How Does Cooking Affect PDCAAS Score? A Comprehensive Guide

December 24, 2025 •

4 min read

A 2020 study on chickpeas found that thermal processing methods differentially affected protein quality scores, with extrusion yielding a higher PDCAAS than cooking. This highlights how the preparation of food is a crucial factor in evaluating protein quality using the Protein Digestibility Corrected Amino Acid Score (PDCAAS). The effect of cooking on a food's PDCAAS depends on a complex interplay of heat intensity, duration, and the food's specific composition.

Quick Summary

The PDCAAS score is significantly influenced by cooking due to changes in protein structure and digestibility. Heat can enhance digestibility but also degrade specific amino acids, with the outcome varying by method and food source.

Key Points

Cooking's Influence: Heat treatment alters protein structure, which directly impacts protein digestibility and, consequently, the PDCAAS score.
Beneficial Denaturation: Moderate heat often denatures protein, making it more accessible to digestive enzymes and potentially increasing the PDCAAS.
Detrimental Overheating: Excessive or prolonged high-heat cooking can cause protein aggregation and form compounds like Advanced Glycation End-products (AGEs), which can lower digestibility and the PDCAAS.
Method Matters: Different cooking methods have varying effects; for example, boiling can leach some nutrients, while roasting can cause browning that affects amino acid availability.
DIAAS as an Alternative: The Digestible Indispensable Amino Acid Score (DIAAS) is now considered a more accurate metric than PDCAAS because it measures amino acid digestibility specifically in the ileum.
Source Specifics: The effect of cooking varies by food source; heat treatment can improve digestibility in some plant proteins like legumes but potentially damage specific amino acids in meat.

What is PDCAAS and How is it Calculated?

The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is a method recommended by the Food and Agriculture Organization (FAO) and World Health Organization (WHO) to evaluate protein quality in human nutrition. It assesses how well a food's protein meets the body's needs for essential amino acids. The calculation involves two main parts:

Amino Acid Score (AAS): This compares the limiting essential amino acid in a protein to a reference pattern.
True Fecal Digestibility (FTPD): This measures protein absorption, traditionally using animal studies, and corrects the AAS based on this percentage.

The PDCAAS Formula

$PDCAAS = Amino~Acid~Score \times Protein~Digestibility~Percent$

Scores are capped at 1.0, a limitation of the method.

The Complex Relationship Between Heat and Protein

Cooking changes protein structure through denaturation, altering its properties. This can improve digestibility by making proteins more accessible to enzymes. However, the effects depend on conditions.

Beneficial Denaturation

Moderate heat unfolds protein chains, exposing areas for digestive enzymes, leading to better digestion and amino acid absorption. Cooking also improves taste and makes food safe.

Detrimental Effects of Overcooking

High or prolonged heat can degrade amino acids via the Maillard reaction, making them unavailable. Excessive heat can also cause protein aggregation, hindering enzyme action and reducing digestibility. A study on sea cucumber showed that while moderate boiling helped, excessive boiling reduced digestibility. High heat can also create harmful compounds like AGEs.

How Cooking Methods Impact PDCAAS

Different cooking methods affect PDCAAS differently:

Boiling and Steaming

Gentle moist-heat methods like boiling and steaming are generally easy on proteins. They can improve the digestibility of legumes by breaking down anti-nutritional factors. However, water-soluble nutrients can leach out, so consuming the cooking liquid is beneficial. Boiling potatoes improved their PDCAAS compared to raw.

Frying and Roasting

Dry-heat methods use higher temperatures, risking the Maillard reaction, which can damage amino acids. A study on breakfast sausage showed lower grilling temperatures resulted in better amino acid scores. Frying can also affect nutrient content due to oil absorption.

Grilling and Broiling

High, direct heat can form harmful compounds like AGEs, which reduce protein bioavailability. Marinating meat can help protect it during grilling.

Cooking Effects on Different Protein Sources

Cooking impacts various proteins differently:

Legumes: Cooking often improves digestibility by deactivating anti-nutritional factors. Cooked chickpeas had increased PDCAAS compared to raw.
Animal Proteins: Cooking tenderizes animal protein, improving digestibility. However, excessive heat can cause aggregation and potential amino acid loss. Boiling camel meat led to more protein degradation than other methods.
Vegetables: Cooking can alter free amino acid levels. Boiling can cause leaching, while roasting can increase certain amino acids.

