GB2524168A - Improvements in and relating to methods for making a pasteurised in-shell soft boiled eggs, and apparatus for doing so - Google Patents

Abstract

A process 200 for producing in-shell soft boiled eggs comprises applying a vacuum 206 to the one or more eggs to at least partially remove any air beneath the shell of the eggs and cooling one or more eggs to a desired base temperature 208, 210. The eggs are cooked at a desired cooking temperature for a length of cooking time 214, 216 and pasteurised for a pasteurisation time at a pasteurisation temperature 220, 222. The eggs are then cooled for a cooling time at a cooling temperature 226. The process provides reproducible results for producing in shell soft boiled eggs consistently and at an industrial scale. Removing air from beneath the shell makes it possible to plunge the egg into hot water without the shell cracking. Also provided is a system suitable for carrying out such as process comprising a tray or other egg support and one or more waterbaths. Automated machinery may transport the tray or support between waterbaths held at temperatures required for pre-cooling, cooking, pasteurising or post-cooking cooling.

Description

IMPROVEMENTS IN AND RELATING TO METHODS FOR MAKING A

PASTEURISED IN-SHELL SOFT BOILED EGGS, AND APPARATUS FOR DOiNG SO The present invention relates to a process and method for making in-shell soft boiled eggs that have been pasteurised. In particular, to a process and method for making soft boiled eggs that are still in their shell, suitable for consumption by users sometime later, and/or suitable for selling to customers some time later. it dso relates to apparatus for producing such soft boiled eggs.

Many people like to eat soft boiled eggs where the white of the egg is cooked and is sohd, and where the yolk of the egg is not solid -it is runny. Some people like the yolk of the egg very runny, whereas others like the yolk of the egg slightly runny. It is also known to cook eggs until they are hard-boiled -where the whole egg is solid throughout. including the yolk.

The importance of the pasteurisation process is that it eliminates thc risk of food poisoning from Salmonella species that has historically been associated with lightly cooked eggs. The egg processing industry is well regulated by local and national authorities and guidelines for the pasteurisation process required to eliminate Salmonella species in egg products is well understood.

There are many, many disclosures and teachings availabk discussing the preparation of eggs for packaging and/or consumption by humans. Some relate to eggs out of their shell, Some relate to eggs that are still in their shell, There are also many disclosures discussing cooking eggs. There are many disclosures discussing sterilising eggs so that they can be stored and then used/sold later, and yet further disclosures related to cooking eggs for immediate consumption by the user, Other disdosures relate to pre-cooking eggs, which are then stored and used/eaten by a user later, Some examples include patent publications US 2004011784, US 2012067874 US 2005081843, JP 5561783, and JP 2002165581.

It is the aim of the invention to provide an &ternative method of producing in-shell soft boiled eggs, and apparatus for doing so.

According to a first aspect of the invention there is provided a process for producing in-shell soft boiled eggs, said process comprising: applying a vacuum to the one or more eggs to at least partiafly remove any air beneath the sheD of the eggs; cooling S eggs to a desired base temperature; cooking the eggs at a desired cooking temperature for a cooking length of time: pasteurising the yolk of the eggs for a pasteurisation time at a pasteurisation temperature; and cooling the eggs for a cooling time at a cooling temperature.

We have appreciated that the shell of an egg cracks when plunged into hot water because air trapped beneath the shell expands, causing the shell to crack. By removing this air we can plunge the egg into hot water (for example as a method of cooking it) without the sheD cracking.

There may be a step of packaging the eggs, possibly in packages with a reduced oxygen environment around the egg (e.g. vacuum packaged or inert gas, such as Nitrogen or Carbon Dioxide packaged) or by sealing the porous surface of the egg with some form of lacquer or impervious film.

According to a second aspect of the invention, there is provided a system for undertaking the process of the first aspect, the system comprising a tray or egg support on which the eggs are placed for processing. and one or more water baths.

A water bath may be provided for each of the pre-cooking cooling, cooking, pastcurising and post-cooking cooling steps in the production of a cooked in-shell soft boiled egg.

