[Rumors Debunked] Why are roasted coffee beans so fragrant? Are flavors and spices added?

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Baking

Roasting

Coffee beans must be roasted to have the aroma of coffee, because when roasting raw beans, the volatile substances and other components will be thermally decomposed or interact with each other to form the unique aroma and flavor of coffee. It is currently known that roasted coffee beans can produce at least 650 kinds of aroma. Therefore, good coffee beans do not need to add any substances at all, they are a "spice" library in themselves!

1

Green coffee beans are a warehouse full of chemicals

Nutritionist Jonny Bowden lists coffee as one of the 150 healthiest ingredients on earth, and it is the number one antioxidant food source in the American diet. Of all the ingredients and drinks, coffee is the most artistic, skillful, and changeable, but also quite controversial. The complex ingredients of coffee, the complicated production process, and the chemical changes produced during processing are all important basic knowledge that coffee researchers and enthusiasts have carefully studied.

Green coffee beans are a warehouse full of chemical substances. For example, a certain type of Arabica coffee has more than a thousand identified ingredients, hundreds of which are aromatic, making it the most fragrant drink for humans.

There are only 150 kinds of aromatic herbs commonly used for flavoring in the catering industry. Even the aroma components of wine and tea are far less rich than those of coffee. Coffee contains many high-quality acids, such as chlorogenic acid, citric acid, malic acid, acetic acid, phosphoric acid and quinic acid, as well as other organic acids, which are produced as carbohydrates decompose during the roasting process. Currently, there are as many as 30 kinds of organic acids measured, 15 of which are volatile. Generally speaking, the concentration of organic acids is highest during medium roasting and decreases with heavy roasting.

[Popular Science] What happens to coffee beans in a coffee roaster?

carbohydrate

The carbohydrates contained in coffee beans can be divided into polysaccharides and low molecular weight sugars. The latter include mono-, di- and tri-saccharides, which can be divided into reducing sugars and non-reducing sugars. In addition, it also contains some sugar derivatives, such as pectin. The contribution of carbohydrates to coffee lies in the changes in aroma and color. In terms of aroma, after being roasted, carbohydrates not only emit aroma themselves, but also absorb other volatile aromas, giving coffee a different special flavor.

The carbohydrate content of green coffee beans is about 38.5%, of which about 8.7% are low-molecular sugars, which will undergo caramelization during the roasting process and transform into ingredients such as caramel pigment; while polysaccharides and pectin are mainly present in the form of cellulose (23.1%) or lignin (6.7%).

Low molecular weight carbohydrates

The main free sugar in green coffee beans is sucrose, and its content varies depending on the variety, source and maturity. Other types of simple sugars, such as reducing sugars, can also be detected in the extract of green coffee beans, in addition to glucose and fructose.

After coffee beans are roasted, low-molecular sugars will change, and the changes vary according to the degree of roasting. Sucrose is lost the fastest, with a loss rate of 97% for light roasting, 99% for medium roasting, and 100% for heavy roasting. As for glucose, fructose and arabinose, there is also a considerable degree of loss.

Polysaccharides

This is a very important component of coffee beans, accounting for about 40-50% of the dry matter. If classified by type, polysaccharides include polymerized galactose, polymerized mannose, polymerized arabinose and cellulose, which are all substances that make up the coffee bean plastid.

Even after baking, polysaccharides will still retain a certain amount. Past studies have found that the degree of baking has little effect, with the retention rate being around 70-75%, with cellulose having the highest retention rate and polyarabinose having the lowest.

Protein and amino acids

The protein content of green coffee beans is about 14.4%. After deducting nitrogen compounds such as caffeine and trigonelline, the protein content is about 11.9%. In addition to crude protein, green coffee beans also contain a variety of enzymes, such as lipase, protease, carbohydrate decomposition enzyme, galactose hydrolase and peroxidase. Green coffee beans contain about 0.15-0.25% free amino acids, which have a greater impact on the flavor of coffee, but a lower impact on taste. Once the green beans are roasted, their protein content will drop to 3.0%.

Lipids

Coffee oil in the endosperm of green beans and the wax on the outer layer of coffee beans together constitute the lipids of green coffee beans. Coffee oil contains triglycerides and a considerable amount of other lipids, but its content and composition vary depending on the variety. Generally speaking, the average content of green beans is about 11.5%. Even after roasting, about 97% is still preserved in the form of lipids.

Volatile substances

Volatile substances are the main source of coffee flavor and have a great impact on coffee quality. There are many types of volatile substances, and their presence will affect the aroma and quality of coffee. When roasting green beans, volatile substances in particular are cut off or derived after reactions. Any thermal decomposition or interaction between components, such as the effects of sugars, amino acids, organic acids and phenolic compounds, will form the unique aroma and flavor of coffee.

In addition, factors that affect the volatile composition of coffee include the variety of beans, climate, soil conditions, storage of raw beans, roasting temperature and time, and roasting equipment.

Green coffee beans must be roasted to produce the coffee aroma we usually smell. Before roasting, there is no special aroma of coffee. It has been determined that the volatile aroma in green beans can produce at least 650 kinds of aromas after roasting, such as hazelnut, cream, caramel, grass, smoky, burnt, spicy and bitter, which is the most diverse volatile aroma components in all foods and beverages. In addition, the degree of roasting will also affect the flavor of coffee.

Moisture

The moisture content of coffee beans varies greatly with different processing stages and products. The moisture content of wet coffee beans with membrane is about 50%, the moisture content of dried green coffee beans is about 11.5%, and the moisture content of roasted coffee beans is only about 4.8%. Since green coffee beans contain a considerable amount of water colloidal macromolecules, such as proteins and polysaccharides, they can combine water in a variety of physical and chemical ways and exist in the beans.

Summarize:

Fresh coffee beans, especially when freshly ground, have a rich, complex, and ever-changing aroma that cannot be imitated by any artificial synthetics such as flavors and spices. Therefore, even if you smell some freshly ground single-origin beans, and the taste is not like the "coffee flavor" you remember, it can still be a "pure natural, additive-free" coffee bean; on the contrary, if you smell some coffee, the taste has not changed from the beginning to the end for several years...

Hehe~

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