Grading, quality control and storing of eggs
Grading is the sorting out of eggs into different categories according to their interior quality and weight. Grading is important because:
- It facilitates packing, uniformity and pricing
- It improves the profit margin
- It aids in reducing wastage
- It facilitates quality assurance to customers
There are two grades of eggs based on quality of the eggs i.e. grade A and B. Out of these two grades there are 4 classes according to the sizes and weight. Quality is determined either of the two ways.
Interior quality
Candling eggs which can be done either by use of a candling torch or other machines to see the interior quality of eggs, is carried out in determining the quality of eggs. If the egg is good all light will pass through and the egg will look transparent and yellow. On the other hand if the egg is defective various observations are made:
- The egg has a very big air sac meaning the egg is undergoing deformities
- The egg has cracks
- The egg has weak spots on the shell
- Abnormal shell
- The yolk or albumin is very weak
Weight
There are various weights observed in eggs. Good eggs have weight ranging from 34 to 60g or more. When candling look at the interior quality of the egg especially the air sac and yolk, the soundness of the shell whether there are cracks; and stages in embryonic development for fertilized eggs. As an embryo develops, the air sacs also develop. Good quality eggs have an air sac approximately 4mm in depth.
Grade A
Grade |
Weight in grams |
Shell |
Air sac |
White albumin |
Yolk |
A – Extra large |
60g and above |
Clean Unbroken Sound and normal shape |
Up to 4mm in depth Regular |
Clear and reasonably formed |
Fairly well centered Free from defects Indistinct outline
|
A – Large |
53 – 59g |
|
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A – Medium |
45 – 52g |
|
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|
A – Small |
38 – 44g |
|
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Not for commercial purposes |
Less than 38g |
|
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Grade B
Grade |
Weight in grams |
Shell |
Air sac |
White albumin |
Yolk |
B – Extra large |
60g and above |
Clean Moderately stained Slightly abnormal shape |
Up to 8mm in depth Slightly bubby |
Clear but slightly weak |
Slightly off centered Slightly visible outline
|
B – Large |
53 – 59g |
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B – Medium |
45 – 52g |
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B – Small |
38 – 44g |
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|
Not for commercial purposes |
Less than 38g |
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Eggs from hatcheries should not be kept for more than 10 days.
Storing eggs
About 56% of eggs are laid in the morning between 9 to 11am. To reduce damage, these eggs should be collected 3 times a day. The important considerations in storing eggs are:
- Infertile eggs keep longer than fertile eggs. Changes in temperature can trigger the embryo of fertilized eggs to start developing and if the temperatures fluctuate the embryo may die thus causing the egg to rot.
- De-fertilization of eggs can be done by immersing the eggs in hot water at 57.2 to 62.7oC for 15 minutes or 15 days in hot weather. This temperature kills germinal disc. Another method of de-fertilization is to dip in lime water or warm coconut oil at the mentioned temperatures. In a sterile environment these eggs can keep for 3 months.
- Cooling of eggs. Eggs are laid at temperatures of 40oC. Cool the eggs to 21oC immediately after collecting by keeping in storage rooms with air conditioners. You can use wet curtains on walls or wet straws on the roof to bring the room temperature down.
- To keep eggs frozen separate the albumen and yolk and freeze them separately.
- The albumen and yolk can be dried separately, stored and packed then sold in supermarkets. These frozen or dried products can be used for making bread and other confectionaries.