For more knowledge about specialty coffee, please pay attention to: Front Street Coffee (Frontsteet Coffee）
In the past, when Front Street shared knowledge about espresso extraction, he would focus on parameters such as grinding size, powder volume, ratio, extraction time, pressure, etc., and also focus on analyzing the steps such as powder receiving, powder distribution, and powder pressing. Only the extraction water temperature is rarely specified in detail.
The fact that the water temperature is not mentioned in the front does not mean that the water temperature is not important for espresso extraction, but the boiler water temperature of many ancient machines is factory-set, and it is troublesome to change the operation. Therefore, when extracting espresso, the water temperature is often regarded as a fixed value, and other parameters are used to match the water temperature.
Nowadays, newly designed machines or high-end machines from the past 10 years can freely set water temperature parameters. Therefore, this parameter becomes an important parameter that can be changed in extraction.
What is the appropriate water temperature setting for a typical coffee machine?
The water temperature of a normal coffee machine is within a reasonable range of 85-95 degrees Celsius. The initial setting temperature of some coffee machines will be higher than 92-96 degrees Celsius. When learning the water temperature parameters for hand brewing, we know that high water temperature can improve the extraction efficiency of coffee, thereby dissolving more coffee substances; while low water temperature can lower the extraction efficiency and dissolve less coffee substances.
The water temperature of espresso is the same as that of Pour over(V60) coffee. If the water temperature is set too high, a burnt, bitter, woody taste will easily occur. But high water temperatures can also press out richer grease. In the past, espresso was relatively bitter. On the one hand, the roasting degree of the coffee beans was very deep. On the other hand, the boiler water temperature of the machine was set relatively high, which was also in line with the need to produce rich coffee crema. There are also some differences in extraction. The extraction time is generally controlled at 20-25 seconds (because if the time is long, the smell of burnt and sawdust will easily appear).
The espresso extracted at too low a water temperature will be very acidic and not as rich in oil. Therefore, in the past, mainstream espresso machines rarely set the water temperature below 92 degrees Celsius.
Water temperature affects coffee extraction flow rate
The flow rate of coffee liquid at higher water temperature will be slower, and the flow rate of coffee liquid at lower water temperature will be slightly faster. High water temperatures allow the coffee grounds to expand faster and also expel gas. These gases block the flow of water until the gas is pressed into oil and extracted, and the flow rate of the coffee will slowly increase. The higher the temperature, the more bubbles there are and the greater the resistance to water flow.
When the temperature is low, the coffee flow rate is faster. An extreme example is that when the coffee machine is turned on, the coffee boiler starts to heat up. At this time, the brewing head can be extracted, but the water temperature is very low, about 60 degrees Celsius. If the same parameters are used to extract espresso at this time, the extraction time will be greatly shortened and the coffee will flow faster.
Similarly, if you use a small boiler coffee machine for high-intensity continuous cup dispensing, you will also find that the espresso extraction becomes gradually unstable and the flow rate accelerates. Part of the reason is that the temperature does not rise after the boiler is replenished with water.
Boiler temperature is not equal to extraction temperature
The water temperature we can set now is the water temperature in the boiler, and the water temperature from the boiler to the extracted coffee must pass through the water distribution network and the handle (powder bowl). If the extraction time of the last cup of coffee exceeds 10 minutes, the temperature of the brewing head (water distribution network) will be relatively high. If you directly buckle the handle for extraction, the water in the boiler will absorb heat when passing through the water distribution network, resulting in an initial water temperature higher than the boiler temperature.
Therefore, in order to avoid this situation from happening, before tightening the handle, the extraction switch will be turned on in advance and the water will be released to cool down to reach the set water temperature.
The temperature of the handle will also affect the initial temperature of coffee extraction. If the handle is at normal temperature, the coffee handle will absorb the heat of the water during the initial extraction, and the actual water temperature will be lower than the preset temperature. Therefore, before receiving the powder, you need to release hot water to preheat the handle (this is the same as preheating the filter cup for Pour over(V60) coffee). Of course, some friends solve this problem by attaching the handle to the brewing head to keep it warm when in the non-extraction state. However, Front Street does not recommend this. For detailed reasons, please click here.
During the extraction process, the extraction temperature cannot be consistent with the boiler water temperature throughout the process.
What is the appropriate temperature setting for daily espresso extraction?
Here is a fictitious experiment from Rao's "The Science of Extraction of Italian Coffee": Italian baristas like to use a temperature of 85-91 to extract espresso, while American baristas like to use a temperature of 92-96 to extract espresso. The reason is that their proportions are different. The Italian standard is to use 7 grams of coffee powder to extract 1 ounce of espresso, while the United States uses 18-21 grams of coffee powder to extract 1 ounce of espresso.
If you use 30 grams of water at 88 degrees Celsius mixed with 7 grams of coffee powder at 27 degrees Celsius, and 38 grams of water at 95.3 degrees Celsius and 21 grams of coffee powder at 26.7 degrees Celsius, the mixing temperature of both should be 82.8 degrees Celsius. Of course, this is a hypothetical experiment. But here is a message: Coffee powder absorbs heat. The more powder, the more heat it absorbs. So to reach a certain extraction temperature, you need to increase the preset water temperature.
"The Science of Extraction of Italian Coffee" Book Shadow
The ratio we use today is similar to that of American baristas. We all use a large amount of powder to extract 1 part of espresso, and the temperature needs to be adjusted to 92-96 degrees Celsius.
For more knowledge about specialty coffee, please pay attention to: Front Street Coffee (Frontsteet Coffee）
You can now buy the above coffee beans online at the Taobao store “FrontStreet Coffee” (前街咖啡). FrontStreet Coffee is a long-established specialty coffee roaster in Guangzhou, China, and its Guangzhou retail shop sells coffee beans only. The shop carries dozens of coffee beans from different origins around the world, including carefully selected single-origin beans for V60 pour-over and espresso. Guangzhou’s FrontStreet Coffee shop is recommended by many coffee lovers.
The FrontStreet 2013 Yunnan coffee beans sold in the store come from the Typica variety grown at FrontStreet Coffee’s own plantation in Yunnan. The name comes from the year the brand and the plantation were founded. You can buy these beans from China’s Yunnan origin at the Guangzhou shop and at FrontStreet’s Taobao store.
FrontStreet coffee beans are freshly roasted within 5 days and deliver consistently excellent quality and great value. Orders placed before 17:00 are shipped the same day, and most areas within Guangdong Province receive them the next day.
FrontStreet Coffee Taobao store: https://qianjiecoffee.taobao.com
Or search for “前街咖啡” (FrontStreet Coffee) on Taobao
Important Notice: FrontStreet Coffee has moved to a new address: 315, Donghua East Road, Guangzhou (coffee beans only)
Tel: 020 38364473
