SG177045A1 - A method and apparatus for preparing soft-boiled eggs - Google Patents

Abstract

A METHOD AND APPARATUS FOR PREPARING SOFT-BOILED EGGSA method of preparing soft-boiled eggs comprising the steps of immersing one ormore eggs in a heat transfer medium, raising the temperature of the heat transfermedium to a first temperature value and thereafter cooling the heat transfermedium at a rate such that the temperature thereof falls to a second temperaturevalue over a predetermined time interval. An apparatus for performing the methodincludes a vessel (21) for containing the heat transfer medium, means for heatingthe heat transfer medium, means for cooling the heat transfer medium,temperature sensing means for sensing the instantaneous temperature of the heattransfer medium and control means for energising the heating means until thetemperature sensor detects the attainment of the first temperature and forenergising the cooling means thereafter for the predetermined time interval.Figure 3

Description

A METHOD AND APPARATUS FOR PREPARING SOFT-BOILED EGGS

The present invention relates to a method and associated apparatus for preparing soft-boiled eggs. As used in this specification the term “soft-boiled” when applied to eggs will be understood to relate to a condition in which the egg yoke is cooked, but remains in a fluid state, whilst the albumen or “white” of the egg has achieved a set state. If the eggs are under-cooked the albumen does not achieve the set state and remains fluid and partly transparent. If the eggs are over-cooked the yoke passes from its fluid state to a solid state. Traditionally, soft-boiled eggs are made by placing the eggs in boiling water for a fixed short time period between three and four minutes, and then cooled rapidly to prevent further cooking, unless, of course, they are to be consumed immediately. This is only suitable, however, for one or a small number of eggs, whereas commercially it may be appropriate to cook a very much larger number of eggs, say between 50 and 100 eggs at one time. Traditional techniques are unsuitable for such large quantities.

Moreover, in commercial establishments, particularly retail establishments, it is necessary to be able to serve a large number of soft-boiled eggs in a short period of time within a range of temperatures suitable for consumption. The present invention seeks, therefore, to provide a method of preparing soft-boiled eggs which can be used for preparing a large quantity of soft-boiled eggs and maintaining them in a soft-boiled state at a temperature suitable for consumption without further cooking so that the consistency of the eggs remains unchanged over an extended period of time.

Prior art attempts to produce such commercial machines have resulted in a device capable of cooking seven or so eggs, comprising a vessel into which the eggs are placed, and into which boiling water is then introduced. The vessel has an opening allowing the boiling water to drain out at the given rate so that, provided a fixed quantity of water is introduced at boiling temperature (and the vessel has a suitable mark to indicate the appropriate filling level), the eggs will be processed to the right condition by the time all the water has drained from the vessel. It is, however, necessary to cool the eggs after the water has drained out, typically by a brief cold shower of water, or by being soaked in ice cold water for two or three minutes, in order to prevent further cooking which would result in the eggs becoming over-cooked. This apparatus is, however, not suitable for preparing a large quantity of eggs, nor does it maintain the eggs in a warm state ready for consumption over an extended period of time without varying the consistency of the eggs.

According to the present invention, therefore, there is provided a method for preparing soft-boiled eggs comprising the steps of immersing one or more eggs in a heat transfer medium, raising the temperature of the heat transfer medium to a first value, and thereafter cooling the heat transfer medium at a rate such that the temperature thereof falls to a predetermined second temperature value over a predetermined time interval.

In the method of the invention the “first temperature” to which the heat transfer medium (typically water) is raised does not have to be as high a temperature as boiling water.

The inventor of the present invention has discovered that there is a relationship between the rate at which eggs cook and the temperature at which they are held, and that if eggs are maintained between a first or starting temperature and a second or transition temperature for a given period of time the yokes become cooked to a perfect fluid consistency. In order to prevent overcooking, therefore, the present invention provides for the heat transfer medium, and therefore the eggs, to cool from the first or starting temperature to the second or transition temperature in the desired cooking time, which can be determined empirically for any given apparatus. If the apparatus is so arranged that the heat transfer medium and therefore the eggs contained in it have reached the second or transition temperature at the end of the predetermined time interval, such that after further time the heat transfer medium and, consequently, the eggs contained in it, fall to a temperature below the second or transition temperature, no substantial further cooking of the yokes takes place.

The heat transfer medium may be cooled from the first to the second temperature in the said predetermined time interval by forced cooling, for example, by a flow of cooling fluid delivered at a flow rate established to cool the body of heat transfer fluid from the first to the second temperature in the said predetermined time interval. It will be appreciated that the larger the body of heat transfer medium the greater the quantity of thermal energy, and therefore the more energetic the cooling required to bring the temperature value down from the first temperature value to the second temperature value within the said predetermined time interval.

