What are the "chemical" ingredients in a cup of coffee?

"the taste is delicious", "Didi is fragrant, but the meaning is not enough"-from the advertising words of coffee, we can see that flavor is the soul of coffee. Recently, "Coffee Flavor Chemistry", co-written by Dr. Zeng Fankui of Lanzhou Institute of Chemical Physics of Chinese Academy of Sciences and Professor ou Shiyi of Food Department of Jinan University, was published by Jinan University Publishing House. This is the first academic monograph on coffee processing in China.

Holding a handful of coffee beans in his hand, Zeng Fankui said: "Raw coffee beans basically do not smell fragrance, and the flavor substances in coffee are mainly produced through the thermal reaction of the roasting process." The process of roasting is the process of chemical changes in coffee beans-sucrose, chlorogenic acid, protein, trigonelline, fat and other components will form the flavor of coffee through maillard reaction and strecker degradation reaction. The origin, roasting degree and brewing mode of coffee will affect the flavor of coffee.

Coffee flavor chemistry has been studied for more than 200 years. Researchers have been committed to the separation and identification of coffee flavor substances. At present, more than 1000 coffee flavor substances have been reported. People can smell the aroma of coffee, because of the volatility of chemical molecules, the flavor of these chemical molecules is combined to form the taste of coffee. A doctor from the Swiss Federal Institute of Technology once said in his graduation thesis: "people like coffee not because it has good nutritional value or health care function, but because it has a little exciting effect." its flavor is also unique.

Recent studies in the United States, Japan and Finland have shown that drinking coffee can reduce the incidence of depression. However, Zeng Fankui said that at present, instant coffee sold in the domestic market generally contains plant fat powder, which is allowed to be used as a food raw material containing trans fatty acids, so it is best to drink freshly ground coffee and brew with condensed milk (fresh milk and sugar is also fine). Coffee partners also try not to use it, there is the same problem.

In the book Coffee Flavor Chemistry, the author describes in detail the research history, development status, research methods and formation mechanism of coffee flavor, and introduces the flavor characteristics of special varieties of coffee, such as Blue Mountain Coffee, Special roasting Coffee, Kopi Luwak and so on. At the same time, the analytical method of distinguishing Arabica coffee mixed with Roberta coffee by high performance liquid chromatography was introduced in detail.

When it comes to the original intention of writing this book, I would like to start with a story six years ago when Zeng Fankui was a PhD student: "at that time, I saw that the teacher wanted to entertain a German friend with freshly brewed coffee. He put the crushed coffee powder in the cup and made a cup of coffee like tea. Because the dregs were not separated, the foreign friend stood by the sink and took a sip of coffee and spit out dregs. The scene was quite awkward at that time. " Zeng Fankui said that only after that did he want to really understand coffee.

Since then, Zeng Fankui began to study the knowledge and a series of processes in the process of coffee processing, from picking coffee from the fields to peeling, degumming, shelling, roasting, and so on. He also helped Hainan farmers set up coffee estates and spread coffee processing knowledge and coffee culture. He learned that many people in China know little about coffee. They think that drinking coffee is a petty bourgeoisie, and they care more about the experience of drinking coffee than drinking coffee. At present, most of the domestic coffee books are about daily life, mainly about the origin of global coffee, brewing coffee utensils and how to make coffee.

Zeng Fankui was really asked to write a professional book on coffee flavor because in 2011 he read such a passage in a foreign book, the Handbook of Coffee appreciation: it is said that China also produces coffee, but the origin and output are not clear. "Let foreigners know about Chinese coffee, let Chinese people know about our own coffee, and stimulate people's interest in coffee." With such an idea, Zeng Fankui combined with his own research, referred to a large number of foreign coffee papers, journal papers, patents and so on to write such a book.