Roasting technology Coffee roasting awakens the world's most intense aromas

Grab a handful of coffee raw beans smell, there is always a pungent smell, very different from the impression of the charming smell of coffee. However, after roasting "fragrance" correctly, raw beans will emit the strongest aroma in the world.

The small, high-altitude raw Arabica coffee beans are like a warehouse full of chemicals. At present, scientists have identified more than 2, 000 known ingredients, of which 70 to 850 are aromatic ingredients, which can be called the most fragrant in the human diet. There are only 150 kinds of vanilla used for seasoning in the catering industry, and the mellow composition of wine is not nearly as rich as coffee.

Baking awakens fragrant elves

However, the 700 or 800 kinds of fragrance "elves" in raw coffee beans will not come out on their own, but must be "awakened" by professional baking. without this procedure, coffee can only be tasted in the sun or washed in water, and it smells uncomfortable, let alone drink it. After five to 25 minutes of heating, the chemical composition of raw beans has undergone drastic changes, giving off a rare fragrance in the human world. This complex chemical reaction cannot be simulated even in today's most sophisticated laboratories, but it can probably be summed up into several key items.

First of all, after baking raw beans at more than 200 degrees Celsius, the moisture begins to evaporate, the volume expands by 60%, and the weight is reduced by 10% to 25. Depending on the degree of baking, the deeper the baking, the greater the weight loss. No wonder many operators do not like re-baking to save costs. Another important phenomenon is exhaust. Raw beans release carbon dioxide during baking and will continue to exhaust for 30 days after baking. Interestingly, carbon dioxide emissions contribute to the preservation of coffee beans, because during the exhaust process, oxygen molecules are not easy to invade, that is, the oxidation that destroys the flavor of coffee cannot be carried out, but the exhaust gradually slows down after seven days of baking. Oxygen molecules are easily attached to the bean surface, and the flavor of coffee decays quickly, which is an important reason why coffee beans are best used within a week after opening.

The secret of baking: get the highest caramel and the least carbonization

Caramelization is a link that has the greatest impact on the flavor of coffee. After six to seven minutes of baking, raw beans absorb a lot of heat and start the pyrolysis reaction, resulting in the first explosive sound. Some sugars are converted into carbon dioxide, and water continues to evaporate. New aromatic components gradually develop into the so-called coffee oil. And combine with hundreds of aromatic substances such as nicotinic acid, citric acid, quinic acid, malic acid, acetic acid, caffeine and so on. Pyrolysis reaction can continue to the second explosion, although caramelization is an important process to awaken aromatic elves, but with the extension of baking time, some ingredients will also be carbonized to form a bad astringent bitter substance, how to obtain the highest caramelization, but also to minimize carbonization, which seems to be contradictory, but it is the biggest challenge for bakers.

Pay attention to the changes in sound, color and taste

The above chemical reactions can be judged by listening to the sound, seeing the color and smelling the smell when baking. As the color of coffee beans continues to heat up, the color of coffee beans will change from gray to golden yellow to light brown, then to a trace of reddish brown of oil, and then a large amount of oil will show a dark brown of oil. if it goes on baking, the coffee oil on the bean surface will become dry and dead black. and emit a lot of blue smoke, sandwiched with a scorching smell, this is a warning that is close to the burning point. Prepare to call 119 to help put out the fire. Experienced bakers will choose between light brown to oily dark brown for safety. Coffee beans change from shallow to deep because of changes in caramelization and acidity.

Listening to sound is also the basis for judging the degree of baking. If the temperature of the roaster is hot enough, coffee beans will burst twice during the roasting process. For example, high-temperature-resistant raw beans such as Mantenin and Angelica will burst for the first time in about seven minutes, and the sound will be low and sparse. This means that the "pyrolysis" is started, that is, the starch begins to be converted into caramel, and water is ejected from the bean surface with carbon dioxide, making a low burst sound, which is quiet for two minutes. At about 12 minutes, there was a more violent and sharp burst, which was the sound of broken fibers in coffee beans, which indicated that the baking was coming to an end, and the fragrance would fade if it went on. We can see that coffee beans can talk.

In addition, Brazil and Java and other less heat-resistant beans, the first explosion and the second explosion came earlier, the heat control should pay special attention.