In a preferred embodiment of the invention the volume of heat transfer medium is substantially predetermined and the rate at which the cooling fluid is delivered, preferably at ambient temperature, is also predetermined so that the operator has the minimum of input to the working of the device, simply filing a vessel to a predetermined level to provide a given volume of heat transfer fluid and switching on the apparatus which will then automatically heat the heat transfer fluid to the first temperature, thereafter switch off the heating and turn on the cooling such that the heat transfer medium, and therefore the eggs contained within it, cool from the first temperature to the second temperature in the said predetermined time interval at the end of which the eggs will be perfectly cooked and ready for consumption.

In a more sophisticated version of the apparatus of the invention, however, there may be provided means for setting controls which take account of the volume of heat transfer medium actually present in the vessel, and also the ambient temperature which, once set, will ensure that the heat transfer medium is brought from the first temperature value to the second temperature value in the said predetermined time. With a smaller volume of heat transfer medium the rate of delivery of the cooling fluid will need to be lower in order to achieve the desired cooking conditions, and likewise, if the ambient temperature is lower the cooling will likewise need to be less energetic.

The cooling fluid may be delivered at ambient temperature or at a selected temperature, which may be related to the ambient temperature.

Preferably, however, the rate of flow of cooling fluid is predetermined to be that which will bring the given volume of heat transfer medium to the vicinity of the said second temperature value within the said predetermined time interval. Likewise, it is preferred that the flow of cooling fluid is continuous and uninterrupted for the duration of the said predetermined time interval.

The cooling of the heat transfer medium may be continued after the said predetermined time interval for a further time interval.

The heat transfer medium is preferably a liquid, and may be water.

The cooling fluid may be air, and the cooling air may be driven by a fan.

In this latter case the fan may be such as to deliver a rate of flow of cooling air which will bring the said heat transfer medium from the said first temperature value to the said second temperature value in the said predetermined time interval. The rate of flow of cooling air may, however, be varied in dependence on the ambient temperature.

Preferably, the said further time interval is such that the heat transfer medium has reached a third temperature value at the expiry of the said further time interval, below which no further cooking of the eggs occurs.

After the expiry of the said further time interval the temperature of the heat transfer medium is sensed whereby to determine the application of heat to maintain the temperature of the heat transfer medium above a fourth temperature value lower than the said third temperature value. The fourth temperature value is the lowest temperature at which the soft-boiled eggs may reasonably be served for consumption as warm eggs.

The apparatus of the present invention may be so arranged that, as mentioned above, no adjustments are required providing the volume of water and ambient temperature remain within certain limits. In a preferred embodiment of the invention the said first temperature value is approximately 64°C. This may vary above and below the target temperature by approximately + 1°C.

The said second temperature is preferably between approximately 62.5°C and approximately 62.75°C. This so-called “transition” temperature is that above which the yokes in the eggs will cook, and below which no further yoke cooking will take place although some slight further cooking of the albumen will.

With the temperature values indicated above the said first time interval is preferably substantially 20 minutes.

The third temperature value is preferably approximately 59.5°C. With these values the said further time interval is preferably approximately 30 minutes.

The said fourth temperature is preferably approximately 44°C and this may vary by approximately + 2°C.

The method of the invention may further include the step of providing a visual indication of the expiry of the said predetermined time interval. A visual indication of the expiry of the said further time interval may also be provided, as may be a visual indication that the heating of the heat transfer medium is taking place.

The present invention also comprehends apparatus for preparing one or a plurality of soft-boiled eggs, comprising a vessel for containing a heat transfer medium, means for heating the heat transfer medium, means for cooling the heat transfer medium, temperature sensing means sensing the instantaneous temperature of the heat transfer medium and control means for energising the heating means until the temperature sensor detects the attainment of a first temperature and for energising the cooling means thereafter for the said predetermined time interval.

The said control means may energise the said cooling means for a further time interval after the expiry of the said predetermined time interval.

Preferably the heat transfer medium is a liquid such as water and the cooling means is a fan delivering air to the vessel containing the heat transfer medium whereby to cool it.

The control means may comprise a CPU programmed to operate the cooling means for a time comprising the sum of the said predetermined and the said further time intervals upon attainment by the heat transfer medium of the said first temperature.

There may be provided indicator lamps for providing an indication of the expiry of the said predetermined time interval and/or the expiry of the said further time interval.

One embodiment of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a general perspective view of apparatus for performing the method of the invention;

Figure 2 is a rear view of the apparatus of Figure 1;

Figure 3 is an exploded view showing the components of the apparatus of

Figures 1 and 2;

Figure 4 is a flow diagram illustrating the sequence of operations of the apparatus of Figures 1 to 3; and

Figure 5 is a graph showing the variation of temperature with time in the method of the invention.

