Why is coffee made at home always better than coffee made in a cafe?

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How is the coffee made by a professional barista different from what you make at home?

In a new book on the principle of coffee Water for Coffee: Science Story Manual, Christopher Hendon, one of the authors and associate professor of computational materials and chemistry at the University of Oregon, explains the principle of coffee extraction from a chemical and physical perspective. In his view, professional baristas make better coffee, which of course has something to do with their well-trained and skilled skills, but a more important reason is that they know more about the principles of chemistry and physics and have more time to experiment with recipes.

For the average person, a cup of coffee contains 1.2% of the coffee ingredients (a mixture of organic acids, Maillard reaction products, aromatic esters, heterocyclic compounds, etc.) and 8% of the coffee ingredients. The former happens to be the percentage of most filtered coffee, while the latter corresponds to the composition ratio of Espresso espresso.

There are very few ways to extract 8%, 10% of the coffee ingredients, and espresso machines are the most common. But there are many ways to achieve 1.2% Mel 1.5% extraction ratio, such as hand-flushing, Turkish, Arabian, Aeropress, French pressure filtration, siphon or American drip filter coffee machine. The devices of these methods have one thing in common: they are all cheaper than Italian coffee makers. Of course, the espresso machine can also make 1.2% Mel 1.5% coffee-dilute a cup of espresso with hot water to get what we often call "American coffee" (Americano).

So the question is, since these coffee drinks have the same coffee content, why do they taste so different?

When coffee meets water

In the 1.2% Muay 1.5% camp, it is roughly divided into two groups, one is to soak all the coffee powder in water to extract, and the other is to let the water flow through the coffee powder, that is, "filter".

From a physical point of view, the water temperature of immersion is higher. In the process of coffee extraction, "the process of dissolving compounds from the surface of coffee particles into water" is not the slowest. In contrast, the process of "coffee flavor from the inside of coffee particles to the interface between water and coffee particles" takes more time. The increase in the temperature of the water will speed up the process.

SCAA's coffee flavor wheel

Higher particle temperatures mean more coffee-scented compounds will be released, but high water temperatures can also cause many bad compounds to flow into the water. Specialty Coffee Association has published an odor wheel to help people analyze the aroma of coffee.

Coffee brewed by hand and other filtering methods is more complicated. The time of soaking can be controlled, while the extraction time of filtration depends on the thickness of coffee powder, because it directly affects the speed of water flow.

The ratio of coffee to water is also important. The finer the coffee powder, the more fully extracted, but the speed at which the water flows will be correspondingly slower. If you reduce the amount of coffee at this time, the extraction time will also be shorter than before-that is, filtered coffee is a chain reaction of "pulling together and starting the whole body", with more and more complex variables.

Other influencing factors

Even if you can fully master the steps of hand-brewing coffee and accurately copy a barista you like, it is still possible that you may not get the same taste. There are three factors that can affect the taste of coffee: water quality, the thickness of coffee powder, and the freshness of coffee.

First of all, water quality. Coffee is a sour drink, the acidity of the brewing water itself will greatly affect your product. Soft water with less soluble calcium and magnesium compounds will flush out coffee with higher acidity, while hard water, that is, water with more carbonic compounds, is more likely to make a cup of powdery coffee because carbonic acid neutralizes the cup with more flavor.

The ideal water quality is between too soft and too hard, but it is difficult to figure out whether a certain kind of water is soft or hard at home, and there is a way to do experiments: test it with French Evian water. The hardness of Evian water is 306mg/L, and the total soluble solid is 489. it is one of the water brands with the highest hardness on the market. Use Evian water and your usual water to make a cup of coffee at the same time, and then compare, you can roughly understand the water quality of your home.

Your bean grinder is also critical. The propeller bean grinder (blade grinders) is "rejected" by many people because the coffee powder it grinds is uneven; if there are conditions, it is best to choose a disc bean grinder (burr grinder), where two parallel gears grind each other, and the coffee powder is evenly ground.

As for how fine it should be ground, there has always been a debate. Some people think that the finer the coffee beans are ground, the better, to maximize the surface area of the particles in contact with water, in order to extract the best coffee flavor; others say that the thicker the better, so as not to release astringency from excessive extraction. Is it thick or thin? This, you may still have to trouble you to adjust slowly according to your own taste.

Finally, the freshness of coffee is also critical. Roasted coffee contains large amounts of carbon dioxide and other volatile gases, which are slowly released from coffee beans. Most cafes do not try beans that have been roasted for more than a month, emphasizing the importance of fresh coffee. Freezing after sealing can significantly prolong the "outgassing" process of coffee to maintain its freshness.

So, if the coffee you make at home is not as good as it tastes good in the store, don't be discouraged. It's normal. But keep in mind that no chemical formula can compare with your own tongue, and it may be more important than any variable to make your own favorite taste through daily practice.