GB2463010A

GB2463010A - Rice cooking method and apparatus

Info

Publication number: GB2463010A
Application number: GB0815508A
Authority: GB
Inventors: Gordon Smart
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-08-26
Filing date: 2008-08-26
Publication date: 2010-03-03
Anticipated expiration: 2028-08-26
Also published as: WO2010023472A1; GB2463010B; GB0815508D0

Abstract

A method for cooking rice in a cooking vessel having a lid, comprising the steps of; mixing the rice with an initial amount of water to form a rice/water mixture; applying heat to the rice/water mixture to raise it to or maintain it at an elevated temperature in the cooking vessel; placing a waterproof, heat resistant sheet member between the lid of the vessel and the vessel to form a seal or partial seal capable of maintaining an internal pressure in the vessel greater than that sustainable using the lid alone and reducing the heat applied to the rice/water mixture, whilst maintaining this applied heat at a level and for a time sufficient to complete cooking of the rice. The waterproof sheet member comprises a retaining means to assist in securing it to the cooking vessel. The present invention also provides an apparatus for use in the cooking of rice comprising a cooking vessel 3, a lid 2 and a waterproof, heat resistant sheet member 1 for use between the lid of the cooking vessel and the vessel.

Description

Intellectual Property Office mm For Creetity and Innovation Application No. GBO8 15508.7 RTM Date:24 November 2008 The following terms are registered trademarks and should be read as such wherever they occur in this document: Teflon', Pyrex' & Golden Sun'.

UK Intellectual Property Office is an operating name of The Patent Office

RICE COOKING METHOD

Field of the Invention

The present invention relates to a method for cooking rice and a device for use in this method.

Background of the Invention

Rice is the main staple foodstuff of a large proportion of the world's population. It contains complex carbohydrates, which give a slow release of energy over a prolonged period of time. Rice also contains various essential minerals and B group vitamins.

Consequently, rice is considered a versatile and healthy food option.

The quality of rice and its nutritional value are both strongly dependent on the cooking method used. Efficient methods of cooking rice to a high level of quality are therefore of considerable importance.

In order for rice to be cooked to a consumable standard, it is necessary for it to be heated in the presence of water (which may be in the form of steam). During the cooking process, hot water is absorbed by the rice so that the rice is cooked in layers from the outside in, The process is complete once the core of the rice grain has been cooked.

One of the rate determining steps in the cooking process is therefore the time required for water to fully penetrate the individual rice grains during cooking. The cooking time may be reduced by pre-soaking the rice so that at least some water is absorbed by the rice before the rice is cooked. However, pre-soaking is time consuming and the use of this technique increases the total preparation and cooking time of the rice compared to cooking without pre-soaking.

Therefore, one desirable element in the efficient preparation of high quality rice is a short cooking time.

Regarding the quality of rice obtained using a given cooking method, one of the indicators that rice has been cooked to a high quality is that the individual grains are easily separable. A contributing factor to this separability is the presence of amylose starch on the surface of the individual rice grains. The amylose starch originates from the core of the rice grains. Therefore, in order for the amylose to be released, it is necessary for the exterior fibre layer of the rice grain to be softened sufficiently to allow amylose to pass through to the surface. This softening process typically takes place when the rice is exposed to hot water.

When cooking rice it is also desirable to maintain the original nutrient levels of the rice at as high a level as possible. As mentioned previously, natural rice contains complex carbohydrates and B group vitamins. In addition, genetically modified rice strains have been developed to express additional vitamins and proteins (eg Iactoferrni, lysozymes and human serum albumin). These nutrients are known to decompose under excessively harsh cooking conditions.

Some known methods of rice cooking involve boiling the rice in water until cooking is completed i.e. until each individual rice grain is cooked through to the core.

For example, the rice may be boiled in a large excess of water until cooked. This is a comparatively simple method of cooking rice but does have a number of associated disadvantages. The use of a large excess of water means that more water is used than necessary -thereby wasting both water and the additional energy required to heat the excess water. In addition, since the end point of the cooking process is not immediately apparent, regular testing of the rice is required in order to determine whether or not it is properly cooked. Also, a large proportion of the nutrients in the rice are either denatured during the cooking process or pass into the cooking water and are then lost when the rice is separated from the remaining water at completion of the cooking process. Finally, the quality of rice obtainable using this method is not high, particularly for lower quality grades of rice. The rice obtained using this method is often stodgy and of inconsistent texture. In addition, a scummy starch is often produced. This method also often gives rise to burning of the rice and sticking of the rice to the cooking vessel.

