Coffee aroma chemicals

Each variety of coffee has its own flavor and other characteristics. Generally, marketed coffee is a blend of different varieties of coffee beans.

The blends are controlled for flavor, aroma, color and strength or body of the beverage from the roasted bean.

It has been established, primarily from gas chromatography evidence, that there are nearly 1000 different more or less volatile compounds present in roasted coffee.

Most results from the thermal decomposition of carbohydrates and phenols, especially chlorogenic acids that are present at significant concentrations in green beans during roasting.

Some compounds are located in the carbohydrate matrix of the roasted bean whereas others are located in the coffee oil distributed within the bean.

Heterocyclic aroma chemicals, which are major constituents of a brewed coffee extract possessed considerable antioxidants activities.

The flavor and aroma of coffee are best when it is freshly roasted. Many of the aromatic components of roasted coffee, and particularly of coffee oil itself, are extremely susceptible to deterioration by the action of moisture and oxygen.

The staleness of coffee exposed to air is due to the oxidative changes that take place with certain coffee constituents.

The major factor affecting coffee quality is the length of storage, as volatile aroma compounds are lost, especially from ground coffee, with methanethiol and 2,3-pnentanedione being used as indicators of coffee freshness, because they are rapidly lost on storage, especially the 2,3-pentanedione.
Coffee aroma chemicals

Chemistry of coffee

Chemistry of coffee
From the flavor point of view, coffee is very interesting. Of all the many varieties produced there are really only two main groups:

a. Brazil: Coffee with a rich mellow aroma and flavor which is full-bodied and has a fine acidity.
b. Milds: All coffee grown elsewhere including those from Colombia, Venezuela, Guatemala, El Salvador, Nicaragua, Costa Rica, Cuba, Santo Domingo, Haiti, Jamaica and Sumatra.

The chemistry of the component of both green and roasted coffee and the nature of the changes which take place during roasting process, which is in effect, a mild pyrolysis, have been the subjects of much research and are as yet incomplete understood. At least 103 aromatic compounds have been reported in the literature but work is still in progress to establish their relative importance in the reconstruction of a coffee flavor.

Most of the components which have been isolated and characterized are derived from the water soluble components, mainly sugars, in the green beans. The fat, which is present to about 13% in the raw bean, is little changed by roasting: but it has the ability to absorb and so protect the aromatics as they are formed reducing their evaporation or degradation during the final stages of the roasting process.
Chemistry of coffee