Referring now to the drawings, the apparatus shown comprises an outer body casing generally indicated 11 mounted on supports 12 and having a cover 13.

The simple array of controls comprises a “start” button 14, a “reset” button 15 and an indicator lamp 16 in the form of a dual colour red/green light-emitting diode. At one side the outer casing has a set of outlet openings 17 in the form of a louvred vent, and at the rear an array of inlet openings 18 for a cooling fan 19. Within the outer casing 11 is an inner vessel 20, which has an upper perimetral flange 21 by which it is suspended from the outer casing 11 with an airspace between itself and the outer casing 11 for the passage of the cooling air in operation.

A heating element 22 is located in the bottom of the vessel 20, and a temperature sensing thermocouple 23 is located in close proximity thereto.

The vessel 20, in this embodiment, has a volume of 22 litres and is capable of receiving up to a maximum of 80 eggs.

The temperature sensor 23 and the “start” and “reset” buttons 14, 15 provide the input to a controller, the outputs from which control the energisation of the heater element 22 and the lighting-emitting diode 16. The apparatus of the present invention, via the controller, which is in the form of a CPU, functions in the following way. First, 22 litres of cold water is introduced into the interior of the vessel 21 and then the charge of eggs to be cooked is placed therein. As mentioned above up to 80 eggs can be placed in the water in the vessel 21. Then the “reset” button is pressed to ensure that the system is normalised and ready for commencement of a new cycle of operation and then the “start” button 14 is pressed. The controller then commences energisation of the heater 22, and simultaneously the dual colour light-emitting diode 16 is illuminated red. The thermocouple 23 senses the water temperature, and when this reaches the set (first) temperature, in the case of this embodiment 64°C, the heater 22 is turned off. At this instance, the red light-emitting diode lamp 16 is still illuminated. A timer forming part of the CPU then starts to operate and the fan 19 is energised to draw ambient air though the inlet 18 from where it is delivered to pass between the casing 11 and the vessel 20, and then out through the louvered vent outlet 17.

The timer is programmed to run for a first time interval (in the case of this embodiment 20 minutes) after which the light-emitting diode 16 is illuminated green to indicate to the user that the eggs have reached a condition suitable for consumption. During this time the water in the vessel 20 has cooled from the first temperature (64°C) to the second temperature in the region between 62.5°C and 62.75°C during which time the yokes in the eggs have been cooking. The fan 19 is maintained in operation for a further 30 minutes during which time the water bath cools from 62.75°C to just below 60°C (say 59.5°C) and in this time period the albumen (the white of the egg) continues to cook, becoming slightly firmer. Below 60°C no further cooking of the eggs takes place and at the end of 30 minutes the fan is turned off. The temperature sensor 23 detects the temperature of the water bath continually and, as this cools, determines the point at which the heater 22 is turned on again to maintain a minimum serving temperature of 44°C. In this second phase of operation, which may be termed the “keeping” phase (the first phase being the “cooking” phase) the eggs remain warm, but do not cook further and can be kept in this state between 44 and 46°C indefinitely.

In a more complex embodiment there may be controls for varying the speed of the fan in dependence on the volume of water actually placed in the vessel 20 and the ambient temperature, bearing in mind that a larger volume of water will take longer to cool from a given temperature, and that the rate of cooling will be dependent on the ambient temperature, cooling more rapidly if the ambient temperature is low than if the ambient temperature is high. The important limitation is that the eggs should be maintained above 62.75°C for a period of time for the egg yolks to cook to a soft consistency, and it has been determined that with this apparatus a cooling period of 20 minutes is required for the water bath to fall from the starting temperature of 64°C to the transition temperature of between 62.5 and 62.75°C. In cooler conditions for the same volume of water it may be necessary to heat the water to a higher starting temperature in order that it should reach the transition temperature after 20 minutes for a given fan capacity, or the fan itself may be operated at a lower speed so that the cooling progresses at the required rate.

In the more complex embodiment described above, the dual colour light-emitting diode may also be supplemented or replaced by a suitable audio output device such as a speaker or a buzzer to provide an audible indication of the expiry of the first time interval and the further time interval explained previously.

Figure 5 illustrates the process graphically with time plotted along the X-axis and temperature plotted along the Y-axis. Here it can be seen that, from the origin, assumed to be the point at which the apparatus is turned on, the water temperature rises rapidly whilst being heated until attaining the temperature 64°C at which point (time Ty) the heating is switched off and the apparatus allowed to cool under the forced ventilation of the fan. After 20 minutes, namely at time To, the water has cooled to the transition temperature of between 62.5 and 62.75°C, and at time T; the water bath has fallen to 59.5°C at which point the fan is switched off. The time interval T, to T, is 20 minutes and the time interval T, to T3 is 30 minutes for this embodiment. Thereafter the fan is switched off and the apparatus cools naturally until reaching 44°C at which point the heater is turned on again to maintain the temperature in the range 44 to 46°C although further cooking of the eggs does not take place below 60°C.