Define the baking degree by data

Understand the "virtue" that will appear when coffee beans are roasted, and then talk about the definition of various baking degrees and tastes. In the United States, the degree of roasting has long been defined by Cinnamon (shallow roasting), City (shallow roasting), Fully City (deep roasting) and Dark roast (heavy deep roasting, including Italian and French). However, the American preference for coffee flavor has always been rich in the west and light in the east, so the shallow roasting on the west coast may have reached the deep roasting level on the east coast, and vice versa, so these terms still belong to their own tune and are not scientific. In recent years, the American Fine Coffee Association has strongly advocated the caramelization value (Agtron number) to determine the baking degree, using the red inner line to determine the caramelization degree of coffee beans. The higher the value, the lower the caramelization, that is, the shallower the baking degree, and the lower the value, the deeper the caramelization, that is, the deeper the roasting degree. With the data, you can more accurately understand the roasting degree of coffee beans, so that the shallow roasted coffee in the United States and the West will not become a joke of re-roasting coffee in the East. This is a good evolution.

Seattle Gourmet Coffee also uses this set of scientific standards to define the degree of roasting. Caramelization value above 70 is the shallowest roasting, Cinnamon,60 above is shallow roasting around City,40, or so-called Fully city, and below 35 is heavy and deep roasting, including French roasting and espresso roasting.

Coffee flavor also varies with roasting degree. Generally speaking, sour taste is inversely proportional to roasting degree. If you prefer sour taste, you might as well buy coffee with light roasting degree. If you like thick and sweet taste, you can choose heavy roasted beans. In addition, caffeine content is inversely proportional to roasting degree, that is to say, light roasted coffee contains more caffeine than re-roasted coffee. Because caffeine can be destroyed during baking. The fruit aroma will also decrease with the deepening of baking degree, but the fermentation flavor, choking taste and sweet taste of mellow wine, shallow roasted coffee is not easy to develop, re-roasted beans have more advantages in this aspect. However, if the rebaking technique is not good, it is likely to produce a stove of rotten coffee that is scorched and bitter.

Shallow baking and deep baking, noisy!

Whether coffee should be roasted lightly or deeply is the most controversial topic in the industry, even to the point of falling out. Generally speaking, the degree of roasting in northern Italy and the eastern United States is relatively shallow, and the caramelization value is mostly around 40. The well-known producers of this group include Illy Caffe, Green Mountain and Vivace Espresso (note: although the company is based in re-roasted Seattle, it goes against the trend and advocates shallow roasting). The coffee beans of these companies immediately cease fire before the second explosion or before the bean surface is about to ooze coffee oil. Their argument is that coffee oil contains a lot of aromatic ingredients and should be preserved in beans as far as possible. Coffee oil seeps out. Although the oil looks good, the aromatic components are also lost. This pie also believes that the coffee beans are baked immediately before the oil comes out, the caramelization degree is the best, the Body (consistency) is also the best, and the acidity and taste of the coffee are the most balanced. The shallow Bakery Group also attacked the re-baking industry for baking coffee oil out of the bean table as a disaster.

However, the re-baked pie in southern Italy and the west coast of the United States, such as Peet's Coffe in San Francisco and Caffe' coffee in Seattle, is 39 Arte), and Coffee beans and Machinery Company (Beans and Machines), however, insist that coffee beans must be roasted out of oil in order to taste good. Their beans have been tested that the caramelization values of beans for espresso are all below 35, and the sour sweet potato is even overbaked at 18 degrees, which is really to the point of "heavy baking, hands are not soft".

Most of this pie glided for a while after the second explosion or the appearance of the bean oil. They did not agree with the shallow baking pie's so-called "loss of aroma components" and criticized the shallow baked pie's beans as "underdeveloped." the sharp sour taste seems to outweigh the sweetness and lacks the choking taste, and the flavor is too monotonous. They even ridicule that the real purpose of shallow baking pie is to save money, because only top Arabica beans can withstand heavy baking and develop an excellent flavor that is rich, choking, sweet and does not bite the throat. will only show a monotonous bitter taste.

The heavy baking pie also calls itself the "glutton coffee that walks the edge of the razor." because the coffee beans change so quickly after the second explosion, the whole furnace will be reimbursed for the slightest mistake, unlike the shallow baking pie, which "withdrew its troops" before the oil burst, and the technical level is relatively low. Bitz coffee, which advocates heavy roasting, enjoys a high status in the coffee industry in the United States. Bitz can produce beans at a high temperature of more than 200 degrees Celsius and operate the oven for more than 15 minutes, and it is thick but not bitter. This work is admirable. Of course, this has something to do with Bitz's ability to refit the roaster. In short, the heavy baking pie insists that only the beans after the second explosion, the flavor is complete.