This can make the cooking vessel difficult to clean following the cooking process or require regular stirring of the rice during cooking to prevent burning.

Another common method of cooking rice involves selecting the initial amount of water used so that at completion of the cooking process, the water has either been absorbed by the rice or has evaporated, thereby reducing wastage compared to methods that require a large excess of water. A disadvantage of this method is the need to accurately determine the starting amount of water required in order to obtain properly cooked rice, If too little water is used, the water will evaporate during cooking before a sufficient amount is absorbed by the rice, resulting in undercooked rice. Conversely, if too much water is used, the rice will be overcooked or soggy. The optimum initial amount of water to give the best quality rice for a given amount of rice when cooked under a given set of conditions is determined by trial and error. However, once the optimum starting amount of water is determined for the cooking of a given amount of rice under one set of process conditions, it is often difficult to determine correctly the appropriate starting amount of water to use when cooking a different amount of rice or when cooking the same amount of rice under different cooking conditions (eg using a different cooker, different applied heat level or different size/shape of cooking vessel) since the amount of water that will evaporate during the cooking process and hence the initial amount of water required to allow for this evaporation will vary unpredictably depending on these parameters.

Another cooking method is the pressure cooker method. In this method, the rice is cooked with water in a sealed, pressurised vessel. The increased pressure within the container means that water reaches a higher temperature than in a vessel open to the atmosphere, with the result that the rice cooks more quickly. However, this method again has a number of associated disadvantages. Firstly, pressure cookers are mechanically complex, and hence expensive, compared to simple pots. They often require the incorporation of a number of safety mechanisms to avoid a dangerous build up of pressure. Due to the high operating temperature associated with the use of a pressure cooker, a large proportion of the nutrients in the food to be cooked are denatured during the cooking process. These high operating temperatures also mean that rice often sticks to the inner walls of the pressure cooker, resulting in burning and the associated difficulty in cleaning the pressure cooker after completion of the cooking process. Finally, the pressure cooker also loses water as steam during the cooking process. This again means that water and heat are wasted during the cooking process and also means that this method suffers from the associated difficulty in calculating the appropriate starting amount of water to use when varying the process conditions.

Another traditional rice cooking method is steaming. In this method, rice is not directly exposed to boiling water but is placed in a receptacle in a sealed container and exposed to steam from boiling water. Steaming has the advantage that a lower proportion of nutrients are lost from the rice into the cooking water. In addition, this method is less susceptible to burning of the rice. However, cooking rice by steaming takes longer than the previously described methods and is therefore wasteful of energy.

It would therefore be advantageous if a method of cooking rice could be found which overcomes some or all of the above disadvantages.

Brief Description of the Invention

In accordance with a first embodiment of the invention, there is provided a method for cooking rice in a cooking vessel having a lid, comprising the steps of: (i) mixing the rice with an initial amount of water to form a rice/water mixture; (ii) applying heat to the rice/water mixture to raise it to or maintain it at an elevated temperature in the cooking vessel; (iii) placing a waterproof, heat resistant sheet member between the lid of the vessel and the vessel to form a seal or partial seal capable of maintaining an internal pressure in the vessel greater than that sustainable using the lid alone; (iv) reducing the heat applied to the rice/water mixture, whilst maintaining this applied heat at a level and for a time sufficient to complete cooking of the rice.

The method of the first embodiment confers some or all of the following advantages

over each of the specified prior art methods:

(a) the rice is cooked more quickly than in traditional methods; (b) the energy input required to cook the rice is reduced; (c) due to the milder process conditions and reduced cooking time, the nutritional value of the rice is preserved better than in prior art methods.

(d) due to the milder process conditions there is no requirement to stir the rice during cooking in order to prevent burning. Therefore the rice cooking process does not need such close supervision as in prior art methods; (e) increased retention of water vapour in the cooking vessel resulting from the use of the waterproof sheet member makes it more straightforward to determine the optimum starting amount of water in the cooking process; (f) the stickiness of the rice is reduced and the individual grains are therefore more easily separable; (g) the apparatus for use in the method is cheaper than a pressure cooker or electric rice cooker; (h) less water is required than open topped or standard lidded pot methods; (i) the method may be used in areas where no electricity or gas supply is present e.g. on a camping trip; and (j) the apparatus for use in the method is lightweight and easily portable.

