What are the water quality requirements for hand-brewed coffee? What water is the best? Why can't coffee machines use pure water to extract coffee?

Whether online or offline, we can often brush up on discussions about coffee water. For example, what water is not suitable for making coffee, and what water is better to make coffee. So if you have communicated with friends or searched for related topics online, you should have encountered such a saying: "It's best not to use purified water to make coffee! "Yesterday, a friend saw it and asked Qianjie when he bought beans at Qianjie store: " Is it really not possible to use purified water to make coffee? "

It is undeniable that the choice of water source does affect the texture of a cup of coffee. Just like tea, coffee made with different waters will have different taste and taste. As for why purified water is said to be unsuitable for making coffee, there are two main reasons.

Reason 1: The extraction efficiency is low. Although most of the water looks transparent and pure on the outside and contains nothing, there are actually some minerals in the water, and the proper presence of these minerals can help extract the coffee's high-quality flavor. In particular, calcium and magnesium ions in water, because they are positively charged, can combine with negatively charged acidic flavor substances (such as chlorogenic acid and citric acid) in coffee, accelerating their dissolution rate.

The mineral content in purified water is very, very low, and the TDS approaches 0ppm. Therefore, compared with water with minerals, purified water is not so easy to brew the flavor substances in coffee when brewing coffee. When the parameters are equivalent, the extraction rate and concentration of coffee washed with purified water will be relatively low, and the coffee will be relatively thin to drink.

Take Qianjie as an example. Qianjie uses purified water and mineral water with TDS37ppm to brew a pot of coffee respectively. The coffee beans used are Qianjie Esseau in the bean list. The parameters are the same. They are all 15g of coffee powder, 10 scale of ground Ek43, 92°C water temperature, 1:15 powder-to-water ratio, and 2 minutes extraction time.

Both present strawberry, citrus, guava, and floral flavors. However, in terms of taste and aroma, compared to Hathiu brewed with mineral water, the concentration of purified water will be slightly lighter. Qianjie also verified the existence of this difference by measuring the extraction rate. The extraction rate of Hathiu washed with mineral water was 19.34%, while that of purified water was 19.01%.

In order to prevent the impact of artificial cooking, Qianjie rushed another group for comparison, and the results were no different. Therefore, we can see that when the parameters are the same, compared with mineral water, pure water that contains nothing will wash out slightly less coffee substance and will not taste as rich. However, it was only a little less. Without direct comparison, it is difficult for ordinary people to taste the obvious difference. And as long as we readjust the extraction plan, even pure water can wash out the same rich substances. Because it just does not easily dissolve the flavor substances in coffee, rather than the flavor substances that cannot dissolve the coffee.

Compared with pure water, hard water with a TDS exceeding 175ppm is not suitable for brewing coffee. Because they are not only difficult to dissolve the flavor substances in coffee, but also have an unflattering taste and texture, especially unfiltered tap water in many cities. Even if we can adjust the extraction plan to make a cup of coffee with a suitable extraction rate, the taste and taste of the coffee will be affected and the quality will be reduced, not to mention the adjustment is very troublesome. Therefore, when brewing coffee, the Front Street Association recommends that everyone use water with a TDS of 175ppm as much as possible for brewing.

Reason 2: It cannot be recognized by the probe. In fact, the reason why purified water is not suitable for making coffee mainly comes from the coffee machine. Lower extraction efficiency is second, because as previously mentioned on Qianjie, the situation of low extraction efficiency can be improved. Because the mineral content of pure water is very small, its conductivity is extremely low, which will affect the detection and control of water in the boiler by the coffee maker's probe. Because the metal probe installed inside the steam boiler of the coffee machine mainly judges the height of the water level by detecting the conductivity of water, when the water lacks minerals and has insufficient conductivity, the boiler's water level detection system may easily fail, which in turn causes excessive replenishment or boiler failure.

Combined with what Qianjie said earlier, the extraction effect of purified water is slightly inferior, so sellers and users related to coffee machines often call on everyone not to use purified water, which may easily lead to machine failure, and at the same time, the effect of coffee extraction is not so good. But if you don't use a coffee machine and just make ordinary coffee, it doesn't matter if you use purified water. After all, as Qian Jie said, the impact on extraction will be, but it won't be too great ~

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