GB2221376A - Apparatus for processing newly-laid eggs - Google Patents

Abstract

An apparatus and method are described whereby eggs (25) are laid on a conveyor (18) that holds the eggs static and that transports the eggs through a cooling tunnel (10) which is provided with cooling units (26) for directing cold air over the eggs to cool then as they proceed through the tunnel so that, as they emerge from the tunnel they have a temperature in the range of 5 to 15 DEG C. The temperature is controlled such that water does not condense on the eggshells. <IMAGE>

Description

APPARATUS FOR PROCESSING NEWLY-LAID EGGS The present invention relates to the processing of eggs used for food and particularly to the processing of hen's eggs, aìthougp the eggs of other species, e.g. duck,. goose, turkey or quail eggs, can also be processed.

When an egg is laid, the temperature of its shell and contents are approximately 38CC and eggs are usually allowed to cool naturally under ambient conditions to room temperature, which can take several hours. During this period, biological processes, probably due to the presence of labile enzymes, cause the albumen to deteriorate which in turn results in a decreasing viscosity of the albumen.

This viscosity, which can be measured physically, is taken as an indication of the freshness of the egg and if the viscosity has decreased below a certain level the egg becomes unsaleable.

In modern egg-prod-ucing plants, the number of eggs being processed is vast; for example, it is not unusual to process one million eggs in a period of five hours. The numbers are so large that, in the past, producers have had no alternative except to allow the eggs to cool to ambient temperatures by natural heat loss or by stacking the eggs in a cooled room. Thus, the present invention is based on the problem of how to prolong the shelf-life of eggs produced in modern egg-producing plants using a process and apparatus that can deal with the vast number of eggs involved.

We have now found that the deterioration in an egg, as measured by its albumen viscosity, can be greatly diminished by chilling the egg to a temperature in the range of between 5 and 150C; the present invention is also based on the realisation that the above chilling can be performed in a modern egg-producing plant by passing the eggs through a cooling tunnel supported on a conveyor that holds the eggs against rolling and that allows the passage of cooling air through the conveyor past the eggs. By processing eggs in this way, the quality of the eggs remains high for much longer even if they are subsequently kept at high ambient temperatures, for example on a supermarket shelf at about 190C.

This allows an increase in the "sell by" date of up to one week, which is clearly advantageous to both producer, retailer and consumer.

It is surprising that the freshness of the eggs can be prolonged by a simple chilling step as soon as the eggs are laid even though the eggs are subsequently kept at a temperature where relatively rapid decomposition can be expected. It is also surprising that eggs can be treated on an industrial scale using the method and apparatus of the present invention to chill eggs consistently.

According to the present invention there is provided a method of processing edible bird eggs, which method comprises passing the eggs through a tunnel kept at a temperature below 150C and above the freezing point of the eggs on a conveyor that holds the eggs static and that allows passage of cooling air through the conveyor past the eggs, the method further comprising circulating air within the tunnel and regulating the temperature profile within the tunnel and the speed that the eggs are moved through the tunnel in such a way that the eggs emerge from the tunnel at a temperature in the range of between 5 and 150C , e.g. 8 to 150C and further that, at no stage of their passage through the tunnel, does water condense on the eggs.

According to a further aspect of the present invention, there is provided an apparatus for processing eggs, which apparatus comprises a tunnel, a conveyor for passing eggs through the tunnel, which conveyor is capable of holding eggs without allowing them to roll, and that allows free passage of cooling air through the conveyor past the eggs, the apparatus further comprising cooling units, which are preferably arranged within the tunnel, that are capable of maintaining the temperature within the tunnel in the range of between the freezing point of the eggs and 150C, e.g. 5 to C.

Generally, the length of the tunnel should be at least 25 metres in order to process a commercially-desirable number of eggs while preserving a temperature profile within the tunnel that allows the eggs to be cooled without freezing and without water condensing on the shells. If water does condense on the shells of the egg, they become mottled and this diminishes the commercial value of the eggs and might, eventually, render them unsaleable. This is particularly relevant to brown eggs on which the mottling effect is readily visible.

The present invention wili be described in greater detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a longitudinal section through a processing apparatus of the present invention; Figure 2 is a partly broken-away perspective view of the apparatus shown in Figure 1; Figure 3 is a sectional view taken at right angles to the longitudinal axis of the apparatus shown in Figure 1; and Figure 4 is a graph showing the effect of cooling eggs using the process and apparatus of the present invention.

Referring initially to Figures 1 and 3, there is shown a tunnel 10 supported on a concrete base 12. The tunnel consists of two side walls 14 and a roof 16 which are each made of an internal and an external skin 14a, 14b; 16a, 16b made of plastic-coated steel sandwiching between the skins a layer of fibreglass lagging 17. The walls and roof 14 and 16 are thus thermally insulated.

The tunnel is 2.25 metres tall, 2.1 metres wide and approximately 100 metres long. A conveyor 18 extends along the length of the tunnel and can be adz3sYd within the tunnel by means of a chain drive 20 (only the upper run of the chain being s:-.own in Figure 3 but in reality the chain is an endless loop driven by a sprocket that is rotated by an electric motor (also not shown!). The conveyor 18, which is also formed as an endless loop although only the top section of the conveyor loop is shown in Figures 1 to 3, is made up of transverse rods 22 that are spaced apart to leave gaps 2A between adjacent rods 22.The spacing between the rods should be such that, when eggs 25 are placed in the gaps, they are supported by the adjacent rods without being alloyed to roll while the conveyor is in motion. Cooling units 26 are provided at intervals along the length cf the tunnel and, in one working embodiment, we provide cooling units at 4 metre intervals. The cooling units each have a thermal capacity of 49,000 BTU/hour (14.4kW) and are capable of passing 12,00 cu ft of air/min (342 m /min).

