Carbon and Nitrogen Natural Stable Isotopes in Slovene Honey: Adulteration and Botanical and Geographical Aspects

Isotope parameters (delta C-13(honey), delta C-13(protein), delta N-15) were determined for 271 honey samples of 7 types (black locust, multifloral, lime, chestnut, forest, spruce, and fir honeys) from 4 natural geographical regions of Slovenia. Carbon and nitrogen stable isotope ratios were measured to elucidate the applicability of this method in the identification of the botanical and geographical origin of honey and in honey adulteration. Only 2.2% of the samples were adulterated according to the internal standard carbon isotope ratio analysis method. Botanical origin did not have any major influence on the honey isotope profiles; only black locust honey showed higher delta C-13 values. Some differences were seen across different production years, indicating that the influence of season should be further tested. Statistical and multivariate analyses demonstrated differences among honeys of various geographical origins. Those from the Alpine region had low delta C-13 (-26.0 parts per thousand) and delta N-15 values (1.1 parts per thousand); those from the Mediterranean region, high delta C-13 (-24.6 parts per thousand) and medium delta N-15 values (2.2 parts per thousand); those from the Pannonian region, medium delta C-13 (-25.6 parts per thousand) and high delta N-15 value (3.0 parts per thousand); and those from the Dinaric region, medium delta C-13 (-25.7 parts per thousand) and low delta N-15 values (1.4 parts per thousand).