Guillaume Lermusieau

Hop aroma extraction and analysis

Hops (Humulus lupulus L.) are dioecious (male and female flowers on separate plants), perennial, climbing plants of the hemp (Cannabis) family and Urticales order. As shown in Fig. 5.1, the female cone, of interest to brewers, is a close grouping of flowers arranged on a zigzagging central axis (strig). At each bend, there are florets with large covering bracts (leaves). Epidermal hair grows on the bract basis, forming a beaker-like gland, called the lupulin gland, secreting resins (bitter substances) and oils (hoppy flavours) (Davies 1960; Moerman 1982; O’Rourke 1994). Picked hops contain 75 to 80% water. Hops are carefully dried at a maximum temperature of 60°C to a water content of 10%. They are then stored in a cool, dark room until used within the year (Stevens 1966; Hughes and Simpson 1993). The composition of the whole hop cone is depicted in Table 5.1.