Egg Preservation Methods and Quality Assessment
Egg Alterations Caused by Microorganisms
- White rot: Caused by coliforms and Micrococcus.
- Red putrefaction: Caused by Pseudomonas.
- Green putrefaction: Caused by a Bacillus that produces pyocyanin.
- Black rot: Caused by melanogenic Proteus.
- Mold growth on the shell: Following the existing humidity in the storage premises, mottled greenish spots of a more or less mucous consistency arise.
- Fungus growth inside the egg: In the area of the colonies, the clear is greenish if the contaminant is Aspergillus, blue if it is Penicillium, and gray if it is Mucor.
Cold Storage of Eggs
- Chilled eggs: Whole eggs stored for longer than 15 days but not longer than 30 from their setting, are kept isolated in a cold environment at temperatures not exceeding 4ºC.
- Preserved eggs: They remain in a chamber at 0ºC for a period exceeding 30 days and less than 6 months.
Traditional Preservation Methods
- Chinese method: Brushing the entire surface of the eggs with a 1% calcium hydroxide slurry, which clogs the pores.
- Use of sodium salicylate: Eggs can be kept for months in caves or cold locations. The eggs are dipped in 1% solutions but acquire a soapy taste.
- Common salt added: The eggs are placed in brine solutions, so they are kept for more than a month.
- Other methods: Burying the eggs with salt and dry wood ash, or brushing them with borax, alum, or glycerin.
The antibacterial action is due to lysozyme, a protein found mainly in the egg white. Eggs are defined as chicken eggs. Eggs from other species should be mandatorily accompanied by the denomination of the species concerned.
Methods for Assessing Egg Freshness
- Egg Tester Use: To appreciate the size of the air cell, the position, size, and turbidity of the yolk.
- Use of Ultraviolet Light: The surface of fresh eggs is covered with a substance that, when exposed to ultraviolet light emitted by a quartz lamp, gives a special blue-violet fluorescence. When eggs are old, the fluorescence is blue, and if they are fresh, it is red-purple.
- Observation Chamber: A thick pole of the egg is opened through an orifice. We look at the existence of liquid inside. It means that it has been preserved in a liquid medium with lime water, which has no stains or growth of a bacterial or fungal agent. Also, observe the smell that follows.
- Observation of the Egg White: Pour the egg into a dish. The egg white should have a gelatinous consistency and be located around the yolk. If the egg white spreads across the dish or mixes with the yolk, the eggs are old.
- Observation of the Yolk: The yolk has to be whole and consistent when pressed gently with your finger.
Abnormalities Prior to Spoilage
- Shell-less eggs: Decalcified birds with poor feeding and lack of vitamin D.
- Eggs with defective shells: The shell is too granular or wrinkled, typical in birds that have had bronchitis.
- Eggs with hemorrhage: Blood spots on the yolk, and even dissolved in the egg white, as well as in the shell.
Mechanical and Physical Alterations
- Dirty eggs: The origin of this dirt is in excrement and dirt from the farm itself.
- Cracked eggs: The shell cracks during handling and transport.
- Egg odor: Due to the proximity of the eggs to materials with strong smells.
- Poorly preserved eggs: Cooling units are in areas that are too cold.
- Hatched eggs: They have suffered overheating.
- Aged eggs: A consequence of the dehydration of the shell through the pores.
- Old eggs: In them, the egg white and yolk become fluid and blend.