It has been appreciated that in order to control the cooking of an in-shell egg carefully enough to cook the white of the egg, but leave the yolk stifl runny, the physical condition of the egg at the start of the process needs to be brought to a standard condition, If we are to cook the egg for a standard amount of time, it needs to start at a standard, fixcd temperature. This is achieved by cooling the eggs in a first step of the process.

In fact, there may be an earlier step of the process. The first step may comprise collecting together or providing a plurality of eggs that are of a standardised size.

In nianv embodiments of the invention we process a arge number of eggs at the same S time. We may process of the order of 100, 500, 1000, 5000, or more, eggs at the same time. That is to say, a large number of eggs may be at the same stage in the cooking process, or a large number may be at some point (possibly different points) in the process at the same time. or both.

Alternatively, the process may be a semi-continuous process. We are primarily (although perhaps not entirely exclusively) concerned with the industrial scale preparation of eggs to achieve hundreds and thousands, and tens of thousands, of soft-boiled eggs per hour.

In some embodiments an example temperatlLre to which an egg is cooled prior to vacuuming it is at or around 5°C to 10°C. The eggs may be stored in a refrigerator at about this temperature prior to cooking.

The eggs may be vacuum packed in an air impermeable packaging, for example a plastics material pouch, after they have been vacuumed, and before they are brought up to a controfled starting temperature in step one of the process.

It is convenient to store the eggs prior to vacuuming, and after vacuum packing, in a refrigerator. The variations in temperature across a refrigerator do not reaHy matter too much from the point of view of stabilising the inner white prior to cooking the egg. The egg may be refrigerated, then vacuum packed, and then cooled down to a desired temperature. Or, the eggs may be vacuum packed without preliminary chilling.

An efficient way of cooling the eggs to a desired starting predetermined temperature is to cool them in a waterbath. Water is cheap, has good thermal conductivity, a relatively high specific heat capacity, and can be used to surround the egg on all sides.

We prefer to control the starting temperature of the egg to within one or two degrees centigrade typical starting temperature may be between 4°C and ° C. This is achieved by chilling the eggs in a waterbath for somewhere around 20 mm depending on the ingoing temperature of the eggs. with the waterbath having a temperature of at or around 4 °C to 8 °C. The eggs may have a temperature of between 5° and 100 C when they are placed in the waterbath prior to the cooling of the eggs to the desired predetermined base temperature.

When applying a vacuum to the eggs we wish to vacuum the egg to achieve as low a vacuum as practical within the constraints of cost-effective machinery, This is currently around 2 mbar to 4 mbar.

In some embodiments, once the vacuumed eggs have been vacuum packed, they can be stored for sometime before being used in the rest of the process, For example, they can be returned to a refrigerator. The eggs may be vacuum packed individually, or with more than one egg in each vacuum pack, or as a series (e.g. a sausage or matrix, such as a grid) of vacuum packed eggs.

In the cooking step we can cook the eggs between 90°C and 100 °C. As mentioncd earlier, the cooking temperature, cooking time, size of the egg, and age of the egg are all interrelated. \.ATe prefer to use a waterbath to cook the eggs because it surrounds the eggs with heat, on all sides. and the cooking process is more controlled than using microwaves, for example.

\J%Te want to cook the egg for long enough to set the white, whilst at the same time ensuring that the thermal transfer of heat to the yolk is such that the yolk does not cook. For a medium sized egg, a typical cooking time is around 7 mm. A suitable range of times is 6.5 to 7,5 minutes, In the pasteurising step we again prefer to use a waterbath, because of the close control this gives comparcd to using microwaves or other heating techniques. The aim of the pasteurising step is to achieve a massive reduction, e.g. greater than a six decimal reduction, or better, in any undesirable microbes that may be present, and in particular in reducing any Salmonella bacteria, This is an accepted standard tolerance level for pasteurisation processes (Campden BR! Guideline 51).

In order to avoid cooking the yolk we need to pasteurise at a relatively low temperature, which means that the pasteurisation step needs to take place for a relatively long time, in one embodiment we pasteurise at a temperature of between 60°C and 70 °C, for the waterbath, for 30 mm, or thereabouts. The pasteurisation time should be a minimum of 15 minutes and a maximum of 45 minutes.

