Reference
Egg White Protein
**Egg white protein** is a complete animal protein derived from the albumen of chicken eggs, historically used as the reference protein against which biological value (BV) was measured. It supplies all nine essential amino acids and is one of the nine major food allergens.
Composition and protein quality
Egg white is almost entirely protein once separated from the yolk. Four egg whites (half a cup from a carton) contain about 13g of protein and carry no saturated fat (Cleveland Clinic Health Essentials, 2025). The dominant protein is ovalbumin, alongside ovotransferrin, ovomucoid, and lysozyme.
On the Protein Digestibility-Corrected Amino Acid Score (PDCAAS), egg protein scores 1.00 — the maximum value — placing it alongside milk, whey, casein, and soy protein isolate, all of which reach the truncated ceiling of 1.00 (Schaafsma, Journal of Nutrition, 2000, PMID:10867064). Under DIAAS, the metric the FAO proposed in 2013 to replace PDCAAS because it uses ileal digestibility and does not truncate scores at 1.0, egg protein is generally reported above 100%, indicating a surplus of digestible essential amino acids relative to human requirements (MacroFactor, 2024).
Biological value as a historical reference
Egg protein was long treated as the standard for protein quality comparisons. Because its amino acid pattern closely matches human requirements and its digestibility is high, early nitrogen-balance work used whole egg as the benchmark against which other proteins were scaled. That historical role is why egg white still appears as a comparison point in discussions of complete proteins, even though DIAAS and PDCAAS have since become the dominant scoring systems.
Allergenicity
Egg is one of the FDA’s major food allergens (the “Big 8,” now nine with sesame added). Egg allergy is among the most common in children, and the relevant allergenic proteins — particularly ovomucoid — are heat-stable, meaning cooking does not reliably eliminate the reaction. This is the central limitation of egg white protein for the allergy-aware household: a high-quality, complete protein that a meaningful share of the population cannot consume.
Relevance to potato protein
Egg white protein is a useful reference point when evaluating alternatives. Potato protein isolate is recognized for nutritional quality comparable to animal proteins such as egg or milk, and it sits outside the major allergen categories. For anyone selecting between sources, comparing complete proteins on quality score, allergen status, and digestibility is covered in our guide to choosing a protein powder.
Related terms