciate that food is not limited to rice, it may also comprise pumpkin, winter squash, red bean, Coix Seed (or also called Pearl Barley), broad bean, soybean, mung bean, red bean, potato, noodle, banana, and other grains, vegetables or fruits rich in starch, whose starch contents is more than 10%, depending on the cultivar, and can be regarded as staple foods. Further, among these staple foods, normally amylose is about 1/3 or 1/4 of amylopectin. In the following embodiments, for simplicity, we use "cooked rice" to describe the state of rice after the cooking process, i.e. cooked rice which is ready for eating.

As shown in Fig. 2, firstly, in step S20, the method obtains information related to the food. This operation is for example carried out by the first unit 101.

Specifically, in one embodiment, the first unit 101 obtains features of the rice as the information related to the rice. Preferably, the features of the rice correspond to at least one of: amount of food;

species of the food;

freshness degree of the food;

region in which the food is produced;

quality of the food.

The first unit 101 may comprise a user interface for receiving the features of the rice selected by the users, or may comprise sensors to detect the features of the rice. For example, the first unit 101 includes a pressure sensor to detect the amount of rice and an ultrasonic sensor/e-tongue to detect the species of the rice.

Ultrasonic sensors work according to a principle similar to that of radar or sonar, which evaluates attributes of a target by interpreting the echoes from radio waves or sound waves, respectively. Ultrasonic sensors generate high frequency sound waves and evaluate the echo which is received back by the sensor. Sensors calculate the time interval between sending the signal and receiving the echo to determine the distance to an object. This technology can be used for measuring fullness of a tank. To measure the amount of liquid in a tank, the sensor measures the distance to the surface of the fluid.

The e-tongue, or electronic tongue, is an instrument that measures and compares tastes. Chemical compounds responsible for taste are perceived by human taste receptors, and the sensors of the e-tongue detect the same dissolved organic and inorganic compounds. Like human receptors, each sensor has a spectrum of reactions different from that of another sensor. The information given by each sensor is complementary and the combination of all sensor results generates a unique fingerprint. Most of the detection thresholds of sensors are similar to or better than those of human receptors.

It should be noted that the features of rice are not limited by the above; and the kind and number of sensors for detecting the different features of the rice are not limited, either. Those skilled in the art could use any known sensor to perform the detection process. This will not be described in detail in the present invention.

In another embodiment, the first unit 101 obtains the target requirement of cooked rice as the information, and the target requirement comprises taste, appearance, texture and aroma of the cooked food. Preferably, the target taste corresponds to at least one of:

hardness;

adhesiveness;

resilience;

cohesiveness;

springiness;

gumminess; and

chewiness.

In practice, the first unit 101 comprises a user interface for receiving data related to the target requirement input by the user, and this target requirement may be the demand for one or more of the above requirement features. Alternatively, the target requirement input by the user may be a menu selection of the cooked rice, such as porridge, rice for frying and so on, and the first unit 101 correlates the menu selection with the demand for the above target requirements.

Alternatively, after the first unit 101 has determined the features of the rice, the first unit 101 may determine the target requirement, for example cooked rice, according to features of the rice. For example, the first unit 101 determines a high hardness and medium adhesiveness for Thai rice, or determines a low hardness and high adhesiveness for glutinous rice (sticky rice). The relationship between the features of rice and the target requirement is pre-stored in a memory of the device. It should be noted that the target requirement of rice is not limited by the above, and any requirement related features, e.g. gustatory, tactual, or olfactory, fall within the range of the target requirement.

The first unit 101 may also obtain a default target requirement from the memory of the rice cooker 10 as the target requirement, in the case that there is no input from the user interface, or in the case that the input comprises wrong information. If the input comprises wrong information, the first unit 101 may also provide a reminder to the user and request the user to re-input. It should be noted that the information related to the rice is not limited to features of the rice and/or target requirements of the cooked rice. In the following, the target requirement is used as the information related to the rice to elucidate embodiments of the invention. Based on the teachings of the description, those skilled in the art could design other embodiments corresponding to other information related to the rice, however, the description will not give further details herein.