Following the pasteurisation step we cool the eggs down to about 3° to 5°C prior to packaging them. This is achieved in another waterbath, typically, by keeping the eggs in a waterbath of a temperature of between 3°C and 5°C for 30 mm.

If this cooling stage is not performed, then there can be concerns about microbial activity. We wish to cool the eggs, force-cooled, rather than just allow them to cool in the ambient environment.

Once the eggs have been cooled there may be a packaging step where the eggs are packaged into packaging for transport and/or sale. The eggs may be stored in a cool environment (for example a refrigerator) prior to being packaged and/or after being packaged. The eggs may be packed in a way that excludes Oxygen, for example vacuum packed or packed with an inert atmosphere such as Nitrogen or Carbon Dioxide, or a mix of Nitrogen or Carbon Dioxide. Alternatively the porous surface of the shell may be scaled by coating the whole egg in an air-impermeable film or lacquer/polymer.

Once the eggs have been pasteurised and then cooled down to a cold temperature, we may package the eggs and supply them to a customer in its existing vacuum packaging, or we may extract the egg from the vacuum packaging and then sell such extracted eggs to customers, repackaged in other packaging. Once the egg has been cookcd there is no air (or hardly any air) between the cooked egg whitc and the shell anyway, and so it is no longer necessary to have the egg vacuum packed or inert-gas packed prior to re-heating to a desired eating temperature by a consumer (but we may nevertheless do that anyway e.g. for an extended shelf life, rather than to avoid cracking when re-heated).

Automation machinery may be used to transport the trays or carriers of eggs between the waterbaths. Robotic arms and/or convcyors may be used to either lift the trays or carriers to and from the waterbaths, or a continuous conveyor may submerge the tray or carrier in waterbaths during the conveyance.

Packaging equipment may also be used to package the eggs after processing for further storage and/or sale to consumers.

Preferred embodiments of the present invention wdl now be described with reference S to the drawings, of which: Figure la is a schematic top view representation of an egg sealed within an airtight vacuum package according to the present invention; Figure lb is a schematic side view representation of the egg of Figure la; Figure 2 is a flow chart outlining the steps used to cook, pasteurise and produce in-shell soft boiled eggs according to the present invention; Figure 3 is a modified flow chart highlighting the key process steps outlined in Figure 2; Figure 4 is a schematic overview of a first embodiment of a system for performing the process of the present invention; and Figure 5 is a schematic overview of a second embodiment of a system for performing the process of the present invention.

Figure Ia shows a schematic top view representation of an egg 100 sealed within an air-tight plastic bag 102. Such techniques are known in sous-vide cooking, for example. First, an egg 100 is placed within a plastic bag 102. The plastic bag 102 is typically made of a polyethylene/nylon blend, although other suitable plastics may be used. In the embodiment shown, the bag 102 is transparent and approximately square shaped. with an opening 106 that forms a pouch for receiving the egg 100. Once the egg 100 is placed within the bag 102, air can be evacuated from bag using a standard vacuum machine as is known in the art. Additionally, crimping 104 is used to seal the bag along the opening 106. This process forms crease marks 108 on the bag 102. The vacuum process and the advantages inherent to this are described in greater detail below.

Figure lb shows a side view of the egg of figure IA. In this view, it can be appreciated how the air has been evacuated from the bag 102 so that the volume of the bag 102 substantially corresponds to the volume of the egg 100, S Figure 2 outlines the steps of the process described herein. Initiafly, in step 202 a plurality of eggs 100 are identified of uniform size and weight. This means that eggs are chosen so that the overall size and/or the overall weight of each egg is within an acceptable range or variance about a mean. By ensuring uniformity in the selection of eggs, a reliabk and consistent result across the s&ection of eggs can be ensured, A suitable number of eggs selected for the process may be 10, or 50, or 100, or 500, or 1000. or more, or any number between the points as ranges of numbers.

