Determination of the Geographical and Botanical Origin of Hops (Humulus lupulus L.) Using Stable Isotopes of C, N, and S

A need exists for a reliable method to determine the geographical and botanical origin of hops. For this study, three sets of samples were collected: the first set comprised 5 German samples; the second set comprised samples of hops from 10 of the world's major hop-growing regions; and the third comprised the 4 main Slovenian regions. The samples were analyzed using isotope ratio mass spectrometry (IRMS) to obtain delta C-13, delta N-15, and delta S-34 values. The delta N-15 (2.2 parts per thousand to 8.4 parts per thousand) and delta S-34 (0.7 parts per thousand to 12.3 parts per thousand) values were the most discriminating parameters for classifying hop according to geographical origin. ANOVA showed distinct groupings for 8 out of the 10 hop-growing regions. Although it was not possible to distinguish the geographical origin of hops based on delta C-13 (-28.9 parts per thousand to 24.7 parts per thousand), in the case of botanical origin, delta C-13 values proved to be the most discriminative albeit with limited success.