QUANTITATIVE EVALUATION OF BITTER ACIDS, XANTHOHUMOL AND ESSENTIAL OILS PRESENT IN FLOWERS OF DIFFERENT CULTIVARS OF Humulus lupulus L. GROWN IN NORTHEASTERN BRAZIL

Hop flowers contain chemical substances that are used to confer sensory properties to beer. Hop flower products have very high commercial value, but national production represents less than 2% of domestic consumption. In this work, flowers from different hop cultivars grown in northeast of Brazil (Rio Grande do Norte and Ceara) were analyzed to quantitate metabolites of industrial interest. Flowers from the initial and three consecutive harvests were collected, and bitter acids and xanthohumol were evaluated by HPLC-UV and essential oils by GC-MS. The cultivar Columbus was subjected to only 10% of the irrigation time during the third flowering phase to evaluate the effect of water stress on the formation of metabolites. Compounds were detected in appreciable quantities in all samples, and consecutive flowering of some cultivars showed a significant increase in total bitter acids with successive harvests. Plants subjected to water stress showed an abrupt decrease in the concentration of compounds. The cultivars evaluated by liquid and gas chromatography showed a significant concentration of bitter acids and essential oils within the expected range, and the chemical composition of the oils showed different compounds characteristic of hops.