Once a suitable sekction of eggs 100 have been chosen, the eggs 100 are refrigerated 204 to between S and 10°C. The precise temperature in this step is less important than ensuring that on the cggs 100 are cooled to a standard fixed temperature. In order to achieve this temperature, the eggs are tvpicafly p'aced within a refrigerator. It will be appreciated that in many processes it is usual to store products prior to processing.

Once the eggs are cooled the eggs may be vacuum processed 206. With reference to Figures Ia and lb. eggs 100 are removed from storage trays and placed within suitable vacuum bags 102 before air is evacuated from the bag to form a vacuum. Typicafly, as good a vacuum as possible is required, typically around 2mbar to 4mbar. Although described with reference to vacuum bags it can be appreciated that the eggs may be vacuum packed individuafly, with more than one egg in each vacuum bag/pack or they may be packed as a series of vacuum packed eggs. Once the eggs have been vacuum packed 206, they may be returned to the refrigerator for further storage. It can be appreciated that the vacuum processing may occur before cooling of the egg in the refridgerator. The aim of this step is to reduce the air content within the egg particulady between the egg white and the sheH, which, if present, increases the susceptibility of the eggs 102 to cracking during the cooking process. Vacuum packing the eggs significantly reduces the chance of egg breakage and also ensures that if the eggs are not immediately processed, but are instead put back into storage, that air does not re-enter the egg.

Once the eggs are prepared and vacuum packed, the first step of the process (or second or third, depending whether sekcting eggs of the correct size is counted, and depending upon whether pre-chilling the selected eggs takes pace and/or is counted) is that the eggs are cooled to a desired predetermined base temperature 208, Typicafly, S the base temperature is between 4 and 8°C. A waterbath is normally used because a waterbath allows a more constant and even temperature than a refrigerator.

Additionally, it ensured that the thermal mass of the waterbath is significantly greater than thc volume of thc cggs so that if the eggs arc left for a period of time within the waterbath. they can be considered approximately the same temperature as the waterbath -the temperature of the eggs do not affect the temperature of the waterbath, Once the eggs 100 have been placed within the waterbath, the eggs arc left for up to minutes -step 210. This stage ensures there is a constant temperature throughout the interna' structure of the eggs of approximately 5°C. A suitabk range of times for the eggs to remain in the water bath is 5 -10 minutes. 10 -15 minutes or 15 -20 minutes.

Once cooled, the eggs are removed from the 1St waterbath 212 and then placed into a second watcrbath 214 set to a cooking temperature, typically 90 to 100°C, although it can be appreciated that variations in the temperature are acceptable, provided the end result does not differ. The eggs are then left within the second waterbath for approximately 7 minutes for a medium sized egg. Eggs of differing mass/size are likely to require shorter/longer cooking times. Preferably a second waterbath is used, however it may be appreciated that the first waterbath may be heated up to the desired cooking temperature, however in that case, the cooking time is likely to vary from described above. A suitable range of times for cooking the eggs in the waterbath 216 is 6 -6.5 minutes, or 6,5 -7 minutes, or 7.5 -8 minutes, The aim of the cooking step 216 is to cook the eggs 100 for long enough to set the egg white whilst at the same time ensuring that the formal transfer of heat to the yolk is such that the yolk does not cook or start to denature and thicken. The cooking step 214, 216 causes the temperature of the egg whites to be higher than the temperature of the egg yolks.

After cooking, the eggs are removed from the second waterbath 218 and paeed into a third waterbath set to 60 to 70 °C, step 220. where they are left for about 30 minutes, step 222. A suitable range of times for step 220, depending on the waterbath temperature, would be 20 -25 minutes, or 25 -30 minutes or 30 -35. Step 222 performs a pasteurisation step to eliminate the problems of microbes. This pasteurisation process is wefl known iii the egg processing industry and is equivalent to be a minimum pasteurisation of 64.4°C for 2,5 minutes; The eggs are left in the third waterbath for sufficient time for the temperature of the egg yolks to be equal to the temperature of the fourth waterbath.

