Do eggs have a high pH?: Understanding the Science Behind Egg Acidity

October 18, 2025 •

4 min read

While whole eggs are considered relatively pH neutral, a fascinating and dynamic change in their pH occurs after they are laid. This shift is not a sign of spoilage, but a natural process that differentiates a fresh egg from an older one, particularly regarding the egg white's increasingly alkaline nature.

Quick Summary

A fresh egg is mildly alkaline, but the pH level changes with storage. Egg white becomes more alkaline due to carbon dioxide loss, while the yolk remains relatively stable. This chemical transformation is a key indicator of an egg's freshness.

Key Points

Egg White pH Increases with Age: A fresh egg white is slightly alkaline (pH 7.6-8.5), but as the egg ages, it becomes more alkaline, reaching a pH of 9.2 or higher due to the loss of carbon dioxide.
Egg Yolk pH is Stable: The egg yolk remains relatively stable and mildly acidic (around pH 6.0), even as the egg ages, only increasing slightly towards neutral.
pH Affects Egg White Viscosity: The rising pH of the egg white causes its protein structure to break down, resulting in a thinner, more watery consistency in older eggs.
High pH Affects Whipping: The high alkalinity of older egg whites can inhibit stable foam formation, which is why an acidic ingredient like cream of tartar is often added to improve whipping.
Refrigeration Slows pH Changes: Storing eggs at cold temperatures dramatically slows the rate of carbon dioxide loss, helping to preserve the egg's internal quality and prevent the pH from rising too quickly.
pH is a Freshness Indicator: The pH level of an egg, particularly the egg white, is a reliable indicator of its freshness, with a lower pH correlating to a fresher egg.

Unpacking the pH of an Egg

The pH scale is a measure of how acidic or alkaline a substance is, ranging from 0 (most acidic) to 14 (most alkaline), with 7 being neutral. When it comes to eggs, the answer to the question, do eggs have a high pH?, isn't a simple yes or no. The pH level of an egg is not constant; it changes significantly over time and varies between the egg's different components: the white and the yolk.

The Surprising Transformation of Egg White

At the time a hen lays an egg, the egg white (or albumen) is only slightly alkaline, with a pH of around 7.6 to 8.5. However, as the egg ages, it loses carbon dioxide ($CO_2$) through the porous shell. This loss of carbon dioxide causes the egg white to become more alkaline, with its pH rising gradually to a maximum value of 9.2 or even higher after several days of storage. The American Egg Board notes this process, explaining that egg white is one of the few food products that is naturally alkaline and becomes more so with age.

The Stable Acidity of the Yolk

In contrast to the egg white, the egg yolk has a more acidic and stable pH. A fresh egg yolk has a pH of approximately 6.0. As the egg ages, the yolk's pH increases slightly, but it remains relatively close to neutral, typically reaching a range of 6.4 to 6.9. The thick membrane surrounding the yolk helps to slow down the exchange of moisture and carbon dioxide, contributing to its more stable pH compared to the albumen.

How pH Affects Egg Freshness and Culinary Uses

The shifting pH of an egg is directly related to its freshness and has practical implications for cooking. The loss of carbon dioxide that increases the egg white's alkalinity also affects its physical properties.

Thinning of the Egg White: The thick, viscous consistency of fresh egg white is a result of its protein structure, which is more stable at a lower pH. As the pH rises, the proteins begin to break down, causing the egg white to thin and spread out more readily when cracked. This is why an older egg forms a flatter fried egg with a wider spread than a fresh one.
Culinary Applications: The pH is also critical for specific cooking techniques, particularly whipping egg whites into a foam. While egg white proteins form a more stable foam at a near-neutral pH (around 7.0), the high alkalinity of an older egg white makes it less functional for whipping. This is why cooks often add an acidic ingredient, like cream of tartar, to egg whites—it lowers the pH, stabilizing the protein structure and improving foam formation.

The Effect of Storage on Egg pH

Temperature and storage time are the primary factors influencing the rate of pH change in an egg. Refrigeration significantly slows the loss of carbon dioxide, which in turn slows the increase in albumen pH. This helps maintain the egg's internal quality, keeping the egg white thick for a longer period. Eggs stored at room temperature will lose carbon dioxide and undergo the pH change much faster than those kept refrigerated.

Comparison of pH Levels in Fresh vs. Stored Eggs


Feature	Fresh Egg (Just Laid)	Stored Egg (1+ Week)
Egg White (Albumen) pH	7.6 to 8.5	Increases to 9.2 or higher
Egg Yolk pH	~6.0	Increases slightly, up to 6.4-6.9
Overall Acidity/Alkalinity	Slightly alkaline, with a mildly acidic yolk	Increasingly alkaline, primarily due to the egg white
Physical Appearance	Firm, viscous egg white that holds its shape	Thinner, more watery egg white that spreads out
Culinary Performance	Excellent for separating, and whipping egg whites	May require an acid (e.g., cream of tartar) for stable foam

Conclusion: The Dynamic Chemistry of an Egg

In conclusion, the question, do eggs have a high pH?, has a nuanced answer. While a freshly laid egg is only slightly alkaline, particularly in its white, the pH level of the egg white rises significantly with age, making it highly alkaline. The egg yolk, in contrast, remains mildly acidic and relatively stable throughout the storage process. This natural chemical shift is a critical indicator of an egg's freshness and directly impacts its properties, from how it cooks to how it tastes. Storing eggs in the refrigerator can slow this process and preserve their quality. Understanding these chemical changes provides valuable insight for home cooks and chefs alike, ensuring optimal culinary results with every egg cracked.

Additional resources

For more detailed scientific information on egg chemistry, you can consult research from the American Egg Board on pH stability.

Frequently Asked Questions

No, a freshly laid egg has a relatively neutral to slightly alkaline pH, particularly in the egg white (albumen). The pH only increases as the egg ages due to the loss of carbon dioxide through the shell.

The pH of an egg increases because it loses carbon dioxide ($CO_2$) through the porous shell as it ages. This loss of $CO_2$ causes the egg white to become more alkaline, raising its pH.

The egg yolk is mildly acidic, with a pH of around 6.0 in a fresh egg. Unlike the egg white, its pH remains relatively stable during storage.

The rising pH in an aging egg white causes it to become thinner, which is less ideal for whipping into stable foams. For better foam stability, especially when baking meringues or soufflés, adding an acidic ingredient like cream of tartar helps to lower the pH.

Yes, the pH of the egg white is a good indicator of freshness. A fresher egg will have a lower, more neutral pH, while an older egg will have a higher, more alkaline pH.

Refrigeration is crucial for slowing the pH change in eggs. By keeping the egg cold, it significantly reduces the rate at which carbon dioxide is lost, thereby preserving the internal quality and keeping the pH from rising rapidly.

Eggs, particularly the egg white, do become increasingly alkaline over time. However, in the context of the alkaline diet, they are generally classified as a protein-rich 'acidifying' food, which is balanced with more alkaline fruits and vegetables.