Is Egg White Strongly Acidic? The Surprising Truth About Egg pH

December 6, 2025 •

3 min read

Most people assume all foods follow a linear pH scale, but the natural chemistry of an egg is more complex. Far from being strongly acidic, a freshly laid egg white starts at a slightly alkaline pH, which becomes even more so over time.

Quick Summary

The acidity of egg whites is a common misconception. A fresh egg white has a pH near neutral, which progressively increases to a more alkaline state as the egg ages and releases carbon dioxide. The chemical composition, including bicarbonate and proteins, drives this shift.

Key Points

Egg White is Alkaline: Fresh egg white starts at a slightly alkaline pH of approximately 7.6, which is not acidic.
pH Increases with Age: The pH of egg white increases significantly over time, reaching values up to 9.5 as carbon dioxide escapes through the shell.
Storage Temperature Affects pH: Refrigerated storage slows down the loss of carbon dioxide, preserving a lower, less alkaline pH for a longer period.
Egg Yolk is Acidic: Unlike the egg white, the yolk is slightly acidic with a pH of about 6.0 in a fresh egg.
Acids Stabilize Foams: Adding an acid like cream of tartar to egg whites lowers the pH, which improves the stability of foams for meringues and other recipes.
Protein Denaturation: The increasing alkalinity of egg whites with age causes proteins to destabilize, leading to the liquefaction and thinning of the albumen.

The Truth Behind Egg White pH

Contrary to the persistent belief that egg white is strongly acidic, the reality is quite the opposite. The pH of a fresh egg white, also known as the albumen, is typically around 7.6, which is slightly alkaline, or basic. This pH level doesn't stay constant, however. The egg's chemistry undergoes a fascinating transformation during storage, causing its alkalinity to increase significantly.

The Chemical Changes During Egg Storage

What causes the pH of an egg white to change from slightly alkaline to noticeably more basic? The answer lies in the egg's shell and its natural chemical buffer system involving carbon dioxide.

Initial Stage: When an egg is first laid, its albumen contains dissolved carbon dioxide in equilibrium with carbonic acid ($H_2CO_3$). This buffer system maintains a pH close to neutral.
Storage Period: As the egg is stored, carbon dioxide slowly escapes through the thousands of pores in the eggshell.
Alkalinization: This loss of carbon dioxide shifts the chemical equilibrium, leading to a decrease in carbonic acid. The result is a progressive increase in the egg white's pH, which can rise to values as high as 9.2 or 9.5 in older eggs.

This rise in alkalinity is a key indicator of an egg's age. The thinning of the egg white and the weakening of the vitelline membrane around the yolk are direct consequences of this increasing pH.

The Role of Egg Yolk pH

To fully understand the acid-base profile of an egg, it's essential to consider the yolk. While the egg white becomes more alkaline, the yolk maintains a more stable, slightly acidic pH. A fresh yolk has a pH of approximately 6.0, which increases only slightly to around 6.4 to 6.9 over the same storage period. This contrast between the white and the yolk is a critical aspect of egg science.

Practical Applications in the Kitchen

Understanding the pH of an egg's components has practical implications for cooking and baking. For example, chefs often add a small amount of an acid, like cream of tartar, to egg whites when making meringue or stabilizing foams. This addition of acid lowers the pH, helping the proteins denature and form more stable foams, which are more desirable for certain culinary preparations. The foaming properties of egg white proteins are most stable near a neutral pH and decline as the alkalinity increases.

Egg White Protein Composition and pH

Egg white contains various proteins with different isoelectric points (pI). Many, such as ovalbumin, ovomucoid, and ovoglycoprotein, have acidic pI values (4.5, 4.1, and 3.9 respectively). However, the overall pH of the albumen is primarily controlled by the bicarbonate buffer system and the loss of carbon dioxide. Lysozyme is a notable exception, being a strongly basic protein with a high pI of 10.7. Interactions between these proteins, particularly the ovomucin-lysozyme complex, contribute to the thick structure of fresh albumen. As pH increases, this complex destabilizes, causing the egg white to thin.

A Comparison of Egg White and Yolk pH


Feature	Fresh Egg White	Stored Egg White	Fresh Egg Yolk	Stored Egg Yolk
Initial pH	~7.6 (Slightly Alkaline)	Can rise up to 9.5 (Strongly Alkaline)	~6.0 (Slightly Acidic)	Rises slightly to ~6.4-6.9
Dominant Chemical Process	Contains dissolved $CO_2$	Loss of $CO_2$ through shell pores	Stable composition	Water diffusion from white, minimal change
Effect on Proteins	Stable protein structure	Protein destabilization, thinning albumen	Minimal protein change	Minimal protein change, absorbs water
Culinary Effect	Good foaming stability	Reduced foaming stability	Adds richness, emulsifying properties	Absorbs water, may thicken slightly

Conclusion

In summary, the notion that egg white is strongly acidic is a myth. The egg white begins as slightly alkaline in a fresh egg and becomes significantly more alkaline over time as it releases carbon dioxide. The egg yolk, in contrast, remains slightly acidic. This dynamic pH is a natural indicator of egg freshness and has important implications for how eggs behave in various culinary applications. The misconception likely arises from the fact that many of the individual proteins within the albumen have acidic isoelectric points, but this does not determine the overall pH of the surrounding fluid. The alkaline nature of the egg white is a natural biological process, not a strong acid, and is crucial for protecting the contents of the egg.

Frequently Asked Questions

A fresh egg white is actually slightly basic, or alkaline, with a typical pH value of around 7.6.

The pH of an egg white increases as the egg ages because carbon dioxide escapes through the shell's pores. This loss of dissolved $CO_2$ and carbonic acid shifts the chemical balance toward a more alkaline state.

You can't test the pH at home without special equipment, but the increasing alkalinity is what causes the thick egg white to become thinner and more watery over time. A fresher egg will have a thicker, more gel-like albumen.

Cream of tartar is added to egg whites because its acidic properties lower the pH, which helps stabilize the protein structure and create a stronger, more stable foam for meringues and other dishes.

No, the egg yolk's pH remains relatively stable compared to the egg white. A fresh yolk has a pH of about 6.0 and only rises slightly during storage.

Yes, storing eggs at refrigerated temperatures slows the rate at which carbon dioxide escapes, thus delaying the increase in the egg white's pH and preserving its freshness for a longer period.

No, the increased alkalinity of older egg whites does not make them unsafe to eat. It is a natural process of aging. The change in pH mainly affects the egg's functional properties in cooking, such as its foaming ability.