After pasteurisation. the eggs are removed from the third waterbath 224 and placed into a fourth waterbath set to 3 to 5°C. step 226, The eggs are left within the fourth waterbath for approximately 30 minutes or until they have cooled. Once cooled, the eggs are removed from the waterbath 228, processed and can be sent for packaging, step 230, The eggs may be packaged within the vacuum bag, or they may be removed from the polLch prior to packaging. Once processed, air entrains into the egg at a greatly reduced rate, so the risk of the egg cracking on reheating of the egg is greatly reduced.

Figure 3 outlines the key steps of the above described process. In particular, it is desirable that the eggs are subjected to the application of a vacuum, 300, to the one or more eggs to at east partially remove any air beneath the shefl of the eggs. The eggs arc then initially cooled to a desired predetermined base temperature, step 310. As noted above, this ensures that all the eggs start from a known reference temperature.

Once cooled, the eggs are then cooked for a desired predetermined temperature for a predetermined length of time, step 320. The predetermined temperature and predetermined length of time are preferably as described above, but are in any ease chosen to ensure that the texture and consistency of the egg white is as desired. Once the required consistency and texture are achieved. the eggs can then be pasteurised, step 330. for a predetermined time at a predetermined temperature. The pasteurisation step ensures that any unwanted microbes and/or bacteria are eliminated, This process also increases the storage and shelf-life of the finished product. Finally, the eggs are cooled for a predetermined time at a predetermined temperature, step 340, before they are dried and packaged ready for the consumer.

Figure 4 shows an overview of a system for performing the process of the present invention. As shown, it is envisaged that eggs are processed in batches and moved between waterbaths according to the process stage. Step one 400 shows a plurality of eggs 410 arranged on a tray or pallet 415. For clarity, it is assumed that any identification and selection steps have already been undertaken. Additionally, for clarity, any vacuum packaging rcsulting from a vacuum processing stcp has bccn omitted from figure 4. It can be appreciated that the following processes and systems stops arc unaffected by this omission.

As noted above, the eggs 410 on the tray 415 are typically kept refrigerated to bctwccn 5 to 10°C. Oncc thcy arc rcady to bc proccsscd, thcy arc rcmovcd from refrigeration and placed into a waterbath 420 filled with water 425. The temperature of the water is approximately set to between 4 and 8°C. The eggs may be manually placed within the waterbath or more preferably an automated system, such as a robotic arm may be used. The eggs arc left for a predetcrmined amount of time until it is considered that the temperature of each egg is approximately equal and taken to be equal to the temperature of the waterbath. This corresponds to step 310 outlined in proccss above and in figure 3.

Once cooled, the eggs 410 arc removed from thc waterbath 420 (stop not shown) and placed into a second waterbatli 430 filled with water 435. The temperature of the water is set to approximately 90 to 100 °C. This is sufficient to cook the eggs provided that the eggs are left for a predetermined length of time. This corresponds to step 320 in Figure 3. After the eggs are cooked to the desired amount (this may be empirically dctcrmincd by measuring the internal tcmpcraturc of a sample or they may be a reliance upon a recipe) the eggs are removed from the waterbath (step not shown) and placed into a third waterbath 440 filled with water 445 set to a temperature of between 60 and 70 °C. The eggs are then left within this third waterbath for a predetermined amount of time until pasteurised. Finally, the eggs are removed from the third waterbath and placed within a fourth waterbath 450 filled with water 455 set to between 3 °C and 5°C for cooling. Once cooled, the eggs are removed from the fourth waterbath 450 and can be placed within packaging 460 ready for further storage and/or delivery to the consumer.

An alternative embodiment for the system is shown in Figure 5. In this embodiment, a continuous conveyor belt system 500 is Shown having a conveyor belt 510 driven at variable speed by one or more rollers 520. The conveyor 500 is used to convey trays 530 containing an array of eggs (siniflar to the array of eggs 410) between one or more waterbaths 540, 542, fiHed with water set to a predetermined temperature. It can be appreciated that the temperature of the water can be set independently for each waterbath.