The container 100 contains rice and water. After the first unit 101 has obtained information related to the rice in step S20, next, in step S21, the method determines a cooking scheme according to said information, wherein the cooking scheme comprises a steam application scheme. Step S21 will be described in detail in the following.

Then, in step S22, the method determines that the food is cooked according to the cooking scheme. The cooking step comprises applying steam to the rice, for example, by using the second unit 103, according to the steam application scheme. Step S22 will be described in detail in the following.

Fig. 3 shows the results of experiments carried out by the inventor of the present invention. The bar charts A, B, C and D in Fig. 3 respectively show the taste features: hardness, cohesiveness, springiness and chewiness. Bar 1 in each chart represents the reference group where the rice is only stewed, or, in other words, no steam is added during the cooking of the rice and the rice is boiled in water throughout the rice cooking process. Bar 2 in each chart represents the steam and stew hybrid mode, wherein water is filled to a level that is just enough to cover the rice when the temperature is 100°C, then the steam is applied to the rice, i.e. the rice is heated up to 100°C with boiling water and steam lingering in the container 100. Bar 3 in each chart represents that the rice in the water is boiled up to 100°C, separated from the water, and then steamed at 100°C. From figure 3 it can be seen that the application of steam has a significant influence on the final quality of the cooked rice in terms of taste features, which is achieved by exploring the effects of steam on the different stages of rice-cooking, such as: amylose-pasting, amylo-pectin water-absorption.

For instance: a) Hardness / springiness / chewiness, as shown in Fig.3 chart A, C and D, share a trend at the steam application temperatures. As steam replaces water in the course of the cooking process, it reduces the pasting effects and the movement of boiling water, as a result of which the grain structure is not swollen as drastically as in the case of a process where the rice is only stewed.

b) Cohesiveness, as shown in Fig.3 chart B, peaked in the steam/water hybrid mode.

When the rice is subjected to stewing only, vigorous water absorption and water movement will open up the amylo-pectin chain violently, reducing the cohesiveness of the rice-grain. By purely steaming it at >100degC, the water absorption will be reduced drastically, and the amylo-pectin chain will not open up fully. With the combination of steam and stew, a more cohesive cooked rice is obtained.

As the steam application temperature is a deterministic parameter, the inventor takes the adhesiveness of the cooked rice as an example to describe the influence thereof. The bar chart E of Fig. 4 shows the correlation between the adhesiveness and the temperatures in the heating process at which the steam is applied to the rice. Bar 1 in Fig. 4 represents the reference group where the rice is purely stewed, in other words, no steam is added during the cooking of the rice and the rice is boiled in water throughout the rice cooking process. Bar 4 in Fig. 4 represents that the rice is separated from the water used for stewing at 60°C, and then the steam is applied to the rice to further heat the rice. Bar 3 in Fig. 4 represents that the rice is boiled at 100°C, separated from the water, and then steamed at temperatures of from 100°C. From Fig. 4 it can be seen that as the temperature rises, the steam is added into the rice, causing the adhesiveness of the cooked rice to decrease. Instead of purely stewing the rice, it is purely steamed at the stage above 60°C, so that the condition to be met for surface amylose -pasting is not fulfilled, and, in addition, the water/grain movement and surface.friction are reduced, causing the adhesiveness of the cooked rice to be reduced.

Based on the above experiment, the steam application scheme may comprise a time point at which the steam is to be applied, that is, the controller 104 may be used for determining the temperature at which the steam is to be applied to the food. In one embodiment, the temperature according to the steam application scheme corresponds to the temperature of the starch pasting stage of starch-rich food. For example, if in step S20 the information obtained by the first unit 101 comprises that the target requirement of the cooked rice is low adhesiveness, this means that rice grains are non-sticky instead of glutinous. Such food may be subsequently fried. Then, the steam application scheme is determined to be such that the temperature at which steam is applied corresponds to the stage at which the pasting of rice starts; for example, the temperature at which the steam is to be applied to the food is 60°C, so that the pasting process will be weakened, due to the lack of water, and the cooked rice will become less sticky.

