The temperature of the water brewed in Chapter 7 of "ESPRESSO COFFEE" is an important element of good coffee.

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Chapter 7

The temperature of the brewed water-- an important element of good coffee

The quality of water temperature control absolutely affects whether a cup of coffee can preserve the delicious substances in the beans. The better your coffee is made, the more intractable the ultimate problem of "water temperature" becomes. The water temperature seriously affects the quality of coffee, but it is difficult to control.

The water temperature is not easy to measure, because the water temperature of the espresso machine is higher than 200 ℉ and the amount of water is small, and the action of measurement will more or less lower the water temperature. This kind of "measurement technology will affect the subject to be measured" is an old problem.

Therefore, I advise you not to measure the water temperature directly. Instead, the "try-error-correct" method is used to determine the temperature. Use your own taste buds as sensors. There is another reason for this: beans with different baking degrees have different optimal cooking temperatures.

However, I will still use "temperature" as a quantitative indicator to give you an idea. (I used the Fluke 51K hand J digital thermocouple J alloy probe. The beans were baked to a dark reddish brown of Beiyi Dali style with no oil on the surface.)

The water temperature is not right.

The ideal water temperature is to indicate that the temperature of the head is 203.5 ℉. The boiled espresso is very dark reddish brown, and the crema will have dark brown spots. (some Italians call it "el tigre" which means "tiger stripes".)

The temperature of the water is too low and the coffee is yellowish brown. Crema is also very thick, smooth and uniform, but the color is relatively light, there are no dark spots. If the temperature is below 195 ℉, it tastes bitter and sour. It couldn't be worse to cook my baked beans like this.

(please refer to pages 106 and 107 of the original book for comparative photos of ideal water temperature and low water temperature.)

On the other hand, the high water temperature will burn out the coffee oil, there will be a "bite the tongue" feeling, the aftertaste is anxious. In the worst case, there will be thick dark black stripes on the surface of the crema. If the water temperature is just a little high, the boiled espresso is ordinary and boring, not bad, but not wonderful.

The characteristics of the taste are determined by the beans. If cooked properly, coffee should smell the same as freshly ground coffee powder

The temperature is well controlled, and the texture is thick and smooth.

As I mentioned in Chapter 5 (Commercial espresso machines), engineers still need to work hard to control the temperature of the outlet head in order to win more applause. Many espresso machine manufacturers have all kinds of patents, but I personally think there is still a long way to go.

The effluent of the water boiler can be maintained at a variation of ±1 ℃ (equivalent to ±1.8 ℉), but it is another matter to maintain the temperature stability of the outlet head. The machines I have tried have a change of at least 6 degrees (equivalent to ±3 degrees).

The structure of the filter handle itself should also be held responsible. It itself is made of heavy metal for the purpose of heat preservation. But metal is easy to dissipate heat. Take your hand off the machine, put coffee powder in it, and press it. Throughout this process, the metal parts continue to dissipate a large amount of heat, and eventually the temperature will be 20 degrees lower than originally expected.

I often say, "the handle must be locked on the machine when it is useless" in order to keep the temperature constant. When opening a shop to do business, the filter basket of coffee powder must not be left idle on the counter. One day you go to an espresso coffee shop and find the handle of the filter handle lying safely on the lift.

Let's not! Let's go to another cafe.

Set temperature

Since it is impossible to use a thermometer to measure the water temperature of the espresso machine, you have to pay for a lightweight digital thermometer that can quickly and accurately measure the tip of the probe. For example, the Fluke 51 thermometer, if you can get it, refer to my method.

The ideal method is to bury the thermocouple sensor directly in the filled coffee cake. In this way, when making coffee, you can monitor the change of water temperature at any time. Make a small hole under the coffee filter basket, just enough to pass through the sensing line. The smaller the hole, the better. The pressed coffee powder will automatically fill the gap in the small hole, not bad! Lift the probe tip up, near the upper surface of the coffee cake.

When most heat exchanger machines are idle, heat slowly accumulates in the outlet head. So the temperature will be higher than the set value.

When there is a dedicated water boiler machine idle, the outlet head temperature will be 3 to 4 ℉ lower than the set value.

Temperature change

In order to keep the water temperature of the filter cake through the handle stable, a very careful and complicated method is needed. This is the difference between the so-called "good" bar and the "master" bar. It's intuitive, but there are still some techniques available.

If the machine I use rushes out 2 ounces of hot water, throw it away immediately. Flush out another 2 ounces of hot water, repeat operation, the temperature is about the same. If used in this way, the temperature change of the outlet head can be minimized. (the basic idea is to keep the idle temperature of the outlet head as close as possible to the working temperature.) Note: do not use more than 2 ounces of hot water at a time.

The longer the machine is idle, the more the temperature of the outlet head deviates. The better the machine, the less deviation.

Commercial espresso machines are designed for continuous use. The more often the machine is used, the more stable the output temperature is.

In Italy, it is rare to see espresso machines with less than three water heads. The bigger the machine, the greater the mass, the more hot water, the more stable the temperature of the outlet head. To make coffee well, I suggest that the machine used at the bar should not be too small (no less than three water heads).

Keep the handle warm

If you make a second cup of espresso after a few minutes, use your time to grind the beans, start the pump and pump 2 ounces of hot water to preheat the handle and used coffee cakes. Let's leave the used coffee powder in the handle before we cook the next cup of espresso, no doubt! Because the residue itself is hot, it helps to keep the hand warm.

When you take off the handle to fill the new coffee powder, act quickly and accurately:

* knock out the old powder, put in an appropriate dose, and compact

* start the pump and flow out 2 ounces of hot water

* quickly lock the handle

* start the pump immediately

(chapter 21 of this book, "the way we cook espresso" will repeat the whole step.)

If you lose too much hot water, there will be trouble

It is mentioned earlier to knock out the old powder, but there will still be some chips attached to the filter basket. The people in our store wipe it off quickly with their fingers, but some people start the pump and wash the residue with hot water. This is wrong! Because this will lead to excessive changes in the water temperature of the machine.

The espresso machine can keep the temperature as stable as possible, but it is limited to using 1 or 2 ounces of hot water at a time. Using too much hot water at a time is really not a good idea to use a machine. So when I mention "using hot water", I always stress that it should not exceed 2 ounces.

If the coffee powder forms a small lump and sticks, it can be flushed with hot water from a steam boiler. This has other benefits: the handle temperature is further raised.

If you think there is something wrong with the water temperature of the machine, ask the technician of the agent to help adjust the heat exchanger type espresso machine and adjust the temperature of the steam boiler.

Selected from: ESPRESSO COFFEE: Professional Techniques 1996