Why is protein so chewy? The science behind texture

January 2, 2026 •

3 min read

According to the National Institutes of Health, collagen makes up 20-25% of the body's total protein content. The answer to why is protein so chewy lies in the very structure of muscle fibers and the tough, fibrous connective tissues like collagen that bind them together, along with how these elements react to heat and processing.

Quick Summary

Chewiness in protein-rich foods stems from factors including the inherent structure of muscle fibers and the presence of connective tissue. Cooking techniques, pH levels, and processing methods also play significant roles in determining the final texture, whether in a piece of meat or a manufactured protein bar.

Key Points

Muscle Fiber Structure: The density and type of muscle fibers directly influence meat chewiness; active muscles contain thicker fibers and are tougher.
Connective Tissue (Collagen): Tough collagen in meat can be broken down by slow, moist heat, converting into tender gelatin, which explains why pot roasts soften with long cooking.
Heat and Moisture: Lean meats toughen when overcooked at high temperatures as muscle fibers contract and lose moisture, while tougher cuts benefit from low-and-slow cooking to dissolve collagen.
Protein Bar Additives: Chewiness in protein bars results from concentrated protein powders absorbing water and the use of binding agents like syrups, fibers, and sugar alcohols.
pH Level's Impact: The pH of meat after slaughter affects natural tenderizing enzymes; an abnormally high or low pH can cause tougher textures like DFD or PSE meat.
Tenderizing Techniques: Methods like marination with acidic ingredients, mechanical tenderization (pounding), and proper cooking technique can all reduce chewiness in meat.
Aging Process: For meat, the aging process allows natural enzymes to tenderize the muscle fibers over time, contributing to a more tender final product.

The Fundamental Role of Muscle Fibers and Connective Tissue

The fundamental structure of animal muscle is a primary reason why protein in meat can be chewy. Muscle is made of long fibers containing proteins like actin and myosin. The orientation and density of these fibers affect texture. Lean cuts with less fat and finer fibers are more tender, while muscles that do more work have thicker fibers and more connective tissue, making them tougher.

The Impact of Collagen and Elastin

Connective tissue, particularly collagen, is a major contributor to chewiness in meat. Collagen's structure provides strength, and slow, low-temperature cooking breaks it down into gelatin, tenderizing tough cuts. Elastin, another fibrous protein, does not break down with heat and remains tough, often needing to be trimmed.

The Effect of Heat and Processing

Cooking significantly alters protein texture. Heat causes muscle fibers to contract and lose moisture. Overcooking lean cuts at high heat leads to dryness and chewiness. Tougher, collagen-rich cuts require long, slow, moist-heat cooking to dissolve collagen.

How Protein Bars Get Their Chewiness

Chewiness in protein bars arises from concentrated protein powders interacting with binding agents and moisture.

Protein-Protein Interactions: Concentrated proteins form firm matrices by absorbing water.
Binding Agents: Syrups and fibers hold ingredients and add to dense texture.
Sugar Crystallization: Sugars and polyols can crystallize over time, increasing hardness.
Maillard Reactions: Browning reactions during storage form cross-links that contribute to firmness.

The Surprising Role of pH in Tenderness

Meat pH impacts texture. After slaughter, pH drops as glycogen becomes lactic acid.

Optimal pH: This range allows enzymes (calpains) to break down proteins and increase tenderness.
High pH (DFD): Stress before slaughter can lead to high pH, limiting enzyme activity and causing tough DFD meat.
Low pH (PSE): Rapid pH drop in warm carcasses causes protein denaturation and water loss, leading to dry, tough PSE meat.

How to Overcome Chewiness

Methods exist to improve tenderness. For meat, understanding the cut is key; for protein bars, preparation helps.

Marination: Acidic marinades and enzymatic ingredients tenderize meat.
Mechanical Tenderization: Pounding or scoring meat breaks down fibers.
Cooking Technique: Use slow, moist heat for tough cuts and quick, high heat for tender cuts.
Hydration (for protein bars): Adequate hydration of protein powder in recipes prevents chalkiness or excessive chewiness.

Comparison of Meat vs. Protein Bar Chewiness Factors


Factor	Chewiness in Meat	Chewiness in Protein Bars
Primary Cause	Muscle fiber density and connective tissue (collagen/elastin) content.	High concentration of protein powders and binding agents.
Effect of Heat	Can either toughen lean cuts by shrinking fibers or tenderize tough cuts by melting collagen.	Can contribute to hardening through protein aggregation and Maillard reactions.
Role of Moisture	Squeezed out of muscle fibers during cooking; leads to dryness.	Absorbed by protein powders, which can lead to a dense, tough matrix.
Impact of pH	Influences post-mortem tenderization; extreme pH can lead to toughness (DFD or PSE meat).	Can affect protein stability and interactions, but less a factor in final chewiness compared to meat.
Aging	Aging meat allows natural enzymes to break down muscle fibers, increasing tenderness.	Storage over time can lead to a hardening effect due to crystallization and reactions.

Conclusion

Chewiness in protein is due to biological structure and changes during cooking/processing. Meat chewiness stems from muscle fiber density and connective tissue like collagen and elastin. Cooking methods are crucial for managing these elements. In protein bars, chewiness results from concentrated protein powders, binders, and their interactions over time. Understanding these principles helps control food texture.

Frequently Asked Questions

No, it depends on the cut. Overcooking lean cuts with little connective tissue, like chicken breast or steak, makes them tough by contracting muscle fibers. However, cooking tougher, collagen-rich cuts for a long time at low temperatures (braising) actually breaks down the collagen, making the meat more tender.

Protein bars are often chewy due to the high concentration of protein powders, which can form rigid networks by absorbing moisture over time. Binding agents like syrups and fibers, used to hold the bar together, also contribute to the dense, chewy texture.

Yes, you can. Techniques include marinating with acidic ingredients to break down proteins, using mechanical tenderizers like a meat mallet, or cooking tough cuts with slow, moist heat to dissolve collagen into gelatin.

The pH level in meat after slaughter determines the activity of natural enzymes that tenderize muscle. A normal pH drop activates these enzymes, leading to tender meat. Abnormal pH levels, caused by pre-slaughter stress, can inhibit these enzymes, resulting in tougher meat.

Collagen is a fibrous protein that melts into gelatin with slow, moist heat, making tough meat tender. Elastin, another fibrous protein, does not break down with heat and remains tough and rubbery.

Manufacturers can adjust the ratios of protein, moisture, and binding agents, as well as use different types of proteins and sweeteners to control texture. Researchers also explore adding antioxidants to prevent reactions that cause hardening over time.

As muscle fibers contract during cooking, they squeeze out moisture. This protein coagulation and water loss, particularly when overcooking lean cuts, result in a dry, dense, and chewy texture.