To brew a truly satisfying cup of coffee, three things are indispensable: the ingredients, the equipment, and the technique. This article starts with coffee bean varieties, systematically sorting out the differences between Arabica and Robusta in growing environment, harvesting methods, caffeine content, taste, and processing techniques, then goes deeper into the roasting stages, storage essentials, and extraction parameters, and compares the actual performance of pump-driven and drip coffee makers. Finally, it introduces the characteristics of six major types of electric coffee makers, helping coffee enthusiasts build a comprehensive knowledge framework from bean selection to the finished cup.
To make coffee of outstanding quality, three prerequisites must be met at the same time: first, the ingredients themselves must be good enough, that is, the quality of the coffee beans must meet the standard; second, the equipment must be suitable and in good condition; third, the operator must master the correct brewing technique.
I. Coffee Knowledge
The two most widely circulated coffee varieties on the market are Arabica and Robusta.
Let's look at growing conditions first. Arabica is mostly grown on hillsides at higher altitudes, while Robusta can grow normally in plain areas. Precisely because Arabica has stricter terrain requirements, its yield is relatively limited; Robusta is not subject to this restriction, so its total output is naturally higher, and the two thus diverge in supply.
Next, let's look at the harvesting stage. Because Robusta is planted on plains, it can be harvested with machinery; Arabica grows on slopes, where machinery is difficult to operate, so it can only rely on coffee farmers to pick it by hand, berry by berry. The difference in harvesting costs directly creates the price gap between the two.
In terms of caffeine content, Arabica is lower than Robusta. Caffeine itself has a certain ability to resist insects and disease, so Arabica is more susceptible to pests and diseases, which further drags down its yield.
When it comes to flavor, caffeine manifests in taste as bitterness and astringency, so Arabica's bitterness and astringency are milder, while Robusta's bitterness and astringency are noticeably stronger.
There are also differences in post-harvest processing methods. For Robusta, the fruit pulp is removed using the dry natural method: machinery picks all the fruit, ripe and unripe alike, in one go, spreads it out on a drying yard to air-dry naturally, and then removes the skin. The advantage of this approach is a large processing volume at one time; the shortcoming is that the fruit comes into direct contact with the ground, absorbing moisture and off-flavors, which affects the final quality, and because the ripeness at harvest is uneven, it is therefore not suitable for processing high-quality coffee. Arabica, by contrast, is picked by coffee farmers in seven to eight rounds of manual selective harvesting during the ripening period, taking only ripe fruit each time, and immediately after picking, the pulp is stripped off with a washed processing machine. Although this guarantees quality, the processing volume at one time is small, and the processing cost is also higher.
Putting the above characteristics together, the division between the two varieties in price and quality becomes clear at a glance.
Taking Yunnan as an example, Robusta costs about 7 yuan per kilogram, while Arabica costs about 70 yuan per kilogram.
Coffee roasting is usually divided into eight stages, of which light roast accounts for two stages, and medium roast and dark roast each account for three stages. Judging by appearance, a lighter, whiter color indicates a light roast; a reddish-brown color belongs to a medium roast; a blackened surface with an oily sheen indicates a dark roast, also called a heavy roast. You can choose the roast level according to personal taste, because the darker the roast, the stronger the flavor.
Once the coffee beans have been roasted, they are ground into powder with various grinders, and then, combined with different brewing devices, they can enter the extraction stage.
Coffee that has just finished high-temperature roasting needs 48 hours of natural breathing before its internal aromatic components can reach their optimal state. To keep this state, packaging for freshness becomes key.
Newly harvested green beans need to be stored for a period before their quality becomes ideal; but once roasting is complete, they must be properly preserved, otherwise the aroma will be greatly reduced. Generally speaking, foil bags with sealed packaging have a freshness period of about three months, ordinary packaging without inert gas filling has about one month, and packaging filled with nitrogen can last two to three years.
When coffee beans are ground, their internal aroma structure is destroyed, and about 20% of the fragrance is lost in an instant. Therefore, ground coffee is harder to preserve than coffee beans.
The degree of dryness is directly related to the extraction yield. During roasting, every jin of coffee beans loses 3 to 4 liang of water, leaving about 6 liang in the end; ordinary coffee beans can yield only about 90 cups.
Each cup of coffee uses about 6 to 7 grams of ground coffee, equivalent to 50 to 55 coffee beans. The ideal temperature for drinking coffee is between 65 and 75 degrees.
The human body itself contains 100 to 500 milligrams of caffeine, usually taken in through diet. When caffeine in the body is below 100 milligrams, a person feels sluggish and drowsy; when it exceeds 500 milligrams, a person becomes highly alert, accompanied by vasodilation and a faster heartbeat.
