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

Abstract

The oxygen and hydrogen isotope composition of the water component of the milk from nine Italian dairy farms were studied together with the farm water for one year. The aim was to verify the importance of farm water and seasonal temperature variation on milk isotope values and propose mathematical relations as new tools to identify the milk origin.METHODS: Milk was centrifuged to separate the solids and then distilled under a vacuum to separate water. δ( 18 O/ 16 O) and δ( 2 H/ 1 H) analyses of the water molecules were carried out using a water equilibrator online with a mass spectrometer. For oxygen and hydrogen isotope determination, water was equilibrated with pure CO2 for 7.5 hours and with pure H2 for 5 hours, respectively. The isotope ratio value is indicated with  (expressed in the VSMOW/SLAP scale) as defined by IUPAC. RESULTS:The average annual isotope value of milk at the different cattle sheds is mostly related to the farm water suggesting that the drinking water is the most important factor influencing the isotopic values of the milk water. The milk/water fractionation factor correlates with the milking time and, thus, the seasonal temperature is best described by a 4 th order This article is protected by copyright. All rights reserved. polynomial regression line. A two level-check model was used to verify the milking provenance. CONCLUSIONS:This study shows that it is essential to analyze both milk and farm water to indicate provenance. A two-step verification tool, based on the difference between the measured and calculated δ( 18 O/ 16 O)M values, and the difference between the calculated and estimated milk-water fractionation factor, allowed the source determination of milk. Both conditions must be met if the milk is considered to be from the Parmigiano-Reggiano production region. Although this approach was developed for this region, it can easily be tested and adapted to other dairy production areas.

Verifying origin claims on dairy products using stable isotope ratio analysis and random forest classification

“…Differences between milk and precipitation δ 18 O and δ 2 H values due to fractionation and enrichment that occur within the milk producing animal have also been reported ( Boito et al, 2021 ). For example, Gregorcic et al (2020) noted that milk water was enriched in 18 O isotopes compared to animal drinking water.…”

Isotope Fingerprinting as a Backup for Modern Safety and Traceability Systems in the Animal-Derived Food Chain

“…Sources of H and O isotopes in milk are the same as those reported for meat, being strongly related to the isotopic composition of drinking water and, in turn, varying according to seasonality, latitude, and altitude [59,60,62]. Evidence of the transfer of the isotopic composition of meteoric waters to milk was provided by Behkami et al, according to whom a strong positive correlation between δ 2 H and δ 18 O values of cow milk with those of the rain exists [86].…”

“…* GO = geographical origin; FR = feeding regime; FS = farming system; PM = production method; SEAS = seasonality; SP = species. Pig Muscle GO 7 Li/ 6 Li, 11 B/ 10 B, 53 Cr/ 52 Cr, 52 Cr/ 50 Cr, 60 Ni/ 58 Ni, 65 Cu/ 64 Cu, 71 Ga/ 69 Ga, 88 Sr/ 86 Sr, 87 Sr/ 84 Sr, 88 Sr/ 84 Sr, 87 Sr/ 86 Sr, 86 Sr/ 84 Sr, 97 Mo/ 95 Mo, 97 Mo/ 94 Mo, 95 Mo/ 94 53 Cr/ 50 Cr, 52 Cr/ 50 Cr, 60 Ni/ 58 Ni, 65 Cu/ 63 Cu, 66 Zn/ 64 Zn, 71 Ga/ 69 Ga, 88 Sr/ 86 Sr, 88 Sr/ 84 Sr, 87 Sr/ 86 Sr, 87 Sr/ 84 Sr, 86 Sr/ 84 Sr, 97 Mo/…”

“…The δ 2 H and δ 18 O in animal tissues are influenced not only by the diet, but are also directly subjected to strong seasonal effects, as well as geographic latitude and altitude effects. H and O are indeed mainly sourced by the animal from the drinking water, whose isotopic composition, in turn, derives mainly from those of precipitation and subsoil waters [59][60][61]. Indeed, it has been reported that precipitation waters fallen during the winter season, and at increasing latitude and altitude, tend to show more negative δ 2 H and δ 18 O values [62].…”