In accordance with a second embodiment of the invention, there is provided a waterproof, heat resistant sheet member for use in the first embodiment of the invention, wherein the sheet member comprises a retaining means to assist in securing it to the cooking vessel.

In accordance with a third embodiment of the invention, there is provided an apparatus for use in the method of the first embodiment comprising a cooking vessel, a lid and a waterproof, heat resistant sheet member for use between the lid of the cooking vessel and the vessel.

Detailed Description of the Invention

In step (i) of the first embodiment of the invention, the rice may be mixed with water either by adding rice to the water or by adding water to the rice. The mixing may take place in the cooking vessel or outside the cooking vessel before the mixture is added to the cooking vessel. In an aspect of the first embodiment, the rice is added to hot (e.g. boiling water) in the cooking vessel. This has the advantage that the rice begins to cook immediately and reduces the time required for the water to be heated to the elevated temperature in step (ii) of the first embodiment.

Alternatively, the rice may be mixed with cold water in the cooking vessel in step (i) and then heated to an elevated temperature in step (ii). This reduces the overall preparation and cooking time since it allows the water to begin permeating the rice and for the rice to begin cooking as the mixture is heated up in step (ii). In addition, the operator does not need to apply the waterproof, heat resistant, sheet member to a hot cooking vessel, thereby minimising the danger of accidental burning.

The initial amount of water should be at least that required for absorption by the rice in order to give cooked rice under the cooking conditions employed. To avoid waste and also to improve the quality of the rice obtained, the initial amount of water is preferably selected so that following completion of the rice cooking process, all of the water initially present in the cooking vessel has evaporated or been absorbed by the rice. The amount of water required to cook a given amount of rice optimally under a given set of process conditions may be determined by cooking the rice under the process conditions until all of the water has been absorbed by the rice and then testing the rice obtained. If the rice is too stodgy, less water is required. If the rice is too hard, more water is required.

Typically, the amount of water used should be less than 10 wt%, for example less than 5wt%, such as less than 2wt% or less than lwt% greater or less than the optimum amount of water.

Optimally cooked rice has a specific final water content. It has been reported that for most types of rice, the optimum water content is between 58 and 64 wt%. Therefore, the initial amount of water required in step (i) will depend on the amount of water initially present in the rice. The higher the initial water content of the rice, the less water is required in the cooking process. The initial water content of the rice may be increased, for example, by pre-.soaking the rice in water before cooking.

In some cases (e.g. where the rice is not pre-soaked), the amount of water required to cook the rice optimally may for example be in a ratio of 60g rice:80-lOOg water; for example 60g rice:85-95g water; or 60g rice: 87-93g water. In an aspect, the ratio of rice to water is 60g rice: about 90g water.

In step (ii) of the first embodiment, the rice/water mixture may be heated to or maintained at a temperature of greater than 70°C, for example greater than 80°C, such as greater than 90°C or greater than 95°C. In an aspect of this embodiment, the rice/water mixture is heated to the boiling point of the water. This is 100°C at latm pressure. However, if the waterproof, heat resistant sheet member is present, the boiling temperature will be slightly higher since the internal pressure of the cooking vessel will be greater than latm. In an aspect, the rice/water mixture is heated to or maintained at a temperature of equal to or less than the boiling point of water, for example less than 95°C, such as less than 90°C or less than 80°C.

In an aspect, in step (ii), the rice water mixture is heated to or maintained at a temperature in the range from 70 -95°C, for example 80 -90°C.

Without wishing to be bound by theory, it is presently believed that this initial heating step results in an initial softening of the outer shells of the individual rice grains. This increases the rate of water absorption by those rice grains during the remainder of the cooking process.

Generally, the time required for the initial softening process to take place will depend on the temperature that the rice/water mixture is raised to or maintained at in step (ii) of the first embodiment. At higher temperatures, the softening process will take place more quickly. Conversely, at lower temperatures, the softening process will take place more slowly.

In addition, the time required for the softening process to take place will depend on the initial temperature of the water in the water/rice mixture. If the initial water temperature is low, the softening process will take longer than at higher temperatures due to the time required to heat the water to a temperature at which softening takes place more quickly.

In cases where the initial water temperature is high, e.g. water at a temperature of 50°C or greater, for example greater than 70°C, or greater than 90°C such as boiling water, the initial softening process will typically take a time greater than 10 seconds, for example greater than 20 seconds or greater than 30 seconds. The softening process will also typically take less than 120 seconds, for example less than 90 seconds, such as less than 60 seconds.