It will be appreciated that the eggs cook in the shaded area of the graph, and cooking commences during the heating phase once the water bath has reached the transition temperature of 62.5°C. The time interval T, during which the temperature is above 62.5°C and the heater is switched on is relatively short and, in view of the magnitude of the energy supplied, can be effectively ignored, although in other embodiments, where a less energetic heater is employed, it may be necessary to take this time period into account when determining the total cook time.

Claims (25)

1. A method of preparing soft-boiled eggs comprising the steps of immersing one or more eggs in a heat transfer medium, raising the temperature of the heat transfer medium to a first temperature value and thereafter cooling the heat transfer medium at a rate such that the temperature thereof falls to a second temperature value over a predetermined time interval.

2. A method of preparing soft-boiled eggs as claimed in Claim 1, in which the temperature of the heat transfer medium is maintained between the said first and second temperatures values by a flow of cooling fluid delivered at a predetermined flow rate for the said predetermined time interval.

3. A method as claimed in Claim 2, in which the cooling fluid is delivered at ambient temperature.

4. A method as claimed in Claim 2 or Claim 3, in which the rate of flow of cooling fluid is determined as that which will bring the heat transfer medium to the vicinity of the said second temperature value within the said predetermined time interval.

5. A method as claimed in any of Claims 2 to 4, in which the cooling flow is continuous and uninterrupted for the duration of the said predetermined time interval.

6. A method as claimed in any preceding Claim, in which the cooling of the heat transfer medium is continued after the said predetermined time interval for a further time interval.

7. A method as claimed in any preceding Claim, in which the heat transfer medium is water.

8. A method as claimed in any of Claims 2 to 8, in which the cooling fluid is air driven by a fan (19).

9. A method as claimed in Claim 8, further comprising the step of adjusting the fan such as to deliver a rate of flow of cooling air which will bring the said heat transfer medium from the said first temperature value to the said second temperature value in the said predetermined time interval in dependence on the volume of the heat transfer medium and/or the ambient temperature.

10. A method as claimed in any of Claims 6 to 9, in which the said further time interval is such that the heat transfer medium has reached a third temperature value at the expiry of the said further time interval, below which no further cooking of the eggs occurs.

11. A method as claimed in any preceding Claim, in which the temperature of the heat transfer medium is sensed after the end of the said further time interval whereby to determine the application of heat to maintain the temperature of the heat transfer medium above a fourth temperature value, lower than the said third temperature value.

12. A method as claimed in any preceding Claim, in which the said first temperature value is approximately 64°C.

13. A method as claimed in any preceding Claim, in which the said second temperature is between approximately 62.5°C and approximately

62.75°C.

14. A method as claimed in any preceding Claim, in which the said first time interval is substantially twenty minutes.

15. A method as claimed in any preceding Claim, in which the third temperature value is approximately 59.5°C.

16. A method as claimed in any of Claims 11 to 15, in which the said further time interval is approximately thirty minutes.

17. A method as claimed in any of Claims 11 to 16, in which the said fourth temperature is approximately 44°C (+ 2°C).

18. A method as claimed in any preceding claim further including the step of providing a visual and/or audible indication of the expiry of the said predetermined time interval.

19. A method as claimed in any of Claims 6 to 18, further comprising the step of providing a visual and/or audible indication of the expiry of the said further time interval.

20. Apparatus for preparing one or a plurality of soft-boiled eggs, comprising a vessel (21) for containing a heat transfer medium, means for heating the heat transfer medium, means for cooling the heat transfer medium, temperature sensing means for sensing the instantaneous temperature of the heat transfer medium and control means for energising the heating means until the temperature sensor detects the attainment of a first temperature and for energising the cooling means thereafter for a predetermined time interval.

21. Apparatus as claimed in Claim 20, in which the said control means energises the said cooling means for a further time interval after the expiry of the said time interval.

22. Apparatus as claimed in Claim 20 or Claim 21, in which the heat transfer medium is water.

23. Apparatus as claimed in any of Claims 20 to 22, in which the cooling means is a fan (19) delivering air to the vessel (21) whereby to cool the heat transfer medium.

24. Apparatus as claimed in any of Claims 20 to 23, in which the control means comprises a CPU programmed to operate the cooling means for a time comprising the said predetermined time interval and the said further time interval upon attainment by the heat transfer medium of the said first temperature value.

25. Apparatus as claimed in any of Claims 20 to 24 further including indicator lamps (16) for providing an indication of the expiry of the said predetermined time interval and/or the expiry of the said further time interval.