Nature has given the egg a natural package - the shell. Despite its relative strength, the egg is an extremely fragile product and even with the best handling methods, serious losses can result from shell damage. Economical marketing generally requires that eggs be protected by the adoption of specialized packaging and handling procedures.
Functions of packaging
Packaging is an important component in delivering quality eggs to buyers. It embraces both the art and science of preparing products for storage, transport and eventually sale. Packaging protects the eggs from:
Proper handling and storage, as seen in the previous chapter, help control moisture loss, but appropriate packaging may also help prevent it. Eggs also need to breathe, hence the packaging material used must allow for the entrance of oxygen. The material used must be clean and odourless so as to prevent possible contamination and tainting. Authentic egg packaging materials can be reused, but careful attention must be paid to possible damage, odours and cleanliness. The packaging must be made to withstand handling, storage and transport methods of the most diverse kind and to protect the eggs against temperatures that cause deterioration and humidity. Finally, consumers like to see what they are buying, especially if it concerns fresh produce. An egg package should be designed so that the customers not only recognize the product as such, but can also see the eggs they are buying.
Many factors must be taken into consideration for packaging eggs. It is important to obtain information regarding the necessary requirements for a particular market, such as:
There are many different types of egg packages, which vary both in design and packaging material used.
Type 1. Packing eggs with clean and odourless rice husks, wheat chaff or chopped straw in a firm walled basket or crate greatly decreases the risk of shell damage. An example of this can be seen in the forefront of Photograph 16.
It is also be possible to pack eggs in a simple basket as seen in Photograph17. The basket has no cushioning material such as straw and therefore damage to the eggs may occur more easily. This kind of packaging may be fit for short distance transport.
Type 2. A very common form of packaging is the filler tray. The fillers are then placed in boxes or cases. An example can be seen in Photograph 18.
Filler trays are made of wood pulp moulded to accommodate the eggs. They are constructed so that they can be stacked one on top of the other and can also be placed in boxes ready for transport. Filler trays also offer a convenient method for counting the eggs in each box, without having to count every single egg. Usually the standard egg tray carries 36 eggs. Therefore, if a box holds five trays, for example, the box has a total of 180 eggs (36 x 5 = 180).
The cases used may be made of sawn wood; however, they are more commonly made of cardboard. When using cardboard cases, special care must be taken in stacking so that excessive weight is not placed on a case at the bottom of a stack.
Fillers can also be made of plastic as seen in Photograph 19. The advantages of using plastic egg fillers are that they can be reused and are washable. The fillers can be covered with plastic coverings and be used as packages for final sale to the buyer. More importantly, however, plastic transparent fillers allow for the inspection of eggs without handling or touching the eggs.
Type 3. Eggs can also be packed in packages that are smaller and specific for retail sale. Each package can hold from two to twelve eggs. These cases can be made of paperboard or moulded wood pulp as seen in Photograph 20, or can be made of plastic as shown in Photograph 21.
It is also possible to pack eggs in small paperboard cases and cover them with plastic film. Egg cases have also been developed from polystyrene. The advantages of using polystyrene are superior cushioning and protection against odours and moisture. The package is also resistant to fungus and mould growth.
The use of small cases is restricted by availability and cost considerations. However, small cases are good for retailers and customers. They are easy for the retailers to handle and customers are able to inspect the eggs.
Labels are a source of important information for the wholesaler, retailer and consumer and not just pieces of paper stuck onto cartons or boxes. The important facts on the label contain information for buyers concerning the eggs, their size and weight and quality/grade description - AA, A or B. Labels may also indicate the producer, when the eggs were laid, how to store them and their expiration date. Persuading the buyer to purchase the product without tasting, smelling or touching is another function of labelling.
A sample label can be seen here below:
Labels can be either printed directly on cartons or attached to the cartons. The cost of labelling must be taken into consideration. Simple methods of labelling are available such as stencil or stamp as can be seen below.
Stencil and stamp labelling
Source: Fellows and Axel, 1993
Costs of packaging
When calculating the costs of packaging, expenses must be considered for:
The storage of shell eggs during the main laying season, in order to conserve them for consumption when they are scarce, has been practised for many centuries.
For the successful storage of eggs, the following conditions must be met.
If all of the above requirements are to be met, refrigerated storage is necessary.