In cases where initial water temperature is lower than 50°C e.g. water at a temperature of less than 30°C, for example less than 20°C or less than 10°C, the initial softening process will typically take a time greater than 90 seconds, for example greater than 150 seconds or greater than 180 seconds, such as greater than 210 seconds. The initial softening process will also typically take less than 480 seconds, for example less than 420 seconds, such as less than 360 or less 300 seconds.

In step (iii) of the first embodiment, the waterproof sheet member may be placed between the lid of the vessel and the vessel either before heating step (ii); or between heating step (ii) and heat reduction step (iv); or during heat reduction step (iv).

Preferably in step (iii) of the first embodiment, the waterproof sheet member is placed between the lid of the vessel and the vessel before heating step (ii) so that vapour loss is minimised and the cooking pressure is maximised over as much of the cooking process as possible. In addition, it is preferable to place the waterproof sheet member in position before heating step (ii) for safety reasons in order to avoid possible injury to the operator due to burning.

The waterproof, heat resistant sheet member may be made from any waterproof, heat resistant material suitable for interaction with food material at rice cooking temperatures. For example, the waterproof sheet member may be made from a heat resistant plastic such as polyethylene or polypropylene, or a nylon film. The waterproof, heat resistant sheet member may optionally be coated, for example with a PTFE coating e.g. Teflon, to improve water resistance.

The waterproof sheet member may be substantially planar but is preferably sufficiently flexible to allow it to flex or deform if required to fit between the cooking vessel and the lid, in order to provide an improved seal between these elements.

In a preferred aspect of the first and third aspects and in accordance with the second aspect, the waterproof sheet member comprises a retaining means to assist in securing it to the cooking vessel. The retaining means may be located at, or secured to, the outer periphery of the sheet member.

In an aspect, the waterproof sheet member or a part of this member is formed from an elastic material. This allows the sheet member to stretch around the perimeter of the vessel, the tension acting to retain the sheet member in position. Securing the sheet member in this way maintains the sheet member under moderate tension. This acts to avoid the build up of ripples in the sheet member, thus contributing to the quality of the seal. Reduction in ripple formation also reduces the amount of water present as condensation on the inner surface of the sheet member, thereby increasing the amount of water present in the rice/water mixture to cook the rice.

Alternatively, the sheet member may be formed from a flexible yet comparatively inelastic material (e.g. polyethylene) but comprise a portion, for example an outer portion, having an elastic component. In yet another alternative, the sheet material may be formed from a flexible yet comparatively inelastic material but comprise in the outer periphery of the sheet member a string, wire, elastic material or other tightening means for securing the sheet member to the pot.

In a further aspect, the waterproof sheet member comprises an outer member, for example a ring member connected to the outer periphery of the sheet member by connecting means (e.g. twine, wire, string or elastic means).

The outer member is selected to have a larger internal diameter than the diameter of the cooking vessel so that in operation it fits around the cooking vessel thereby positioning the heat resistant waterproof sheet member in position over the cooking vessel. The outer member optionally comprises a gap in its circumference to allow it to fit over a handle of a cooking vessel.

The weight of the outer member places tension on the connecting means, which in turn places the waterproof sheet member under moderate tension. This again acts to avoid the build up of ripples in the sheet member, thus contributing to the quality of the seal and reducing the amount of water present as condensation on the inner surface of the sheet member.

Once cooking is completed, the outer member can be used to remove the waterproof sheet member from the cooking vessel without the need for the operator's hand to pass over the cooking vessel. This reduces the risk of injury to the operator caused by steam from the cooking vessel.

The outer member is preferably made of a comparatively rigid material for example, wood, plastic or metal. In an aspect, the outer member is made of a rigid, thermally insulating material such as wood or plastic to ensure that it does not become overheated during the cooking process.

The waterproof sheet member is preferably sufficiently thick to provide a degree of thermal insulation between the lid and the interior of the cooking vessel. However, the sheet material should not be so thick that it inhibits the formation of a good seal between the lid of the vessel and the vessel. Therefore, in an aspect, the sheet material may have a thickness greater than about 0.01mm, such as greater than about 0.02 mm, for example greater than 0.04mm or greater than 0.06mm. In addition, the sheet material may have a thickness of less than 5mm, for example less than 1mm such as less than 0.5mm, less than 0.2mm or less than 0.1mm.

In an aspect, the waterproof, heat resistant sheet member comprises a protruding portion located at or secured to the circumference of the sheet member. This may be used by an operator to remove the waterproof, heat resistant sheet member from the cooking vessel without the need to directly touch the part of the sheet member in contact with the rim of the cooking vessel.