Effects of Cooking Methods on Protein Quality


Cooking Method	Effect on Protein Structure	Impact on Digestibility	Potential for Nutrient Loss
Boiling	Denatures protein, increases solubility	Usually improves, but some protein/amino acids can leach into water	Moderate, particularly for water-soluble nutrients and amino acids
Steaming	Gentle denaturation, preserves structure	High, one of the best for preserving nutrient bioavailability	Minimal, as there is no direct contact with water
Frying	High heat, Maillard reaction, aggregation	Variable, can decrease if overcooked due to aggregation and AGEs	Moderate to High, potential for amino acid damage and unhealthy fat absorption
Roasting	Dry heat, Maillard reaction	Variable, depends on temperature and time; can decrease with excessive heat	Low to Moderate, can be minimized by avoiding overcooking
Grilling	High heat, charring, AGE formation	Variable to Low, high risk of protein degradation and reduced bioavailability	Moderate to High, potential for damage to heat-sensitive amino acids
Microwaving	Quick, gentle heat, minimal structural change	High, generally preserves protein quality well	Low, minimizes exposure to excessive heat

PDCAAS vs. DIAAS: A More Accurate Measure

DIAAS (Digestible Indispensable Amino Acid Score), introduced by the FAO, addresses limitations of PDCAAS. DIAAS measures digestibility at the ileum for greater accuracy and does not cap scores, allowing better differentiation of high-quality proteins. It also uses age-specific reference patterns, unlike PDCAAS.

Conclusion: The Nuance of Protein Quality

Cooking significantly impacts PDCAAS, with outcomes depending on food type and cooking methods. While moderate heat improves digestibility, excessive heat can cause damage. Gentler methods like steaming are often better for preserving protein quality. Newer metrics like DIAAS offer a more refined understanding of protein quality, emphasizing the importance of careful food preparation.

Learn more about the impact of cooking on protein quality by reading a study on russet potatoes

How to Choose the Best Cooking Method

Prioritize Gentle Cooking: Methods like steaming or microwaving retain protein quality best.
Use Cooking Liquids: Use broth from boiled proteins to retain leached nutrients.
Cook Until Tender: Avoid overcooking to prevent amino acid damage and harmful compound formation.
Marinate Before High-Heat: Marinating meat can protect proteins during grilling.

Cooking and PDCAAS in Specific Contexts

Animal vs. Plant Protein

Cooking improves plant protein digestibility by breaking down fibers and anti-nutrients. For animal proteins, cooking tenderizes, but overcooking poses a risk.

Understanding Protein Combinations

Combining complementary proteins, like rice and pea protein, can improve the overall PDCAAS.

A Final Word on Nutrient Density

PDCAAS is one measure of nutritional value. Consider overall nutrient density, including vitamins, minerals, and fiber, for a balanced diet.

The Evolution of Protein Quality Measurement

The shift to DIAAS reflects advancements in understanding digestion. DIAAS is accepted by the FAO and provides a more accurate measure of protein bioavailability than PDCAAS.

The Future of Protein Evaluation

Future methods may consider individual factors like genetics and gut microbiome for personalized protein quality assessment.

Frequently Asked Questions

No, while moderate cooking often improves protein digestibility, excessive or prolonged high heat can damage amino acids and cause protein aggregation, which can lower overall protein quality and the PDCAAS score.

The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is a method for evaluating protein quality based on a food's amino acid profile compared to human needs and its digestibility.

Yes, intense or prolonged heat can cause proteins to form aggregates and complexes that are more resistant to digestive enzymes, ultimately making the protein less digestible.

Yes, methods like frying and high-heat grilling can cause more significant protein damage and lower PDCAAS. Gentler methods like steaming and boiling often preserve protein quality better, though some nutrients may leach into water.

The Maillard reaction is a browning process caused by high heat where proteins bind with sugars. This can make certain amino acids, particularly lysine, less accessible to digestive enzymes, thereby reducing protein quality.

A limiting amino acid is the essential amino acid present in the smallest amount relative to the body's requirements. It restricts the body's ability to synthesize new proteins, regardless of the availability of other amino acids.

The Digestible Indispensable Amino Acid Score (DIAAS) is a more accurate method because it measures amino acid digestibility at the end of the small intestine (ileum), whereas PDCAAS uses less precise fecal measurements. DIAAS also does not cap its score at 1.0, allowing for better differentiation between high-quality proteins.