A must-read for beginners! Essential knowledge for beginners of espresso

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The coffee beans themselves

Carbon dioxide is the main source of crema in espresso (the other smaller source is the emulsified oil in coffee). It is recommended to use coffee beans that have been roasted within a few days or weeks, not beans that have been stored for several months! ! The longer the coffee beans are stored, the carbon dioxide produced during the roasting process will gradually be lost; when you grind the beans, the cell walls of the beans that store carbon dioxide and other volatiles will be broken and released, so in order to get the best results, it is best to grind and press them now, because the carbon dioxide and the aroma of coffee will be lost over time, and oxidation will start quickly! Fresh, freshly ground and pressed coffee can get the best flavor and crema.

The effect of time on crema

The coffee beans used in the above pictures are from the same batch of coffee beans that were roasted 48 hours before shooting, and the coffee powder used for these three cups of espresso was ground 30 seconds, 30 minutes and 16 hours before brewing respectively.

Choosing a grinder

It is recommended to use a burr grinder for making espresso. The size of the powder particles ground by a burr grinder is more uniform than that of a blade grinder, and it also allows you to control the size of the powder particles yourself through settings. So whether you use a hand grinder or an electric grinder, be sure to choose a burr grinder! ! Burr grinders also have different blade designs, such as conical burrs, flat burrs, or ghost teeth burrs. In each major category, each manufacturer has different blade design details! ! Please remember: not all burr grinders are suitable for grinding espresso powder. For example, many grinders with conical or flat blades may be designed for other types of coffee that use coarse coffee powder, such as hand pour, syphon, French press or moka pot, while grinders with serrated blades are mainly designed for hand pour and syphon. The powder used for espresso will be finer, because the increase in the surface area of ​​the coffee powder makes the extraction rate (Extraction yield, that is, the percentage of all soluble solid substances in the weight of coffee powder that eventually dissolve in the coffee liquid) of espresso higher, but these grinders may not be able to grind the fineness of coffee powder required for espresso! ! Therefore, when you choose a grinder with conical or flat blades, please make sure it is suitable for espresso (or called "Italian grinder")! !

Adjust the coarseness of the coffee powder

To make espresso properly, you need to add pressure when brewing. If you use a semi-automatic or fully automatic machine, the machine itself will control the pressure. Generally, for a semi-automatic machine, the powder that needs to be adjusted (Dial in) is about 16-18 grams of coffee, which can produce about 32-36 grams of espresso in about 20-30 seconds. For a self-controlled pressure machine, the coffee powder should be adjusted to produce 6-9 BAR of resistance during brewing, and brewing should be completed within 20-30 seconds. When you change the coffee beans, you may also need to adjust the coarseness again to achieve the ideal pressure and time.

Powder distribution and pressed powder

When putting coffee powder into the powder basket, you should use a good distribution method to eliminate coffee clumps and air pockets in the powder basket and avoid channels when brewing*, such as using the WDT (Weiss Distribution Technique) distribution method, or tapping the powder cup on a cushion. Before tamping, you should also spread the coffee powder in the powder basket (do not put one side of the coffee powder higher than the other side!), and then tamp the powder. This can avoid uneven extraction of the entire powder cake in the powder bowl. If the coffee powder is not flat, the density of the coffee powder on both sides will be different after tamping, resulting in unbalanced extraction of the entire powder cake! And tamping does not necessarily require a lot of force. The purpose of tamping is to flatten the powder bed and use the pressure to remove the extra air pockets that have not been removed.

*When brewing espresso, water will naturally flow faster through the path with the least resistance! ! When "channels" are formed in the coffee powder in the powder basket, hot water will flow through these channels faster, causing uneven extraction. The channels may also cause the so-called "jet effect", causing coffee to spray randomly at the bottom of the bottomless powder basket! ! In addition to spreading and pressing the powder, the possibility of channels can also be reduced through the "pre-infusion" method.

Powder-water ratio

The brew ratio of espresso is the ratio of the amount of coffee powder to the amount of coffee produced. For example, 20 grams of coffee powder can brew 40 grams of espresso, and the brew ratio is about 1:2. The brew ratio of espresso can vary greatly depending on personal preference and regional characteristics, such as from 1:1 to 1:4. Italians also give different concentrations of espresso different names, such as Ristretto espresso, Normale espresso, Lungo espresso, etc. When brewing espresso, the higher the brew ratio, the more coffee is poured into the cup. Although the extraction rate will increase, the coffee will become weaker. The most common brew ratio of espresso is about 1:2 to 1:3. After adding water or milk, milk foam or cocoa, espresso of different concentrations will have different changes and flavors.

pressure

To make a cup of quality espresso, in addition to the factors mentioned above, such as coffee powder itself, powder control, distribution, pressing techniques, and powder-water ratio, there are also factors such as pressure, temperature, and time control during brewing. To make espresso, we need to use a pressure of 6-9 BAR. Many baristas believe that 7-9 BAR is the sweet spot of espresso. There are also studies that show that under other conditions, espresso pressed with a pressure of 6 BAR has the highest and most consistent extraction rate. Of course, pressure is not the only factor that affects the extraction rate, but we should understand that the higher the pressure, the better the espresso will taste! !

Brewing temperature control

To make espresso, water temperature, pressure and time are required to dissolve the soluble solids in the coffee powder. However, if the water temperature is too high or the time is too long, it will cause over-extraction and make the coffee bitter! If the water temperature is too low or the time is too short, the coffee may be weak and sour due to insufficient extraction! Generally speaking, we use a water temperature of about 91-96 degrees Celsius to brew espresso, but the darker the coffee, the lower the temperature should be (because the heavily roasted coffee tastes bitter!), while the lighter the coffee, the higher the temperature should be (because the lightly roasted coffee tastes sour!); all espresso coffee machines, whether fully automatic, semi-automatic or manual, must be preheated to reach the working temperature; water temperature has a great impact on the taste of espresso. It is recommended that you can experiment and adjust your brewing water temperature and preheating time/method when making espresso to achieve your ideal taste.

Brewing time control

As mentioned above, brewing time also affects the taste of espresso. Depending on the pressure/flow rate design of the espresso equipment itself, the diameter/depth/hole design of the powder bowl, the amount of powder/powder fineness and other factors, the espresso brewing time may generally fall between 20-30 seconds. When you want to use less powder to extract less coffee*, it is recommended that you grind the coffee finer, but still aim for a brewing time of 20-30 seconds.

*Each basket has a recommended amount (range) of powder in its design. If the amount of powder you use is lower than the recommended amount or close to the low range, you will find that the coffee powder will be wet or muddy after brewing. Don't worry, as long as the extraction is even, this condition will not affect the quality of your espresso.

‍【Recommended reading】：

How to drink espresso? 5 simple steps to enjoy espresso

Italian coffee making skills | Teach you how to make a satisfying cup of espresso step by step

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