Chemical constituents of coffee bean

Coffee is a main dietary source of polyphenol and phenolic acid. It is consumed by a million people because of its complex aroma and taste.

The coffee bean is composed of many components, including carbohydrate, proteins, lipids, tannin, polyphenols and minerals. It contains 2–3% caffeine, 3–5% tannins, 13% proteins, and 10–15% fixed oils. In the seeds, caffeine is present as a salt of chlorogenic acid (CGA). Also, it contains oil and wax.

Coffee beans contain vitamin of complex B, the niacin (vitamin B3 and PP), and chlorogenic acid in proportions that may vary from 7% to 12% w/w.

Nitrogen and potassium nutrition affects the chemical composition of the raw bean, which, after toasted, produces compounds that give aroma and flavor to the coffee.

In raw Arabica coffee, caffeine can be found in values varying between 0.8% and 1.4% (w/w), while for the Robusta variety these values vary between 1.7% and 4.0% (w/w).
Chemical constituents of coffee bean

Coffee lipids

The lipids of coffee play an important part in the storability of roasted coffee. During storage the lipids can be oxides if oxygen is present and it changes the aroma of coffee, too.

 The total lipid content of coffee varies with the species from about 7 to 17%, with average values of about 15% for arabica and 10% for robusta types.

The largest fraction consists of liquid coffee oil, which is found in the endosperm. Coffee oil is composed mainly of tricylglycerols as well as fatty acids in similar quantities to those found in common edible vegetable oils. About 0.24% (i.e. between 1-2% of the total lipid) is referred to as ‘coffee wax’.

The lipid composition of green coffee beans is as follows:
Triacylglycerol 75.2%
Diterpene esters 18.5%
Free diterpenes 0.4%
Sterol esters 3.2% Free sterols 2.2%
Phosphatides 0.1-0.5%
Carboxylic acid-5-hydroxytryptamides 0.6-1.0%
Tocopherols 0.04-0.06%

The main free fatty acids in the oil are linoleic acid (43-46% of the acids) and palmitic acid (30-35%). Oleic, stearic, arachidic and linolenic acids are also present in lower proportions. The presence of free fatty acid is evidently the most important factor affecting flavor formatting during roasting.

Both green and roasted coffee oils are used industrially, the former in the cosmetic industry and the latter in food applications such as flavorings.
Coffee lipids