The above example illustrates that the steam is applied at a temperature corresponding to the start of the pasting stage. Besides, the steam may also be applied at other temperatures, such as around 80°C corresponding to the stage of water absorption. The application of steam in the water-absorption stage will lead to less friction among the rice grains as compared to the situation where the rice is boiled in water. To be specific, if the rice is boiled in water, the grains usually are vigorously moved about, and friction among grains may occur which may cause starch formation on the surface of the rice, which starch is to be removed from the rice and breaks down into a shorter soluble chain, which will participate in pasting effects and causes the cooked rice to become very sticky. By contrast, the application of steam to the rice results in the rice grains remaining intact. Since the starch on the surface of the grain will not be removed from the grain, the rice will not be very sticky. Additionally, the invention makes use of the superimposition nature of the steaming effects on various cooked-rice features, for example: as the water absorption leads to less friction among the rice grains in the case of steaming, this will deliver greater chewiness (Fig.3 Chart-D) of the rice without causing fluffiness (Fig.3 Chart-A) of the rice.

Besides, steaming could help preserve some nutrients like folic acid and vitamin C, which are mainly dissolved in boiling water.

Based on the above principle, the controller 104 may determine the temperature to be around 80°C if the requirement for the cooked rice is low stickiness or more chewiness. The temperatures for applying steam corresponding to different requirements can be obtained in advance by the manufacturer and stored in the rice cooker 10, and the controller 104 may retrieve the appropriate temperature according to the requirement.

Since the cooking temperature may be correlated with the cooking time, in one varied embodiment, the steam application scheme may comprise a time point at which the steam is to be applied, that is, the controller 104 may also be used for determining the time point at which the steam is to be applied to the food. For example, in step S20 the information obtained by the first unit 101 comprises that the target requirement of the cooked rice is low adhesiveness, which means that rice grains are non-sticky instead of glutinous. Such food may be used for subsequent frying. Then, the controller 104 determines that the time point that the steam is to be applied to the food corresponds to the stage when the pasting of rice starts. The time points of applying steam corresponding to different requirements can be obtained in advance by the manufacturer and stored in the rice cooker 10, and the controller 104 may retrieve the temperature according to the requirement. Also the time point when the application of steam is to be terminated or the time duration that the steam is to be applied can be determined. The time during which steam is applied reflects the amount of steam to be applied.

Although the correlation between the time duration during which the food is cooked and the temperature at which the food is cooked may exists in some situations, those skilled in the art may understand that the temperature at which the food is cooked may also depend on other factors such as the amount of food and water; therefore, the above correlation is a rough one and may vary according to the different situations.

The applicant also has conducted experiments with respect to the influence of the amount of steam to be applied. For example, Fig. 5 shows the correlation between the dose of steam in the heating process and taste aspects such as springiness (C) and resilience (F) of the cooked rice. Bar 5 in Fig. 5 represents the reference group where the rice is purely stewed, in other words, no steam is added during the cooking of the rice and the rice is boiled in water throughout the rice cooking process. Bar 7 in Fig. 5 is referred to as half rice steaming at 60°C, wherein rice is separated from the water used for stewing at 60°C; here, half rice means that the RICE:WATER ratio is 0.5: 1.14. Bar 6 in Fig. 5 is referred to as full rice steaming at 60°C, wherein rice is separated from the water used for stewing at 60°C; here, full rice means that the RICE:WATER ratio is 1 :1.14. In this experiment, the steam is generated by boiling the water inside the container; therefore, the more water there is inside the container, the more steam is generated. Compared to Bar 6, the water dose of Bar 7 is doubled; therefore, the steam generated with respect to Bar 7 increases in comparison with that of Bar 6. It can be seen from the figure that the larger the amount of water, the larger the amount of steam, and the greater the springiness of the cooked rice. Based on this principle, the steam application scheme may comprise the amount of steam to be applied, that is, the controller 104 may also be used for determining the amount of steam to be applied to the food according to the desired springiness. The amount of steam corresponding to different requirements can be obtained in advance by the manufacturer and stored in the rice cooker 10, and the controller 104 may retrieve the amount of steam according to the requirement.