To be fair, light roasting and deep roasting have their own advantages, and drinking coffee is already highly subjective and should respect each other. Fortunately, the dispute in Taiwan's coffee industry is not as obvious as that in the United States.

Stir-fry quickly, slowly, each has its own insistence.

In addition to the degree of baking is divided into factions, even the roaster also has a family view. At present, there are two major professional roasters, one is the traditional rolling furnace (Drum Roaster), and the other is the newly rising hot gas furnace (Hot Air Roaster). The former uses gas to heat the beans across the bottom of the furnace, and the metal blades in the furnace keep stirring the beans, while the latter uses high-temperature hot air to bake the beans. Because of the strong air flow, the beans in the furnace keep flying, so there is no need for leaves to stir the beans. It takes a long time to bake beans in converter, which is generally called slow stew pie, while the speed of baking beans in hot gas stove is faster, which belongs to fast fried pie.

The industry is red-faced over the merits of these two kinds of roasters, and it is also described as a "war between slow stew pie and fast stir-fry pie." slow stew pie prefers the traditional rolling furnace, believing that it should be roasted at a warm temperature at first, and then slowly increase the heat after an explosion, so that the water in the beans can be prevented from evaporating too fast, and the damage to the cell tissue can be minimized. Only by heating step by step can the flavor of coffee beans be fully developed. Those who advocate slow stewing are mostly famous glutton coffee, such as Bitz, Vivac, Allegro and coffee bean and machine companies. Their baking time is about eleven to 25 minutes. Interestingly, the scale of slow speculators is relatively small, emphasizing a small amount of baking, disdain to win by quantity, careless speculation.

Quick fried beans have a strong sour taste, while slow fried beans are more bitter and sweet.

Quick-fried pie likes to use a hot gas stove, thinking that a strong hot air flow has better heat conduction, and beans are heated more evenly, which can achieve the desired baking degree in the shortest time, thereby reducing the disappearance of coffee oil and damage to cells and tissues. the baking time is mostly within three to fifteen minutes. Since quick frying saves time and less weight loss of coffee beans, it can save money, so the heat stove operators are mostly large baking companies that win by quantity, and most of the coffee from Burger King and McDonald's in the United States is made by heat stove operators. Generally speaking, the sour taste of fast fried beans is more obvious, but also more layered, but slow fried beans suppress the sour taste, drinking is relatively low and sweet.

Relationship between fast and slow stir-frying and chlorogenic acid

All plants contain bitter and strong chlorogenic acid "Chlorogenic acids" to resist insect pests or bacteria. Coffee raw beans also contain a lot of chlorogenic acid, which has something to do with the green-blue color of raw beans, and the content of chlorogenic acid is also proportional to caffeine. Low-altitude Robusta raw beans have more caffeine than high-altitude Arabica beans, so the content of chlorogenic acid is also higher. Studies have shown that Robsta contains 10% chlorogenic acid. Arabica is only about 6%. No wonder Robusta has a bitter taste.

Chlorogenic acid is a kind of organic acid with the highest content in raw beans, and it is also the original culprit that causes the acidity and bitterness of coffee. Fortunately, chlorogenic acid will be destroyed in the baking process. More importantly, the degree of chlorogenic acid disintegration is inversely proportional to the baking speed, that is to say, the faster the baking, the more chlorogenic acid remains, the slower the roasting, the less the residue. This is enough to explain why quick fried beans drink more tart while slow fried beans have a smoother flavor. Therefore, espresso beans are more suitable for slow frying. If you stir-fry espresso in a hot stove at 300 to 400 degrees Celsius, a second explosion may occur in less than three minutes. However, too much chlorogenic acid will make espresso sour too sour.

The relationship between baking and high quality acid

In addition to inferior chlorogenic acid, raw beans also contain many high-quality acids, the more important ones are citric acid, malic acid, acetic acid, phosphoric acid and quinic acid, and other organic acids will be born with the disintegration of carbohydrates in the baking process. at present, as many as 34 kinds of organic acids have been determined, of which 15 are volatile. In principle, the concentration of high-quality citric acid, malic acid, phosphoric acid and acetic acid is the highest in moderate baking and decreases with heavy baking. Organic acids affect the flavor of coffee to a great extent. Interestingly, the pleasant and lively acid of light roasted coffee is the overall expression of more than 30 kinds of organic acids, any one of which is particularly prominent and will have a bad taste. Coffee roasting is a great learning. the age, density, hardness and moisture content of raw beans should be considered. even the relative humidity on the baking day, cloudy, sunny, rainy, temperature and wind direction changes can not be ignored. So the baker is not only an artist but also half a scientist!