How is a good cup of coffee made?

How to make a good cup of coffee?

Christopher Hendon, co-author of Water for Coffee: Science Story Manual and associate professor of computational materials and chemistry at the University of Oregon, believes that in addition to basic skills, brewers also need to master chemical and physical principles at the same time. In addition to the quality of coffee beans, variables such as water temperature, water quality, particle distribution, water-to-powder ratio, and time will affect the final taste of the cup. To make good coffee, you must learn to control these variables.

The coffee we usually drink has two densities of ingredients (organic acids, inorganic acids, heterocyclic compounds, Mena reaction products, etc.): one is 1.2-1.5%, such as drip coffee, and the other is 8-10%, such as espresso. Hand-poured, French-pressed, siphon, machine-drained, or Turkish coffee directly heated with coffee powder and ditch water can all reach a density of 1.2-1.5%; and coffee as strong as 8-10% is mostly made with a coffee machine. The density of coffee ingredients is basically the same, and the following factors are important.

1. Temperature and speed

From the above, we can see that the coffee brewing methods are roughly divided into two categories: soaking and dripping. From a physical point of view, the biggest difference is that the temperature of coffee bean particles is higher when soaking than dripping. In fact, the most time-consuming part of the coffee extraction process is not to dissolve the caffeine on the surface of the particles, but to wait for the coffee flavor to pass through all the particles and reach the junction between water and coffee. The length of time it takes varies depending on the water temperature. The higher the coffee bean particles are heated, the more delicious compounds can be extracted. However, too much is as bad as too little. Once the temperature is too high, more unnecessary compounds will dissolve in the water, affecting the taste.

On the other hand, hand brewing and other drip methods are more complicated to calculate because it takes time for water to flow through the coffee beans. The brewing time depends not only on the water temperature, but also on the coarseness of the coffee beans.

2. Coffee bean to water ratio

When using the drip method, too fine coffee beans will increase the brewing time and extraction amount. The brewer can increase the ratio of water to coffee beans by reducing the amount of coffee beans, but at the same time it will also reduce the brewing time accordingly. Therefore, drip brewing is more troublesome than soaking, and only by taking all aspects into consideration can you make a good cup of coffee.

3. Water quality

Even if you follow the above two principles, it is still difficult to guarantee that the coffee you brew will be perfect. Hendon pointed out that there are two other details that can affect the quality of coffee, one of which is the pH value of water.

Coffee is an acidic beverage, so the pH of the water used to brew it is also important. Coffee brewed with low HCO₃⁻ (Bicarbonate) water (also known as soft water) has a higher acidity; if coffee is brewed with water with a high HCO₃⁻ content (i.e. hard water), the strong and prominent sour taste will be neutralized. Ideally, it is best to use water with just the right amount of chemicals to brew coffee, but it is difficult to know the HCO₃⁻ concentration in tap water. Hendon recommends trying Evian mineral water, which has one of the highest HCO₃⁻ contents (up to 360 mg per liter), to brew coffee and compare the effects of the two.

4. Particle distribution

Any experienced coffee lover will tell you that blade grinders are not the best tools for grinding coffee beans, because the coffee beans they grind are of different sizes, which is not conducive to extraction. It is better to use a burr grinder, which grinds with two parallel gears to gradually grind the coffee beans finer and more evenly.

There has always been debate about the ideal coarseness. Some say that the finer the coffee beans are ground, the better, to maximize the particle surface and facilitate the extraction of the best and strongest coffee flavor; others say that the coarser the better, to avoid over-extraction and release of astringency. Hendon believes that the coarseness depends on one's taste.

It seems that if you want to brew a cup of high-quality coffee yourself, there are still many factors that need to be paid attention to. The above article gives you some methods on how to control these factors. How to implement these methods specifically requires more practice, and use this knowledge to constantly find the flavor you like!