In one embodiment, the steam may be supplied from outside of the container. For example, the second unit 103 may comprise a steam generator 105 for generating steam. As shown in Fig. 6, the steam generator 105 may comprise a second container (not shown in Fig. 6) for containing water, and the second container is separate from the first container 100. The steam generator 105 may further comprise a second heater (not shown in Fig. 6). The second heater is mounted, for example, at the bottom of the second container for boiling the water in the second container, and the steam-feeding tube 106 connects the steam generator 105 with the first container 100 for supplying the steam from the steam generator 105 into the first container 100.

In Fig. 6, it can be seen that the volume of the second container is relatively small compared to the first container 100, so that the water in the second container may undergo a fast boiling process to generate steam. In another embodiment, the rice cooker 10 may further comprise a third container 605 for containing water, wherein the third container 605 and the second container may be interconnected via a valve (not shown in Fig. 6), and when the valve is in the open position, the water (indicated by means of horizontal lines) in the third container 605 may flow into the second container for supplementing the water in the second container. Of course, the third container 605 is optional. The second container and the third container can be one and the same.

Alternatively, the steam generator 105 may be an opening for receiving the water for example from the water tap, and the steam generator 105 blends with the steam feeding tube 106; in this case, the second heater may be positioned on the steam feeding tube 106 for heating the water in the steam feeding tube 106 when the water flows through the steam feeding tube 106 from the opening to the first container 100. In another embodiment, the steam may be provided by boiling the water in the first container 100. Fig. 7 illustrates such an embodiment. In Fig. 7, units similar to those already shown in Fig. 6 are not shown for simplicity. In Fig. 7, the carrier 107 is located in the first container 100 for holding the food, and the carrier 107 is movable. The carrier 107 may be moved such that the food can be controlled to be fully immersed in the water (shown by means of slashed lines) or fully out of the water, or partially out of the water in the first container 100. The carrier 107 may take on a plurality of forms, such as a basket, a shelf, a tray, or a curtain, etc. Besides, the carrier 107 has apertures allowing the water and the steam in the first container 100 to pass through. For example, the carrier 107 may be in the form of a meshed tray or basket having apertures smaller than the size of rice grains so as to allow the water and the steam to pass through. And the carrier 107 can be moved upwards to control the rice to be at least partially out of the water, or the carrier 107 is movable downwards to control the rice to be immersed in the water.

It is also appreciated that the embodiments shown in Fig. 6 and Fig. 7 can be combined to yield another embodiment. To be specific, the rice cooker 10 comprises the steam generator 105, the steam feeding tube 106 and the carrier 107, and the food is held by the carrier 107. During the step of cooking food, the carrier 107 may be lifted out of the water, while the steam feeding tube 106 also feeds steam into the water, causing both the bottom and the top of the food to be steamed, as a result of which the taste of the food is more flexible. The application of steam may also influence the appearance (for example, the size and the shine of the cooked grains) and the aroma (for example, the retention of volatile aromatic fatty acid in rice grains) of the cooked rice.

To be specific, controlling the process of cooking starch-rich food is about controlling the degree of amylose leaching-out, the degree of amylopectin expansion and the degree of water absorption. Differences with respect to the above degrees will result in pasting effect differences. Different pasting degrees will create different optical effects of the cooked rice, for example, in terms of shininess or whiteness of the cooked food. When steam is applied during the pasting stage, the pasting degree will be adjusted; therefore, the appearance, for example, color, shininess of the cooked rice will be adjusted accordingly.

Another factor that influences the aroma and appearance of cooked rice is the fat content of the cooked rice. In general, the larger the degree of fat, within a certain range, in the rice, the better the appearance, for example, color, shininess, etc, and aroma will be. Since steam is of high temperature, usually higher than 100°C, and a high temperature will help extract the fat from the rice, this will generally help to improve the appearance and the aroma of the cooked rice.

Besides, free fatty acids will help improve the aroma. A relatively high temperature and pressure (with more steam) will help the extraction of free fatty acids.