Cold storage of eggs
In the tropics, eggs can deteriorate very quickly unless they are stored at low temperatures. The ideal temperature for storage in such climates is 13°C or lower (usually between 10° and 13° C). Here refrigeration is a necessity for successful commercial storage; however, it may be unavailable or the costs too high.
The most important factors in successful cold storage are as follows.
The selection and packaging of eggs for storage. Eggs for storage must be clean, of good interior quality and have a sound shell. If they are to be stored for more then a month, they should be equivalent to the U.S. grade A (see Chapter 2, Table 7). Therefore, it is best to candle all eggs before storage. It may also be advisable to take a sample and to break out these eggs as a further quality check (see Chapter 2). The period of time between laying and storage should not be more than a few days. The eggs should be kept cool during that time.
Packaging materials used for storage should be new, clean, odourless and free from damage. When packaging material is reused, it is extremely important that it is clean, odourless and free from damage. It is important that the material used allow the eggs to "breathe" and to be free from tainting odours. It should also be sturdy in the event that the cases have to be stockpiled on top of one another.
The equipment and preparation of the cold store. The storage room should have a concrete floor that is washable. Walls and ceilings must also be washable. Wooden buildings have been found to be satisfactory, provided they do not impart foreign odours or flavours to the eggs. The room should be scrubbed thoroughly with hot water and soap or an odourless detergent sanitizer before being used. A final rinse with a hypochlorite solution will help greatly in deodorizing the storeroom. A liberal application of freshly slaked lime to unpainted plaster surfaces will also help. The storage room should be aired and dried out thoroughly after cleaning, then closed up and the refrigeration turned on. It is best to allow several days for the temperature and humidity to stabilize before introducing the eggs.
Proper temperature, humidity and air circulation. Careful and accurate control of the air condition is essential. A temperature between - 1.5° and - 0° C is recommended. At a temperature of - 2.5° C eggs freeze. The room should be well constructed and insulated and the refrigeration should be capable of maintaining an adequate uniform temperature in all areas. The cases of eggs should be separated by wood-strips and kept well away from the walls so as not to obstruct air circulation. Aisles left for the convenience of handling specific egg cases also help air circulation. Periodic ventilation of the storage room is advisable to promote air exchange.
The relative humidity should be between 80 and 85 percent at a cold storage temperature of - 1° C. At cold storage temperatures of about 10° C the relative humidity should be between 75 and 80 percent. In such instances, on average, egg weight loss should not exceed 0.5 percent per month. During the early stages of storage when the packaging material is absorbing moisture at a high rate, the floors should be sprinkled with clean water several times a day. If forced-air circulation is feasible, a controlled temperature water-spray air washer may be used. If the humidity becomes excessive, part of the air can be cycled through a unit containing calcium chloride. Where eggs have been oiled less attention can be paid to the humidity level.
Periodic testing for quality. Periodic quality checks are essential if the risk of heavy egg losses is to be avoided. Every month or so a sample of eggs should be selected from the various lots and tested. Usually a sample of about 1 percent of all eggs in storage may be sufficient. For example, if 3 000 eggs are kept in storage, 30 eggs sampled from various egg cases will enable a good estimation of the general quality level of the eggs. If there is evidence of excessive deterioration, it is best to dispose of the eggs quickly, after eliminating those that are unfit for consumption.
The gradual adjustment of eggs to higher temperatures. Care must be taken in removing eggs from storage to avoid the condensation of moisture on shells. This is minimized by raising the temperature slowly or by moving the eggs through rooms with intermediate temperatures. If condensation occurs, the eggs should be held under conditions that allow the moisture to evaporate within a day or so.
As indicated earlier, eggs should not be stored with products that may taint them. For the long term, eggs are best stored alone, while for the short term they may be kept with dairy products such as milk and mild-flavoured cheese. The average storage life for eggs is between six and seven months.
Economics of cold storage
There is a tendency to underestimate the difficulties involved in providing good cold storage facilities and to recommend their installation without adequate investigation of their cost and potential economic return. The following factors should be considered when contemplating cold storage.
The potential available business must be appraised as well as its distribution over the different seasons of the year and the costs involved. Egg storage to even out the availability of supplies is likely to provide business for only a part of the year. The average - not maximum - price difference between the plentiful and scarce seasons must be calculated. If projected returns do not significantly exceed the costs envisaged for storage, there is little incentive for egg traders to make use of storage.
