Abstract: A buttery and/or winey flavor of which diacetyl and acetoin are the major flavor constituents is produced by the fermentation of a coffee substrate. The process involves forming a nutrient media containing water and soluble coffee solids as the nutrient component, the soluble solids concentration being at least 0.5%. A microorganism which is either a strain of lactic acid producing bacteria or yeast capable of producing diacetyl is added the nutrient media and the combination is mixed and simultaneously placed into an environment of a pH of from 4.0 to 7.0, a temperature of from 16.degree. to 37.degree. C., for a period of time effective to produce diacetyl and aeration conditions wherein the nutrient media contains sufficient oxygen to allow for diacetyl production. The aforementioned process will produce diacetyl and acetoin. The diacetyl which is produced is recovered and or concentrated and added to a coffee product.