Detailed analysis of the influence of fat on the appearance and aroma of rice can be found in Zhang Rui-xia, Xiong Shan-bai, Zhao Si-ming, Xu Fan et al, Effect of Cooking Technologies on Lipids and Sensory Quality of Cooked Rice [J] Chinese Cereals and Oils Association, September 2008, Vol. 23, No. 5, 5-8.

The above embodiment provides a description of applying steam to food. In addition, the water in the first container 100 for cooking the food may also be adjusted. To this end, the controller 104 may also be used for determining the water application scheme, that is, the cooking scheme further comprises a water application scheme, said water application scheme comprising at least one of the following: time points at which the water is to be added into the first container 100 and/or drained from the first container 100; the amount of water to be added into the first container 100 and/or drained from the first container 100; and the food cooker 10 further comprises a third unit 108 (shown in Fig. l, not shown in Fig. 6 or 7) for adding water into the first container 100 according to the determined water application scheme, and/or a fourth unit 109 (shown in Fig. 1, not shown in Fig. 6 or 7), for draining the water from the first container 100 according to the determined water application scheme.

The third unit 108 may comprise the third container 605, a pump within the third container 605 for example, and a pipe connecting the pump with the first container 100. Therefore, the water in the third container 605 may be pumped by the pump to the first container 100 via the pipe.

The fourth unit 109 may comprise a water drainer located at the bottom of the first container 100, for draining at least part of the water from the first container 100. Those skilled in the art may understand that the food cooker 10 may comprise the third unit 108 and/or the fourth unit 109, and the third unit 108 and the fourth 109 may be integrated.

The embodiment relating to adjusting the water level in the first container 100 may be combined with the embodiment shown in Fig. 6. For example, if the information with respect to food obtained by the first unit 101 comprises that the target requirement of the food includes two kinds of target tastes, namely one taste exhibiting medium cohesiveness and the other taste exhibiting low cohesiveness for further use, i.e. for preparing fried rice, then the controller 104 determines the water amount to be drained from the container when the steam is applied, such as for example 350ml, so that the rice is partially out of the water. Therefore, the water drainer may drain 350ml of water from the first container 100.

Of course, the embodiment relating to adjusting the water level in the first container 100 may be combined with the embodiment shown in Fig. 7.

Practically, referring to Fig. 6, a detailed implementation of the rice cooker 10 will be described, wherein the first container 100 takes the form of an inner pot 100 for containing the rice R and the water W (shown using slashed lines). The first heater 102 is implemented by two heaters 601 and 602 which heat the inner pot 100 from the bottom and the side, respectively. The second heater is implemented by one heater. The second unit 103 may be implemented by a water tank 105, a steam feeding tube 106, and a plurality of nozzles 603, wherein the water tank 105 stores water, and the second heater boils the water in the water tank 105 to steam and the steam feeding tube 106 conveys the steam to the plurality of nozzles 603 at the top of the inner pot 100, and the plurality of nozzles 603 transfer the steam to the inner pot 100. The rice cooker 10 further comprises an outer housing 600 and an upper lid 604. In the embodiment shown in Fig. 6, the steam is provided through a plurality of nozzles 603 distributed evenly at the top of the inner pot 100. Alternatively, the nozzles 603 may be gathered together. Preferably, the steam generator 105 may further be capable of generating steam with high pressure before the steam is transferred into the inner pot 100.

The above units can be implemented by way of software, hardware or combinations thereof. For example, the first unit and the second unit can be implemented by hardware components. The first controller, the second controller, the third controller and the fourth controller can be implemented by software and the program codes achieving the functions are stored in a memory and are loaded and executed by a microcontroller unit (MCU). The MCU also controls the hardware components. Those skilled in the art could implement embodiments of the invention in various ways according to the concept and principle taught by the description.

Those of ordinary skill in the art could understand and realize modifications to the disclosed embodiments, through studying the description, drawings and appended claims. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims. The word "comprising" does not exclude the presence of elements or steps not listed in a claim or in the description. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. In the practice of the present invention, several technical features in the claim can be embodied by one component. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Claims

What is claimed is:

1. A method of cooking food contained in a container of a cooker, comprising the steps of:

- obtaining (S20) information related to the food;

- determining (S21) a cooking scheme according to the information, wherein the cooking scheme comprises a steam-application scheme;

- cooking (S22) the food according to the cooking scheme;

wherein said cooking step comprises applying steam to the food according to the steam application scheme.

