Few foods are so complete and versatile like eggs. Having already overcome the false myth that they pose a risk to cardiovascular health, we can eat perfectly one a day without fear. Choosing the healthiest ways to cook it, that’s for granted.
Rich in nutrients, a source of high quality protein, vitamins and minerals, it is also one of the most delicate foods that can cause poisoning. It all starts with a good conservation, but sometimes we can doubt whether the eggs we have in the fridge are still in good condition or are out of date. To check this, there is a very simple method that we can all apply at home: immersing them in water.
To understand the spoilage process and why this method works, let’s first see what is the composition and structure of a fresh egg and what internal processes occur over the days. Because in the kitchen, as in any field, nothing happens by chance or magic, everything has its scientific explanation.
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The structure of the egg
A fresh common egg is made up of several clearly differentiated parts that are basically divided inside, the nutritious food that, if fertilized, would give rise to the embryo from which a chick would be born. Nature is wise and provides physical and chemical barriers that protect the yolk – the ovule – from the outside.
If we made a cross section of a raw fresh egg, we would distinguish the following parts:
- Shell. The outermost hard part, which however is not completely hermetic. Its surface is very porous and sensitive to external gases and odors, it also allows the entry of water vapor.
- Inner and outer membrane. Barriers that separate the shell from the interior, of different thickness.
- Air chamber. Empty space that is formed due to the contraction of the albumen after laying, and that progressively increases in size as the egg ages.
- Clear or albumen. It usually occupies 60% of the total egg and is made up of different layers of different density, more fluid or thicker. It is made up of almost 90% water.
- Bud. The ovule of the egg that contains the germ cells and is also made up of various parts. When the egg is very fresh it is placed in the center and it is the nutritional jewel of this food.
What happens when an egg loses freshness
As the days pass since the setting, the egg is losing quality. The water it contains evaporates through the pores of the shell, causing an increase in the internal air chamber and a gradual loss of weight.
In addition, as well described by the food technologist Miguel A. Lurueña, an egg also contains carbonic acid dissolved in the white and the yolk. This acid is also gradually lost, producing an increase in pH (acidity or alkalinity) with several consequences: the yolk becomes decentred and swells and the white loses density, becoming more transparent.
That is to say, a very fresh and quality egg weighs more and, if we were to open it by pouring its contents on a plate, we would see a centered yolk, with the two parts of albumen well differentiated and remarkably dense, gelatinous and with a certain height. An old egg would be more fluid, with an irregular and more inflated yolk, diverted to the side, mixed with a white with less volume and liquid.
How to tell if an egg is fresh without opening it
After the theory, what interests us is to be able to determine the state of an egg without having to break it. And the method could not be simpler: you just have to put it in a glass full of water cold stream.
Taking into account all of the above, it is easy to deduce that the fresher an egg, the more it will sink. If it goes down to the bottom of the glass, it is a very recently laid egg; as you get older it will go up until fully floating. This happens because the air chamber increases and the egg loses weight.
The freshest egg should sink completely, depositing horizontally at the bottom of the container. As the days went by, it would first begin to rise, remaining at the bottom but vertical, to gradually rise, until it floated on the surface, horizontal again. In this case, the egg must be discarded.
This method should only be applied with eggs that we are going to use or consume. immediately. Eggs should never be wet or washed before storing them.
How to keep eggs at home
The aforementioned porosity of the shell is the main reason why eggs are kept in stores at room temperature, but you have to refrigerate them once we got home. The change in temperature could cause condensation of water on the shell, causing internal contamination by microorganisms.
The cold in the refrigerator lengthens the useful life of the egg, slowing down its gradual deterioration. In addition, it must be remembered that the date that appears marked next to the identification codes is not expiration, but preferential consumption. This is set counting 28 days from the day of laying, its subsequent consumption being adequate if the quality is maintained, checking it for example with the method described.
In addition, we can take into account the following recommendations for conserve properly eggs at home and avoid poisoning:
- Save the eggs in the fridge as soon as you get home.
- Keep them in their own container or in a special, clean, closed container. avoiding the door, since it is the area most exposed to thermal changes.
- Do not wash them before storing them.
- Keep them away from strong odors or heat sources.
- Take them out only at the time in which they are to be used.
- Avoid cross contamination separating utensils and surfaces that have been in contact with the raw egg from other cooked foods or dishes.
- Avoid separating yolks and whites using the own shell, even less unwashed.
- Do not break the eggs on the edge of the container in which they are to be handled or mixed with other ingredients.
- For elaborations in raw, use the freshest eggs and keep the preparation properly refrigerated, consuming it in a few hours (for example, mayonnaise).
Photos | iStock – Institute for Egg Studies – Unsplash
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