II. Making Coffee
The most common extraction method is undoubtedly the Italian-style coffee machine, because only through this method can the most essential part of the coffee be fully released. The coffee extracted directly with an espresso machine is espresso, also called espresso. People who drink coffee regularly compare it to the soul of coffee, because this extraction method can keep the coffee components in their most ideal state.
First, the standard amount of ground coffee needed for a cup of espresso is 6 to 7 grams, equivalent to about 50 coffee beans. The amount of powder affects the strength, and 6 to 7 grams is the most suitable.
Second, the standard water temperature for extracting espresso is 92 degrees, with a fluctuation of no more than two degrees.
Third, extracting espresso must be completed at 9 to 15 atmospheres of pressure. Too much pressure leads to over-extraction, adding unnecessary bitterness to the coffee; too little pressure causes under-extraction.
During extraction, some external factors affect pressure, namely the coarseness of the ground coffee. If the grind is too fine, the gaps between particles are very small, and when water flows through, resistance increases, the flow slows, and as time lengthens, pressure gradually rises, ultimately causing over-extraction; conversely, if the grind is too coarse, the gaps become larger, resistance is very low, water flow speeds up, and this directly causes under-extraction.
Fourth, the standard water amount for extracting espresso is 30cc.
Fifth, the standard time for extracting espresso is 25 to 30 seconds.
In other words, the longer the water is in contact with the ground coffee, the higher the caffeine content of the cup. This also explains why, no matter which extraction method is used, the time should preferably not exceed 8 minutes.
Coffee extracted by the drip method has a caffeine content of about 360 milligrams; coffee extracted by an espresso machine has a caffeine content of about 80 milligrams.
Comparison of Pump-Driven Coffee Machines and Drip Coffee Pots
1. Drip coffee makers apply no pressure at all during extraction, so the coffee components are not released sufficiently.
2. Filter extraction takes a longer time, so the caffeine content is relatively high.
3. Drip coffee pots do not have an independent thermostat to control water temperature, so the extracted coffee's tannic acid content fluctuates with temperature changes and is not stable enough.
4. The heater of a drip coffee pot is located beneath the carafe. During extraction, the heating plate reaches extremely high temperatures, and after the first one or two drops of coffee fall into the carafe, they are affected by the high temperature and become scorched, giving the final product more or less a burnt taste.
5. The brewing principle of the siphon coffee pot is not very different from that of the drip type, and the pot body is made of glass, so it is not very suitable for daily household use.
l The standard amount of ground coffee for espresso is 6 to 7 grams per cup.
l The standard extraction temperature for espresso is 92 degrees, with a fluctuation of no more than 2 degrees.
l The standard extraction pressure for espresso is 9 atmospheres.
l The standard water amount for espresso is 30cc per cup, with a fluctuation of no more than 5cc.
l The standard extraction time for espresso is 20 to 30 seconds.
III. Coffee Machine Knowledge
Electric coffee machines can be grouped into six major categories.
Fully Automatic Coffee Machines
Just put the coffee beans into the machine, add water to the water tank, and press the corresponding button, and a cup of rich, aromatic coffee is made automatically. It has functions such as automatic grinding, flavor adjustment, automatic milk frothing, and automatic cleaning, making it the most effortless and convenient choice. De'Longhi even exclusively features the globally patented IFD brewing system.
Pump-Driven Coffee Machines
Clean water is pumped from the water tank into the heater, where the temperature rises to 92 degrees Celsius and the pressure reaches 15 bar. The high-temperature water flow passes through the filter holding ground coffee or a coffee puck, and the extracted coffee is injected into a special container or flows directly into the cup.
Drip Coffee Makers
Clean water is placed in the pot body, and after heating at the bottom, it rises under pressure along an internal tube, drips into the coffee filter, and is finally collected in the glass pot.
Percolator Coffee Makers
In a percolator coffee maker, only part of the clean water comes into contact with the heater at the bottom of the machine. After the water temperature rises, the water is forced by pressure through an internal tube and seeps into the filter containing ground coffee. This process continues until all the clean water has percolated through the ground coffee and become coffee.
Moka Coffee Makers
Clean water is placed in the lower half of the coffee pot, and ground coffee is filled into the container in the middle of the pot body. After heating to boiling, the water is forced upward by pressure through the ground coffee and enters the coffee container above. Different amounts of ground coffee and water can create different flavors.
The above content is compiled by CoffeeHunters, a coffee news website.