The protruding portion may be any convenient shape, for example rectangular and is typically less than 20%, for example less than 10% or less than 5% of the surface area of the main body of the heat resistant sheet member.

In aspects in which the waterproof, heat resistant sheet member comprises a single protruding portion, in use, the protruding portion is preferably positioned on the opposite side of the cooking vessel from the operator. This ensures that on removal of the sheet member from the cooking vessel using the protruding portion, the hand of the operator does not pass over an uncovered part of the cooking vessel.

The sheet member may comprise a graphical representation on one surface, which may be written or symbolic, indicating the preferred orientation of the sheet member relative to the operator.

The heat resistant, waterproof sheet member may comprise a plurality of these protruding portions around the circumference of the sheet member. These enable the operator to conveniently grip a protruding portion without the need to rotate the cooking vessel.

For example, the heat resistant waterproof sheet member may comprise any of 2, 3, 4, 5, 6, 7, 8, 9 or 10 protruding portions around the outer perimeter of the sheet member.

These may be approximately equally spaced.

In an aspect, the heat resistant waterproof sheet member comprises 3 or 4 protruding portions, which are preferably rectangular and preferably equally spaced around the outer perimeter of the sheet member.

The protruding portions may be made from the same material as the heat resistant, waterproof sheet member or may be made from a higher friction material to provide a better grip. If the protruding portions are made from a different material, this material is preferably also heat resistant.

The cooking vessel may be any vessel suitable for cooking rice in which the lid is held in position by its own weight. The cooking vessel is preferably regularly shaped and may be a generally cylindrical vessel having a circular cross section. For example, the cooking vessel may be a standard circular cross section cooking pot or saucepan, such as a 5", 6", 7", 8", 9", 10", 11" or 12" diameter pot. The particular pot used may be selected according to the quantity of rice to be cooked. If less rice is to be cooked, a smaller pot may be used. The advantage of using a smaller diameter pot is that the effect of variations in height of rice layers on the bottom of the pot is reduced since the water level is higher for a given amount of water. This reduces the likelihood of an upper layer of rice becoming uncovered by water too early in the cooking process and hence being undercooked.

In an aspect, the external surface of the cooking vessel (e.g. a pot) slopes outwardly towards the upper rim of the pot. This assists retention of the sheet member in aspects where the sheet member is stretched around the perimeter of the pot.

In an aspect, the vessel and lid comprise complementary contact surfaces. For example, the vessel may comprise a stepped rim and the lid a complementary stepped surface. This arrangement assists in holding the lid in position and also in the formation of a good seal when the sheet member is placed between the main body of the vessel and the lid.

In an aspect of the invention, the lid comprises a depression in the inner surface bordered by the rim of the lid. This means that the waterproof sheet member contacts the underside of the lid only at the outer rim of the lid and the contact surface between the lid and the vessel. When the waterproof sheet member is placed between the lid and the vessel the depression in the inner surface of the lid gives rise to an air gap between part of the lid and the sheet member. This acts to partially insulate the lid from the heat of the cooking vessel, thereby improving heat retention.

In an aspect, the cooking vessel may be made of a transparent material (e.g. a glass such as borosilicate glass e.g. pyrex). This allows the user to determine the cooking stage more easily for example by allowing observation of boiling if present in the stage (ii) heating stage, or the degree of absorption of the cooking water by the rice.

The inner surface of the cooking vessel may also be coated with a non-stick coating (e.g. PTFE) to reduce sticking of the rice to the cooking vessel. The cooking vessel, which may be a pot, may also comprise an encapsulated base in order to improve heat transfer into the pot. The encapsulated base may be formed from stainless steel, copper, or aluminium galvanised with stainless steel.

In an aspect, the lid comprises a temperature measuring device e.g. a temperature sensitive strip capable of registering an increase in temperature of the lid. During the cooking process, some of the heat applied to the cooking vessel causes the evaporation of water from the rice/water mixture. This then condenses on the waterproof sheet member before recycling back into the rice/water mixture without contacting the inner surface of the lid. Once the water has been absorbed by the rice, more of the applied heat is then conducted up to the lid, through the walls of the cooking vessel, resulting in an increase in the lid temperature. This temperature increase therefore acts as an indicator that the water has been absorbed by the rice and hence that the cooking process has been completed. Typically, a lid temperature of greater than 100°C indicates absorption of all of the water in the cooking vessel by the rice.

