The General Effects Of Heat On The Protein In Foods

Proteins are complex biological molecules, made up of many amino acids linked together. When you eat a protein-containing food, your digestive system breaks the protein down into its individual amino acids, and your body uses this supply of amino acids to create new proteins on an as-needed basis. As your body creates a new protein, it joins amino acids together in a chain and then folds the protein into a three-dimensional globular structure. Heating the protein in foods causes several changes in the chemistry and function of the protein

Denaturation

Denaturation of a protein describes the structural changes a protein experiences when exposed to environmental factors such as heat. When you heat a food protein, the chemical bonds holding the protein in its three-dimensional conformation become weak. The more you heat the protein, the more the chemical bonds weaken until finally the bonds break. As the bonds break, the protein unfolds. If the heat you apply is minimal and brief, the protein may be able to refold to its original shape, but high heat renders the unfolding of the food protein permanent.

Digestibility

Heating the protein in foods affects how your body digests the protein. Your digestive enzymes are unable to penetrate a food protein's three-dimensional structure to break the protein down and separate the amino acids. Once the denaturation process opens up the food protein's structure, your digestive enzymes can access the protein in a way to clip off individual amino acids and add them to the pool of amino acids available for new protein synthesis.

Enzyme Activity

Enzymes are protein molecules that function as biological catalysts; that is, they alter the rate of a biological reaction without undergoing any changes themselves. Enzymes are sensitive to heat, and most lose their functional activity when you apply heat to them. This characteristic may be important in the processing of foods. For example, the food protein bromelain, an enzyme found in pineapple, will hydrolyze and destroy the structure of gelatin if it is not heat-inactivated first. For this reason, commercial packages of gelatin warn you that the use of fresh or frozen pineapple in your gelatin mix will not allow your gelatin to gel.

Allergic Reaction

Applying heat to food proteins may alter their ability to initiate an allergic response in your body. In the June 2009 issue of "Current Opinion in Allergy and Clinical Immunology," A. Nowak-Wegrzyn of Mt. Sinai School of Medicine in New York City reports that heating some food proteins, such as those in shrimp and peanuts, may elicit an allergic response in susceptible individuals. Other foods, including milk and egg proteins, show a decreased allergic response when they are extensively heated.