This investigation introduces students to the changes which take place during storage with respect to both white and yolk. as well as changes which relate to air sac size.

The investigation enables students to:

• Examine the components of the egg and effects of short and longer-term storage.
• Relate results of calculations to the relative freshness of the egg components.
• Undertake sensory evaluation in relation to texture and odour analysis.
• Consider, by sensory evaluation, the acceptability of stored eggs by utilising them in a cooked dish.

Please note that all eggs should be approximately the same age on purchase. E.g. With the same number of days before the best before date.

Egg quality grading

Class A eggs are the highest of these and must be naturally clean, fresh, internally perfect and with intact shells. These are the eggs we buy in the shops for eating.

Class B eggs are used by food and other manufacturers.
Eggs that do not reach either of these two standards are classified as unfit for human consumption but are used by industry in products such as shampoo.

Practical notes

Ideally, a range of eggs could be used which have been stored for varying lengths of time, although only two storage periods have been suggested for comparison with the newly purchased egg. The two storage periods suggested are:

• An egg stored for two weeks in a domestic airing cupboard in which the cistern is kept hot. This will accelerate the changes in structure and illustrates the effect of extremes of temperature.
• An egg stored for two weeks under normal conditions in a refrigerator. By extending the range available it would be possible to provide pupils with an even clearer visual indication of changes that occur on storage. Eggs and their shells will be used for a number of tasks in this investigation. They should therefore be carefully labelled and retained.

The sensory evaluation technique used is the simple selection of descriptors to describe aroma and texture.

The chopping board is used throughout to support the eggs although a bench or work surface may be used. However, it is useful to use the chopping board in the section of the investigation where white and yolks are examined further. An egg cup may be used to contain the yolk to keep it on the board. whilst the board may be tilted to allow all the white to run off into the jug.

Glass, china or stainless steel bowls should be used for whisking egg whites; aluminium bowls will cause discolouration of the egg white foam.

A soufflé omelette has been chosen in order to use the eggs, particularly since egg white foams will be produced in the final section of the investigation. This enables students not only to use up the egg in a recipe which demonstrates useful practical skills, but also shows the acceptability of eggs even after prolonged storage. Eggs which have been assessed as non-consumable due to age should, of course, be discarded.

The soufflé omelette recipe used in the investigation is obviously not the usual recipe as students will be starting with already whisked egg whites. The whisked egg whites will stand successfully with no leakage for a considerable time so that the soufflé omelettes should be quite acceptable.