Nobody likes several weeks-old eggs—their quality has diminished significantly. Unlike foods like cheese or wine, eggs are best consumed when fresh, especially when cooked sunny side up or scrambled. Fresh eggs also be used in many cooking methods that require eggs as an ingredient. Most recipes call for eggs as a foaming, binding, emulsifying, or leavening agent. But these processes may not go well if old eggs are used.
Most grocery stores source their eggs from local farms to ensure freshness. But this isn’t always a guarantee. So make it a habit to read the “best before” date or “sell by” date on the carton before purchasing it. Because not all eggs on the store shelves are fresh.
USDA recommends to use eggs within 3 to 5 weeks of the date you purchase them.
If you visit the nearest chicken farm in the neighborhood for fresh eggs for your family, better. Otherwise, you can check the freshness of eggs you buy from the grocery store with a few simple tests.
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How do eggs become stale?
The eggshell is a semi permeable membrane. It has thousands of microscopic pores. In fact, an egg shell can have as many as 17,000 pores. These pores allow gas and moisture into the egg to keep the inside from drying out while the egg develops.
However, once the egg is laid, the moisture starts to escape through the pores. This result in shrinking of the inside as the air cell slowly expands by slowly pulling in air (around 4 ml of air each day). The air cell is located just between the shell and the egg membrane at the egg’s larger end.
The changes in the yolk also signal the egg’s age. As the vitelline membrane thins, the yolk flattens. Furthermore, the surrounding thick white becomes thinner as sulfide bonds break. The result is the yolk no longer sitting in the middle. The egg pH level (acidity) also rises from 7.6 to 9.6, allowing bacterial growth.
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How do you check the freshness of eggs?
One easy way to check the freshness is by holding the egg close to your ear and then shaking it gently. If you do not hear a sound from the interior, then the egg is fresh. But if you hear a swishing sound, it suggests that the air bubble or air cell has already expanded enough for the inside to move and splash around.
Combine this method with either water test or crack test to be certain if the eggs are indeed fresh.
1. Water test or float test
The water test or float test uses the size of the air cell when determining the freshness of eggs.
To perform this test, cautiously place an egg in a bowl of water.
- The egg is fresh if it is dense enough to sink horizontally to the bottom of the bowl since the air cell is very small.
- If the egg sinks to the bottom and is upright or tilting, it is already past its peak of freshness but still good for consumption. Eggs this old are good for boiling since they are easier to peel.
- If the egg floats, the air cell has already grown in size that it is no longer dense to sink. A considerably large amount of moisture has also escaped. An egg this old should be discarded.
Look at the below table.
| AGE | WHAT HAPPENS | HOW IT SHOULD LOOK |
| Fresh | A fresh egg has a small air cell. It is dense enough to sink |  |
| 1 week | The egg slowly loses moisture. This makes the egg less dense and start to tilt. |  |
| 2 weeks | The egg is almost upright as the air cell continues to expand. |  |
| 3 weeks | The egg is already upright as it continues to lose density. Still good for consumption. | |
| 5 weeks or more | Excessive loss of moisture makes the egg float. Must be thrown away. |  |
2. Crack test
To perform this, simply crack open an egg on a plate and check it visually.
- The egg is fresh if it has a high yolk, which sits in the middle. While the white must be thick and slightly cloudy.
- A week or 2, the white becomes thinner.
- By the 3rd week, the yolk starts to flatten and the white loses color.
- A 5-week old egg has a flat yolk and the white is runny or watery and spreads out more. An egg like this must be discarded.