As well as assisting in water retention, the presence of the waterproof sheet member between the lid of the vessel and the vessel means that the pressure in the vessel is greater than atmospheric pressure during the rice cooking process. This also assists in reducing the rice cooking time.

The internal pressure maintained by the vessel when the sheet member in position between the lid and the vessel will depend on factors such as the weight of the lid, the quality of the seal, and the heat applied to the vessel. Typically, the lid is maintained in position only by its own weight and its interaction with the sheet member and the cooking vessel and is not secured to the vessel by clamps or other securing means.

The lid is usually pressed into the sheet member gently, without undue pressure. It is generally undesirable to apply excessive external pressure to the lid in order to force a tighter seal since this may result in an undesirably high internal pressure and cooking temperature, which may cause burning of the rice and may also constitute a safety hazard if the pressure should suddenly force the lid off.

The pressure in the interior of the cooking vessel is usually greater than ambient pressure by more than about 0.1 atm during the cooking process, for example greater than about 0.2 atm such as greater than about 0.3 atm. This pressure difference will normally also be less than about 2 atm, for example less than about 1 atm such as less than about 0.8 atm or less than about 0.5atm.

In step (iv) of the first embodiment, the heat applied to the cooking vessel is reduced and the cooking process allowed to go to completion. The level of heat applied in step (iv) should be sufficient to retain the internal pressure and temperature of the cooking vessel sufficiently above ambient in order to allow the rice cooking process to go to completion.

The temperature of the water in the rice/water mixture during step (iv) may be the same as that at the end of step (ii), for example in the case that the temperature of the water in the rice/water mixture at the end of step (ii) is at boiling point. Alternatively, the temperature of the water in the rice/water mixture may increase during step (iv), for example in the case that the temperature of the water in the rice/water mixture at the end of step (ii) is in the range from 70 -95°C, for example 80 -90°C. Where the temperature of the rice/water mixture increases during step (iv), the rate of increase is less than in step (ii) due to the reduced heat applied to the cooking vessel and the increased temperature differential between the cooking vessel and the external environment.

In some aspects, the temperature of the water in the rice/water mixture will increase to boiling point during step (iv). In such aspects, the temperature of the water in the rice/water mixture will remain at the boiling point for the remainder of step (iv).

The difference in temperature between the maximum temperature attained during step (ii) and the maximum temperature attained during step (iv) may be less than 30°C, for example less than 20°C, or less than 10°C, for example less than 5°C or less than 2°C.

As mentioned above, in some aspects e.g. where the temperature of the water in the rice/water mixture at the end of step (ii) is at boiling point, the temperature during step (iv) does not change significantly.

The rice is often found to become progressively less consumable after cooking for more than about 8 minutes during step (iv).

Therefore, during step (iv), the rice is usually cooked for greater than 240s, for example greater than 300s, such as greater than 360s or greater than 400s. During step (iv), the rice is usually cooked for less than 1 500s, for example less than 1 000s, such as less than 720s, less than 660s or less than 600s. In an aspect, the rice is cooked during step (iv) for a time less than 540s such as less than 500s. In an aspect, the rice is cooked during stage (iv) for a time in the range from 400 -500s.

The method of the invention may be applied to any type of rice, for example rice categorised as long or short grain rice.

Brief Description of the Drawings

Figure 1 shows an exploded, sectional view of a heat resistant, waterproof sheet member positioned between the lid of a cooking vessel and the main body of the cooking vessel.

Figures 2a and 2b show an end view and a plan view respectively of an embodiment of the waterproof, heat resistant sheet member.

Figure 2c shows an alternative embodiment of the waterproof, heat resistant sheet member.

Detailed Description of the Drawings and Examples

Figure 1 shows the waterproof sheet member (1) of the invention positioned between the lid (2) of the cooking vessel and the main body (3) of the cooking vessel. The outward sloping rim (4) of the main body of the cooking vessel assists the securing of the waterproof sheet member (1) to the cooking vessel via the elastic securing means (5).

The main body of the cooking vessel and the lid each comprise a stepped surface (6a, 6b) and complementary contact surfaces (7a,7b), which assist in the formation of a good seal with the waterproof, heat resistant sheet member. The water/rice mixture (8) is contained within the cooking vessel, which comprises a copper encapsulated base (10).

The lid (2) comprises a depression (9) in its inner surface, to create an air gap between the lid and the sheet member to reduce heat loss through the lid.

