Chemistry and physics govern how the world around us works. These fields are almost always present even in areas where they might not seem apparent. One everyday activity that chemistry plays a significant role in is cooking.

While cooking, you use chemistry constantly, likely without even knowing it! If preparing food for a person with an egg allergy, a chef would have to decide on a different binder to use. Water must reach boiling temperatures before pasta can be cooked in it.

What other instances of chemistry are there in cooking? How is cooking chemistry relevant to you? Let’s find out!

Changes during cooking

Physical changes are very common in cooking. Physical changes alter the state of matter of an object. These are opposed to chemical changes, which alter the chemical composition of something. Freezing juice is a physical change, as is cutting up a carrot. So is mashing a banana. 

To determine whether a physical or chemical change has occurred, there are a few indicators to look out for. Production of bubbles, a change in color or smell, and the inability to undo a change are all typical of chemical changes (though not always). One example of a physical change involving the formation of a new color is the dissolving of a drink mix into water. 

Many different chemical changes are important in cooking. Any type of “cooking” suggests a chemical change is occurring – be it braising, broiling, or baking. New chemical compounds are made during cooking, which is why the flavor of a food  usually changes when cooked. 

Cooking something will lead to hundreds of chemical reactions. Protein denaturation, condensation, and fragmentation are just a few types of those reactions.

Placing a piece of bread into a container of cookies is an example of a chemical reaction in cooking that doesn’t require heat. Sugar is hygroscopic, meaning it draws water from its surroundings. Bread is not hygroscopic. So when in the same area, cookies (which are usually high in sugar) will take the water available from the bread. The cookies therefore become softer in the process. 

Another chemical change in cooking is the Maillard reaction, which causes flavor and texture changes in a food. The Maillard reaction is a browning reaction between amino acids and sugars. It occurs in breads that are browned, marshmallows that are toasted, dumplings that are fried, or a number of other foods when being cooked. 

Nobel laureate and chemist Jean-Marie Lehn called the Maillard reaction the most frequently performed chemical reaction. It forms thousands of different molecules in foods. While many are tasty, some of those compounds are thought to be harmful to health. 

Delicious and dangerous

Acrylamide is a probable carcinogen produced as a byproduct of the Maillard reaction of asparagine. Some studies have found a link between acrylamide and developing cancer, while others have not. The darker the product, the more acrylamide has been produced. So try to avoid eating burnt toast regularly!

Reheating the same oil over and over again can produce 4-hydroxy-2-trans-nonenal (HNE), a known toxin. HNE is produced during the peroxidation (oxidative breakdown) of lipids (fats). While you likely don’t reuse oils much at home, restaurants often do. This means you might be at risk of absorbing HNE and subsequently developing cancer, a neurodegenerative disease, or atherosclerosis

Other cooking activities that should be done with caution include anything else done with heat. Hot objects will burn you, and unlike the possibility of acrylamide causing cancer, burns are virtually guaranteed to happen! 

Nitrites, commonly found in processed meats, have been linked to an increased risk of gastric cancer. Nitrites are used as preservatives, so by buying organic foods you can forego the chance that you are consuming high nitrite levels.

Also be mindful of the plants you are consuming. While some parts of plants are edible, the others aren’t always so. Rhubarb fruits, for example, can be eaten, but its leaves produce oxalic acid. In high concentrations, oxalic acid leads to kidney failure in humans.

As a project, cook up your favorite recipe. Make note of all the steps that involve a chemical or physical change, specifying which. For practice, decide whether the following food preparation processes are chemical or physical changes:

  • Separating egg whites from egg yolks
  • Making brownie batter
  • Marinating a steak
  • Thawing frozen chicken nuggets
  • Caramelization of onions

What other instances of chemistry in cooking did you discover?

Comment and share below.


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