2. A method as claimed in claim 1, wherein the steam application scheme comprises at least one of the following:

- time point at which the steam is to be applied;

- temperature at which the steam is to be applied;

- the amount of steam to be applied;

- time duration that the steam is to be applied.

3. A method as claimed in claim 2, wherein the food comprises starch-rich food, and the temperature according to the steam application scheme corresponds to the temperature of the starch pasting stage of the starch-rich food, or the temperature of the water absorption stage of the starch-rich food, or the water boiling temperature.

4. A method as claimed in claim 1, wherein the step of applying the steam comprises at least one of the following:

- supplying the steam from outside of the container;

- generating the steam by boiling the water in the container.

5. A method according to claim 1, wherein the cooking scheme comprises a water application scheme, and the water application scheme comprises at least one of the following:

- time points at which the water is to be added into the container and/or drained from the container;

- the amount of water to be added into the container and/or drained from the container; wherein the method further comprises adjusting the water level in the container according to the determined water application scheme during the cooking procedure.

6. A method as claimed in claim 1, wherein the information related to the food comprises at least one of the following:

- features of the food;

- target requirements of the cooked food.

7. A method as claimed in claim 6, wherein the features of the food correspond to at least one of the following:

- amount of the food;

- species of the food;

- freshness degree of the food;

- region in which the food is produced;

- quality of the food;

and wherein the food comprises starch-rich food, and the target requirements of the cooked food correspond to at least one of the following:

- hardness;

- adhesiveness;

- resilience;

- cohesiveness;

- springiness;

- gumminess;

- chewiness; - aroma;

- appearance.

8. A food cooker (10) comprising:

a first container (100) for containing food;

a first unit (101) for obtaining information related to the food;

a controller (104), electrically coupled to the first unit (101), for determining a cooking scheme according to the information, wherein the cooking scheme comprises a steam application scheme;

a first heater (102), coupled with the first container, for cooking the food contained in the first container according to the cooking scheme;

a second unit (103), electrically coupled to the controller (104), for applying steam to the food according to the steam application scheme.

9. A food cooker as claimed in claim 8, wherein the steam application scheme comprises at least one of the following:

- time point at which the steam is to be applied;

- temperature at which the steam is to be applied;

- time duration that the steam is to be applied; and

- the amount of steam to be applied.

10. A food cooker as claimed in claim 9, wherein the food comprises starch-rich food, and the temperatuire according to the steam application scheme corresponds to the temperature of the starch pasting stage of the starch-rich food, or the temperature of the water absorption stage of the starch-rich food, or the water boiling temperature.

11. A food cooker as claimed in claim 8, wherein the second unit (103) comprises:

a steam generator (105) for generating steam; a steam feeding tube (106) connecting the steam generator (105) with the first container (100), for supplying the steam from the steam generator (105) to the first container (100).

12. A food cooker as claimed in claim 11, wherein the steam generator (105) further comprises:

a second container for containing water,

a second heater, coupled with the second container, for generating steam by heating the water contained in the second container.

13. A food cooker as claimed in claim 8, wherein the second unit (103) further comprises: a carrier (107) located in the first container (100) for holding the food, the carrier (107) being movable such that the food can be controlled to be fully immersed in the water or fully out of the water or partially out of the water.

14. A food cooker as claimed in claim 13, wherein the carrier (107) comprises apertures for allowing the water in the first container (100) to pass through, and/or the carrier (107) is detachable from the food cooker (10).

15. A food cooker as claimed in claim 8, wherein the cooking scheme further comprises a water application scheme, the water application scheme comprising at least one of the following:

- time points at which the water is to be added into the first container (100) and/or drained from the first container (100);

- the amount of water to be added into the first container (100) and/or drained from the first container (100); and

the food cooker further comprises a third unit (108) for adding water into the first container (100) according to the determined water application scheme, and/or a fourth unit (109) for draining the water from the first container (100) according to the determined water application scheme.