In use, the conveyor beft 510 transports the trays 530 along the conveyor 500. As the trays move, they are transported between waterbaths 540, 542. The conveyor can be configured to ensure that the trays 530 remain within the waterbaths for the designated predetermined time according to the process of the current invention. For example, the relative size of the waterbath may be tailored to ensure the eggs remain within a waterbath for the correct length of time. Alternatively, or additionally, the speed of the conveyor 500 can be altered to the same effect. The conveyor may include a number of hifls 550 that separate the waterbaths 540, 542. The conveyor may be configured to move the trays more quickly over the hills 550, Although hiHs are shown, other conveyor techniques may be used. Additionally, although shown as a single conveyor, multiple conveyor systems may be used, for example a separate conveyor for each process step is envisaged.

It can be appreciated that the conveyor belt 510 system can be automated using one or more robots to assist in the transit of the eggs along the conveyor. Such a system can be computer controlled, the computer having at least memory and a processor upon which a program can run, The program containing instructions for the movement of batches of eggs between processing areas, the relative temperature and timings of the temperature based process steps, speed of the conveyor and how this can be varied as outlined above, etc..

Using the systems described above, continuous batches of eggs can be processed, providing efficient and high throughput of the process described above, The eggs may be chicken eggs, or ostrich, or duck, or quafl, or goose, or any egg. The pre-cooling. cooking, pasteurising and coohng times can then be adjusted according the size and diameter of the shell egg, as well as the species of egg.

The eggs may not be eggs: they may be food products which when cooked have a solidified/gelled outer layer and a liquid inner region.

Claims (8)

1. CLAIMS1 A process for producing in-shell soft boiled eggs, the process comprising: app'ying a vacuum to the one or more eggs to at kast partially remove any air beneath the shefl of the eggs; cooling the one or more eggs to a desired base temperature; cooking the eggs at a desired cooking temperature for a length of cooking time; pasteurising the yolk of the eggs for a pasteurisation time at a pasteurisation temperature; and cooling the eggs for a cooling time at a cooling temperature.
2. 2, The process of claim 1, wherein the one or more eggs are of a standardised size,
3. 3. The process of claim I or claim 2, wherein the one or more eggs are seketed so that mass of each egg differs from the mean mass of the one or more eggs by less than 5 %,
4. 4. The process of any preceding claim, wherein applying the vacuum to the one or more eggs inc'udes vacuum packing the one or more eggs in an air impermeable packaging.
5. 5, The process of any preceding claim, wherein the vacuum apphed is between imbar and lUmbar and preferably 2mbar to 4mbar.
6. 6. The process of any preceding claim, further comprising: cooling the one or more eggs for a predetermined chilling time to a predetermined chilled temperature prior to app'ying a vacuum and wherein optionafly or preferably the chifled temperature is between 5 °C and 10 °C.
7. 7. The process of any preceding claim, wherein the one or more eggs of each step of the process are at least 100 eggs.
8. 8. The process of any preceding claim, wherein the process is a semi-continiLous process 9, The process of ally preceding c'aim, further comprising: applying an S impermeabk coating to the shell of the cooked, pasteurised and cooled egg to seal the whole cgg in an air-impermeable film or lacquer.10. Thc process of any preccding claim, further comprising: packaging the cooked, pasteurised and cooled one or more eggs into packaging for transport and/or sale.11. The process of any preceding claim wherein the pasteurisation temperature is between 60 °C and 70 °C.12. Thc process of any preccding claim, wherein the temperatures are applied to the one or more eggs using one or more waterbaths.13. The process of any preceding claim, wherein the times and temperatures of each process step are tailored to the species of birds.14. A system for undertaking the process of any one or claims I to 13, the system comprising a tray or other egg support on which the eggs are placed for processing; and one or more waterbaths corresponding to any one of the steps ofclainis Ito 13.15. The system of claim 14. further comprising automation machinery for transporting the tray or other slLpport between the one or more waterbaths.16. The system of claim 15, wherein the automation machinery is one or more robotic arms and/or conveyors ab'e to move the trays or egg supports between the one or more waterbaths.17. The system of any one of claims 14 to 16, further comprising packaging equipment to package the eggs after processing for further storage and/or s&e.18. A process for producing in-shell soft boiled eggs substantially as described herein and with reference to the figures.19. An egg processed according to any preceding process dairn,