Abstract
Coffee is one of the most consumed beverages all over the world, as well as in Thailand especially in recent years.Two species of coffee are harvested in Thailand, Coffea arabica in the northern part and Coffea canephora var. robusta in the southern part. Arabica coffee plantation in the north of Thailand cover about 9000 hectares, distributed in eight provinces.Arabica coffee is mainly grown in the cooler highlands, wet processed in order to obtain high quality green bean and used in roasted coffee for domestic use. Wet-processed beans are characterized by more fruity and acidic notes and less bitter and burnt attributes, compared with dry-processed beans. Moreover, the wet method allows the preservation of intrinsic properties of the beans, leading to coffees with a more desirable aroma[2]. Coffee aroma is the main responsible for organoleptic properties and therefore appeal of coffee. It is developed during the roasting process and depends on operative conditions such as temperature and time, but also on variety, origin and composition in terms of aroma precursors in green beans. In particular, caramelization of sugars leads to the production of furans (responsible for burnt and caramel notes), Maillard reaction of sugars develops pyrazines (characterized by roasty notes, mainly responsible for the coffee aroma), trigonellines are the precursors of pyridines (which confer smoky notes to the coffee) and lipids metabolism leads to the production of carbonyls [2, 3, 4, 5]. The effect of three different factors, such as altitude of harvesting (900 and 1500 meters above sea level), germination time (0, 24, 28 and 72 hours) and roasting level (light, medium and dark) on the volatile profile found in 24 different types of coffee were analyzed by Proton Transfer Reaction Quadropole-Mass Spectrometry (PTR-QMS) and by Gas Chromatography Mass Spectrometry (GC-MS). The best conditions to minimize undesirable odor and maximize the desirable ones were evaluated by Design Expert