The water temperature of hand-poured coffee is inclined to be extracted at a higher temperature, because high temperature can not only improve the extraction efficiency, but more importantly, it can bring out a rich sweet and sour aroma and flavor. Basically, the water used for pour-over coffee rarely drops below 80 degrees Celsius. So, is it possible to brew coffee at a temperature lower than this? The reason why this idea was born in Front Street is because recently an office friend, he wants to "play" in the office, the only hot water in the office can only be heated to about 70 degrees, in our experience of coffee making, this is simply not up to the water temperature required for hand coffee.
However, 70 degrees of water is not necessarily impossible to brew coffee! If we break down all the parameters and talk about the subjective things like flavor, and just talk about the effect of water temperature on the extraction rate of coffee, the answer is very simple, that is, the extraction efficiency, that is, the unit dissolution rate. Just like when we dissolve the granule, the higher the temperature, the faster the granules will dissolve, and the lower the temperature, the more time it will take for the impact to dissolve, and if necessary, stir it to speed up the dissolution.
The same is true for brewed coffee, when the water temperature becomes low, can the same extraction rate be obtained by extending the extraction time, just like the way iced drip coffee is made, the temperature of ice water is about 7 degrees Celsius, at this temperature the extraction efficiency is very low, but it can be compensated for by a long extraction of 6-8 hours.
So Front Street came to test whether this was possible. For the water temperature, Qianjie chose 70 degrees Celsius, which is also the temperature that can be reached by the corresponding water dispenser. The coffee beans used are Panamanian flower butterflies, and the flavors brewed with the standard parameters of Front Street are jasmine, lemon, honey, oolong tea, and other flavors.
To extend the extraction time of coffee, the most common practice in pour-over coffee is to fill the water in stages, control the water flow, adjust the grind, and replace the filter bowl with a slower flow rate. So the front street used all these means, the filter cup front street used hario's infinite filter cup, of course, such as the fan filter cup, kono filter cup slow flow rate can also be used.
The grinding degree of the front street is used in the 5 of the EK-43S5 scales (10 scales are usually used), don't look at the difference of almost 1 times the scale, in fact, the thickness level of the grinding is not exaggerated as everyone thinks, and the sieving with a 20-gauge screen is 93% (relatively fine for pour-over coffee). The ratio is still 1:15.
In the water injection stage, the front street uses multi-stage water injection and small water flow injection, also to extend the extraction time as much as possible. For the first time, 30ml is injected and steamed for 30 seconds, then 70ml is injected, and 65ml is continued to be injected when the coffee liquid can see the powder bed, and the last 60ml of water is injected when the powder bed is seen, and the time for the coffee liquid to be fully dripped and filtered is 3 minutes and 33 seconds. After brewing, the coffee powder layer is muddy, which shows that the coffee powder is still quite fine.
Qianjie first used a concentration meter to measure the concentration of coffee liquid as 149%, which is a pretty high concentration for pour-over coffee, and the coffee extraction rate is calculated to be 205%。
Next, in terms of aroma, the whole cup of coffee does not have a fresh floral aroma, and it smells very sweet and caramel. After tasting it, I didn't feel the discomfort caused by the strong coffee, which surprised Front Street. The sourness of the whole cup of coffee is not obvious, and the sweetness is strong, the rich sweetness of brown sugar. However, there is some bitterness in the tail section that makes it uncomfortable. As a result, Front Street made some minor tweaks to change the grind to 65 scales, which is about the thickness of 90% of the pass rate of the No. 20 screen. Front Street brewed again in the same way, and this time the extraction time was not reduced too much, waiting for the coffee droplet in the filter cup to be 3 minutes and 20 seconds.
Similarly, the concentration was measured at 1 using a concentration meter on the front street46%, the concentration did not decrease much, and the corresponding extraction rate was 2009%。
The aroma of this cup of coffee is also not full of floral aromas, but smells like sweet potato syrup. The acidity of this cup of coffee is a little more pronounced than the previous cup, a bit like mandarin, the sweetness is like nectar, very sweet, and the end is tea. Although the deviation from the flavor of this cup is still noticeable from the standard brew method, this cup tastes really good. Next, the front street adjusted the grind to 75 scales (87% pass rate for No. 20 screens) to test if the flavor will be better. In the case that only the grind is changed, and the rest is unchanged, the extraction time is 3 minutes and 2 seconds.
Front Street measured the coffee at a concentration of 135%, and the extraction rate was calculated to be 1855%。Again, there is still no floral aroma on the aroma, and the smell is some sweetness of preserved fruit. The sourness of the fruit is obvious, like the sweetness of small green mandarin and honey. However, the middle and back sections have a taste similar to southern apricots.
Finally, for the extraction rate, the decrease in temperature can be compensated for by extending the extraction time. But when it comes to flavor, especially aroma, this cannot be replicated. The high water temperature results in a rich floral and fruity aroma as well as more acidity in the early stages of extraction.
By lowering the water temperature, these flavor compounds are not extracted at a higher level, and due to the prolonged extraction time, the release of sweet and bitter substances makes the whole cup of coffee sweeter and more balanced overall. And during the brewing process, the extraction time also determines whether the coffee is bitter or sweeter, or more sour. For example, in this test, the sweetness of the extraction time was controlled at about 3 minutes to 3 minutes and 30 seconds using a water temperature of 70 degrees Celsius, and the first cup tended to be bitter at 3 minutes and 33 seconds, and the third cup at 3 minutes and 02 seconds was sour.
If you use a lower water temperature, such as 40 degrees or 50 degrees, it may take longer to extract and the flavor profile will be more balanced (no characteristics).
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