Heat from cooking changes the shape of protein in foods and, in some cases, triggers reactions between amino acids and other substances. Most of these changes are good because they make foods more digestible and develop flavor. But when red meat is exposed to very high temperatures, amino acids produce substances that may increase the risk of cancer.
Change in Structure
The first step in protein production occurs when amino acids connect together to form a long chain. In the next step, the chain coils or folds to form a secondary structure. In the final step, it folds again to create a three-dimensional form known as the tertiary structure.
In a process called denaturation, heat breaks the bonds that hold together the secondary and tertiary structures, but it doesn’t alter the original chain of amino acids. Some proteins denature at 110 degrees Fahrenheit, but most unfold around 130 degrees Fahrenheit, reports Bellevue College.
Since the chain of amino acids stays the same even after proteins are heated, the amino acids are still available for your body to absorb and use. In fact, proteins must be denatured before they’re digested. Eliminating the secondary and tertiary structures is the only way for digestive enzymes to reach the primary chain of amino acids.
Boost of Flavor
When they’re heated, proteins on the surface of food combine with sugars, which causes browning and develops flavors. This process, called the Maillard reaction, begins when foods are heated above 285 degrees Fahrenheit, according to the Science of Cooking website.
While the Maillard reaction improves flavor, you’ll also lose some nutrients. The amino acids that combine with sugar change form, so they’re no longer available as amino acids.
Effect on Milk Proteins
Milk contains two groups of proteins -- casein and whey -- which react with one another at high heat. This is beneficial for some purposes, such as making cheese, because it prevents curds from forming.
Casein and whey have different physical characteristics that make whey proteins more sensitive to heat. Whey withstands pasteurization but denatures at higher temperatures. Denatured whey can bind with more water, which improves the consistency of products such as yogurt, reports Milk Facts.
Dangers of High Heat
At high temperatures, amino acids react with creatine, which is naturally found in muscles, to form heterocyclic amines. HCAs are a concern because they may increase your risk of cancer.
Beef, pork, fish and poultry can all form HCAs, but the biggest danger comes from red meat, according to a study in Nutrition and Cancer in October 2013. HCAs are more likely to develop when meat is in direct contact with a metal pan and cooked at 300 degrees Fahrenheit or higher.
Acrylamide is formed when a specific amino acid -- asparagine -- reacts with sugars, which happens at high temperatures reached during frying, roasting and baking. You don’t have to worry about acrylamides developing in meat, fish or dairy. They only form in plant foods, especially carbohydrate-rich potatoes that are fried. Acrylamide increases the risk of cancer in lab animals, but its effect in people is still being studied.
- Bellevue College: Protein
- Science of Cooking: Why Foods Brown
- Dairy Cattle: Milk Protein Behavior at High Temperature
- Milk Facts: Milk Protein
- National Cancer Institute: Chemicals in Meat Cooked at High Temperatures and Cancer Risk
- U.S. Food and Drug Administration: Acrylamide Questions and Answers
- Nutrition and Cancer: Red Meat-Derived Heterocyclic Amines Increase Risk of Colon Cancer: A Population-Based Case-Control Study
- Photo Credit Kanawa_Studio/iStock/Getty Images
The Effects of Too Much Protein in the Diet
Protein is a major nutrient your body uses to build, maintain and repair itself. It's recommended that adults get 0.8 gram of...
Do Protein Shakes Have Side Effects?
Protein shakes are used by health buffs, athletes and body builders to enhance performance, lose weight or to supplement nutrition. Protein is...
The Effect of Temperature on Cell Membranes
All living cells are protected by their cellular membrane which is made up of phospholipids with embedded proteins. The structure of the...
Negative Effects of Protein Supplements
Many bodybuilders and athletes report that protein supplements help them gain muscle and strength, and also recover from training faster. But protein...
The Effects of Cooking on the Nutritional Value of Food
Cooking first came about as a way to preserve foods and kill any potentially harmful organisms that could make you sick. While...
The Effect of Temperature on Respiration Rate
The rate of respiration increases with increasing temperature until an optimum temperature is reached, after which, it decreases. This is due to...
How Does Temperature Affect Catalase Enzyme Activity?
Hydrogen peroxide is the byproduct of numerous biological processes, and to break down this molecule, the body uses an enzyme called catalase....
Science Projects on Denaturation of Proteins
To denature a protein is to break it down without changing its chemistry. Denaturation is frequently seen in cooking principles. Heat denatures...
How Does Temperature Affect Molecules?
Temperature can affect both the structure of a molecule and how it interacts with surrounding molecules. Heating some molecules, particularly large, biological...
Causes for Denaturing
Molecules such as proteins generally have a characteristic three-dimensional shape that allows that molecule to participate in chemical reactions. Denaturing occurs when...
The Effect of Temperature on Enzyme Activity in Beef Liver
Enzymes are organic or biological catalysts that drive metabolic reactions. In order for a reaction to take place within cells, enzymes must...
What Is Egg Coagulation?
Egg coagulation refers to the process that occurs when heat is applied to the protein molecules in the eggs, which thicken into...