Milk Authentication: Stable Isotope Composition of Hydrogen and Oxygen in Milks and Their Constituents

Abstract

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 δ18Owater 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 δ18Omilk and δ18Olactose 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.

Isotope partitioning between cow milk and farm water: A tool for verification of milk provenance

“…Several empirical studies have demonstrated the utility of oxygen and hydrogen stable isotope measurements on milk for verifying the origin of milk [1][2][3][4][5][6][7][8][9][10][11][12][13] . In fact, like many other natural products, milk retains its the isotopic features acquired at the time of its production.…”

“…All these studies indicate that the δ( 18 O/ 16 O) and δ( 2 H/ 1 H) values in milk water were isotopically enriched with the heavier isotope relative to cow drinking water. For δ( 18 O/ 16 O), an enrichment of 2-6 ‰ was documented 6,[9][10][11]12 . Seasonal variations in H and O the isotopic composition in milk water have also been observed, with higher values on summer days and lower values during winter.…”

Special Issue “Isotopic Techniques for Food Science”

“…The authors found that isotopes could distinguish milk products from different regions, except in cases where the feed type, farming environment, and agriculture practice were similar. Hamzić Gregorčič et al [ 3 ] found that δ 18 O 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. Potočnik et al [ 4 ] focused on the determination of δ 13 C in milk fatty acids as a useful biomarker for determining the authenticity and regional traceability of milk.…”

“…When the δ 18 O value of the diluted must is higher than −5‰, δ 2 H should also be analyzed. The study performed by Hamzić Gregorčič et al [ 3 ] uses δ 18 O values in lactose to identify the adulteration of milk and detection of water addition. The results are promising and indicate that δ 18 O values in lactose can be used as an internal standard in the detection of the illegal watering of milk (>7%).…”

“…Some of the manuscripts [ 3 , 4 , 8 , 10 ] presented their raw data in the supplementary material supporting the open-access of research data. Much of this data is also in the e -component of different projects such as METROFOOD-RI research infrastructure and FNS-Cloud.…”