The Impact of Temperature on Coffee: How to Experience Coffee Flavors at High Temperatures and When Cooled

Have you ever experienced getting a cup of hot coffee, only to find that its flavor and aroma change as it cools down?

When this happens, you might start tasting delicate flavors and aromas that you couldn't perceive before. You might discover that your coffee now has noticeable sweetness, fruitiness, or floral notes, and this flavor transformation is attributed to specific chemical reactions triggered by temperature fluctuations. To understand what's really happening, FrontStreet Coffee believes you need to understand the science behind it.

How Do We Perceive Flavor and Aroma?

Coffee is an extremely complex beverage containing over a thousand aromatic compounds that, through coffee brewing and tasting, form what we perceive through our sense of smell and taste. Among these thousand compounds, forty are relatively common and distinct aromas found in coffee. These aromatic compounds are produced during the coffee roasting process when substances like sugars, carbohydrates, and nitrogen compounds are generated through heating. The sugars in raw coffee beans degrade during roasting heat, at which point they either turn caramel-colored (producing the familiar caramel flavor) or become brown through the Maillard reaction.

This process produces volatile compounds that transform into gases that evaporate at room temperature. During the evaporation process, we strongly perceive these aromas, and through our tongues and noses, we sense these tastes and aromas, which are various aromatic compounds related to sweetness. Flavors can range from chocolate notes to fruit aromas.

The taste buds on our tongues have receptors for sour, bitter, and sweet tastes that react to certain chemical compounds and then transmit taste perceptions to our brain. Chemical compounds from the volatile substances travel from our mouth to our nose to stimulate the retro-nasal olfactory system. The collection of these retro-nasal olfactory organs is also very important for our perception of flavor and aroma.

When we perceive other flavors, they may result from the interaction of many substances like organic acids, sugars, and oils. The chlorogenic acids in raw beans produce bitter sensations, while quinic acid creates bitter and astringent feelings. If the coffee we drink has acidity, it can enhance our perception of sourness. When drinking, we connect these acids with volatile compounds, such as linking the acidity we taste with lemon aromas. Once we can make these connections, our sensory abilities are enhanced.

How Does Temperature Affect Coffee Extraction?

We all know that extraction significantly affects the flavors and aromas we perceive in coffee, and the water temperature used for brewing also greatly impacts coffee extraction rates. The molecules in coffee are extracted at different stages depending on water temperature. Hot water can extract most of the compounds we perceive in coffee. The higher the water temperature, the more easily the compounds in coffee are extracted. The more these molecular interactions occur, the greater the extraction. When this happens, water molecules dissolve more compounds from the coffee molecules, thereby affecting the taste and smell we perceive in the coffee.

If we use low-temperature water for extraction, we cannot extract the complete coffee flavor, including these fascinating volatile compounds. However, research indicates that when using low temperatures to brew coffee, this situation changes, such as extracting coffee at low temperatures (ranging from room temperature to zero degrees) for several hours. This forms complex flavor characteristics because this extraction method alters the extraction balance of most compounds, including sugars, organic acids, chlorogenic acids, caffeine, and other insoluble compounds that require more extraction time.

Long-term, low-temperature extraction allows sugars to be fully extracted, making cold brew coffee noticeably sweet with caramel-like aromas, while the bitterness and astringency of the coffee are lower.

Higher Temperatures Extract Flavor and Aroma

Typically, freshly brewed coffee has a temperature between 82°C to 85°C. However, this temperature is too high and can cause burns, and at this temperature range, you might not perceive the coffee's flavor and aroma well. The best way to drink coffee this way is to take small sips or slurps, only drawing in small amounts of coffee liquid while inhaling air to quickly cool the liquid.

When the temperature reaches around 70°C, the coffee's flavor and aroma become more noticeably perceptible. At this temperature, coffee releases a large amount of steam, which can enhance the perceived aroma but suppresses the tongue's taste perception, thereby affecting flavor perception. Volatile compounds are released faster and evaporate quickly during this stage.

Stronger aromas are also perceived at temperatures around 70°C and can continue until around 60°C. During this stage, it's often more difficult to perceive flavors, especially when the coffee flavors are very delicate. In fact, research indicates that different coffees with the same roast degree might taste very similar when consumed at higher temperatures. What we primarily perceive at 70°C might be bitterness and aromas, while flavors are usually limited to roasted notes.

These tastes continue until the coffee cools another 10°C. At this temperature, we might find increased bitterness, with some people reporting that coffee's bitterness is most intense around 56°C.

Flavor and Aroma During Cooling

At temperatures below 50°C, you'll notice another significant change in the coffee's flavor and aroma. Aromas become less pronounced, mainly due to reduced steam production as the coffee cools. Bitterness decreases, allowing the body to perceive more complex flavors. Between 31-50°C, the most flavors can be perceived, primarily those related to acidity and sweetness. Sweetness peaks around 44°C, while bitterness is least noticeable around 42°C.

Interesting subtle changes might occur between 31-37°C. Within this temperature range, volatile compounds related to sweetness, fruit aromas, floral notes, herbaceousness, acidity, and nutty flavors become more apparent. This is when we can truly experience a coffee's flavor characteristics. Compared to 44°C or 70°C, at lower temperatures (such as 25°C), acidity perception is optimal. For example, drinking a Kenyan coffee at this temperature makes its flavors more vibrant and acidity brighter. It allows us to taste the complete flavor profile of this single-origin coffee and shows us that the same coffee can produce different tastes at different temperatures, with the same coffee tasting less pleasant at higher temperatures.

Whether you prefer hot or cooled coffee, understanding how temperature affects the flavors and aromas you perceive is very important.

Next time you brew coffee yourself, you can record the flavors and aromas you perceive at different temperature ranges, trying to find the "ideal range" between acidity, sweetness, bitterness, and aroma.

This will help you identify your preferred coffee types (coffees with more noticeable acidity or sweetness) or which flavor characteristics you prefer in coffee.

Regardless of which method you choose, at any temperature, you can better appreciate the flavors in your coffee.

Important Notice :

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