It must be considered that some egg producers, according to their circumstances and possibilities, maintain yearly production through special breeding and feeding programmes and by providing illumination in the hen laying houses. This may even out the rate of egg production throughout the year and hence long-term storage should not be considered.
Layout of packaging and storing facilities for shell eggs
A model layout of a packaging and storing room for shell eggs is seen below.
Figure 11 - Layout of packaging and storage facility
1. Eggs enter the packing/storage facility
2. Temporary store room
3. Candling room
4. Weighing/cleaning room
5. Packaging area
6. Long-term storage
7. Eggs ready for transport
The layout for the packaging and storing facility is of great importance for efficient and effective management. The various rooms should be kept clean, well ventilated and, where necessary, refrigeration provided. All personnel working in the facility should wear clean outer garments, use caps or head bands and wash their hands when handling eggs and equipment. All equipment used should be clean.
1. Eggs enter the packing/storage room. Eggs from production are brought into the packing/storage facility. Eggs can be brought in by hand or by conveyor belt. In intensive egg production, the birds lay eggs that roll out of the cage onto conveyor belts, which transport the eggs directly to the packing/storage facilities. This can be seen in Photograph 22. Photograph 23 shows how eggs could be stacked for manual movement if brought in by hand from production to the packing/storage facilities.
2. Temporary storage room. Here eggs are stored temporarily before they are moved to the candling room.
3. Candling room. Eggs are brought into the candling room, where candlers verify the interior and external quality of eggs. The small squares (see Figure 11, No. 3) represent candling benches. The candling machine in Photograph 24 is used in fully mechanized or semi-mechanized systems, where the eggs are brought onto the candling machine by a conveyor belt.
4. Cleaning/weighing room. After candling, eggs are transported by conveyor belts to the cleaning/weighing room. Here eggs are cleaned with abrasives, where possible, and sorted by weight. Usually the size indicates which category eggs should fall into - small, medium or large. This can be done by hand; however, automated weighing machinery is available.
5. Packaging area. After weighing, the eggs are taken to the packaging area. Packaging can be done either by hand (see Photograph 25) or automatically by machinery. As seen in Photograph 26 the eggs arrive at machine No. 1. If we look at Photograph 27, there are three weighing machines numbered one to three. Each machine is set to pack only predetermined egg weights. For example, machine No.1 (see Photograph 26) packs only 60-gram eggs. If the eggs are below that weight, they will be conveyed to machine No. 2 (see Photograph 28). The eggs are then packed automatically.
After packing, eggs may either be kept in long-term storage (No. 6 in Figure 11) or may be ready for immediate transport (No. 7 in Figure 11).
For the successful transport of shell eggs three essential requirements must be met.
1. The containers and packaging materials must be such that the eggs are well protected against mechanical damage.
2. Care should be taken at all stages of handling and transport. Workers handling eggs should be instructed so that they appreciate the need for careful handling. The provision of convenient loading platforms at packing stations, loading depots and railing stations, and handling aids, such as hand trucks and lifts, are of great help.
3. The eggs must be protected at all times against exposure to temperatures that cause deterioration in quality as well as contamination, especially tainting.
The permissible range of temperatures during loading and transport depends on the local climatic conditions and the duration of the journey. Table 8 shows recommended temperatures for transport and loading.
Care is needed to avoid excessive shaking, especially where roads are bad. Egg containers should be stacked tightly and tied down securely to minimize movement. Covers should be used to protect them from the heat of the sun, rain and extreme cold where applicable. Where bicycles are used, a device such as a special carrier suspended on springs may be helpful.
Recommended temperatures for loading and transport
Transport over 2 or 3 days
Transport over 5 or 6 days
Maximum on loading
Recommended for transport
-1° to + 3° C
-1° to + 1° C
Acceptable for transport
1° to + 6° C
1° to + 3° C
A basic prerequisite for all long-distance transport is that arrangements be made for proper reception, handling and storage at the end of the journey. This is especially important where large lots are delivered to a relatively small market. Without access to suitable storage facilities, the eggs may have to be marketed quickly under adverse climatic conditions, which may cause substantial quality deterioration and price losses.
Delivery of high quality eggs over long distances, especially in hot climates, generally calls for refrigeration. Requirements for the successful operation of refrigerated transport equipment are rather rigid especially as regards the following factors:
Decisions on the establishment of new refrigerated transport services for eggs should be based on thorough economic as well as technical evaluations.
The following criteria should be taken into consideration.