How can you tell if an egg is bad?

How can you tell if an egg is bad?
Posted on 02-07-2023

How can you tell if an egg is bad?

Determining the freshness and quality of an egg is an important skill, especially when it comes to food safety. Eggs can spoil over time, and consuming a bad egg can lead to foodborne illnesses. This article aims to provide you with a comprehensive guide on how to tell if an egg is bad, focusing on various methods, signs, and factors that can help you make an informed judgment about the freshness of an egg.

  1. Understanding Egg Basics: Before delving into the signs of a bad egg, it is essential to understand some basic concepts related to eggs. Eggs are laid by hens and have a protective shell, albumen (egg white), and yolk. The shell is porous, allowing air and moisture to pass through, and it plays a crucial role in determining the freshness of an egg. Over time, eggs undergo changes, such as the loss of moisture and the formation of air cells, which affect their quality.

  2. Expiration Date and Packaging: One of the simplest ways to assess the freshness of an egg is by checking the expiration date on the carton. Eggs typically have a shelf life of about 4-5 weeks from the time they are laid, depending on storage conditions. Manufacturers usually stamp the carton with a "best before" or "sell by" date, indicating the date by which the eggs are expected to remain fresh. It is important to note that eggs can still be consumed after the expiration date if stored properly and show no signs of spoilage.

  3. The Float Test: The float test is a widely used method to determine the freshness of an egg. It relies on the principle that as an egg ages, the air cell within it grows larger. To perform the float test, fill a bowl with water and gently place the egg in it. If the egg sinks and lays flat on its side, it is considered fresh. A slightly older egg may stand upright at the bottom, but it is still safe to eat. However, if the egg floats to the surface, it is likely bad and should be discarded. The floating occurs because the larger air cell inside the egg causes it to become buoyant.

  4. Shake Test: Another method to assess the freshness of an egg is the shake test. Hold the egg close to your ear and gently shake it. A fresh egg will produce minimal or no sound, indicating that the egg yolk and white are still tightly held within the shell. In contrast, a bad egg will produce a sloshing sound, suggesting that the contents have become more watery due to evaporation or bacterial action. This method, while quick, should be used in conjunction with other signs to make a reliable judgment.

  5. Visual Inspection: Visual inspection is a crucial step in assessing the freshness of an egg. Start by looking at the shell's appearance. A fresh egg will have a clean, unblemished shell with a smooth texture. Check for any cracks, leaks, or discoloration, as these may indicate spoilage or contamination. Additionally, inspect the shell for a thin film called the cuticle, which is a natural protective layer. A shiny and intact cuticle indicates a fresh egg, while a dull or missing cuticle can increase the risk of contamination.

  6. Odor Evaluation: The smell of an egg can provide valuable information about its freshness. Fresh eggs generally have a mild odor or no smell at all. However, as an egg ages, chemical reactions occur, resulting in the production of volatile sulfur compounds. These compounds are responsible for the characteristic rotten egg smell associated with bad eggs. To evaluate the odor, crack the egg open onto a clean plate and give it a sniff. If you detect a strong, unpleasant odor, it is a clear indication that the egg is spoiled.

  7. Yolk and White Examination: Examining the appearance and texture of the yolk and egg white can help determine the freshness of an egg. A fresh egg will have a yolk that sits tall and round, with a vibrant yellow or orange color. The white should be clear and slightly thick, without any signs of cloudiness or pink or green discoloration. A bad egg may have a flattened yolk, runny white, or discolored yolk and white. Clumps or blood spots in the egg are generally harmless but can be an indication of poor quality.

  8. Bacterial Contamination: Bacterial contamination is a significant factor contributing to egg spoilage. The most common bacterial culprit is Salmonella, which can cause food poisoning. To minimize the risk of bacterial contamination, it is crucial to handle and store eggs properly. Store eggs in a refrigerator at or below 40°F (4°C) to slow down bacterial growth. Avoid leaving eggs at room temperature for an extended period, as this can promote bacterial proliferation.

  9. Candling: Candling is a technique used in the egg industry to assess the quality and freshness of eggs. While it may not be practical for everyday use, understanding the process can provide insights into determining egg freshness. Candling involves shining a bright light through the shell to observe the internal contents. Fresh eggs will show a small air cell, a clear white, and a well-defined yolk. As an egg ages, the air cell becomes larger, and the yolk may appear less distinct or show signs of deterioration.

  10. Preservation and Storage Tips: Proper storage can significantly impact the freshness and longevity of eggs. To maximize freshness, keep eggs in their original carton, as it provides protection and reduces moisture loss. Store eggs in the main body of the refrigerator rather than the door, as temperature fluctuations are minimal in this area. Avoid storing eggs near pungent foods, as eggs can absorb odors. If you plan to consume raw or undercooked eggs, such as in homemade mayonnaise or eggnog, consider using pasteurized eggs to reduce the risk of foodborne illness.

  11. Quality Grading: In some countries, eggs undergo quality grading based on specific standards. These standards consider factors such as shell integrity, yolk positioning, and internal quality. For example, the United States Department of Agriculture (USDA) grades eggs as AA, A, or B based on exterior and interior quality. While grading is not a direct indicator of egg freshness, it can provide some assurance of overall quality and help consumers make informed choices.

  12. Local Regulations and Practices: It is important to note that specific regions or countries may have different regulations and practices regarding egg production, storage, and labeling. Familiarize yourself with the guidelines and requirements in your area, as they can vary. Local authorities often provide resources and information to educate consumers about egg safety, storage, and handling practices. Stay updated with the latest recommendations to ensure you are making informed decisions about egg freshness.


In conclusion, assessing the freshness of an egg is a combination of various factors, including expiration dates, packaging, the float test, shake test, visual inspection, odor evaluation, yolk and white examination, bacterial contamination, candling, preservation, and storage. By employing these methods and considering these factors, you can become adept at determining the freshness and quality of eggs, enabling you to make informed decisions regarding their consumption. Remember, ensuring food safety is essential for maintaining good health and well-being.

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