The study, from Virginia Tech’s Department of Food Science and Technology, and published in the June edition of the Journal of Dairy Science, says iron contamination decreases the quality, sensory profile, and nutritional value of milk and related dairy products.
The authors looked at the protein composition, oxidative stability, and mineral composition of milk under conditions of iron ingestion through infused bovine drinking water as well as direct iron addition to commercial milk.
Four ruminally cannulated cows received aqueous infusions (based on water consumption of 100 liters) of 0, 2, 5, and 12.5 mg/L of iron, as ferrous lactate, in a 4 × 4 Latin square design for a 14-day period.
For comparison, ferrous sulfate solution was directly added into commercial retail milk at the same concentrations.
Caseins and whey proteins affected
The study found that in both cases, an iron concentration as low as 2 mg of iron/L caused oxidative stress.
Infusion affected both caseins and whey proteins in the milk, whereas direct addition of iron to milk primarily influenced caseins.
Although iron infusion did not significantly affect oxidation state and mineral balance (with the exception of iron), it did induce oxidized off-flavor and partial degradation of whey proteins.
Source: Journal of Dairy Science, Volume 99, Issue 6, June 2016, Pages 4206–4219
“Milk protein composition and stability changes affected by iron in water sources”
Authors: Aili Wang, Susan E. Duncan, Katharine F. Knowlton, William K. Ray, Andrea M. Dietrich