Inside Raw Coffee Beans

Raw coffee beans (i.e., green coffee) are very dense. Approximately, half of the raw coffee bean consists of carbohydrates (in various forms) and the other half a mixture of water, proteins, lipids, acids, and alkaloids. Below is a more detailed breakdown of the primary components of green coffee.

Sugars (6% – 9%  of green coffee dry weight)

Sugars in green coffee mainly occur in the form of sucrose and provides sweetness to the coffee drank after roasting. During the roasting process, sucrose caramelises which produces acetic acid. The acetic acid contributes to the development of acidity.

Lipids (around 16% of green coffee dry weight)

The fatty, waxy or oily compounds soluble in organic solvents and insoluble in polar solvents (e.g., water) are referred to as Lipids. Lipids in green coffee, are triglycerides (i.e., fats and oils). Lipids, in the context of coffee, help preserve aroma and adds to the coffee’s mouthfeel. Green coffee with higher lipid content tends to be associated with higher green coffee quality.

Lipids could also provide challenges to coffee quality, as it’s vulnerable to oxidation and rancidity during storage of roasted coffee beans.

Proteins (about 10%-13% of green coffee dry weight)

Proteins and the associated free amino acids, interact and combine with the reducing sugars during the coffee roasting process. These interactions occur in the form of Maillard reactions (i.e., nonenzymatic browning reactions). The Maillard reactions produce melanoidins contributing to coffee’s bittersweet flavour, brown colour, roasted baked aromas.

Alkaloids (approximately 2% of coffee dry weight)

Green coffee mainly contains two alkaloids namely caffeine an trigonelline. These alkaloids contribute towards coffee’s bitterness and it’s stimulating properties.

During the coffee roasting process, Trigonelline degrades to pyridines and nicotinic acid (also known as niacin or Vitamin B3). As an approximation, about 200 grams of brewed coffee contains around 20 – 80 ml of niacin (depending on the roast degree).

Moisture

Water should be around 10% to 12% of green coffee’s weight. In the case where the moisture content is too low, the bean colour might come across as being faded and the final cup of coffee could have tasting notes of hay and straw.

Organic Acids (Chlorogenic Acids contributes about 7% - 10% of green coffee dry weight)

Chlorogenic Acids (CGAs) adds to coffee’s acidity, bitterness and sourness. CGAs offer antioxidant benefits. Robusta tends to have higher CGA content, which is likely why it tends to have greater bitterness.