Figures 2a and 2b show end and plan views respectively of a waterproof sheet member (1) comprising an elastic retaining means (2) around its circumference and 1 rectangular protruding portion (3) positioned on its circumference.

Figure 2c shows another embodiment of the waterproof, heat resistant sheet member (1) comprising an outer member (3) connected to the waterproof sheet member using twine connectors (2). The outer member comprises a space (4) to allow the outer member to fit over the handle of the cooking vessel.

Examples

Example 1 -cooking of rice according to the method of the invention 240 grams of Basmati "Golden Sun" rice was mixed with 360g of water at ambient temperature (approximately 20°C) in a 7" aluminium Teflon saucepan. A polyethylene sheet member comprising a string around the periphery was placed between the lid of the saucepan and the saucepan. The string was then tightened to secure the outer edge of the sheet member to the exterior of the saucepan.

The saucepan was placed on an element of a standard electric cooker, preheated to gas mark 6 and heated for 3 minutes and 30 seconds to give a water temperature in the range from 80-85°C. At this stage starch was observed on the surface of the rice/water mixture.

The saucepan was then removed from the cooking element and placed on a second element operating at low heat (gas mark 1) for a further 8 minutes, at which point no unabsorbed water was present in the saucepan. The rice was then removed from the cooking vessel and found to be perfectly fluffy, easily separable and not sticky.

This experiment shows that an easily affordable rice type may be cooked quickly, economically and easily using the method of the invention to produce a high quality cooked rice product.

Example 2 -comparative example using a cloth member instead of a waterproof sheet member Example I was repeated using a water permeable cloth member between the lid of the saucepan and the saucepan instead of the waterproof sheet member used in Example 1. In addition, the second stage cooking time was extended by 50 seconds to 8 minutes 50 seconds to give a total cooking time of 12 minutes 20 seconds.

During the cooking process, steam was observed coming from between the lid and the saucepan. In addition, following completion of the cooking process, condensed water was observed around the underside of the saucepan lid.

Even after extending the cooking time, the rice was still found to be only partially cooked with the core of the rice grains still hard. This gave the rice a bitty texture.

The poor cooking of the rice in this example relative to that of the invention is believed to be due to a combination of increased water loss, increased heat loss and reduced cooking pressure during the cooking process due to the absence of the waterproof sheet member.

Example 3 -comparison between method of invention and open topped boiling method using excess of water In this example, the same quantity of rice was cooked in the same saucepan as in Example 1. 1028g of water at ambient temperature (approximately 20°C) was added.

The saucepan was then heated at Gas Mark 6 and the rice cooked in the saucepan without the lid or sheet member present.

Boiling was observed after 5 minutes and 30 seconds and the temperature of the rice/water mixture was retained at boiling point for a further 21 minutes and 30 seconds to give a total cooking time of 27 minutes. Stirring was required to avoid sticking of the rice to the saucepan.

The rice obtained by this method was found to be undercooked compared to that of Example 1 with insufficient water absorbed to soften the centre of the rice, This rice was not suitable for consumption.

Example 4 -comparison between method of invention (Example 1) and open topped boiling method using same amount of water Example 3 was repeated except that the same quantity of water was used as in Example 1 (360g of water at a temperature of approximately 20°C). The saucepan was heated at Gas mark 6 for 3 minutes and 40 seconds. At the end of this time, all of the water in the saucepan had either been absorbed by the rice or evaporated.

The rice was found to be undercooked compared to the rice obtained by the method of the invention and not suitable for consumption.

Example 5 -comparison between method of invention (Example 1) and boiling method using excess of water where lid present In this example, the same quantity of rice was cooked in the same saucepan as in

Example 1.

1028g of water at ambient temperature (approximately 20°C) was added. The saucepan was then heated at Gas Mark 6 and the rice cooked in the saucepan without the lid or sheet member present.

Boiling was observed after 5 minutes and 30 seconds and the temperature of the rice/water mixture was retained at boiling point for a further 12 minutes and 50 seconds after which the rice was strained through a colander.

Once strained, the rice was found to have a congealed, starchy consistency. The rice required further drying. Once dried, it was found to be suitable for consumption but of lower quality than the rice obtained by the method of the invention in Example 1.

Example 6 -comparison between method of invention and boiling method using same amount of water where lid present Example 5 was repeated except that the same quantity of water was used as in Example I (360g of water at a temperature of approximately 20°C).

The saucepan was heated at Gas mark 6 for 3 minutes and 23 seconds at which point, all of the water in the saucepan had either been absorbed by the rice or evaporated.