Internal walls 28 and 30 are provided within the tunnel; these walls extend up to the cooling units 26 and down to below the conveyor 18 and are designed to constrict the flow of air (shown by arrows 32) from the cooling unit to the conveyor. Because of the gaps 24 between the rods 22 of the conveyor, the cooling air can pass freely through the conveyor past the eggs and in this way a free interchange of heat from the eggs to the cooling air takes place. The contact between the eggs and the rods is practically point-contact so that the whole surface of an egg is subjected to cooling air flowing past it. After the air has passed through the conveyor 18, it is recirculated back to the cooling unit as shown by arrows 34 in the space between the external walls 14 and the internal walls 28, 30.

The cooling units 26 may be placed below the conveyor 18 in which case walls 28, 30 should also be placed below the conveyor.

The temperature profile within the tunnel should be such that the eggs are slowly cooled during their passage through the tunnel but they are not cooled so rapidly that the contents of the eggs freeze or that water condenses on the shells. In one example, we maintain the tunnel at a temperature below 100C, e.g.

approximately 0 to 50 (although the temperature near the enos of the tunnel might be slightly higher than 1000) and acjust the speed of the conveyor such that, by the time the eggs reach the outlet of the tunnel, they have cooled to approximately 100C.

We have found that the optimum duration of the cooling process is about 20 minutes although it could be reduced if the temperature in the tunnel is lowered but this could lead to problems of water condensation on the shells and/or freezing of the egg contents.

In practice, the speed at which the eggs are passed through the tunnel, the speed of the cooling air past the eggs ar.d the temperature within the tunnel should be determined empirically to ensure that the eggs are chilled sufficiently when they leave the tunnel but the rate of cooling is not so rapid that water condenses on the egg shells.

Eggs from a laying unit are fed as soon as possible after they are laid to the cooling tunnel where they are placed on the continuously moJ'ng conveyor 18 in the gaps between the rods 22 and this is done ether manually or by known egg handling machines.

The eggs then pass into the tunnel through the entrance 21 (see Figure 1) where they are cooled gradually to about 1000 by cooling air circulating within the tunnel and pass out of the tunnel through exit 23 to a grading and packing station. The entrance 21 and/or the exit 23 to the tunnel are preferably provided with a curtain composed of vertical hanging strips of plastics sheeting which minimise the escape of cold air to the atmosphere. The tunnel can be straight (as shown) or arranged around a circular conveyor or may even be arranged in a helix if space is very limited.

Using the tunnel, it is possible to handle hundreds of thousands of eggs per hour without the egg shells becoming mottled thereby producing the benefits described below in Example 1.

Example 1 A batch of Size 1 eggs from 50 week old hens, ccllected immediately after oviposition, was divided into two parts.

The first part of the batch was allowed at ambient room temperature (190C) to cool and was then stored at this temperature over a period of 7 days.

The second part was processed through the cold tunnel that forms the basis of the present invention, the tunnel conditions being set to chill the eggs down to a temperature cf 1000 during a processing time of 20 minutes. Having thus been rapidly chilled, this part of the batch was then stored alongside the unchilled eggs at ambient temperatures.

Immediately after oviposition, and at daily intervals thereafter, a random sample of 60 eggs was taken from the part of the batch which had been allowed to cool naturally and from the part of the batch that had been cooled in the chilling-tunnel. jThe eggs were broken individually and the viscosity of the albumen measured (the Haugh Value) by conven tidal methods.

The results are shown in Diagram 4 in which average Haugh units are plotted against storage time. It can be seen that in the 7 days of storage, chilling the eggs according to the present invention markedly reduces the deterioration of the eggs both in rate and degree.

It should be remembered that egg quality is believed to have deteriorated to an unacceptable level once the Haugh value has fallen below 70.

Claims (7)

1. A method of processing edible bird eggs, which method comprises passing the eggs through a tunnel kept at a temperature below 150C and above the freezing point of the eggs on a conveyor that holds the eggs static and that allows passage of cooling air through the conveyor past the eggs, the method further comprising circulating air within the tunnel and regulating the temperature profile within the tunnel and the speed that the eggs are moved through the tunnel in such a way that the eggs emerge from the tunnel at a temperature in the range of from 5 to 15 C, e.g. 8 to 1 < :C and preferabl; 1000, and further that, at no stage of their passage tbrcsgh t:r:p tunnel, does water condense on the eggs.

2. A method as claimed in claim 1, wherein the tunnel is maintained at a temperature of 2 t 120C, e.g. 5 to 1200.

3. A method as claimed in claim 1 or claim 2, wherein the time taken for each egg te move through the tunnel is at least 10 minutes, e.g. approximately 20 minutes.

4. An apparatus for processing eggs, which apparatus comprises a tunnel, a conveyor for passing eggs through the tunnel, which conveyor is capable of holding eggs static and allows passage of cooling air through the conveyor past the eggs, the apparatus further comprising cooling units that are capable of maintaining the temperature within the tunnel in the range of, between the freezing point of the eggs and 15 C, e.g. 5 to 1500.

5. An apparatus as claimed in chain 4, which contains walls extending from the cooling unit(s) to the conveyor and defining a flow path for conducting air from the unit(s) to and through the conveyor.

6. An apparatus as claimed in claim 4 or claim 5, wherein the cooling units are located within the tunnel.

7. An apparatus as claimed in claim 6, wherein the cooling units are arranged above the conveyor.