To link and harmonize different knowledge repositories with respect to isotopic data, we propose an ISO-FOOD ontology as a domain ontology for describing isotopic data within Food Science. The ISO-FOOD ontology consists of metadata and provenance data that needs to be stored together with data elements in order to describe isotopic measurements with all necessary information required for future analysis. The new domain has been linked with existing ontologies, such as Units of Measurements Ontology, Food, Nutrient and the Bibliographic Ontology. To show how such an ontology can be used in practise, it was populated with 20 isotopic measurements of Slovenian food samples. Describing data in this way offers a powerful technique for organizing and sharing stable isotope data across Food Science.

This study used elemental and stable isotope composition to characterize Slovenian truffles and used multi-variate statistical analysis to classify truffles according to species and geographical origin. Despite the fact that the Slovenian truffles shared some similar characteristics with the samples originating from other countries, differences in the element concentrations suggest that respective truffle species may respond selectively to nutrients from a certain soil type under environmental and soil conditions. Cross-validation resulted in a 77% correct classification rate for determining the geographical origin and a 74% correct classification rate to discriminate between species. The critical parameters for geographical origin discriminations were Sr, Ba, V, Pb, Ni, Cr, Ba/Ca and Sr/Ca ratios, while from stable isotopes δ¹⁸O and δ¹³C values are the most important. The key variables that distinguish T. magnatum from other species are the levels of V and Zn and δ¹⁵N values. Tuber aestivum can be separated based on the levels of Ni, Cr, Mn, Mg, As, and Cu. This preliminary study indicates the possibility to differentiate truffles according to their variety and geographical origin and suggests widening the scope to include stable strontium isotopes.

This paper summarises the isotopic characteristics, i.e., oxygen and hydrogen isotopes, of Slovenian milk and its major constituents: water, casein, and lactose. In parallel, the stable oxygen isotope ratios of cow, sheep, and goat’s milk were compared. Oxygen stable isotope ratios in milk water show seasonal variability and are also ¹⁸O enriched in relation to animal drinking water. The δ¹⁸O_water values were higher in sheep and goat’s milk when compared to cow milk, reflecting the isotopic composition of drinking water source and the effect of differences in the animal’s thermoregulatory physiologies. The relationship between δ¹⁸O_milk and δ¹⁸O_lactose is an indication that even at lower amounts (>7%) of added water to milk can be determined. This procedure once validated on an international scale could become a reference method for the determination of milk adulteration with water.

Rationale: The isotope ratio for the internationally agreed but virtual zero‐point of the carbon isotope‐delta scale, Vienna Peedee belemnite (VPDB), plays a critical role in linking carbon isotope delta values to the SI. It is also a quantity used for various data processing procedures including ‘ ¹⁷ O correction’, clumped isotope analysis and conversion of carbon isotope delta values into other expressions of isotopic composition. A value for R _VPDB ( ¹³ C/ ¹² C) with small uncertainty is therefore desirable to facilitate these procedures. Methods: The value of R _VPDB ( ¹³ C/ ¹² C) was determined by errors‐in‐variables regression of isotope delta values traceable to VPDB measured by isotope ratio mass spectrometry against isotope ratios traceable to the SI by use of gravimetric mixtures of ¹² C‐ and ¹³ C‐enriched d ‐glucose measured by multicollector inductively coupled plasma mass spectrometry. Results: A value of R _VPDB ( ¹³ C/ ¹² C) = 0.0111105 ± 0.0000042 (expanded uncertainty, k = 2) was obtained. Conclusions: The new value for R _VPDB ( ¹³ C/ ¹² C) agrees very well with the consensus values calculated from previous measurement results proposed by Kaiser and by ourselves, as well as recent determinations independent of mass spectrometry. The expanded uncertainty of 0.4‰ when expressed as an isotope delta value is a tenfold improvement over the previous best measurement of the isotopic composition of carbon.