The role of some chemicals in coffee

Carbohydrates: The carbohydrate content in dry coffee is about 60%. Most of them are polysaccharides that are soluble or insoluble in water and a small part are sucrose, glucose…

During the roasting process, carbohydrates change a lot, they can decompose into different compounds or disappear almost completely like the sugars mentioned above. Reducing sugars participate in some reactions that create color and aroma for roasted coffee. Polysaccharides are insoluble in water, they form the cell walls of coffee beans and after brewing become coffee grounds.

Fats: In green coffee, the total fat content is about 13%. During the roasting process, fatty compounds lose 1 – 2%. The main fats that form coffee oil are triglycerides and diterpenes, which are esters of saturated acids, especially palmitic, behenic, arachidic. These diterpenes are very sensitive to acid, heat and light. The decrease in diterpene content during storage as well as roasting may be due to the formation of volatile terpenes, naphthalene and quinoline.

Acids: The most important representatives of the acid group are chlorogenic acids. These are acids specific to coffee. During the roasting process, they are decomposed by 30-70%, after roasting, some volatile acids are formed. All of these acids contribute to the sour taste of coffee. Proteins: Almost absent in roasted coffee, due to roasting at high temperatures, a part is decomposed, the rest combines with carbohydrates and chlorogenic acids to form brown substances. By hydrolysis, people found the following amino acids in the protein composition of coffee: cysteine, alanine, phenylalanine, histidine, leucine, lysine, …. These amino acids are rarely found in the free state, they are usually in the bound form. When heated, the polypeptide chains are broken down, the released amino acids react with each other or react with substances that create the aroma and flavor of roasted coffee. Among the amino acids mentioned above, the most notable are sulfur-containing amino acids such as cysteine, methionine and proline, which contribute to the characteristic flavor of roasted coffee. In particular, methionine and proline have the effect of reducing the oxidation rate of aromatic substances, making roasted coffee retain its flavor during storage. During processing, only a part of the protein is broken down into amino acids, while the majority is converted into insoluble compounds.

Alkaloids: During roasting, the caffeine content remains almost unchanged. Trigoneline is reduced by about 75%, forming products including nicotinic acid (niacin), nicitinamide and volatile aromatic substances such as pyrine and pyrol. The most notable of these is niacin, which acts as a vitamin in the human body.

Aromatic substances: In the composition of aromatic compounds, there are about 50% aldehydes, 20% ketones, 8% esters, 7% heterocyclics, 2% dimethylsulfide, a smaller amount of other organic sulfides, and a small amount of nitrile, alcohol or low molecular weight saturated and unsaturated hydrocarbons such as isoprene.

Minerals: The mineral content in coffee is about 3 – 5%, mainly potassium, magnesium nitrogen, phosphorus, chlorine. In addition, aluminum, iron, copper, iodine, sulfur, … these substances have a negative effect on the taste of coffee. The quality of coffee is high when the mineral content is low and vice versa.

Collected