What effect does the water temperature of hand-brewed coffee have on the flavor of coffee? What is the right temperature for hand-brewed coffee? What happens if the water temperature of hand-brewed coffee is low?

I don't know if it is because Qianjie has been teasing for too long that the temperature in Guangdong has plummeted overnight. Very good, finally a little bit of winter feeling! But because of this, I believe everyone has found a problem today, that is, the coffee is not as good as it used to be!

Even if the parameters and methods used are the same as before, the flavor and taste of the coffee are inferior to those washed out before cooling. The reason is simple: the extraction efficiency of our cooking is not as high as before. This has been affected in many ways, and the initiator can actually blame the cold air! When we make coffee, there is a difference between the set water temperature and the actual water temperature that comes into contact with coffee powder for extraction, because the hot water will come into contact with the air before it comes into contact with the coffee powder, and the air will be relatively low relative to the hot water. So it absorbs some of the heat from the hot water. (the principle is explained below)

For example, if the temperature of the hot water in our pot was 92 °C, it might have dropped to about 90 °C by the time it passed through the air and then came into contact with coffee powder. The specific cooling depends on the height of water injection and the temperature of the environment. The higher the water injection height is, the lower the ambient temperature is, and the more hot water is absorbed. Therefore, the consistent parameters we think exist only on the surface. In the cold winter, the cold air cools the hot water more seriously. The extraction rate has been reduced, and it is naturally impossible to make coffee as delicious as before. The solution is actually very simple, that is to slightly increase the boiling water temperature of 1 ~ 2 °C! In this way, the excess temperature taken away by cold air can be balanced.

But! Yes! The effect of cold air is not limited to injected hot water. If it is like the front street, friends who use a non-temperature-controlled kettle and need a thermometer to measure the water temperature will find that the water temperature in the kettle will drop faster than usual! Because the non-temperature-controlled injection kettle has no heat preservation effect, the water will continue to cool down. Under the action of cold air, the temperature will drop faster. Well, in a case like this, it will also affect the overall extraction, so Qianjie will be more suggested to improve by increasing the hot water in the kettle. When there is more hot water in the pot, the rate of temperature loss will naturally slow down, which can also promote the stability of the injected water, which can be said to kill two birds with one stone.

In addition to these two points, we also need to pay attention to the impact of appliances on the temperature of coffee. This is the point mentioned in Qianjie in the article "the influence of filter cup material"-"heat transfer", a common physical phenomenon. Heat transfer refers to the phenomenon of heat transfer caused by temperature difference, as long as there is a temperature difference within or between objects, then heat energy will be transferred from high temperature to low temperature through heat conduction, thermal radiation and thermal convection (one or more of them). In fact, the above water temperature will be drawn by cold air heat is also derived from this principle, two objects colliding with each other will eventually have the same temperature. So it's not just cold air that affects water temperature and extraction. In the process of cooking to the product, the spout, the filter cup, the sharing pot and the product cup of the hand punch will affect the temperature of the liquid without preheating.

Qianjie once did an experimental comparison in the summer, using an unpreheated sharing pot and a preheated sharing pot to catch coffee seeping out of the filter cup. In the end, the coffee temperatures of the two were 65 °C and 70 °C (both left and right), with a difference of exactly 5 °C. In winter, the gap will be magnified. If we still need to pour into the export cup, then the temperature will drop further.

Therefore, in the wet filter paper before brewing coffee, Qianjie suggests using hot water to wet it. In this way, you can not only wet the filter paper, but also preheat the spout, filter cup and sharing pot. The temperature of hot water and coffee can not be asked too much, we can not only make a good cup of coffee more easily, but also keep the coffee warm for longer in this cold winter.

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