Is Cooking a Physical or Chemical Change? (And Why?)

Cooking is generally considered a chemical change because it involves the application of heat, which induces chemical reactions and alters the composition, structure, and properties of the ingredients being cooked. ^{1 2}

Well, this was just a simple answer. But there are few more things to know about this topic which will make your concept super clear.

So let’s dive right into it.

Why is cooking a chemical change?

Cooking is considered a chemical change because it involves a series of chemical reactions that result in the transformation of food ingredients. During cooking, various chemical processes occur, such as denaturation, caramelization, Maillard reaction, and fermentation, which bring about changes in the chemical composition of the ingredients.

Here is a short information about each process.

1. Denaturation: Many cooking methods, such as heating, cause the proteins in food to undergo denaturation. Denaturation involves the disruption of the protein’s structure, leading to changes in its properties, such as texture and flavor. ³
2. Caramelization: When sugars are subjected to heat, they undergo caramelization. This process involves the breakdown of complex sugars into simpler compounds, resulting in the characteristic brown color and distinct flavor of caramelized foods. ⁴
3. Maillard reaction: The Maillard reaction occurs when amino acids and reducing sugars react at high temperatures. ⁵ This reaction leads to the browning and development of flavors in cooked food, such as the crust on bread or the sear on a steak.
4. Fermentation: Cooking processes like baking or brewing often involve fermentation. Fermentation is a metabolic process carried out by microorganisms, such as yeast or bacteria, which convert sugars into alcohol, acids, or gases, thereby changing the taste, texture, and nutritional content of the food. ⁶

All these chemical reactions and processes contribute to the transformation of raw ingredients into cooked food, resulting in changes in taste, texture, color, and nutritional profile. Therefore, cooking is considered a chemical change rather than a physical change, as it involves the alteration of the chemical properties of the ingredients.

Why is cooking not a physical change?

Cooking is not considered a physical change because it involves chemical reactions that bring about permanent changes in the molecular structure and composition of the ingredients. These chemical reactions result in the creation of new substances with different properties, such as the formation of new flavors, textures, and aromas.

In cooking, various chemical processes occur that lead to the transformation of food. Heat applied during cooking can cause the breakdown of complex molecules, such as proteins and carbohydrates, into simpler compounds.

This breakdown alters the chemical composition of the ingredients and gives rise to new flavors, textures, and aromas that are distinct from the raw ingredients.

Additionally, the combination of different ingredients and the interaction of their chemical components during cooking can result in the formation of entirely new substances.

This can be observed in processes like the Maillard reaction, where the reaction between amino acids and sugars creates a complex mixture of flavor compounds that contribute to the unique taste of cooked food. ⁷

In summary, cooking involves chemical reactions that produce permanent changes in the molecular structure and composition of food, leading to the creation of new substances with distinct properties. These transformations go beyond physical changes and are why cooking is considered a chemical change.

Further reading

Why is Digestion of Food a Chemical Change?
Is Milk Souring a Physical or Chemical Change?
Is Baking a Cake a Physical or Chemical Change?
Is Silver Tarnishing a Physical or Chemical Change?
Is Wood Rotting a Physical or Chemical Change?

1. Why Do We Cook Our Food and What Happens When We Do? | Eufic. https://www.eufic.org/en/food-safety/article/the-why-how-and-consequences-of-cooking-our-food
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3. Hawaii.edu https://pressbooks-dev.oer.hawaii.edu/humannutrition/chapter/the-role-of-proteins-in-foods-cooking-and-denaturation/
4. Caramelization – Wikipedia. (2021, February 1). Caramelization – Wikipedia. https://en.wikipedia.org/wiki/Caramelization
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6. Maicas, S. (2020, July 28). The Role of Yeasts in Fermentation Processes. Microorganisms, 8(8), 1142. https://doi.org/10.3390/microorganisms8081142
7. Rufián-Henares, J., & Pastoriza, S. (2016). Maillard Reaction. Encyclopedia of Food and Health, 593–600. https://doi.org/10.1016/b978-0-12-384947-2.00435-9