The best part of waking up is, of course, the hot bean juice in your cup. But, as Dr. explains in his new book. Kate “Chemist” Biberdorf It is ElementalIf you want to constantly enjoy the best cuppa joe you can create – perfectly caffeinated and not too bitter – it takes a little math. And it’s not just coffee. Biberdorf takes readers on a journey through everyday moments of everyday life, illustrating how amazing they really are – if you stop to examine the chemistry behind them.
Separated from It is Elemental – Kate Biberdorf, Copyright © 2021 – Kate Biberdorf. Published by Park Row Books.
Coffee and tea are much more powerful sources of caffeine than soda. You will probably take about 100 mg of caffeine in one cup of coffee, but it can be up to 175 mg with the appropriate coffee beans and technique. The whole process of making coffee beans (and the coffee itself) is pretty fascinating if you’ve never thought about it too much. For example, espresso machines and percolators get the most caffeine from lighter roasted beans, but the drip method is the best way to get the most trimethylxanthine from darker grains. However, in general, light and dark roasted coffees usually have the same relative number of caffeine molecules in each cup of coffee (excluding espresso).
Let’s look at the frying processes to determine why this is so. When beans are initially heated, it absorbs energy in what we call the endothermic process. However, at about 175 ° C (347 ° F), the process suddenly becomes exothermic. This means that the beans have absorbed so much heat that they now radiate heat back into the atmosphere of the roasting machine. When this happens, the settings must be adjusted on the equipment to avoid excessive roasting of the beans (which sometimes results in coffee of a burnt taste). Some roasters will even switch beans between the endothermic and exothermic reaction several times to achieve different flavors.
Over time, the roasting of coffee beans slowly changes from green to yellow, and then to a number of different shades of brown. We call tamu beans its “roast”, where the darker roasted coffee beans are much darker in color than the lighter roasted beans (surprise, surprise). Their color comes from the temperature at which they are fried. Lighter beans are heated to about 200 ° C (392 ° F), and darker fried beans to about 225–245 ° C (437–473 ° F).
But just before the beans begin, in the absence of better words, to lightly roast, the coffee beans go through their first “crack”. This is a sound process that occurs at 196 ° C (385 ° F). During this process, the beans absorb heat and double. But because water molecules evaporate from the grain at high temperatures, they actually reduce the mass by about 15%.
After the first crack, the coffee beans are so dry that they stop absorbing heat easily. Instead, all the heat energy is now used to caramelize the sugar on the outside of the coffee beans. This means that heat is used to break the bonds in sucrose (sugar) into much smaller (and more fragrant) molecules. The easiest roasts – like roasting on cinnamon and roasting from New England – are heated just before the first crack before being removed from the coffee roaster.
There is another crack that occurs during baking, but at a much higher temperature. At 224 ° C (435 ° F) coffee beans lose their structural integrity, and the beans are just beginning to decay. When that happens, you can usually hear it with another “pop”. Dark roasting usually classifies any bean that is heated after another crack – like French and Italian roasting. In general, due to hot temperatures, dark beans tend to caramelize more sugar, while light beans have less. The variations in taste due to these methods are wild, but it doesn’t really affect how they react in the body – just the taste.
Once you buy perfectly roasted coffee beans, you can do the rest of the chemistry at home. With the help of a cheap coffee grinder, you can grind coffee beans in several different sizes, which will definitely affect the taste of your morning coffee. Small, finely ground products have a large surface area, which means that caffeine (and other flavors) can be easily extracted from miniaturized coffee beans. However, this can often result in the secretion of too much caffeine, which gives the coffee a bitter taste.
On the other hand, coffee beans can be coarsely ground. In this case, the inside of the coffee beans is not exposed to approximately the same degree as the finely ground coffee beans. The resulting coffee can often be sour – and sometimes even slightly salty. But if you combine the right size coffee grounds with the right way of cooking, you can make yourself the best cup of coffee in the world.
The simplest (and easiest way) to make coffee is to add extremely hot water to the coarse coffee grounds. After soaking in water for a few minutes, the liquid can be poured out of the container. This procedure, called decoction, uses hot water to dissolve molecules inside the coffee bean. The most modern methods of making coffee use a version of decoction, which allows us to drink a cup of hot coffee, instead of murmuring on roasted beans. However, since this method does not involve a filtration process, this version of coffee – called cowboy coffee – is prone to floating coffee beans. For this reason, it is usually not the preferred method of cooking.
By the way, did you notice that I was avoiding that term boiling? If you’re trying to brew a half-decent cup of coffee, you should never boil hot water. Instead, the ideal water temperature is around 96 ° C (205 ° F), which is slightly below boiling (100 ° C, 212 ° F). At 96 ° C, the coffee aroma molecules begin to dissolve. Unfortunately, when the water is only four degrees hot, the molecules that give coffee its bitter taste also dissolve. This is why nerds and baristas are so obsessed with water temperature. In my house, we even use an electric kettle that allows us to choose whatever temperature we want it to be.
Depending on how strong coffee you like to taste, you may be attached to a French press or some other way of soaking. Like cowboy coffee, this technique also soaks coffee grounds in hot water, but the residue is slightly smaller (coarse versus extra coarse). After a few minutes, the piston is used to push all the bases to the bottom of the device. The remaining liquid above the precipitate is now perfectly clear and delicious. Because coarse coffee grounds are used in this method, more molecules can be dissolved in the coffee solution, giving us a more intense flavor (compared to cowboy coffee).
Another technique: when hot water drips over coffee grounds, it absorbs aromatic molecules before dripping into a cup of coffee. This process, aptly referred to as the drip method, can be performed manually or using a high-tech machine, such as a coffee filter. But sometimes this technique is used with cold water, which means that fragrant, aromatic molecules (those that give your coffee a distinctive smell) cannot be dissolved in water. The result is called Dutch iced coffee, a drink that is ironically favored in Japan, and its preparation takes about two hours.
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