Detailed Analysis of Coffee Bean ingredients basic knowledge of Fine Coffee

Moisture:

The moisture content of coffee beans varies greatly with different processing stages and products. The moisture content of wet coffee beans with film is about 50%, while that of dry green coffee beans is about 10%~ 13%. The moisture content of roasted coffee beans is only about 5%. The presence of water in coffee beans, like other foods and beverages, because it contains a considerable amount of hydrocolloid macromolecules, such as proteins and polysaccharides, makes water exist in coffee beans in a variety of physical and chemical combinations.

Minerals:

Minerals in coffee beans are relatively small, accounting for about 4% of the dry weight of raw coffee beans, but they are very important. It contains a variety of different elements, of which potassium content is the most, accounting for about 40% of all mineral mass, followed by calcium, magnesium, phosphorus, sodium and sulfur. There are also many other trace elements in PPM level, such as zinc, manganese, copper, rubidium and so on more than 33 kinds. The minerals contained in coffee beans cannot be used to indicate the content of coffee or coffee powder products, which are added to water during brewing or processing and will be affected by water quality and generate different changes. In addition, the most important factors affecting the mineral content and type of green coffee beans were soil and fertilization during cultivation. At least 90% of minerals can be extracted from roasted coffee beans during coffee brewing, so the relationship between potassium or other mineral content and coffee soluble yield can be used to evaluate coffee extraction rate.

Carbohydrates:

The carbohydrates contained in coffee beans can be described as polysaccharides and low molecular weight sugars, the latter including mono-, di-, and tri-carbohydrates. In addition, it can be divided into reducing sugar and non-reducing sugar. Also contains some derivatives, such as glue. Carbohydrates contribute to coffee taste, aroma and color. In terms of flavor, carbohydrates not only emit coffee aroma after roasting, but also absorb volatile aroma, making coffee present a special flavor.

Low molecular weight carbohydrates:

Sucrose is the most important free carbohydrate in green coffee beans, and its content varies according to variety, source and maturity. In general, Arabica coffee beans contain more sucrose than Robusta coffee beans; other simple sugars, including reducing sugars, can also be detected in the extract of green coffee beans. Green coffee beans also contain glucose and fructose, Arabica content is lower than Robusta content, in addition to Arabica total reducing sugar is also lower than Robusta.

After roasting coffee beans, the changes of low molecular weight carbohydrates vary with the roasting degree, sucrose loss is the fastest, the loss rate of light roasting is 97%, moderate roasting is 99%, heavy roasting is 100%. Others, such as glucose, fructose and arabinose, also have considerable losses.

Polysaccharides:

Polysaccharides are very important components in green coffee beans, accounting for about 40% ~ 50% of dry matter. According to the type, there are polygalactose, polyfructose, polyarabinose and cellulose, which are the substances that make up the plastid of coffee beans and are related to the hardness of coffee beans.

A considerable amount of polysaccharide remains after roasting. According to the data obtained from one study, the difference between different roasting degrees is not very large, and its retention rate ranges from 70% to 75%. Among them, the retention rate of cellulose is the highest and that of polymeric arabinose is the lowest. In extraction, some polysaccharides were extracted, depending on the solvent. When extracted with water, arabinose, galactose and some mannose were extracted more.

Organic acids:

When brewing coffee, acidity performance is very important, in good conditions and skills, can develop a refreshing acidity of the special taste, is a necessary condition for senior coffee. Generally speaking, the more deeply roasted coffee beans, the less or even no acid development, and assume another pure coffee characteristics.

Raw Arabica coffee beans contain nonvolatile acids including citric acid, malic acid, oxalic acid and tartaric acid. No significant amount of volatile acids was detected. When green coffee beans after roasting, acid content generated a great change, which volatile acid changes the largest. After roasting, the acid contained in raw beans loses about 15%, and the chemical change of acid is worth noting. Formic acid and acetic acid increased at the beginning of roasting, and increased with the increase of roasting degree. Citric acid and malic acid decreased gradually with the roasting process, forming their decomposition products.

Protein and amino acids:

In terms of crude protein, the content of raw coffee beans is about 13%~ 16%. If caffeine and nitrogen-containing compounds such as trigonelline are deducted, the real protein content is about 8.8%~ 9.7%. Raw coffee beans also contain a variety of enzymes, such as lipase, proteolytic enzymes, saccharolytic enzymes, galactohydrolase and peroxidase. Green coffee beans contain about 0.15 ~ 0.25 of free amino acids, Robusta content is higher than Arabica, these free amino acids have a higher degree of impact on coffee flavor, less impact on taste.

