A Little Science: Temperature

Coffee is one of those amazing beverages that can exhibit different characteristics and flavors at different temperatures. I am just going to be focusing on hot coffee for now. There aren’t many things that are as satisfying and invigorating as a cup of hot coffee. Hot coffee is comforting, aromatic, complex, and damn delicious. But how else does temperature play a role in coffee? Can it be too hot? What happens when it becomes lukewarm?

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Heat has some interesting effects on coffee. I want to focus on how it breaks down, and extracts acidic and basic flavor compounds. When hot water is introduced to coffee grounds, acidic flavor compounds are extracted first. This is where we experience fruity notes in our cups of coffee. As time goes on, and hot water is still being introduced to the coffee grounds, more bitter flavor compounds are extracted. I don’t want to focus too much on brewing, and brew methods, because that will be a different, extensive post. Just understand that in the context of flavor compounds, hot water increases the rate in which acidic and bitter flavor compounds are extracted. The longer the hot water stays in contact with the coffee grounds, the more bitter the end product will be.

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I think most people are familiar with the lawsuit regarding the extremely hot coffee that burned a McDonald’s customer. Coffee can be too hot for reasons other than giving us third degree burns. Our brains process heat at different levels. Warmth makes us feel comfortable, and happy. As heat increases, our brains start to send warning signals telling our body that danger is a sip away. These signals are intense, and take top priority. This hinders our brain’s ability to process the complex flavors a coffee may offer when consuming a cup that is 200-212 F. This plays no role in brewing coffee. We will discuss temperature and brewing a different day.
This doesn’t necessarily mean that lukewarm coffee will exhibit the complex flavors of the coffee. Oxidation plays a large role in the flavor of coffee, and oxidation occurs a lot faster in hot coffee. To avoid getting “sciencey,” oxidation causes coffee to taste stale, bitter, and for lack of better term, like “coffee.” As the temperature of a finished brewed coffee decreases, a chemical change begins to happen, and acidic compounds become basic. If I were to recommend how fast a cup of coffee should be consumed, I would say avoid letting it sit for more than 15 minutes.

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Delicious coffee is fleeting. Have it too hot, and you will only experience pain. Let it cool too much, and you will miss the beauty in the cup. Good people won’t let good, hot coffee get cold.