Distribution of chemical residues among fat, skim, curd, whey, and protein fractions in fortified, pasteurized milk

Authors: Shelver, Weilin; Lupton, Sara; Shappell, Nancy; Smith, David; Hakk, Heldur

Submitted to: ACS Omega
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2018
Publication Date: 8/6/2018
Citation: Shelver, W.L., Lupton, S.J., Shappell, N.W., Smith, D.J., Hakk, H. 2018. Distribution of chemical residues among fat, skim, curd, whey, and protein fractions in fortified, pasteurized milk. ACS Omega. 3(8):8697-8708. https://doi.org/10.1021/acsomega.8b00762.
DOI: https://doi.org/10.1021/acsomega.8b00762

Interpretive Summary: Milk is a complex food that is often processed into other commercial products. During milk processing trace-level chemical contaminants might become concentrated in fractions such as skim milk, milk fat (cream products), curd (cheese products), whey, or whey powder, possibly to levels of potential concern. To test whether chemicals differentially partition into milk fractions, laboratory experiments mimicking milk processing operations were conducted on 12 potential chemical contaminants. The selected chemicals varied widely with respect to chemical properties. Highly fat soluble chemical contaminants concentrated into milk fat, while moderately fat soluble chemicals tended to concentrate in curd, and water soluble chemicals ended up in whey. A chemical’s fat solubility was reasonably predictive of its partitioning into milk fractions, though additional factors such as chemical-protein interactions also influenced partitioning. Our study demonstrated that a chemical contaminant’s movement into processed milk products could be reasonably predicted by a contaminant’s chemical properties.

Technical Abstract: The distribution of twelve environmental contaminants or metabolites with diverse polarities (BDE-99; bisphenol A; estrone; glyphosate; ß-HBCD, imidacloprid; PCB-118; 3-methylsulfone PCB-101; 1,2,7,8-TCDD; 2-hydroxy-1,3,7,8-TCDD; tetrabromobisphenol A; and triclocarban) among skim milk, fat, curd, whey, whey retentate and whey permeate was characterized. Analysis of these compounds along with 15 drugs previously studied, provided a robust linear model predicting the distribution between skim and fat and the chemical’s lipophilicity (log P, r2 = 0.71; log D, r2 = 0.81). Similarly, distribution between curd and whey was correlated to lipophilicity (log P, r2 = 0.63; log D, r2 =0.75). Phenolic compounds had less predictable distribution patterns based on their lipophilicities. Within the whey fraction, chemicals with greater lipophilicity associated with whey proteins more than hydrophilic chemicals. The resultant model could help predict the potential distribution of chemical contaminants among milk products in cow milk, if present.