Chlorogenic acid:

Chlorogenic acid has at least three isomers, and its functions mainly lie in physiological regulation of coffee plants, including: promoting growth, rhizome formation, antibacterial, pest control, and becoming lignin. In green coffee beans, Robusta content is more than Arabica, wet processing of green coffee beans content is about 40% lower than dry processing. After roasting, this substance will disappear through different actions, resulting in extremely complex products, which are closely related to the quality of coffee.

Fat:

The fat of green coffee beans consists of coffee oil (Coffee Oil) present in the endosperm and wax present in the outer layer of coffee beans. Coffee oil not only contains triglycerides, but also contains considerable amounts of other fat components. It forms the characteristics of coffee and is very important for coffee.

According to many studies and statistics, the average content of Arabica coffee beans is 15% of the dry matter, with a standard deviation of 0.78%, and the content of Robusta coffee beans is 10%, with a standard deviation of 1.41%.

Volatile substances:

Volatiles are the main source of coffee flavor and are especially important for coffee quality. There are many kinds of volatile compounds in coffee, and their existence will affect the aroma quality of coffee. The main source is derived from non-volatile substances from raw beans, which are broken off or reacted during roasting. Thermal decomposition, other reactions or interactions between components, such as carbohydrates, amino acids, organic acids and phenolic compounds, form coffee's unique aroma and flavor. The factors affecting the volatile components of coffee include: coffee bean varieties, cultivation climate, soil conditions, storage of green beans, roasting temperature and time, roasting equipment and other factors.

Raw coffee beans do not contain the special aroma of coffee, so they are not eaten directly. They must be roasted before they generate a large number of volatile aroma substances. After roasting, the main volatile aroma components of raw coffee beans were analyzed and confirmed to have at least 660 kinds, which was the most volatile aroma components in all foods and beverages. The aroma generated in the roasting process, such as hazelnut flavor, cream flavor and caramel flavor, or grassy flavor, smoky flavor, burnt flavor, spicy flavor and bitter flavor, mostly came from volatile substances. The difference of roasting degree would also affect the flavor characteristics of coffee.

Pectin and lignin:

Pectin is composed of a variety of polysaccharides. Its main components are galactonic acid polymer, aronic acid and rhamnose, etc., and its content is more than 3%. Lignin is the insoluble residue remaining after the treatment of plants with sulfuric acid and caustic, that is, the so-called coffee fiber, and its content is about 2.4%.

Nitrogen-containing compounds:

The nitrogen-containing compounds contained in green coffee beans can be divided into phytoalkaloids, Trigonelline, nicotinic acid, protein and free amino acids, etc., as follows:

1. Alkaloids:

Caffeine is mainly used, and the content in raw coffee beans varies greatly due to different varieties. Robusta content is higher, about 2.2%, Arabica content is lower, about 1.2%. In Java and Cote d'Ivoire, low-caffeine coffee beans have been cultivated in recent years, with a caffeine content of only 0.2%. Caffeine can be removed by a variety of methods to make a variety of decaffeinated products, decaffeinated instant coffee powder caffeine content of 0.3%, general commodities are controlled between 0.1%~ 0.2%. Caffeine is arguably the spirit of coffee and the most controversial issue.

Caffeine, although not odorous, has a pronounced bitter taste. Although some people have tried to use the bitterness of coffee to judge the amount of caffeine content, they have not been completely successful because caffeine bitterness accounts for only a small part of coffee bitterness, so it does not have much influence on decaffeinated coffee bitterness.

After caffeine is digested by the body, it is rapidly absorbed and metabolized and excreted in urine. Caffeine in the human blood content increased status, according to the stomach content may be. The most significant physiological effect of caffeine on the human body is the stimulation of the central nervous system. As for the changes in brain activity, the dose required is extremely high, which is much higher than the normal intake. Other physiological effects that attract more attention are the influence on blood pressure and heart vessels.

2. Trigonelline:

Trigonelline is a hygroscopic colorless crystal with excellent solubility in water. It also has a low degree of physiological effects, mainly for the central nervous system, bile secretion and intestinal motility. Trigonelline directly on the quality of coffee caused by the impact is very small, its bitterness is only a quarter of caffeine, due to its presence in small quantities, so the impact on taste is not very large. The content in green coffee beans varies according to the variety, Arabica content is higher than Robusta. Trigonelline is rapidly decomposed during roasting, with a loss rate of about 50 - 80%, depending on the roasting temperature and time. Trigonelline decomposes into a variety of compounds, including non-volatile nicotinic acid, etc., and 29 volatile substances, 9 of which have been identified as pregnant coffee aroma substances.

3. Nicotinic acid:

Nicotinic acid in green coffee beans content is very small, but after roasting, there is an increase in the phenomenon, the main reason is that it comes from trigonelline decomposition results. But the study found that niacin continued to break down into volatile chemicals at the high temperatures of roasting, so the real increase was small.