Why does the coffee become astringent and mixed smell when it gets cold? What is the suitable temperature for coffee?

There are few take-out hand-made coffee in Qianjie stores, but at the repeated request of guests, the barista in Qianjie will say, "it's best to drink coffee while it's hot, but it won't taste good when it's cold."

I do not know if you have encountered this kind of situation, in the just made hand coffee, drink a sip, fragrant, smooth and delicious. And for some reason, it took more than half an hour to take a second sip. "Hey, it doesn't taste right. It's so sour, astringent and miscellaneous."

Is the coffee switched? Apparently not. Friends who have learned to taste coffee may know that in the process of tasting coffee, it will be divided into high temperature, medium temperature and low temperature to taste the flavor of coffee. In other words, it's no secret that coffee flavors change. Usually a good cup of coffee can withstand the test of these three temperatures, but after it is cooled, the flavor of the coffee is no longer within the scope of this taste. Why does the coffee turn sour when it gets cold? The main reason is that our senses have different perceptions of different temperatures of coffee. When the temperature is close to the temperature of the human body, we are more likely to sense sweetness. when the temperature drops, the perception of sweetness is no longer obvious, but highlights the sour taste, which causes us to think that the coffee has become sour. Another reason is that, on the one hand, the sweetness of coffee comes from the aroma of coffee, when the coffee becomes cool, the aroma of coffee is less volatile, naturally will not be aware of sweetness, that is, highlight the acid.

So why does the coffee taste astringent when it gets cold? These bad flavors will appear after the coffee is cooled, mainly "oil oxidation", "pigment oxidation polymerization" and "condensation". These three nouns seem very strange, but it is easy to understand by listening to Qianjie's explanation. -Oil oxidation-We now use filter paper to filter coffee grounds, coffee will be cleaner, but the filter paper can only block most of the oil and fine powder, and still a small amount of oil will flow into the coffee liquid (the smooth taste of coffee comes from these oils). But the cooled fat cakes, leaving a layer of oil floating on the surface of the coffee. This layer of oil is very easy to deteriorate in direct contact with air (oxygen) to produce a strong sense of acidity, and this layer of perishable oil is also the source of fuel consumption.

-oxidative polymerization of pigments-it is easier to observe that when you finish brewing coffee, do not clean up the filter paper, after a period of time, the color of the edge of the filter paper will become dark brown, this circle of dark brown is "pigment oxidative polymerization".

Coffee beans in the roasting process will produce "brown pigment" (caramelization reaction), mainly for coffee to provide caramel, chocolate and other flavor. However, if the flavor is oxidized and deteriorated over time, the flavor will gradually become bitter and mixed taste will appear. Condensation-if the color of a cup of coffee is clear when it is hot and becomes cloudy when it is cold, it is called condensation. This will affect the taste of the coffee and become rough and sandy.

Therefore, drink good coffee while it is hot, so that you can feel the rich flavor and taste of the coffee.