In the past, when Front Street shared the knowledge of making espresso, he focused very much on explaining the preparation steps before attaching the handle to the brewing head, such as powder spreading and pressing, which are highly operational and have a great impact on the coffee.
After attaching the brewing head, turn on the brewing button, and the machine will do the rest. However, we must also understand how the coffee is extracted after pressing this button in order to adjust better parameters.
Stage 1: Pre-soaking
Pre-soaking is similar to the steaming stage in hand brewing. A small amount of hot water is first released to moisten the coffee powder and expel carbon dioxide gas. Some older coffee machines may not have a pre-soaking function, so the cultivation of Italian coffee beans is particularly demanding. If the beans are cultivated for a short time, there will still be a large amount of carbon dioxide in the coffee beans, which will make the flavor of the espresso liquid weak and the oil rough.
Almost all coffee machines nowadays have this function. The general operation process is to fasten the coffee handle to the brewing head, and then discharge the water without pressurization. It lasts for about 2-3 seconds and then stops. After the coffee powder absorbs water, it will expand and exhaust, thereby improving the subsequent extraction efficiency and stability.
When pre-soaking water, there is no need to pressurize, because if the normal 9 bar pressure is used for pre-soaking, it is likely to break through the powder layer on the coffee surface and easily cause perforation (channel effect).
Another important thing about pre-soaking is time. The pre-soaking time is related to the freshness of the coffee beans. If the coffee beans are too fresh, a longer pre-soaking time is needed to release carbon dioxide. Generally, the pre-soaking time is controlled at about 5-10 seconds, and you can adjust it according to the time situation.
The operation of electronically controlled coffee machines with pre-soaking function is relatively simple. You only need to set the number of seconds you need for the pre-soaking time, and then you can achieve one-click extraction. If it is a manual coffee machine with a pre-infusion function, then you need to manually control the pressure and the flow rate of the water in the extraction head.
The second stage: extraction of flavor substances
After the pre-soaking is completed, the main extraction stage of coffee begins. At this time, the brewing head will release hot water with a pressure of 9 bar to impact the coffee powder cake. The pre-moistened coffee powder cake will quickly dissolve the coffee substances and come out. Under normal circumstances, after pre-soaking, the coffee liquid will flow out after the brewing head meter reaches 9bar.
Initially, the very strong sour substances are extracted first, then the sweet substances, and finally the bitter substances. If you use three cups to cut the front, middle and back sections of the espresso, you will see that the coffee oil in the front section is the darkest, brown, and richest, and tastes rich and sour. The coffee oil in the middle section is lighter, golden yellow, and has better fluidity. The concentration is not as high as in the first cup, and it tastes more balanced. The oil in the back section is thin, light yellow, and tastes light bitter and sweet, like barley tea.
The taste of espresso depends on the coffee beans used. Generally, it is made from medium-dark roasted espresso beans such as Front Street Black Cocoa Basic Blend and Front Street Premium Blend, which emphasizes the nutty aroma and sweetness. When using Front Street Classic Blend and Front Street Commercial Blend, two formulas designed for milk coffee, the coffee will show the characteristics of low acidity and mellowness.
For those who like coffee with a weak bitterness and a floral and fruity aroma, the barista will recommend the Front Street Strawberry Candy espresso Italian blend. The coffee produced has the flavors of roses, grapes, dried blueberries, berries, and almonds. The American style is sweet and sour and refreshing, and the latte has the smoothness of a cream cookie.
The third stage: end of extraction
When is the end of espresso extraction? What criteria should we rely on? Is it time, liquid volume, or should we stop extraction at the moment when the oil turns white.
Front Street believes that the basis for ending is based on the judgment of these three factors. When the oil turns white, it is actually telling you that the delicious substances in the coffee have been extracted, and you should stop extracting. Many times, we end the process before we even see the oil turning white, because the whitening of the oil means that some unpalatable flavors have been extracted, but we don’t know whether this amount will affect the flavor. Therefore, we generally avoid this risk and end it early.
But ending it early will also cause another problem, that is, your espresso may be missing the tail section. Coffee without the tail section will be very strong and have a short aftertaste. Therefore, the two parameters of time and liquid volume must be used to assist judgment. The time is what we often call 20-30 seconds. This is not a hard and fast rule, just a reference standard...
Even for a semi-automatic coffee machine with one-button extraction, in addition to the basic operations of spreading and pressing powder, you also need to understand the extraction process behind your button. After all, this one-button extraction also requires people to set it.
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
