How Your Morning Coffee Relies on Chemical Reactions?

The chemistry behind your morning coffee

julianawrites
GapsScience
4 min readFeb 24, 2023

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Have you ever wondered how your morning cup of coffee gives you that jolt of energy to kickstart your day? Well, it’s not just the caffeine that’s responsible for the boost—there are a lot of chemical reactions involved in making your perfect cup of coffee.

First things first, let’s talk about the beans themselves. Coffee beans are actually the seeds of the Coffea plant, which is native to tropical regions of Africa. The beans are harvested when they are ripe, which means they have turned from green to a deep red or purple color. The beans are then washed to remove any dirt or debris, and they are left to dry in the sun or in a special machine.

Once the beans are dried, they are roasted. Roasting is a crucial step in the coffee-making process because it transforms the chemical composition of the beans. During roasting, the beans are exposed to high temperatures, usually between 370–540 degrees Fahrenheit, depending on the desired roast level. One of the most important chemical reactions that occurs during roasting is the Maillard reaction. This is a non-enzymatic browning reaction that occurs between amino acids and reducing sugars when they are heated. The Maillard reaction is responsible for the characteristic brown color and rich flavor of coffee. It also produces a wide range of new compounds, including pyrazines, furans, and thiophenes, which contribute to the aroma and flavor of coffee.

Another important reaction that occurs during roasting is the breakdown of carbohydrates. When the beans are heated, the carbohydrates in the beans break down into simple sugars. These simple sugars then react with amino acids to form new compounds, such as furans, which contribute to the sweetness and caramel-like flavor of coffee.

Lipids, or fats, in the coffee beans also undergo changes during roasting. When the beans are heated, the lipids break down into fatty acids and glycerol. The fatty acids then react with other compounds in the beans to form new compounds, such as aldehydes, which contribute to the aroma and flavor of coffee.

Once the beans are roasted, they are ground and brewed with hot water. During brewing, water acts as a solvent, dissolving a wide range of compounds from the coffee grounds. One of the most important compounds that is extracted during brewing is caffeine. Caffeine is a bitter compound that stimulates the central nervous system. It is also responsible for the energizing effect that most people experience after drinking coffee.

Acids are another important group of compounds that are extracted during brewing. Acids contribute to the sour taste of coffee and help to balance the sweetness of the sugars that are extracted. One of the most important acids in coffee is chlorogenic acid, which is responsible for the bright, fruity notes in coffee.

In addition to acids, oils are also extracted during brewing. These oils contribute to the body and mouthfeel of coffee. One of the most important oils in coffee is caffeol, which is responsible for the aroma and flavor of coffee.

After brewing, there is one more chemical reaction that occurs, and that is oxidation. Oxygen in the air reacts with the compounds in the coffee, causing it to go stale over time. That’s why it’s important to drink your coffee as fresh as possible. To minimize oxidation, it’s best to store your coffee in an airtight container and consume it within a few days of brewing.

Milk is a common addition to coffee, and it too undergoes chemical changes when added to hot coffee. When milk is heated, the proteins in the milk denature or unravel, causing them to form new bonds with each other. This process, called coagulation, causes the milk to thicken and form a foam or froth on top of the coffee. The heat also causes the lactose, a sugar found in milk, to break down into simpler sugars, making the milk taste sweeter. The fats in the milk also emulsify or mix with the coffee, adding to the richness and smoothness of the drink.

Your morning cup of coffee relies on a whole host of chemical reactions, from roasting the beans to brewing them with hot water. So, next time you take a sip of your favorite brew, take a moment to appreciate all the science that went into making it taste so good!

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julianawrites
GapsScience

i do everything from professional sports to entrepreneurship and language learning. currently taking a gap year with baret scholars and building talpact.com ❤️