Denatured protein loses its shape, which in turn affects its ability to function, but that doesn’t change its value. Since the amino acids remain intact, your body still absorbs, uses and benefits from denatured protein. In fact, protein must be denatured during digestion for proper digestion and maximum absorption. Denaturation is a simple process performed by acids in your stomach.
When proteins are produced, they begin as long chains of amino acids connected together in a specific sequence. This strand of amino acids is the protein’s primary structure. But the protein isn’t complete yet. Next, the strand twists into a helixlike shape, and new bonds between amino acids form to hold this shape together. This is called the secondary structure. Then it goes through a third change, in which the helix folds in various locations. Once again, new bonds form to stabilize this tertiary structure. Now the protein is complete. The sequence of amino acids determines how the protein twists and folds, while the final shape dictates the protein's function.
Denaturation During Digestion
Protein denaturation disrupts the secondary and tertiary structures by breaking the bonds holding them together. The primary structure is not affected, so even when proteins are denatured, the essential amino acids are not destroyed. During digestion, protein denaturation takes place in your stomach. Smelling, tasting and eating food triggers cells in the lining of your stomach called parietal cells to secrete hydrochloric acid. As proteins land in your stomach, they’re denatured by hydrochloric acid.
Purpose of Denaturation
Denaturation is the first step in protein digestion. It’s a vital step because it enables digestive enzymes to do their job. Digestive enzymes break the bonds between amino acids, but they work at the surface of the protein. Proteins are so large, containing up to 2,000 amino acids, and they have such a complex structure that enzymes would not be able to penetrate throughout the structure if proteins remained in their original shape. Since your small intestine only absorbs individual amino acids, or very small pieces with only two or three amino acids, denaturation ensures proteins are digested into small units you can use.
Tips and Considerations
Enzymes are made from protein, and all of the proteins you consume are denatured in the stomach. If you take supplemental digestive enzymes, they won't be effective unless they have an enteric coating, which protects them from stomach acid, notes NYU Langone Medical Center. Proteins are denatured during cooking or processing by heat, acids, alcohol, a high concentration of salt, and even mechanical agitation such as mixing. Since they would be denatured in your stomach anyway, cooking doesn't affect their nutritional benefit. Your body only needs the individual amino acids, which it uses to rebuild new proteins.
- Bellevue College: Protein
- University of Washington: Regulation of Acid Secretion
- Colorado State University: Absorption of Amino Acids and Peptides
- National Institute of General Medical Sciences: Proteins Are the Body’s Worker Molecules
- NYU Langone Medical Center: Proteolytic Enzymes
- Elmhurst College: Denaturation of Proteins