Example 7 -comparison between method of invention and pressure cooker method 240 grams of Basmati "Golden Sun" rice was mixed with 360g of water at ambient temperature (approximately 20°C) in a standard pressure cooker saucepan.

The pressure cooker was placed on an element of a standard electric cooker, preheated to gas mark 6 and heated for 3 minutes and 18 seconds. The pressure cooker was then removed from the cooking element and placed on a second element operating at low heat (gas mark 1) for a further 8 minutes 30 seconds.

At the completion of the experiment, the rice was very starchy and undercooked with approximately 1 20g of water still remaining in the cooking vessel.

Example 8 -comparison between method of invention and electric rice cooker method 240 grams of Basmati "Golden Sun" rice was mixed with 360g of water at ambient temperature (approximately 20°C) in a standard electric rice cooker and cooked for eleven minutes.

The rice was undercooked, stodgy, starchy and sticky compared to the rice obtained by the process of the invention. In addition, some burning of the rice on the walls of the cooker was observed.

Claims

CLAIMS1 A method for cooking rice in a cooking vessel having a lid, comprising the steps of: (i) mixing the rice with an initial amount of water to form a rice/water mixture; (ii) applying heat to the rice/water mixture to raise it to or maintain it at an elevated temperature in the cooking vessel; (iii) placing a waterproof, heat resistant sheet member between the lid of the vessel and the vessel to form a seal or partial seal capable of maintaining an internal pressure in the vessel greater than that sustainable using the lid alone; (iv) reducing the heat applied to the rice/water mixture, whilst maintaining this applied heat at a level and for a time sufficient to complete cooking of the rice.
2. A method according to claim 1, wherein the initial amount of water is selected so that following completion of the rice cooking process, all of the water initially present in the cooking vessel has evaporated or been absorbed by the rice.
3. A method according to claim 1 or claim 2, wherein the initial amount of water is selected to be in a ratio of 60g rice:80-lOOg water.
4. A method according to any preceding claim, wherein in step (ii) of the first embodiment, the rice/water mixture may be heated to or maintained at a temperature of greater than 70°C.
5. A method according to any preceding claim, wherein the waterproof sheet member is placed between the lid of the vessel and the vessel before heating step (ii).
6. A method according to any preceding claim wherein the cooking vessel is a standard circular cross section cooking vessel.
7. A method according to claim 6, wherein the external surface of the cooking vessel slopes outwardly towards its upper rim.
8. A method according to claim 6 or claim 7, wherein the vessel and lid comprise complementary contact surfaces.
9. A method according to claim 8, wherein the main body of the vessel comprises a stepped rim and the lid comprises a complementary stepped surface.
10. A method according to any preceding claim wherein the lid of the cooking vessel comprises a depression in the inner surface bordered by the rim of the lid.
11. A method according to any preceding claim wherein the cooking vessel is made of a transparent material.
12. A method according to any preceding claim wherein the lid comprises a temperature measuring device.
13. A waterproof, heat resistant sheet member for use in the method of any preceding claim, wherein the waterproof sheet member comprises a retaining means to assist in securing it to the cooking vessel.
14. A waterproof, heat resistant sheet member according to claim 13, wherein the retaining means is located at, or secured to, the outer periphery of the sheet member.
15. A waterproof, heat resistant sheet member according to any one of claims 13 to 14, wherein the member is formed from an elastic material.
16. A waterproof, heat resistant sheet member according to any one of claims 13 to 14, wherein the member is formed from a flexible yet comparatively inelastic material but comprises an outer portion, having an elastic component.
17. A waterproof, heat resistant sheet member according to any one of claims 13 to 14, wherein the member is formed from a flexible yet comparatively inelastic material but comprises in the outer periphery of the sheet member a tightening means for securing the sheet member to the pot.
18. A waterproof, heat resistant sheet member according to any one of claims 13 to 17, wherein the sheet member comprises a protruding portion located at or secured to the circumference of the sheet member.
19. A waterproof, heat resistant sheet member according to any one of claims 13 to 17, wherein the sheet member comprises an outer member, connected to the outer periphery of the sheet member by connecting means.
20. A waterproof, heat resistant sheet member according to claim 19, wherein the outer member is a metal ring.
21. An apparatus for use in the method of any of claims 1-12 comprising a cooking vessel, a lid and a waterproof, heat resistant sheet member for use between the lid of the cooking vessel and the vessel.