Acid, noun: Acids make up approximately 5% of green coffee. Chlorogenic acids make up the lion’s share. As polyphenols, chlorogenic acids, together with caffeic acid, belong to the secondary phytochemicals with antioxidant properties. When roasting, up to a third of the acids are broken down. They stimulate digestion. And they are essential for the development of the coffee’s taste. The longer the roasting, the more (undesirable) acids are broken down. (see also: chlorogenic acid)