DETERMINATION OF ESSENTIAL OILS IN HOPS BY HEADSPACE SOLID-PHASE MICROEXTRACTION

A solid-phase microextraction (SPME) method is described for the deter mination of the essential oils, humulene and caryophyllene, in the hea dspace of female hop cones and male hop lupulin samples. Optimized SPM E sampling parameters for the determination of the humulene to caryoph yllene (H/C) ratio for female hops (50 mg) and male lupulin (25 mg) sa mples include a 100 mu m poly(dimethylsiloxane) SPME fiber and a 4 h s ample exposure period at a temperature of 50 degrees C. Increasing the temperature to 90 degrees C or increasing the length of sample exposu re at 50 degrees C promoted caryophyllene oxidation, In a survey of fi ve female hop varieties, good agreement was found between the H/C rati o obtained by headspace SPME and conventional steam distillation. The H/C ratio for 10 male lupulin varieties determined by headspace SPME a nd pentane extraction also indicated good agreement between the two ex traction methods.